Bo Xu

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Name: 胥波; Xu, Bo

Organization: Donghua University , China

Department: College of Chemistry

Title: Professor(PhD)

Chemicals
References

A Chlorinating Reagent Yields Vinyl Chlorides with High Regioselectivity under Heterogeneous Gold Catalysis

Co-reporter:Shengzong Liang, Rene Ebule, Gerald B. Hammond, and Bo Xu

Organic Letters September 1, 2017 Volume 19(Issue 17) pp:

Publication Date(Web):August 15, 2017

DOI:10.1021/acs.orglett.7b02101

A novel chlorinating reagent with a high concentration of HCl has enabled the highly regioselective hydrochlorination of unactivated alkynes using a commercial nanogold catalyst. No overchlorination or hydration products were formed, and various functional groups were tolerated. This hydrochlorination method could be conducted under open air.

Chloride-Tolerant Gold(I)-Catalyzed Regioselective Hydrochlorination of Alkynes

Co-reporter:Rene Ebule, Shengzong Liang, Gerald B. Hammond, and Bo Xu

ACS Catalysis October 6, 2017 Volume 7(Issue 10) pp:6798-6798

Publication Date(Web):September 7, 2017

DOI:10.1021/acscatal.7b02567

We have developed a highly regioselective homogeneous gold(I)-catalyzed anti-hydrochlorination of unactivated alkynes at room temperature. We have overcome the incompatibility between conventional cationic gold catalysts and chloride by using a hydrogen-bonding activation of the Au–Cl bond. This approach is scalable, exhibits excellent functional group tolerance, and can be conducted in open air.Keywords: alkyne; chloride-tolerant; gold catalysis; HCl/DMPU; hydrochlorination;

Predicting Counterion Effects Using a Gold Affinity Index and a Hydrogen Bonding Basicity Index

Co-reporter:Zhichao Lu, Junbin Han, Otome E. Okoromoba, Naoto Shimizu, Hideki Amii, Cláudio F. Tormena, Gerald B. Hammond, and Bo Xu

Organic Letters November 3, 2017 Volume 19(Issue 21) pp:5848-5848

Publication Date(Web):October 23, 2017

DOI:10.1021/acs.orglett.7b02829

We have developed a gold affinity index and hydrogen bonding basicity index for counterions and have used these indexes to forecast their reactivity in cationic gold catalysis.

Metal-free, Regio-, and Stereo-Controlled Hydrochlorination and Hydrobromination of Ynones and Ynamides

Co-reporter:Xiaojun Zeng, Zhichao Lu, Shiwen Liu, Gerald B. Hammond, and Bo Xu

The Journal of Organic Chemistry December 15, 2017 Volume 82(Issue 24) pp:13179-13179

Publication Date(Web):November 23, 2017

DOI:10.1021/acs.joc.7b02257

We developed an atom-economical and metal-free method for the regio- and stereo-selective hydrohalogenation of ynones and ynamides using easy to handle DMPU/HX (X = Br or Cl) reagents. The reaction operates under mild conditions and a range of functional groups is well tolerated. We propose that the hydrohalogenation of ynones gives the anti-addition products via a concerted multimolecular AdE3 mechanism and that the hydrohalogenation of ynamides produces the syn-addition products via a cationic keteniminium intermediate.

(E)-Alkene Synthesis via Nano-Copper/Homogeneous Palladium Co-Catalysis and Selectivity Amplification

Co-reporter:Shiwen Liu;Xiaojun Zeng;Dr. Bo Xu

Asian Journal of Organic Chemistry 2017 Volume 6(Issue 5) pp:507-511

Publication Date(Web):2017/05/01

DOI:10.1002/ajoc.201700091

AbstractA practical regio- and stereoselective synthesis of multisubstituted (E)-alkenes via a nano-copper/Pd(PPh3)4 co-catalyzed tandem hydroborylation/Suzuki coupling sequence has been developed. This catalytic system circumvented the common problem of isolation and purification of organoboron intermediates and gave only (E)-alkenes in good to excellent yields and excellent functional group tolerance. The key for the very high regioselectivity is the selectivity amplification of two tandem steps.

