Yu Lan

Cp*CoIII-Catalyzed Branch-Selective Hydroarylation of Alkynes via C–H Activation: Efficient Access to α-gem-Vinylindoles

Co-reporter:Xukai Zhou, Yixin Luo, Lingheng Kong, Youwei Xu, Guangfan Zheng, Yu Lan, and Xingwei Li

ACS Catalysis October 6, 2017 Volume 7(Issue 10) pp:7296-7296

Publication Date(Web):September 12, 2017

DOI:10.1021/acscatal.7b02248

An efficient, atom-economical, and regioselective insertion of indoles into terminal alkynes has been realized via cobalt(III)-catalyzed C–H activation under mild conditions, leading to efficient synthesis of α-gem-vinylindoles. The insertion of the alkynes follows a rare 1,2-selectivity, and silyl alkynes, alkyl alkynes, propargyl alcohols, and protected propargyl amines are all applicable. The mechanism of this hydroarylation system has been studied in detail by a combination of experimental and computational approaches. In the reaction of silyl terminal alkynes, the regioselectivity is dictated by the steric effects of the alkyne substituent, especially in the protonolysis stage. However, for protected propargyl amines, the selectivity results from electronic effects during the insertion step, with protonolysis being insignificant in the determination of selectivity. An internal alkyne also coupled in high efficiency but with low regioselectivity. Comparisons of cobalt, rhodium, and iridium catalysts have also been made in terms of regioselectivity and reactivity, and both are high for cobalt catalysts.Keywords: alkyne insertion; cobalt; C−H activation; hydroarylation; indole;

Rhodium/Copper Cocatalyzed Highly trans-Selective 1,2-Diheteroarylation of Alkynes with Azoles via C–H Addition/Oxidative Cross-Coupling: A Combined Experimental and Theoretical Study

Co-reporter:Guangying Tan, Lei Zhu, Xingrong Liao, Yu Lan, and Jingsong You

Journal of the American Chemical Society November 8, 2017 Volume 139(Issue 44) pp:15724-15724

Publication Date(Web):October 17, 2017

DOI:10.1021/jacs.7b07242

Transition metal-catalyzed addition of diaryl alkynes with arylating reagents for the synthesis of tetraarylethylenes generally encounters rigorous reaction conditions and relies on the use of prefunctionalized substrates such as organic halides or surrogates and organometallic reagents. In this work, we establish a highly trans-selective 1,2-diheteroarylation of alkynes with azoles via a rhodium/copper cocatalyzed C–H addition/oxidative coupling process. Moreover, the diheteroarylation developed herein could open a door for the synthesis of heteroarene-doped tetraarylethylenes, and the photoluminescence (PL) spectra in THF–water mixtures and solid powder verify that these tetra(hetero)arylethylenes are aggregation-induced emission (AIE) active, building a new AIE molecule library. With a combination of experimental and theoretical methods, the reaction mechanism for addition/oxidative cross-coupling of internal alkynes with azoles has been investigated. Theoretical calculations reveal that the metalation/deprotonation of azole could occur with either rhodium or copper species. When azolylrhodium is formed, an alkyne could insert into the Rh–C bond. Another azolyl group could then transfer to rhodium from azolylcopper compound. The subsequent intramolecular trans-nucleophilic addition generates the second C–C bond. Meanwhile, the putative pathway for the formation of the hydroheteroarylated byproduct has also been explained by theoretical calculations.

Nine-Membered Benzofuran-Fused Heterocycles: Enantioselective Synthesis by Pd-Catalysis and Rearrangement via Transannular Bond Formation

Co-reporter:Zi-Qiang Rong, Li-Cheng Yang, Song Liu, Zhaoyuan Yu, Ya-Nong Wang, Zher Yin Tan, Rui-Zhi Huang, Yu Lan, and Yu Zhao

Journal of the American Chemical Society November 1, 2017 Volume 139(Issue 43) pp:15304-15304

Publication Date(Web):October 17, 2017

DOI:10.1021/jacs.7b09161

The first enantioselective formal [5+4] cycloaddition is realized under palladium catalysis to deliver benzofuran-fused nine-membered rings. These medium-sized heterocycles and derivatives undergo unique rearrangements induced by transannular bond formation, resulting in the production of two classes of densely substituted polycyclic heterocycles in excellent efficiency and stereoselectivity.

Mechanism, Regio-, and Diastereoselectivity of Rh(III)-Catalyzed Cyclization Reactions of N-Arylnitrones with Alkynes: A Density Functional Theory Study

Co-reporter:Yingzi Li, Chunhui Shan, Yun-Fang Yang, Fuqiang Shi, Xiaotian Qi, K. N. Houk, and Yu Lan

The Journal of Physical Chemistry A June 15, 2017 Volume 121(Issue 23) pp:4496-4496

Publication Date(Web):May 10, 2017

DOI:10.1021/acs.jpca.7b01020

Nitrones have been used for rhodium-catalyzed cyclization C–H bond activation and O atom transfer of arylnitrones with alkynes by Chang et al. ( J. Am. Chem. Soc. 2015, 137, 4908−4911). Density functional theory method has been used to study the mechanism, regio-, and diastereoselectivity of type reactions. The results elucidated that the reaction pathway for Rh(III)-catalyzed cyclization of N-arylnitrones with alkyne contains a C–H bond activation, an alkyne insertion into Rh–C bond, a reductive elimination to form a Rh(I) complex, an oxidative addition leading to N–O cleavage, an imine insertion into the Rh–C bond, and the final protonolysis to regenerate the products and the active catalyst. The regioselectivity of this reaction with asymmetric alkyne is controlled by the electronic effect in alkyne insertion type instead of steric effects. The distortion–interaction analysis is also used to explain the regioselectivity. The diastereoselectivity is controlled by the imine insertion step. In this step, the sterically less hindered transition state is favored, leading to stereoselective product formation.

Ir(III)/Ir(V) or Ir(I)/Ir(III) Catalytic Cycle? Steric-Effect-Controlled Mechanism for the para-C–H Borylation of Arenes

Co-reporter:Lei Zhu, Xiaotian Qi, Yingzi Li, Meng Duan, Lufeng Zou, Ruopeng Bai, and Yu Lan

Organometallics June 12, 2017 Volume 36(Issue 11) pp:2107-2107

Publication Date(Web):May 30, 2017

DOI:10.1021/acs.organomet.7b00151

Density functional theory method N12 was used to study the mechanism of the [Ir(cod)OH]2/Xyl–MeO–BIPHEP-catalyzed para-selective C–H borylation reaction. The results revealed that the use of a bulky diphosphine ligand such as Xyl–MeO–BIPHEP was unfavorable for the previously proposed iridium(III)/iridium(V) catalytic cycle because it resulted in considerable steric repulsion in the hepta-coordinated iridium(V) intermediate. Inspired by this steric effect, we have proposed a novel iridium(I)-/iridium(III)-based catalytic cycle for this transformation and shown that it can be used to account for the experimental results. The iridium(I)/iridium(III) catalytic cycle induced by this steric effect consists of several steps, including (i) the oxidative addition of the C–H bond of the substrate to an active iridium(I) boryl complex; (ii) the reductive elimination of a C–B bond; (iii) the oxidative addition of B2pin2 to an iridium(I) hydride complex; and (iv) the reductive elimination of a B–H bond. Notably, the computed regioselectivity of this reaction was consistent with the experimental observations. The high para-selectivity of this reaction was also explained using structural analysis and a 2D contour model, which revealed that the strong steric repulsion between the diphosphine ligand and the meta-substituents resulted in a higher energy barrier for meta-C–H activation.

Room-Temperature Coupling/Decarboxylation Reaction of α-Oxocarboxylates with α-Bromoketones: Solvent-Controlled Regioselectivity for 1,2- and 1,3-Diketones

Co-reporter:Xiaotian Qi;Zhen He;Junbin Tang;Zhijie She;Shiqing Li;Yinsong Zhao;Ge Gao;Jingsong You

The Journal of Organic Chemistry February 3, 2017 Volume 82(Issue 3) pp:1403-1411

Publication Date(Web):January 4, 2017

DOI:10.1021/acs.joc.6b02575

A transition-metal-free and room-temperature coupling/decarboxylation reaction between α-oxocarboxylates and α-bromoketones is reported herein. It represents the first mild and regioselective synthesis of either 1,2- or 1,3-diketones from the same starting materials. Notably, the regioselectivity is simply controlled by solvents. The preliminary experimental data and DFT calculations suggest sequential Darzens-type coupling, alkaline hydrolysis, KOH-promoted oxirane opening and decarboxylation in one pot. This method is efficient for the synthesis of α,β-epoxy-γ-butyrolactone and curcuminoids.

C–O Functionalization of α-Oxyboronates: A Deoxygenative gem-Diborylation and gem-Silylborylation of Aldehydes and Ketones

Co-reporter:Lu Wang, Tao Zhang, Wei Sun, Zeyu He, Chungu Xia, Yu Lan, and Chao Liu

Journal of the American Chemical Society April 12, 2017 Volume 139(Issue 14) pp:5257-5257

Publication Date(Web):March 17, 2017

DOI:10.1021/jacs.7b02518

A deoxygenative gem-diborylation and gem-silylborylation of aldehydes and ketones is described. The key for the success of this transformation is the base-promoted C–O bond borylation or silylation of the generated α-oxyboronates. Experimental and theoretical studies exhibit that the C–O bond functionalization proceeds via an intramolecular five-membered transition-state (9-ts) boryl migration followed by a 1,2-metalate rearrangement with OBpin as a leaving group. The transformation occurs with an inversion on the carbon center. Direct conversion of aldehydes and ketones to gem-diboron compounds was achieved by combining copper catalysis with this base-promoted C-OBpin borylation. Various aldehydes and ketones were deoxygenatively gem-diborylated. gem-Silylborylation of aldehydes and ketones were achieved by a stepwise operation, in which B2pin2 initially react with those carbonyls followed by a silylation with Bpin-SiMe2Ph.

Chiral phosphine-mediated intramolecular [3 + 2] annulation: enhanced enantioselectivity by achiral Brønsted acid

Co-reporter:Weijun Yao;Zhaoyuan Yu;Shan Wen;Huanzhen Ni;Nisar Ullah;Yixin Lu

Chemical Science (2010-Present) 2017 vol. 8(Issue 7) pp:5196-5200

Publication Date(Web):2017/06/26

DOI:10.1039/C7SC00952F

Enantioselective intramolecular [3 + 2] annulation of chalcones bearing an allene moiety has been successfully developed. The reaction was effectively promoted by amino acid-derived phosphines, in combination with achiral Brønsted acids. Dihydrocoumarin architectures were constructed in high yields and with excellent enantiomeric excesses. Theoretical studies via DFT calculations revealed that the hydrogen bonding network induced by achiral Brønsted acids/chiral phosphines could more efficiently distinguish between two enantioselective pathways, thus leading to enhanced enantioselectivity.

Bond dissociation energy controlled σ-bond metathesis in alkaline-earth-metal hydride catalyzed dehydrocoupling of amines and boranes: a theoretical study

Co-reporter:Dongdong Xu;Chunhui Shan;Yingzi Li;Xiaotian Qi;Xiaoling Luo;Ruopeng Bai

Inorganic Chemistry Frontiers 2017 vol. 4(Issue 11) pp:1813-1820

Publication Date(Web):2017/11/07

DOI:10.1039/C7QI00459A

Dehydrocoupling of amines and boranes is an efficient method for the formation of N–B bonds; however, the strong B–H bond dissociation energy (BDE) always restricts non-catalytic reaction pathways. Therefore, alkaline-earth-metal (Ae) hydrides are used as catalysts for this type of reaction because of their lower Ae–H bond energy. A theoretical study was performed to study the mechanism of Ae-catalyzed dehydrocoupling reactions. The computational results show that such reactions are initiated from σ-bond metathesis between Ae hydride catalysts and amines to release molecular hydrogen, followed by borane bonding with amino Ae intermediates. Subsequent hydride transfer yields an amino-borane product and, in the process, regenerates the Ae hydride catalyst. Our theoretical calculations revealed that dehydrogenation is the rate-determining step during σ-bond metathesis in the presence of a magnesium hydride catalyst. We predicted that beryllium hydride could not function as a catalyst because the apparent activation free energy is significantly high. Furthermore, we observed that in calcium or strontium hydride-catalyzed reactions, the rate-limiting step changed to the hydride transfer step. Further density functional theory calculations showed that the BDEs of the Ae–H bond controlled the reactivity of the σ-bond metathesis step.

Catalyst-controlled regioselectivity in phosphine catalysis: the synthesis of spirocyclic benzofuranones via regiodivergent [3 + 2] annulations of aurones and an allenoate

Co-reporter:Huanzhen Ni;Zhaoyuan Yu;Weijun Yao;Nisar Ullah;Yixin Lu

Chemical Science (2010-Present) 2017 vol. 8(Issue 8) pp:5699-5704

Publication Date(Web):2017/07/24

DOI:10.1039/C7SC02176C

Catalyst-controlled regiodivergent [3 + 2] annulations of aurones and allenoates have been developed. When a dipeptide phosphine catalyst with an L-D- configuration was employed, α-selective [3 + 2] annulation products could be obtained with good regioselectivities and enantioselectivities. With the employment of L-L- dipeptide phosphines, γ-selective annulation products could be selectively obtained with excellent enantioselectivities. By simply tuning the catalyst configurations, a wide range of α-selective or γ-selective spirocyclic benzofuranones with either aryl or alkyl substitutions could be readily prepared. DFT calculations suggest that the conformation of the dipeptide phosphines influences the hydrogen bonding interactions or the distortion energy, resulting in delicate energy differentiation in the transition states, and accounting for the observed regioselectivity.

Thiolate–palladium(IV) or sulfonium–palladate(0)? A theoretical study on the mechanism of palladium-catalyzed C–S bond formation reactions

Co-reporter:Dongdong Xu;Xiaotian Qi;Meng Duan;Zhaoyuan Yu;Lei Zhu;Chunhui Shan;Xiaoyu Yue;Ruopeng Bai

Organic Chemistry Frontiers 2017 vol. 4(Issue 6) pp:943-950

Publication Date(Web):2017/05/31

DOI:10.1039/C6QO00841K

The density functional theory (DFT) method M06-L was used to study the general mechanism of palladium-catalyzed C–S bond formation reactions. Our theoretical calculations revealed that this type of reaction starts with a palladium-assisted metalation–deprotonation step. Oxidative addition of the sulfur source affords a thiolate–palladium(IV) intermediate, and subsequent reductive elimination generates the new C–S bond. A final protonation regenerates the active palladium(II) catalyst and releases the product. Our proposed mechanism could be applied to a series of palladium-catalyzed C–S bond formation reactions used for the construction of dibenzothiophene derivatives. The rate-limiting step of the catalytic cycle is oxidative addition to yield the thiolate–palladium(IV) intermediate. In contrast, formation of a sulfonium intermediate is unfavourable. In addition, the effect of substituents on the rate-determining step was studied with Hammett plots. Our calculations showed that incorporation of electron-withdrawing groups at the 4-position and electron-donating groups at the 15 and 16-positions would promote intramolecular oxidative addition of thioethers to palladium.

Reactivity and regioselectivity in Diels–Alder reactions of anion encapsulated fullerenes

Co-reporter:Cheng-Xing Cui;Zhao-Pei Zhang;Lei Zhu;Ling-Bo Qu;Yu-Ping Zhang

Physical Chemistry Chemical Physics 2017 vol. 19(Issue 45) pp:30393-30401

Publication Date(Web):2017/11/22

DOI:10.1039/C7CP06365B

Encapsulation and surface chemical modification are methodologies to enhance the properties of fullerenes for various applications. Herein, density functional theory calculations are performed to study the Diels–Alder (DA) reactivity of anion encapsulated C60, including [X@C60]− (X = F, Cl, Br, or I), [S@C60]2−, and [N@C60]3−. Computational results reveal that encapsulated Cl−, Br−, I−, or S2− anions are located close to the center of the C60 molecule; however, encapsulated F− is displaced from the center. Encapsulated N3− bonds to the inner surface of the carbon cage, which leads to a negative charge transfer to the C60. In [N@C60]3−, C–C bonds near to the encapsulated N atom are more reactive. Our calculations reveal that encapsulated halogen or S anions decrease the DA reactivity because of the stronger closed-shell repulsion of the encapsulated anion. However, encapsulated N3− increases the DA reactivity. The higher distortion energy of the halogen- or S2−-anion encapsulated C60 leads to lower reactivity of the 6-5 bond. Opposite regioselectivity of the DA reaction with [N@C60]3− is attributed to distortion energy of the cyclopentadiene (CPD) moiety. The asymmetrical transition state geometry leads to a lower distortion energy of the CPD moiety.

Computational Investigation of the Role Played by Rhodium(V) in the Rhodium(III)-Catalyzed ortho-Bromination of Arenes

Co-reporter:Tao Zhang;Xiaotian Qi;Song Liu;Dr. Ruopeng Bai; Dr. Chao Liu; Dr. Yu Lan

Chemistry - A European Journal 2017 Volume 23(Issue 11) pp:2690-2699

Publication Date(Web):2017/02/21

DOI:10.1002/chem.201605188

AbstractIn this study, M11-L was used to evaluate the feasibility of the formation of rhodium(V) species using the rhodium(III)-catalyzed ortho-bromination of arenes as a model reaction. In most cases for these types of reactions, DFT calculations reveal that the bromination step involves a Br transfer from N-bromosuccinimide to the reacting arylrhodium to form a bromonium intermediate, followed by a Br shift to generate a new C−Br bond, which is more favorable than the previously proposed RhIII/RhV catalytic cycle. The rhodium catalyst remains in its +3 oxidation state throughout. The substituent effects of the reacting arene were studied, and computational results showed that the introduction of electron-donating groups on the reacting arene was favorable for this pathway. In contrast, the inclusion of a strong electron-withdrawing group on the aromatic ring would hinder the formation of a bromonium intermediate. Therefore, the RhIII/RhV catalytic cycle is favorable in cases that involve a RhV intermediate, which is generated by oxidative addition with NBS. In this pathway, the C−Br bond is formed by reductive elimination from the RhV intermediate. Additionally, a distortion–interaction analysis model along the reaction pathway was used to explain the directing-group effects. The results showed that the interaction energy controlled the reactivity because of the difference in electronic nature of various directing groups.

Readily Accessible and Highly Efficient Ferrocene-Based Amino-Phosphine-Alcohol (f-Amphol) Ligands for Iridium-Catalyzed Asymmetric Hydrogenation of Simple Ketones

Co-reporter:Jianfei Yu;Meng Duan;Weilong Wu;Xiaotian Qi;Peng Xue; Yu Lan; Xiu-Qin Dong; Xumu Zhang

Chemistry - A European Journal 2017 Volume 23(Issue 4) pp:970-975

Publication Date(Web):2017/01/18

DOI:10.1002/chem.201604855

AbstractWe have successfully developed a series of novel and modular ferrorence-based amino-phosphine-alcohol (f-Amphol) ligands, and applied them to iridium-catalyzed asymmetric hydrogenation of various simple ketones to afford the corresponding chiral alcohols with excellent enantioselectivities and conversions (98–99.9 % ee, >99 % conversion, turnover number up to 200 000). Control experiments and density functional theory (DFT) calculations have shown that the hydroxyl group of our f-Amphol ligands played a key role in this asymmetric hydrogenation.

Bioinspired Total Synthesis of Homodimericin A

Co-reporter:Dr. Jun Huang;Yueqing Gu;Kai Guo;Lei Zhu; Dr. Yu Lan; Dr. Jianxian Gong; Dr. Zhen Yang

Angewandte Chemie 2017 Volume 129(Issue 27) pp:7998-8002

Publication Date(Web):2017/06/26

DOI:10.1002/ange.201702768

AbstractHomodimericin A is a remarkable fungal metabolite. This highly oxygenated racemic unsaturated polyketide poses a significant synthetic challenge owing to its sterically demanding central cagelike core containing eight contiguous stereogenic centers (including three quaternary stereocenters) and several carbonyl functionalities. On the basis of its proposed biogenetic synthesis, we designed a total synthesis of homodimericin A that proceeds in seven steps and features a double Michael reaction, an intramolecular Diels–Alder reaction, and an ene reaction.