Encapsulation of nano-catalysts in permeable silicone elastomers

Co-reporter:Lei Xu, Bo Xu

Tetrahedron Letters 2017 Volume 58, Issue 26(Issue 26) pp:

Publication Date(Web):28 June 2017

DOI:10.1016/j.tetlet.2017.05.041

•Encapsulation of multiple types of nano-catalysts.•Encapsulated catalysts are unbreakable in normal stirring condition.•Low metal leaching.Download high-res image (90KB)Download full-size image

Hydrogen Bonding Cluster-Enabled Addition of Sulfonic Acids to Haloalkynes: Access to Both (E)- and (Z)-Alkenyl Sulfonates

Co-reporter:Xiaojun Zeng, Shiwen Liu, Zhenyu Shi, and Bo Xu

Organic Letters 2016 Volume 18(Issue 19) pp:4770-4773

Publication Date(Web):September 15, 2016

DOI:10.1021/acs.orglett.6b02061

We developed an efficient synthesis of alkenyl sulfonates via hydrogen bonding cluster-enabled addition of sulfonic acids to haloalkynes. The reactivity of sulfonic acids could be significantly enhanced in the presence of strong hydrogen bonding donors. This metal-free method results in good chemical yields for a wide range of haloalkyne substrates and demonstrates good functional group tolerance. What is more, we can control the stereoselectivity of addition (cis vs trans) by varying the steric bulk of the sulfonic acid.

Supported gold nanoparticles catalyzed cis-selective semihydrogenation of alkynes using ammonium formate as the reductant

Co-reporter:Shengzong Liang, Gerald B. Hammond and Bo Xu

Chemical Communications 2016 vol. 52(Issue 35) pp:6013-6016

Publication Date(Web):01 Apr 2016

DOI:10.1039/C6CC01318J

TiO2 supported gold nanoparticles with low loading (0.5 mol%) are able to semihydrogenate non-fluorinated and gem-difluorinated alkynes to cis-alkenes with high selectivity, using cost-effective and easy-to-handle ammonium formate as the reductant. No over-reduction was observed. The good recyclability of Au/TiO2 allows for “green” semireduction of alkynes. A difluorinated pyran and α,β-unsaturated δ-lactone were easily prepared from the obtained gem-difluoro alkene building blocks.

Synthesis of Fluorinated Homoallylic Compounds by Fluoroalkyl Radical Mediated Ring Opening of Methylenecyclopropanes

Co-reporter:Huajun Xie

European Journal of Organic Chemistry 2016 Volume 2016( Issue 15) pp:2594-2598

Publication Date(Web):

DOI:10.1002/ejoc.201600380

Abstract

The fluoroalkyl (Rf) radical mediated ring opening of methylenecyclopropanes (MCPs) 1 and subsequent atom transfer were investigated. In the first part, a copper-initiated radical reaction of Rf–X (X = I, Br) with MCP 1 gave homoallylic halides 2 in excellent yields. Similarly, radical reaction of the RfTMS/CsF/PhI(OCOR)₂ system with MCP 1 led to homoallylic alcohol esters 3 in moderate to good yields.

Stable yet reactive cationic gold catalysts with carbon based counterions

Co-reporter:Xiaojun Zeng, Shiwen Liu and Bo Xu

RSC Advances 2016 vol. 6(Issue 81) pp:77830-77833

Publication Date(Web):11 Aug 2016

DOI:10.1039/C6RA19064B

L–Au–[TsC(CN)2] are new cationic gold catalysts with a carbon based counterion, which are widely applicable for gold catalyzed reactions. For reactions which need highly reactive gold catalysts, a Lewis acid co-catalyst can be added to increase the reactivity of L–Au–[TsC(CN)2]. L–Au–[TsC(CN)2] also have advantages of easy reaction steps and high functional group tolerance.

Synthesis of -Fluoroketones by Insertion of HF into a Gold Carbene

Co-reporter:Xiaojun Zeng;Shiwen Liu;Zhenyu Shi;Guangchang Liu ;Dr. Bo Xu

Angewandte Chemie 2016 Volume 128( Issue 34) pp:10186-10190

Publication Date(Web):

DOI:10.1002/ange.201603914

Abstract

Reported is an efficient synthesis of α-fluoroketones by insertion of hydrogen fluoride (HF) into the gold carbene intermediate, generated from a cationic gold catalyzed addition of N-oxides to alkynes. This method results in excellent chemical yields for a wide range of alkyne substrates and demonstrates good functional-group tolerance.