Bioinspired Asymmetric Synthesis of Hispidanin A

Co-reporter:Fuzhuo Li;Qian Tu;Sijia Chen;Lei Zhu; Dr. Yu Lan; Dr. Jianxian Gong; Dr. Zhen Yang

Angewandte Chemie International Edition 2017 Volume 56(Issue 21) pp:5844-5848

Publication Date(Web):2017/05/15

DOI:10.1002/anie.201700838

AbstractThe first enantiospecific synthesis of hispidanin A (4), a dimeric diterpenoid from the rhizomes of Isodon hispida, was achieved with a longest linear sequence of 12 steps in 6.5 % overall yield. A key component is the use of the abundant and naturally occurring diterpenoids (+)-sclareolide and (+)-sclareol as starting materials, which enables the gram-scale preparation of the key intermediates totarane (1) and s-trans-12E,14-labdadien-20,8β-olide (2). Subsequently a thermal or an erbium-catalyzed intermolecular Diels–Alder reaction of totarane (1) with labdadienolide (2) provide convergent and rapid access to the natural product hispidanin A (4). The synthetic studies have offered significant impetus for the efficient construction of these architecturally complex natural products.

Mechanistic Study of the Fluoride-Induced Activation of a Kobayashi Precursor: Pseudo-SN2 Pathway via a Pentacoordinated Silicon Ate Complex

Co-reporter:Song Liu;Yang Li

European Journal of Organic Chemistry 2017 Volume 2017(Issue 42) pp:6349-6353

Publication Date(Web):2017/11/16

DOI:10.1002/ejoc.201701249

Density functional theory calculations were used to reveal the mechanistic pathway of benzyne formation from a Kobayashi precursor, for which two methods were employed: (1) direct geometry optimization in solvent; (2) single-point energy calculations in solvent on the basis of the gas-phase-optimized geometries. The first method suggested that the overall process involved fluoride ion attack to afford a pentacoordinate silicon ate complex, aryl–Si bond cleavage, and consequent irreversible triflate dissociation to produce the benzyne intermediate. The rate-determining step was found to be the addition of the fluoride ion to the trimethylsilyl group. However, this step was missing in the second method. Moreover, the mechanism and reactivity of this transformation were also studied by natural population charge analysis and the Hammett model.

Bioinspired Asymmetric Synthesis of Hispidanin A

Co-reporter:Fuzhuo Li;Qian Tu;Sijia Chen;Lei Zhu; Dr. Yu Lan; Dr. Jianxian Gong; Dr. Zhen Yang

Angewandte Chemie 2017 Volume 129(Issue 21) pp:5938-5942

Publication Date(Web):2017/05/15

DOI:10.1002/ange.201700838

AbstractThe first enantiospecific synthesis of hispidanin A (4), a dimeric diterpenoid from the rhizomes of Isodon hispida, was achieved with a longest linear sequence of 12 steps in 6.5 % overall yield. A key component is the use of the abundant and naturally occurring diterpenoids (+)-sclareolide and (+)-sclareol as starting materials, which enables the gram-scale preparation of the key intermediates totarane (1) and s-trans-12E,14-labdadien-20,8β-olide (2). Subsequently a thermal or an erbium-catalyzed intermolecular Diels–Alder reaction of totarane (1) with labdadienolide (2) provide convergent and rapid access to the natural product hispidanin A (4). The synthetic studies have offered significant impetus for the efficient construction of these architecturally complex natural products.

Bioinspired Total Synthesis of Homodimericin A

Co-reporter:Dr. Jun Huang;Yueqing Gu;Kai Guo;Lei Zhu; Dr. Yu Lan; Dr. Jianxian Gong; Dr. Zhen Yang

Angewandte Chemie International Edition 2017 Volume 56(Issue 27) pp:7890-7894

Publication Date(Web):2017/06/26

DOI:10.1002/anie.201702768

AbstractHomodimericin A is a remarkable fungal metabolite. This highly oxygenated racemic unsaturated polyketide poses a significant synthetic challenge owing to its sterically demanding central cagelike core containing eight contiguous stereogenic centers (including three quaternary stereocenters) and several carbonyl functionalities. On the basis of its proposed biogenetic synthesis, we designed a total synthesis of homodimericin A that proceeds in seven steps and features a double Michael reaction, an intramolecular Diels–Alder reaction, and an ene reaction.

Enantioselective alkynylation of N-sulfonyl α-ketiminoesters via a Friedel–Crafts alkylation strategy

Co-reporter:Ren-Rong Liu;Lei Zhu;Jiang-Ping Hu;Chuan-Jun Lu;Jian-Rong Gao;Yi-Xia Jia

Chemical Communications 2017 vol. 53(Issue 43) pp:5890-5893

Publication Date(Web):2017/05/30

DOI:10.1039/C7CC01015J

Enantioselective alkynylation of cyclic N-sulfonyl α-ketiminoesters with terminal alkynes was developed by using an Ni(ClO4)2/(R)-DTBM-Segphos complex as a catalyst. A range of propargylic amides bearing quaternary stereocenters were afforded in excellent enantioselectivities (up to 97% ee). Theoretical studies revealed that this reaction proceeded via a Friedel–Crafts-type reaction pathway.

Mild Acylation of C(sp3)–H and C(sp2)–H Bonds under Redox-Neutral Rh(III) Catalysis

Co-reporter:Songjie Yu, Yingzi Li, Lingheng Kong, Xukai Zhou, Guodong Tang, Yu Lan, and Xingwei Li

ACS Catalysis 2016 Volume 6(Issue 11) pp:7744

Publication Date(Web):October 13, 2016

DOI:10.1021/acscatal.6b02668

Carbonyl groups are ubiquitous in functional molecules. Although C–H bond acylation has been well-studied via different mechanisms, transition-metal-catalyzed redox-neutral C(sp3)–H acylation under mild conditions is unprecedented. In this work, ketene is designed as a acylating reagent for both C(sp3)–H and C(sp2)–H bonds under Rh(III) catalysis, affording a diverse array of carbonyl compounds in high yields and high atom economy under mild conditions.Keywords: acylation; arene; C−H activation; ketene; rhodium

Rhodium(III)-Catalyzed Annulation between N-Sulfinyl Ketoimines and Activated Olefins: C–H Activation Assisted by an Oxidizing N–S Bond

Co-reporter:Qiang Wang, Yingzi Li, Zisong Qi, Fang Xie, Yu Lan, and Xingwei Li

ACS Catalysis 2016 Volume 6(Issue 3) pp:1971

Publication Date(Web):February 9, 2016

DOI:10.1021/acscatal.5b02297

C–H activation under redox-neutral conditions, especially by Rh(III) catalysis, has offered attractive synthetic strategies. Previous work in redox-neutral C–H activation relied heavily on the cleavage of oxidizing N–O and N–N directing groups, and cleavable N–S bonds have been rarely used, although they may offer complementary coupling patterns. In this work, N-sulfinyl ketoimines were designed as a novel substrate for the redox-neutral coupling with different activated olefins via a Rh-catalyzed C–H activation pathway. The coupling with acrylate esters afforded 1H-isoindoles with the formation of three chemical bonds around a quaternary carbon. Furthermore, the coupling with maleimides furnished pyrrolidone-fused isoquinolines. A broad scope of substrates has been established. The mechanism of the coupling with acrylates has been studied in detail by a combination of experimental and computational methods. This coupling proceeds via imine-assisted C–H activation of the arene followed by ortho C–H olefination to afford a Rh(III) olefin hydride intermediate which, upon deprotonation, may exist in equilibrium with a Rh(I) olefin species. Cleavage of the N–S bond occurs only after C–H olefination to generate a Rh(III) imide species. DFT studies indicated that the imide group can undergo migratory insertion to produce a Rh(III) secondary alkyl which isomerizes under the assistance of acetic acid to a Rh(III) tertiary alkyl that is prone to insertion of the second acrylate.Keywords: C−H bond activation; isoindole; N-sulfinyl imine; N−S bond cleavage; olefin; Rh(III) catalyst

Gold(I)-Catalyzed Angle Strain Controlled Strategy to Furopyran Derivatives from Propargyl Vinyl Ethers: Insight into the Regioselectivity of Cycloisomerization

Co-reporter:Shengfei Jin, Chongguo Jiang, Xiaoshi Peng, Chunhui Shan, Shanshan Cui, Yuanyuan Niu, Yang Liu, Yu Lan, Yongxiang Liu, and Maosheng Cheng

Organic Letters 2016 Volume 18(Issue 4) pp:680-683

Publication Date(Web):February 3, 2016

DOI:10.1021/acs.orglett.5b03641

A unique strategy for the regiospecific synthesis of bicyclic furopyran derivatives has been developed via a gold(I)-catalyzed propargyl-Claisen rearrangement/6-endo-trig cyclization of propargyl vinyl ethers. The introduction of angle strain into the substrates significantly altered the reaction’s regioselectivity. Insight into the regioselectivity of the cycloisomerization was obtained with density functional theory calculations.

Iridium Catalysts with f-Amphox Ligands: Asymmetric Hydrogenation of Simple Ketones

Co-reporter:Weilong Wu, Shaodong Liu, Meng Duan, Xuefeng Tan, Caiyou Chen, Yun Xie, Yu Lan, Xiu-Qin Dong, and Xumu Zhang

Organic Letters 2016 Volume 18(Issue 12) pp:2938-2941

Publication Date(Web):June 3, 2016

DOI:10.1021/acs.orglett.6b01290

A series of modular and rich electronic tridentate ferrocene aminophosphoxazoline ligands (f-amphox) have been successfully developed and used in iridium-catalytic asymmetric hydrogenation of simple ketones to afford corresponding enantiomerically enriched alcohols under mild conditions with superb activities and excellent enantioselectivities (up to 1 000 000 TON, almost all products up to >99% ee, full conversion). The resulting chiral alcohols and their derivatives are important intermediates in pharmaceuticals.

Regio- and Stereoselective Syntheses of 7-Oxabicyclo[2.2.1]heptanes via a Gold(I)-Catalyzed Cycloisomerization of Alkynediols: Asymmetric Total Synthesis of Farnesiferol C

Co-reporter:Yue-Qing Gu;Peng-Peng Zhang;Jun-Kai Fu;Song Liu;Jian-Xian Gong;Zhen Yang

Advanced Synthesis & Catalysis 2016 Volume 358( Issue 9) pp:1392-1397

Publication Date(Web):

DOI:10.1002/adsc.201600218

Mechanism of Ruthenium-Catalyzed Direct Arylation of C–H Bonds in Aromatic Amides: A Computational Study

Co-reporter:Chunhui Shan, Xiaoling Luo, Xiaotian Qi, Song Liu, Yingzi Li, and Yu Lan

Organometallics 2016 Volume 35(Issue 10) pp:1440-1445

Publication Date(Web):April 21, 2016

DOI:10.1021/acs.organomet.6b00064

Ruthenium-catalyzed arylation of ortho C–H bonds directed by a bidentate 8-aminoquinoline moiety not only is important to construct new biaryl derivates but also merges important research areas. In this study, the density functional theory (DFT) method M11-L was employed to predict the mechanism of this C–H bond arylation reaction. The computational results indicate that the initial step for this reaction is catalyst loading by electrophilic deprotonation to generate a substrate-coordinated Ru(II) intermediate, which is the key compound in the complete catalytic cycle. The catalytic cycle includes electrophilic deprotonation by carbonate, oxidative addition of bromobenzene, reductive elimination to form a new aryl–aryl bond, proton transfer to release the product, and ligand exchange to regenerate the initial Ru(II) intermediate. Theoretical calculations suggest that the oxidative addition of bromobenzene is the rate-determining step of the whole catalytic cycle, and the apparent activation free energy is 32.7 kcal/mol. The ligand effect was considered in DFT calculations, and the calculated results agree well with experimental observations.

Anthranil: An Aminating Reagent Leading to Bifunctionality for Both C(sp3)H and C(sp2)H under Rhodium(III) Catalysis

Co-reporter:Dr. Songjie Yu;Guodong Tang;Yingzi Li;Xukai Zhou; Yu Lan; Xingwei Li

Angewandte Chemie 2016 Volume 128( Issue 30) pp:8838-8842

Publication Date(Web):

DOI:10.1002/ange.201602224

Abstract

Previous direct C−H nitrogenation suffered from simple amidation/amination with limited atom-economy and is mostly limited to C(sp²)−H substrates. In this work, anthranil was designed as a novel bifunctional aminating reagent for both C(sp²)−H and C(sp³)−H bonds under rhodium(III) catalysis, thus affording a nucleophilic aniline tethered to an electrophilic carbonyl. A tridendate rhodium(III) complex has been isolated as the resting state of the catalyst, and DFT studies established the intermediacy of a nitrene species.

Rhodium-Catalyzed Cyclocarbonylation of Ketimines via C–H Bond Activation

Co-reporter:Bao Gao, Song Liu, Yu Lan, and Hanmin Huang

Organometallics 2016 Volume 35(Issue 10) pp:1480-1487

Publication Date(Web):March 9, 2016

DOI:10.1021/acs.organomet.6b00072

A novel rhodium-catalyzed oxidative cyclocarbonylation of ketimines via cleavage of two C–H bonds was established, which provided a direct and reliable method for the synthesis of a wide range of 3-methyleneisoindolin-1-ones with mostly moderate yields. Preliminary experimental mechanistic studies and DFT calculations revealed that this reaction proceeds via imine–enamine tautomerization, N–H cleavage, C–H bond activation, CO insertion, and reductive elimination. The mechanism studies further ruled out an isolated cyclometalated rhodium complex being involved in the present reaction, which was different from many other documented rhodium-catalyzed C–H cyclization reactions.

Computational Studies on an Aminomethylation Precursor: (Xantphos)Pd(CH2NBn2)+

Co-reporter:Xiaotian Qi, Song Liu, and Yu Lan

Organometallics 2016 Volume 35(Issue 10) pp:1582-1585

Publication Date(Web):May 2, 2016

DOI:10.1021/acs.organomet.6b00234

(Xantphos)Pd(CH2NBn2)+ is an important precursor for aminomethylation reactions. In this study, density functional theory is used to clarify the structure of the complex and the mechanism of these types of reactions. The complex can be described as a mixture of square-planar nitrogen-coordinated aminomethyl–Pd(II) and triangular iminium-coordinated Pd(0). Frontier molecular orbital analysis favors the latter. The mechanisms of selected aminomethylation reactions are investigated by density functional theory calculations. The computational results reveal that the Xantphos ligand aids in forming iminium-coordinated palladium complexes, promotes the reductive elimination step of aminomethylation, and can stabilize Pd(0) species.

Rhodium-Catalyzed Hetero-(5 + 2) Cycloaddition of Vinylaziridines and Alkynes: A Theoretical View of the Mechanism and Chirality Transfer

Co-reporter:Lei Zhu, Xiaotian Qi, and Yu Lan

Organometallics 2016 Volume 35(Issue 5) pp:771-777

Publication Date(Web):February 18, 2016

DOI:10.1021/acs.organomet.6b00007

A newly reported density functional theory method, M11-L, was performed to study the mechanism and chirality transfer for the intramolecular formal hetero-(5 + 2) cycloaddition of vinylaziridines with alkynes. Both (E)- and (Z)-olefinic substrates were considered in the density functional theory calculations. The computational results suggested a metallahydropyridine pathway for the generation of azepines, which involves aziridine cleavage, 2π insertion of the alkyne group into the Rh–C bond, and reductive elimination from a rhodium(III) cation. The chirality transfer process for the (E)-alkene substrate is shown to occur on the re face of the alkene, whereas the (Z)-alkene cycloaddition chirality transfer occurs on the si face. The high enantioselectivity in this type of reaction is attributed to the greater ring strain in the trans allylic rhodium complex.

Anthranil: An Aminating Reagent Leading to Bifunctionality for Both C(sp3)H and C(sp2)H under Rhodium(III) Catalysis

Co-reporter:Dr. Songjie Yu;Guodong Tang;Yingzi Li;Xukai Zhou; Yu Lan; Xingwei Li

Angewandte Chemie International Edition 2016 Volume 55( Issue 30) pp:8696-8700

Publication Date(Web):

DOI:10.1002/anie.201602224

Abstract

Previous direct C−H nitrogenation suffered from simple amidation/amination with limited atom-economy and is mostly limited to C(sp²)−H substrates. In this work, anthranil was designed as a novel bifunctional aminating reagent for both C(sp²)−H and C(sp³)−H bonds under rhodium(III) catalysis, thus affording a nucleophilic aniline tethered to an electrophilic carbonyl. A tridendate rhodium(III) complex has been isolated as the resting state of the catalyst, and DFT studies established the intermediacy of a nitrene species.

Mechanism of Rhodium-Catalyzed Formyl Activation: A Computational Study

Co-reporter:Xiaoling Luo, Ruopeng Bai, Song Liu, Chunhui Shan, Changguo Chen, and Yu Lan

The Journal of Organic Chemistry 2016 Volume 81(Issue 6) pp:2320-2326

Publication Date(Web):February 24, 2016

DOI:10.1021/acs.joc.5b02828

Metal-catalyzed transfer hydroformylation is an important way of cleaving C–C bonds and constructing new double bonds. The newly reported density functional theory (DFT) method, M11-L, has been used to clarify the mechanism of the rhodium-catalyzed transfer hydroformylation reported by Dong et al. DFT calculations depict a deformylation and formylation reaction pathway. The deformylation step involves an oxidative addition to the formyl C–H bond, deprotonation with a counterion, decarbonylation, and β-hydride elimination. After olefin exchange, the formylation step takes place via olefin insertion into the Rh–H bond, carbonyl insertion, and a final protonation with the conjugate acid of the counterion. Theoretical calculations indicate that the alkalinity of the counterion is important for this reaction because both deprotonation and protonation occur during the catalytic cycle. A theoretical study into the formyl acceptor shows that the driving force of the reaction is correlated with the stability of the unsaturated bond in the acceptor. Our computational results suggest that alkynes or ring-strained olefins could be used as formyl acceptors in this reaction.

Effective Chirality Transfer in [3+2] Reaction between Allenyl-Rhodium and Enal: Mechanistic Study Based on DFT Calculations

Co-reporter:Xiaotian Qi, Song Liu, Tao Zhang, Rong Long, Jun Huang, Jianxian Gong, Zhen Yang, and Yu Lan

The Journal of Organic Chemistry 2016 Volume 81(Issue 18) pp:8306-8311

Publication Date(Web):August 22, 2016

DOI:10.1021/acs.joc.6b01429

Theoretical calculation was performed to study the chirality transfer in a newly reported intramolecular [3+2] cycloaddition of enal and alleno rhodium species, generated in situ from an enynol precursor. [3.3.0] bicyclic system which contains two bridgehead quaternary carbons that can be achieved, the chirality of which are controlled by those of the starting material, and the product stereoselectivity is only determined by the α-position of the acetylene moiety. Density functional theory calculations predicted that only the cis [3.3.0] bicyclic product could be generated, regardless of either erythro or threo substrate, which was also confirmed by experimental observations.

Mechanism of Synergistic Cu(II)/Cu(I)-Mediated Alkyne Coupling: Dinuclear 1,2-Reductive Elimination after Minimum Energy Crossing Point

Co-reporter:Xiaotian Qi, Ruopeng Bai, Lei Zhu, Rui Jin, Aiwen Lei, and Yu Lan

The Journal of Organic Chemistry 2016 Volume 81(Issue 4) pp:1654-1660

Publication Date(Web):January 25, 2016

DOI:10.1021/acs.joc.5b02797

An in-depth theoretical study of synergistic Cu(II)/Cu(I)-mediated alkyne coupling was performed to reveal the detailed mechanism for C–C bond formation, which proceeded via an unusual dinuclear 1,2-reductive elimination. Because the reactant for dinuclear 1,2-reductive elimination was calculated to be triplet while the products were singlet, the minimum energy crossing point (MECP) was introduced to the Cu/TMEDA/alkyne system to clarify the spin crossing between triplet state and singlet state potential energy surfaces. Computational results suggest that C–H bond cleavage solely catalyzed by the Cu(I) cation is the rate-determining step of this reaction and Cu(II)-mediated dinuclear 1,2-reductive elimination after the MECP is a facile process. These conclusions are in good agreement with our previous experimental results.