Synthesis of -Fluoroketones by Insertion of HF into a Gold Carbene

Co-reporter:Xiaojun Zeng;Shiwen Liu;Zhenyu Shi;Guangchang Liu ;Dr. Bo Xu

Angewandte Chemie International Edition 2016 Volume 55( Issue 34) pp:10032-10036

Publication Date(Web):

DOI:10.1002/anie.201603914

Abstract

Revisiting the Influence of Silver in Cationic Gold Catalysis: A Practical Guide

Co-reporter:Zhichao Lu, Junbin Han, Gerald B. Hammond, and Bo Xu

Organic Letters 2015 Volume 17(Issue 18) pp:4534-4537

Publication Date(Web):September 3, 2015

DOI:10.1021/acs.orglett.5b02224

An excess amount of silver salt to generate cationic gold from a gold catalyst precursor such as L–Au–Cl almost always has adverse effects on the reactivity of the cationic gold catalyst. A preformed L–Au+X– complex, generated by sonication followed by centrifugation, increases the reactivity in a gold catalyzed reaction. The adverse silver effect might be caused by the interaction of silver salts with gold intermediates.

Preparation of Fluorinated Tetrahydropyrans and Piperidines using a New Nucleophilic Fluorination Reagent DMPU/HF

Co-reporter:Otome E. Okoromoba, Gerald B. Hammond, and Bo Xu

Organic Letters 2015 Volume 17(Issue 16) pp:3975-3977

Publication Date(Web):August 11, 2015

DOI:10.1021/acs.orglett.5b01919

DMPU/HF (HF content 65 wt %/wt) is an ideal nucleophilic fluorination reagent for the diastereoselective synthesis of substituted 4-fluorotetrahydropyrans and 4-fluoropiperidines via a fluoro-Prins reaction. When compared to classical nucleophilic fluorination reagents like pyridine/HF, DMPU/HF gives both higher yields and better diastereoselectivity.

Potassium tris(triflyl)methide (KCTf3): a broadly applicable promoter for cationic metal catalysis

Co-reporter:Junbin Han, Zhichao Lu, Weibo Wang, Gerald B. Hammond and Bo Xu

Chemical Communications 2015 vol. 51(Issue 72) pp:13740-13743

Publication Date(Web):14 Jul 2015

DOI:10.1039/C5CC05306D

KCTf3, a commercially available, easily handled neutral salt, enhanced the reaction rates and the chemical yields of a wide spectrum of cationic metal catalyzed reactions, ranging from traditional Lewis acid catalysis to transition metal catalysis.

Achieving regio- and stereo-control in the fluorination of aziridines under acidic conditions

Co-reporter:Otome E. Okoromoba, Zhou Li, Nicole Robertson, Mark S. Mashuta, Uenifer R. Couto, Cláudio F. Tormena, Bo Xu and Gerald B. Hammond

Chemical Communications 2016 - vol. 52(Issue 91) pp:NaN13356-13356

Publication Date(Web):2016/10/19

DOI:10.1039/C6CC07855A

We developed an efficient fluorination protocol that converts easily accessible aziridines into β-fluoroamines, which are important motifs in biologically active molecules. In contrast with traditional fluorination approaches, DMPU–HF has shown both higher reactivity and regioselectivity and good functional group tolerance; thus, a wide scope of β-fluoroamines can now be accessed conveniently. The stereochemical behavior of the ring opening depends on the substitution pattern of the aziridine substrate.

Supported gold nanoparticles catalyzed cis-selective semihydrogenation of alkynes using ammonium formate as the reductant

Co-reporter:Shengzong Liang, Gerald B. Hammond and Bo Xu

Chemical Communications 2016 - vol. 52(Issue 35) pp:NaN6016-6016

Publication Date(Web):2016/04/01

DOI:10.1039/C6CC01318J

Potassium tris(triflyl)methide (KCTf3): a broadly applicable promoter for cationic metal catalysis

Co-reporter:Junbin Han, Zhichao Lu, Weibo Wang, Gerald B. Hammond and Bo Xu

Chemical Communications 2015 - vol. 51(Issue 72) pp:NaN13743-13743

Publication Date(Web):2015/07/14

DOI:10.1039/C5CC05306D

Au/TiO2 catalyzed reductive amination of aldehydes and ketones using formic acid as reductant

Co-reporter:Shengzong Liang, Paige Monsen, Gerald B. Hammond and Bo Xu

Inorganic Chemistry Frontiers 2016 - vol. 3(Issue 4) pp:NaN509-509

Publication Date(Web):2016/02/18

DOI:10.1039/C5QO00439J

The combination of commercial easily available Au/TiO2 as catalyst and cost-effective formic acid as reductant was able to render reductive amination of various carbonyl compounds. Aldehydes and ketones were converted into secondary and tertiary amines in good to excellent yields. The supported gold nanoparticles could be easily recycled by simple filtration.