Regiodivergent Enantioselective γ-Additions of Oxazolones to 2,3-Butadienoates Catalyzed by Phosphines: Synthesis of α,α-Disubstituted α-Amino Acids and N,O-Acetal Derivatives

Co-reporter:Tianli Wang; Zhaoyuan Yu; Ding Long Hoon; Claire Yan Phee; Yu Lan;Yixin Lu

Journal of the American Chemical Society 2015 Volume 138(Issue 1) pp:265-271

Publication Date(Web):December 2, 2015

DOI:10.1021/jacs.5b10524

Phosphine-catalyzed regiodivergent enantioselective C-2- and C-4-selective γ-additions of oxazolones to 2,3-butadienoates have been developed. The C-4-selective γ-addition of oxazolones occurred in a highly enantioselective manner when 2-aryl-4-alkyloxazol-5-(4H)-ones were employed as pronucleophiles. With the employment of 2-alkyl-4-aryloxazol-5-(4H)-ones as the donor, C-2-selective γ-addition of oxazolones took place in a highly enantioselective manner. The C-4-selective adducts provided rapid access to optically enriched α,α-disubstituted α-amino acid derivatives, and the C-2-selective products led to facile synthesis of chiral N,O-acetals and γ-lactols. Theoretical studies via DFT calculations suggested that the origin of the observed regioselectivity was due to the distortion energy that resulted from the interaction between the nucleophilic oxazolide and the electrophilic phosphonium intermediate.

Rhodium-Catalyzed C–H Activation of Phenacyl Ammonium Salts Assisted by an Oxidizing C–N Bond: A Combination of Experimental and Theoretical Studies

Co-reporter:Songjie Yu; Song Liu; Yu Lan; Boshun Wan;Xingwei Li

Journal of the American Chemical Society 2015 Volume 137(Issue 4) pp:1623-1631

Publication Date(Web):January 8, 2015

DOI:10.1021/ja511796h

Rh(III)-catalyzed C–H activation assisted by an oxidizing directing group has evolved to a mild and redox-economic strategy for the construction of heterocycles. Despite the success, these coupling systems are currently limited to cleavage of an oxidizing N–O or N–N bond. Cleavage of an oxidizing C–N bond, which allows for complementary carbocycle synthesis, is unprecedented. In this article, α-ammonium acetophenones with an oxidizing C–N bond have been designed as substrates for Rh(III)-catalyzed C–H activation under redox-neutral conditions. The coupling with α-diazo esters afforded benzocyclopentanones, and the coupling with unactivated alkenes such as styrenes and aliphatic olefins gave ortho-olefinated acetophenoes. In both systems the reactions proceeded with a broad scope, high efficiency, and functional group tolerance. Moreover, efficient one-pot coupling of diazo esters has been realized starting from α-bromoacetophenones and triethylamine. The reaction mechanism for the coupling with diazo esters has been studied by a combination of experimental and theoretical methods. In particular, three distinct mechanistic pathways have been scrutinized by DFT studies, which revealed that the C–H activation occurs via a C-bound enolate-assisted concerted metalation–deprotonation mechanism and is rate-limiting. In subsequent C–C formation steps, the lowest energy pathway involves two rhodium carbene species as key intermediates.

Silver Migration Facilitates Isocyanide-Alkyne [3 + 2] Cycloaddition Reactions: Combined Experimental and Theoretical Study

Co-reporter:Xiaotian Qi, Heng Zhang, Ailong Shao, Lei Zhu, Ting Xu, Meng Gao, Chao Liu, and Yu Lan

ACS Catalysis 2015 Volume 5(Issue 11) pp:6640

Publication Date(Web):September 30, 2015

DOI:10.1021/acscatal.5b02009

Silver-mediated isocyanide-alkyne [3 + 2] cycloaddition has been developed as a new method for the synthesis of pyrroles. Density functional theory (DFT) calculations toward this reaction reveal that terminal alkynes participated cycloadditions proceed through two successive 1,5-silver migrations, in which the silver migrates between two carbon atoms and finally returns to original carbon. Natural population analysis (NPA) indicates that silver migration guides the move of charge into a rational way, thereby facilitating the cycloaddition. An analogous silver-migration mechanism is also suitable to explain the reactivity of the cycloaddition between isocyanide and internal alkynes, which shows the generality of the silver-migration process. Moreover, competitive experiments are consistent with the computational results, which provides further support for the mechanism.Keywords: competitive experiments; DFT calculation; NPA charge; silver migration; [3 + 2] cycloaddition

Highly enantioselective construction of tertiary thioethers and alcohols via phosphine-catalyzed asymmetric γ-addition reactions of 5H-thiazol-4-ones and 5H-oxazol-4-ones: scope and mechanistic understandings

Co-reporter:Tianli Wang, Zhaoyuan Yu, Ding Long Hoon, Kuo-Wei Huang, Yu Lan and Yixin Lu

Chemical Science 2015 vol. 6(Issue 8) pp:4912-4922

Publication Date(Web):02 Jun 2015

DOI:10.1039/C5SC01614B

Phosphine-catalyzed highly enantioselective γ-additions of 5H-thiazol-4-ones and 5H-oxazol-4-ones to allenoates have been developed for the first time. With the employment of amino-acid derived bifunctional phosphines, a wide range of substituted 5H-thiazol-4-one and 5H-oxazol-4-one derivatives bearing heteroatom (S or O)-containing tertiary chiral centers were constructed in high yields and excellent enantioselectivities. The reported method provides facile access to enantioenriched tertiary thioethers/alcohols. The mechanism of the γ-addition reaction was investigated by performing DFT calculations, and the hydrogen bonding interactions between the Brønsted acid moiety of the phosphine catalysts and the “CO” unit of the donor molecules were shown to be crucial in asymmetric induction.

Tuning radical reactivity using iodine in oxidative C(sp3)–H/C(sp)–H cross-coupling: an easy way toward the synthesis of furans and indolizines

Co-reporter:Shan Tang, Kun Liu, Yue Long, Xiaotian Qi, Yu Lan and Aiwen Lei

Chemical Communications 2015 vol. 51(Issue 42) pp:8769-8772

Publication Date(Web):17 Apr 2015

DOI:10.1039/C5CC01825K

Molecular iodine was found to be an effective redox catalyst for the oxidative cross-coupling of carbonyl compounds with terminal alkynes. In this work, we demonstrated that iodine could tune radical reactivity through reversible C–I bond formation for controlling the reaction selectivity. This iodine catalysis protocol provided an easy way for the synthesis of various furans and indolizines.

Revealing the halide effect on the kinetics of the aerobic oxidation of Cu(I) to Cu(II)

Co-reporter:Yi Deng, Guanghui Zhang, Xiaotian Qi, Chao Liu, Jeffrey T. Miller, A. Jeremy Kropf, Emilio E. Bunel, Yu Lan and Aiwen Lei

Chemical Communications 2015 vol. 51(Issue 2) pp:318-321

Publication Date(Web):03 Nov 2014

DOI:10.1039/C4CC05720A

In situ infrared (IR) and X-ray absorption near-edge structure (XANES) spectroscopic investigations reveal that different halide ligands have distinct effects on the aerobic oxidation of Cu(I) to Cu(II) in the presence of TMEDA (tetramethylethylenediamine). The iodide ligand gives the lowest rate and thus leads to the lowest catalytic reaction rate of aerobic oxidation of hydroquinone to benzoquinone. Further DFT calculations suggest that oxidation of CuI–TMEDA involves a side-on transition state, while oxidation of CuCl–TMEDA involves an end-on transition state which has a lower activation energy.

Nickel-Catalyzed Selective Oxidative Radical Cross-Coupling: AnEffective Strategy for Inert Csp3–H Functionalization

Co-reporter:Dong Liu, Yuxiu Li, Xiaotian Qi, Chao Liu, Yu Lan, and Aiwen Lei

Organic Letters 2015 Volume 17(Issue 4) pp:998-1001

Publication Date(Web):February 4, 2015

DOI:10.1021/acs.orglett.5b00104

An effective strategy for inert Csp3–H functionalization through nickel-catalyzed selective radical cross-couplings was demonstrated. Density functional theory calculations were conducted and strongly supported the radical cross-coupling pathway assisted by nickel catalyst, which was further confirmed by radical-trapping experiments. Different arylborates including arylboronic acids, arylboronic acid esters and 2,4,6-triarylboroxin were all good coupling partners, generating the corresponding Csp3–H arylation products in good yields.

Bimetallic zinc complex – active species in coupling of terminal alkynes with aldehydes via nucleophilic addition/Oppenauer oxidation

Co-reporter:Jiwen Yuan, Jing Wang, Guanghui Zhang, Chao Liu, Xiaotian Qi, Yu Lan, Jeffrey T. Miller, A. Jeremy Kropf, Emilio E. Bunel and Aiwen Lei

Chemical Communications 2015 vol. 51(Issue 3) pp:576-579

Publication Date(Web):03 Nov 2014

DOI:10.1039/C4CC08152H

A mechanistic study on the zinc-promoted coupling between aldehydes and terminal alkynes via nucleophilic addition/Oppenauer oxidation using operando IR, XANES/EXAFS techniques and DFT calculations was demonstrated. It was determined that a bimetallic zinc complex was the active species.

Dinuclear versus mononuclear pathways in zinc mediated nucleophilic addition: a combined experimental and DFT study

Co-reporter:Xiaotian Qi, Yingzi Li, Guanghui Zhang, Yang Li, Aiwen Lei, Chao Liu and Yu Lan

Dalton Transactions 2015 vol. 44(Issue 24) pp:11165-11171

Publication Date(Web):08 May 2015

DOI:10.1039/C5DT01366F

Employing the oxidative coupling of phenylacetylene with benzaldehyde as a model reaction, a density functional theory (DFT) study combined with extended X-ray absorption fine structure (EXAFS) experiment was carried out to reveal the difference between dinuclear and mononuclear zinc mediated nucleophilic addition. Newly reported DFT method M11-L computed results suggest that the mononuclear zinc mediated pathway, in which nucleophilic addition occurs via a four-membered ring transition state, is unfavourable both thermodynamically and kinetically. The dinuclear zinc mechanism, which appropriately explains the experimental observations, involves a six-membered ring transition state for nucleophilic addition. Subsequent in situ EXAFS experiment confirmed the existence of dinuclear zinc active species. Moreover, frontier molecular orbital (FMO) analysis and distortion–interaction energy analysis along the whole reaction pathways have provided interpretations for the advantage of dinuclear zinc mediated nucleophilic addition. Consequently, we believe this dinuclear zinc pathway will open up a general consideration of the dinuclear zinc mechanism for nucleophilic additions.

Distortion–interaction analysis along the reaction pathway to reveal the reactivity of the Alder-ene reaction of enes

Co-reporter:Rui Jin, Song Liu and Yu Lan

RSC Advances 2015 vol. 5(Issue 75) pp:61426-61435

Publication Date(Web):10 Jul 2015

DOI:10.1039/C5RA10345B

The reactivity of hetero-substituted propylene in uncatalyzed Alder-ene type reactions was investigated using CBS-QB3, G3B3, M11, and B3LYP methods, and the results are interpreted by distortion–interaction analysis of both the transition states and the complete reaction pathways. The reactivity trend for third-period element substituted ene reactants (ethylidenesilane, ethylidenephosphine, and ethanethial) is higher than that of the corresponding second-period element substituted ene reactants (propylene, ethanimine, and acetaldehyde). Theoretical calculations also indicate that for the same period element substituted ene reactants, the reactivity trend is ethylidenesilane > ethylidenephosphine > ethanethial, and propylene > ethanimine > acetaldehyde. Application of distortion–interaction analysis only of the transition states does not give a satisfactory explanation for these reactivities. Using distortion–interaction analysis along the reaction pathways, we found that the reactivity is mainly controlled by the interaction energy. A lower interaction energy along the reaction pathway leads to an earlier transition state and a lower activation energy, which also can be attributed to orbital interaction, closed-shell repulsion, and static repulsion. In some cases, the distortion energy also influences the reactivity.

Mechanism and selectivity for zinc-mediated cycloaddition of azides with alkynes: a computational study

Co-reporter:Yingzi Li, Xiaotian Qi, Yu Lei and Yu Lan

RSC Advances 2015 vol. 5(Issue 61) pp:49802-49808

Publication Date(Web):28 May 2015

DOI:10.1039/C5RA02703A

Density functional theory (DFT) method B3LYP with a dispersion term (B3LYP-D3BJ) has been used to clarify the regioselectivity of zinc mediated 1,3-dipolar cycloaddition of azides and alkynes. Computational results indicate that the dipolar cycloaddition takes place via a concerted five-membered-ring transition state, leading to a 1,5-disubstituted 1,2,3-triazole product, which is consistent with the experiment reported by Greaney's group. The coordination of imidazole ligand to zinc is reversible, and the regioselectivity is irrelevant to the coordination of imidazole ligand. Moreover, substituent effect of alkynes has also been studied. Finally, distortion–interaction analysis along the reaction pathways and frontier molecular orbital theory are used to explain the reactivity and 1,5-regioselectivity.

Development of a Rhodium(II)-Catalyzed Chemoselective C(sp3)H Oxygenation

Co-reporter:Yun Lin;Lei Zhu;Dr. Yu Lan;Dr. Yu Rao

Chemistry - A European Journal 2015 Volume 21( Issue 42) pp:14937-14942

Publication Date(Web):

DOI:10.1002/chem.201502140

Abstract

We report the first example of Rh^II-catalyzed chemoselective double C(sp³)H oxygenation, which can directly transform various toluene derivatives into highly valuable aromatic aldehydes with great chemoselectivity and practicality. The critical combination of catalyst Rh(OAc)₂, oxidant Selectfluor, and solvents of TFA/TFAA promises the successful delivery of the oxidation with satisfactory yields. A possible mechanism involving a unique carbene–Rh complex is proposed, and has been supported by both experiments and theoretical calculations.

Transition-Metal-Free Formal Decarboxylative Coupling of -Oxocarboxylates with -Bromoketones under Neutral Conditions: A Simple Access to 1,3-Diketones

Co-reporter:Zhen He;Xiaotian Qi;Shiqing Li;Yinsong Zhao;Dr. Ge Gao;Dr. Yu Lan;Yiwei Wu;Dr. Jingbo Lan;Dr. Jingsong You

Angewandte Chemie International Edition 2015 Volume 54( Issue 3) pp:855-859

Publication Date(Web):

DOI:10.1002/anie.201409361

Abstract

A transition-metal-free formal decarboxylative coupling reaction between α-oxocarboxylates and α-bromoketones to synthesize 1,3-diketone derivatives is presented. In this reaction, a broad scope of substrates can be employed, and neither a metal-based reagent nor an additional base is required. DFT calculations reveal that this reaction proceeds through a coupling followed by decarboxylation mechanism and the α-bromoketone unprecedentedly serves as a nucleophile under neutral conditions. The rate-determining step is an unusual hydrogen-bond-assisted enolate formation by thermolysis.

Inside Back Cover: Diastereoselective Synthesis of Cyclopentanoids: Applications to the Construction of the ABCD Tetracyclic Core of Retigeranic AcidA (Chem. Eur. J. 36/2015)

Co-reporter:Junlin Zhang;Xiao Wang;Shuang Li;Dian Li;Song Liu;Dr. Yu Lan;Dr. Jianxian Gong;Dr. Zhen Yang

Chemistry - A European Journal 2015 Volume 21( Issue 36) pp:

Publication Date(Web):

DOI:10.1002/chem.201583603

Diastereoselective Synthesis of Cyclopentanoids: Applications to the Construction of the ABCD Tetracyclic Core of Retigeranic AcidA

Co-reporter:Junlin Zhang;Xiao Wang;Shuang Li;Dian Li;Song Liu;Dr. Yu Lan;Dr. Jianxian Gong;Dr. Zhen Yang

Chemistry - A European Journal 2015 Volume 21( Issue 36) pp:12596-12600

Publication Date(Web):

DOI:10.1002/chem.201502423

Abstract

A concise and efficient approach for the construction of the tetracyclic carbon skeleton of retigeranic acid A is described. The key transformations include a novel Rh-catalyzed [3+2] cycloaddition of enyol to afford cyclopentanoid E, bearing two contiguous quaternary stereocenters at the bridgehead positions, and an intramolecular Pauson–Khand reaction to construct the advanced tetracyclic core structure of retigeranic acid A.

Copper-catalyzed aerobic oxidative coupling: From ketone and diamine to pyrazine

Co-reporter:Hong Yi;Chao Liu;Lingkui Meng;Kun Wu;Jeffrey T. Miller;Jyh-Fu Lee;Zhiliang Huang;Emilio E. Bunel;Chih-Wen Pao;Xiaotian Qi;Yingzi Li;Guanghui Zhang;Aiwen Lei

Science Advances 2015 Volume 1(Issue 9) pp:e1500656

Publication Date(Web):09 Oct 2015

DOI:10.1126/sciadv.1500656

A new copper-catalyzed reaction toward the synthesis of pyrazine compounds is demonstrated.

Cu(II)–Cu(I) Synergistic Cooperation to Lead the Alkyne C–H Activation

Co-reporter:Ruopeng Bai ; Guanghui Zhang ; Hong Yi ; Zhiliang Huang ; Xiaotian Qi ; Chao Liu ; Jeffrey T. Miller ; A. Jeremy Kropf ; Emilio E. Bunel ; Yu Lan ;Aiwen Lei

Journal of the American Chemical Society 2014 Volume 136(Issue 48) pp:16760-16763

Publication Date(Web):November 10, 2014

DOI:10.1021/ja5097489

An efficient alkyne C–H activation and homocoupling procedure has been studied which indicates that a Cu(II)/Cu(I) synergistic cooperation might be involved. In situ Raman spectroscopy was employed to study kinetic behavior, drawing the conclusion that Cu(I) rather than Cu(II) participates in the rate-determining step. IR, EPR, and X-ray absorption spectroscopy evidence were provided for structural information, indicating that Cu(I) has a stronger interaction with alkyne than Cu(II) in the C–H activation step. Kinetics study showed Cu(II) plays a role as oxidant in C–C bond construction step, which was a fast step in the reaction. X-band EPR spectroscopy showed that the coordination environment of CuCl2(TMEDA) was affected by Cu(I). A putative mechanism with Cu(I)–Cu(II) synergistic cooperation procedure is proposed for the reaction.

Transition-Metal-Assisted Radical/Radical Cross-Coupling: A New Strategy to the Oxidative C(sp3)–H/N–H Cross-Coupling

Co-reporter:Liangliang Zhou, Shan Tang, Xiaotian Qi, Caitao Lin, Kun Liu, Chao Liu, Yu Lan, and Aiwen Lei

Organic Letters 2014 Volume 16(Issue 12) pp:3404-3407

Publication Date(Web):June 12, 2014

DOI:10.1021/ol501485f

A transition-metal-assisted oxidative C(sp3)-H/N–H cross-coupling reaction of N-alkoxyamides with aliphatic hydrocarbons is described. During the reaction, nitrogen radicals were generated from the oxidation of N-alkoxyamides. Experiments and DFT calculations revealed that transition-metal catalyst could lower the reactivity of the generated nitrogen radical by the coordination of the transition metal, which allowed the selective radical/radical cross-coupling with the transient sp3 carbon radical to construct C(sp3)–-N bonds. Various C(sp3)–H bonds could be transformed into C(sp3)–N bonds through this radical amidation strategy.

Hexahapto-chromium complexes of graphene: a theoretical study

Co-reporter:Song Liu, Yu Lei, Yingzi Li, Tao Zhang, Huan Wang and Yu Lan

RSC Advances 2014 vol. 4(Issue 54) pp:28640-28644

Publication Date(Web):11 Jun 2014

DOI:10.1039/C4RA03702B

Chromium fragments coordinated with graphene provide a potentially powerful method for the modification of graphene. The newly reported density functional theory method, M11-L, was employed to elucidate the coordination of chromium fragments with graphene. Oligoacenes were chosen to model graphene. The radii of the centrosymmetric oligoacenes were systematically increased to find the limit required to model graphene. meta-Trisubstituted benzene coordinated chromium fragments were employed to study the electronic effect of the complexation of chromium with graphene. The movement and arrangement of the chromium fragments on graphene is also studied.

Chemoselective Carbophilic Addition of -Diazoesters through Ligand-Controlled Gold Catalysis

Co-reporter:Yumeng Xi;Yijin Su;Zhaoyuan Yu;Boliang Dong;Edward J. McClain; Yu Lan; Xiaodong Shi

Angewandte Chemie 2014 Volume 126( Issue 37) pp:9975-9979

Publication Date(Web):

DOI:10.1002/ange.201404946

Abstract

The chemoselective addition of arenes and 1,3-diketones to α-aryldiazoesters was achieved through ligand-controlled gold catalysis. Unlike a dirhodium catalyst (which promotes CH insertion and cyclopropanation) and a copper catalyst (which catalyzes OH and NH insertions), the gold catalyst with an electron-deficient phosphite as the ancillary ligand exclusively gave the carbophilic addition product, thus representing a new and efficient approach to form “carbophilic carbocations”, which selectively react with carbon nucleophiles.

Theoretical study of the electron-donating effects of thiourea ligands in catalysis

Co-reporter:Song Liu, Yu Lei, Zhen Yang, Yu Lan

Journal of Molecular Structure 2014 1074() pp: 527-533

Publication Date(Web):25 September 2014

DOI:10.1016/j.molstruc.2014.06.034

•Explained why thiourea and its derivatives often act as strong electron-donating ligands in palladium-catalyzed reactions.•A new p–d–π interaction model is proposed to explain the intensity of d–π interaction between metal and π-acid ligand.•The molecular orbitals of thiourea and its derivatives are clarified to the coordination model of thiourea with metals.Thiourea and its derivatives often act as strong electron-donating ligands in palladium-catalyzed reactions. Density functional theory calculations were performed to investigate the electronic effects of thiourea ligands in palladium complexes, and a p–d–π interaction model is proposed. In this model, a Pd(d)S(p) interaction is responsible for the increased binding of π acceptor ligands such as CO and olefins, which are present in important intermediates in Pd-catalyzed reactions. This d–p interaction is a four-electron, two-orbital interaction; it raises the energy of the Pd(dyz) orbital, bringing it closer to the π* orbital of the CO or olefin ligand, and increases back donation. Thiourea-ligated transition metals are therefore favorable for the binding of acidic π ligands.Thiourea and its derivatives often act as strong electron-donating ligands in palladium-catalyzed reactions. Density functional theory calculations were performed to investigate the electronic effects of thiourea ligands in palladium complexes, and a new p–d–π interaction model is proposed.

Reactivity for the Diels–Alder Reaction of Cumulenes: A Distortion-Interaction Analysis along the Reaction Pathway

Co-reporter:Song Liu, Yu Lei, Xiaotian Qi, and Yu Lan

The Journal of Physical Chemistry A 2014 Volume 118(Issue 14) pp:2638-2645

Publication Date(Web):February 27, 2014

DOI:10.1021/jp411914u

Cumulenes, including allene, ketenimine, and ketene, can be employed as dienophiles in Diels–Alder type reactions. The activation energies of a Diels–Alder reaction between cyclopentadiene and either the C═C bond or the other C═X (X = C, N, or O) bond in cumulenes have been calculated by G3B3, CBS-QB3, M06-2X, and B3LYP methods. The reactivity trend for the C═C bond in cumulenes is allene > ketenimine > ketene and that of the C═X bond in cumulenes is ketene > allene > ketenimine. Application of distortion-interaction analysis only at transition states does not give a satisfactory explanation for these reactivities. By employing distortion-interaction analysis along reaction pathways, we found that the reactivity of the C═C and C═X bond in cumulenes is controlled by both of its distortion and interaction energies. The lowest distortion energy of allene leads to its highest reactivity; the higher interaction energy results in higher activation energy of ketene than that of ketenimine. Compared with the reactivity of the C═X bond in cumulenes, the C═O bond in ketene has the lowest activation energy to react with cyclopentadiene, due to its lowest interaction energy, whereas the lower distortion energy of ketenimine than that of allene leads to a higher reactivity. The distortion energy of the reactants can be attributed to folding ability and molecule strain. The corresponding interaction energy of the reactants is controlled by orbital interaction, closed-shell repulsion, and static repulsion.

What Controls Stereoselectivity and Reactivity in the Synthesis of a trans-Decalin with a Quaternary Chiral Center via the Intramolecular Pauson–Khand Reaction: A Theoretical Study

Co-reporter:Song Liu, Hongjuan Shen, Zhaoyuan Yu, Lili Shi, Zhen Yang, and Yu Lan

Organometallics 2014 Volume 33(Issue 22) pp:6282-6285

Publication Date(Web):November 5, 2014

DOI:10.1021/om500840q

The Co2(CO)8-mediated intramolecular Pauson–Khand reaction is an efficient approach to the trans-decalin subunit with a defined C1 quaternary chiral center. The newly developed density functional theory method M11-L was employed to study the mechanism, reactivity, and stereoselectivity for this reaction. The rate- and stereoselectivity-determining step is the intramolecular alkene insertion into the carbon–cobalt bond. Insertion of the alkene by the re- and si-face was studied to explain the stereoselectivity. The effects of varying the substituent on the acetylene and the C3 chirality were investigated experimentally and theoretically.

Chemoselective Carbophilic Addition of -Diazoesters through Ligand-Controlled Gold Catalysis

Co-reporter:Yumeng Xi;Yijin Su;Zhaoyuan Yu;Boliang Dong;Edward J. McClain; Yu Lan; Xiaodong Shi

Angewandte Chemie International Edition 2014 Volume 53( Issue 37) pp:9817-9821

Publication Date(Web):

DOI:10.1002/anie.201404946

Abstract

The chemoselective addition of arenes and 1,3-diketones to α-aryldiazoesters was achieved through ligand-controlled gold catalysis. Unlike a dirhodium catalyst (which promotes CH insertion and cyclopropanation) and a copper catalyst (which catalyzes OH and NH insertions), the gold catalyst with an electron-deficient phosphite as the ancillary ligand exclusively gave the carbophilic addition product, thus representing a new and efficient approach to form “carbophilic carbocations”, which selectively react with carbon nucleophiles.

Mechanism of Rhodium-Catalyzed Carbon–Silicon Bond Cleavage for the Synthesis of Benzosilole Derivatives: A Computational Study

Co-reporter:Zhaoyuan Yu and Yu Lan

The Journal of Organic Chemistry 2013 Volume 78(Issue 22) pp:11501-11507

Publication Date(Web):October 11, 2013

DOI:10.1021/jo402070f

Rhodium-catalyzed carbon–silicon bond cleavage reaction is an efficient approach for the synthesis of silole derivates. The newly reported density functional theory method M11 is employed in order to elucidate how to cleave the inactive C(methyl)–Si bond. The computational results indicate that oxidative addition/reductive elimination pathway is favored over direct transmetallation in the C(methyl)–Si bond cleavage step. Alternatively, 1,4-rhodium–silicon exchange could take place before oxidative addition/reductive elimination. The rate-determining step for both pathways has been targeted on the initial transmetallation of 2-trimethylsilylphenyl boronic acid. The active catalytic species is a monomeric hydroxyrhodium complex, which could be regenerated from the hydrolysis of methylrhodium complex. In addition, theoretical calculations show that the hydrolyses of both aryl and vinyl intermediates are inhibited by intramolecular π-coordinated groups.

Dinuclear versus mononuclear pathways in zinc mediated nucleophilic addition: a combined experimental and DFT study

Co-reporter:Xiaotian Qi, Yingzi Li, Guanghui Zhang, Yang Li, Aiwen Lei, Chao Liu and Yu Lan

Dalton Transactions 2015 - vol. 44(Issue 24) pp:NaN11171-11171

Publication Date(Web):2015/05/08

DOI:10.1039/C5DT01366F

Employing the oxidative coupling of phenylacetylene with benzaldehyde as a model reaction, a density functional theory (DFT) study combined with extended X-ray absorption fine structure (EXAFS) experiment was carried out to reveal the difference between dinuclear and mononuclear zinc mediated nucleophilic addition. Newly reported DFT method M11-L computed results suggest that the mononuclear zinc mediated pathway, in which nucleophilic addition occurs via a four-membered ring transition state, is unfavourable both thermodynamically and kinetically. The dinuclear zinc mechanism, which appropriately explains the experimental observations, involves a six-membered ring transition state for nucleophilic addition. Subsequent in situ EXAFS experiment confirmed the existence of dinuclear zinc active species. Moreover, frontier molecular orbital (FMO) analysis and distortion–interaction energy analysis along the whole reaction pathways have provided interpretations for the advantage of dinuclear zinc mediated nucleophilic addition. Consequently, we believe this dinuclear zinc pathway will open up a general consideration of the dinuclear zinc mechanism for nucleophilic additions.

Bimetallic zinc complex – active species in coupling of terminal alkynes with aldehydes via nucleophilic addition/Oppenauer oxidation

Co-reporter:Jiwen Yuan, Jing Wang, Guanghui Zhang, Chao Liu, Xiaotian Qi, Yu Lan, Jeffrey T. Miller, A. Jeremy Kropf, Emilio E. Bunel and Aiwen Lei

Chemical Communications 2015 - vol. 51(Issue 3) pp:NaN579-579

Publication Date(Web):2014/11/03

DOI:10.1039/C4CC08152H

A mechanistic study on the zinc-promoted coupling between aldehydes and terminal alkynes via nucleophilic addition/Oppenauer oxidation using operando IR, XANES/EXAFS techniques and DFT calculations was demonstrated. It was determined that a bimetallic zinc complex was the active species.

Mechanism, chemoselectivity and enantioselectivity for the rhodium-catalyzed desymmetric synthesis of hydrobenzofurans: a theoretical study

Co-reporter:Zhaoyuan Yu, Xiaotian Qi, Yingzi Li, Song Liu and Yu Lan

Inorganic Chemistry Frontiers 2016 - vol. 3(Issue 2) pp:NaN216-216

Publication Date(Web):2015/12/03

DOI:10.1039/C5QO00334B

Rhodium-catalyzed desymmetrization of cyclohexadienones is an efficient method for the asymmetric synthesis of hydrobenzofurans. The newly reported density functional theory (DFT) method MN12-L is used to investigate the mechanism, chemoselectivity and enantioselectivity for this type of reaction. Computational results indicate that the preferred pathway involves transmetallation to form an aryl–rhodium compound, alkyne insertion, intramolecular olefin insertion, and protonation to generate the hydrobenzofuran product. The enantioselectivity is controlled by the intramolecular olefin insertion step, which is ascribed to the steric repulsions between the ligand and substrate. In addition, the generation of a side product via a second intermolecular alkyne insertion has also been considered in calculations.

Chiral phosphine-mediated intramolecular [3 + 2] annulation: enhanced enantioselectivity by achiral Brønsted acid

Co-reporter:Weijun Yao, Zhaoyuan Yu, Shan Wen, Huanzhen Ni, Nisar Ullah, Yu Lan and Yixin Lu

Chemical Science (2010-Present) 2017 - vol. 8(Issue 7) pp:NaN5200-5200

Publication Date(Web):2017/05/17

DOI:10.1039/C7SC00952F

Enantioselective intramolecular [3 + 2] annulation of chalcones bearing an allene moiety has been successfully developed. The reaction was effectively promoted by amino acid-derived phosphines, in combination with achiral Brønsted acids. Dihydrocoumarin architectures were constructed in high yields and with excellent enantiomeric excesses. Theoretical studies via DFT calculations revealed that the hydrogen bonding network induced by achiral Brønsted acids/chiral phosphines could more efficiently distinguish between two enantioselective pathways, thus leading to enhanced enantioselectivity.

C8–H bond activation vs. C2–H bond activation: from naphthyl amines to lactams

Co-reporter:Renyi Shi, Lijun Lu, Hangyu Xie, Jingwen Yan, Ting Xu, Hua Zhang, Xiaotian Qi, Yu Lan and Aiwen Lei

Chemical Communications 2016 - vol. 52(Issue 90) pp:NaN13310-13310

Publication Date(Web):2016/10/17

DOI:10.1039/C6CC06358F

Pd-catalyzed selective amine-oriented C8–H bond functionalization/N-dealkylative carbonylation of naphthyl amines has been achieved. The amine group from dealkylation is proposed to be the directing group for promoting this process. It represents a straightforward and easy method to access various biologically important benzo[cd]indol-2(1H)-one derivatives.

Enantioselective alkynylation of N-sulfonyl α-ketiminoesters via a Friedel–Crafts alkylation strategy

Co-reporter:Ren-Rong Liu, Lei Zhu, Jiang-Ping Hu, Chuan-Jun Lu, Jian-Rong Gao, Yu Lan and Yi-Xia Jia

Chemical Communications 2017 - vol. 53(Issue 43) pp:NaN5893-5893

Publication Date(Web):2017/05/10

DOI:10.1039/C7CC01015J

Enantioselective alkynylation of cyclic N-sulfonyl α-ketiminoesters with terminal alkynes was developed by using an Ni(ClO4)2/(R)-DTBM-Segphos complex as a catalyst. A range of propargylic amides bearing quaternary stereocenters were afforded in excellent enantioselectivities (up to 97% ee). Theoretical studies revealed that this reaction proceeded via a Friedel–Crafts-type reaction pathway.

Thiolate–palladium(IV) or sulfonium–palladate(0)? A theoretical study on the mechanism of palladium-catalyzed C–S bond formation reactions

Co-reporter:Dongdong Xu, Xiaotian Qi, Meng Duan, Zhaoyuan Yu, Lei Zhu, Chunhui Shan, Xiaoyu Yue, Ruopeng Bai and Yu Lan

Inorganic Chemistry Frontiers 2017 - vol. 4(Issue 6) pp:NaN950-950

Publication Date(Web):2017/01/17

DOI:10.1039/C6QO00841K

The density functional theory (DFT) method M06-L was used to study the general mechanism of palladium-catalyzed C–S bond formation reactions. Our theoretical calculations revealed that this type of reaction starts with a palladium-assisted metalation–deprotonation step. Oxidative addition of the sulfur source affords a thiolate–palladium(IV) intermediate, and subsequent reductive elimination generates the new C–S bond. A final protonation regenerates the active palladium(II) catalyst and releases the product. Our proposed mechanism could be applied to a series of palladium-catalyzed C–S bond formation reactions used for the construction of dibenzothiophene derivatives. The rate-limiting step of the catalytic cycle is oxidative addition to yield the thiolate–palladium(IV) intermediate. In contrast, formation of a sulfonium intermediate is unfavourable. In addition, the effect of substituents on the rate-determining step was studied with Hammett plots. Our calculations showed that incorporation of electron-withdrawing groups at the 4-position and electron-donating groups at the 15 and 16-positions would promote intramolecular oxidative addition of thioethers to palladium.

Revealing the halide effect on the kinetics of the aerobic oxidation of Cu(I) to Cu(II)

Co-reporter:Yi Deng, Guanghui Zhang, Xiaotian Qi, Chao Liu, Jeffrey T. Miller, A. Jeremy Kropf, Emilio E. Bunel, Yu Lan and Aiwen Lei

Chemical Communications 2015 - vol. 51(Issue 2) pp:NaN321-321

Publication Date(Web):2014/11/03

DOI:10.1039/C4CC05720A

In situ infrared (IR) and X-ray absorption near-edge structure (XANES) spectroscopic investigations reveal that different halide ligands have distinct effects on the aerobic oxidation of Cu(I) to Cu(II) in the presence of TMEDA (tetramethylethylenediamine). The iodide ligand gives the lowest rate and thus leads to the lowest catalytic reaction rate of aerobic oxidation of hydroquinone to benzoquinone. Further DFT calculations suggest that oxidation of CuI–TMEDA involves a side-on transition state, while oxidation of CuCl–TMEDA involves an end-on transition state which has a lower activation energy.

Catalyst-controlled regioselectivity in phosphine catalysis: the synthesis of spirocyclic benzofuranones via regiodivergent [3 + 2] annulations of aurones and an allenoate

Co-reporter:Huanzhen Ni, Zhaoyuan Yu, Weijun Yao, Yu Lan, Nisar Ullah and Yixin Lu

Chemical Science (2010-Present) 2017 - vol. 8(Issue 8) pp:NaN5704-5704

Publication Date(Web):2017/06/12

DOI:10.1039/C7SC02176C

Catalyst-controlled regiodivergent [3 + 2] annulations of aurones and allenoates have been developed. When a dipeptide phosphine catalyst with an L-D- configuration was employed, α-selective [3 + 2] annulation products could be obtained with good regioselectivities and enantioselectivities. With the employment of L-L- dipeptide phosphines, γ-selective annulation products could be selectively obtained with excellent enantioselectivities. By simply tuning the catalyst configurations, a wide range of α-selective or γ-selective spirocyclic benzofuranones with either aryl or alkyl substitutions could be readily prepared. DFT calculations suggest that the conformation of the dipeptide phosphines influences the hydrogen bonding interactions or the distortion energy, resulting in delicate energy differentiation in the transition states, and accounting for the observed regioselectivity.

Tuning radical reactivity using iodine in oxidative C(sp3)–H/C(sp)–H cross-coupling: an easy way toward the synthesis of furans and indolizines

Co-reporter:Shan Tang, Kun Liu, Yue Long, Xiaotian Qi, Yu Lan and Aiwen Lei

Chemical Communications 2015 - vol. 51(Issue 42) pp:NaN8772-8772

Publication Date(Web):2015/04/17

DOI:10.1039/C5CC01825K

Molecular iodine was found to be an effective redox catalyst for the oxidative cross-coupling of carbonyl compounds with terminal alkynes. In this work, we demonstrated that iodine could tune radical reactivity through reversible C–I bond formation for controlling the reaction selectivity. This iodine catalysis protocol provided an easy way for the synthesis of various furans and indolizines.

Highly enantioselective construction of tertiary thioethers and alcohols via phosphine-catalyzed asymmetric γ-addition reactions of 5H-thiazol-4-ones and 5H-oxazol-4-ones: scope and mechanistic understandings

Co-reporter:Tianli Wang, Zhaoyuan Yu, Ding Long Hoon, Kuo-Wei Huang, Yu Lan and Yixin Lu

Chemical Science (2010-Present) 2015 - vol. 6(Issue 8) pp:NaN4922-4922

Publication Date(Web):2015/06/02

DOI:10.1039/C5SC01614B

Phosphine-catalyzed highly enantioselective γ-additions of 5H-thiazol-4-ones and 5H-oxazol-4-ones to allenoates have been developed for the first time. With the employment of amino-acid derived bifunctional phosphines, a wide range of substituted 5H-thiazol-4-one and 5H-oxazol-4-one derivatives bearing heteroatom (S or O)-containing tertiary chiral centers were constructed in high yields and excellent enantioselectivities. The reported method provides facile access to enantioenriched tertiary thioethers/alcohols. The mechanism of the γ-addition reaction was investigated by performing DFT calculations, and the hydrogen bonding interactions between the Brønsted acid moiety of the phosphine catalysts and the “CO” unit of the donor molecules were shown to be crucial in asymmetric induction.

TOPICS

Abstract

Abstract

Abstract

Abstract

Abstract

Abstract

Abstract