Kazuhiko Takai

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Organization: Okayama University

Department: Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology

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Chemicals
References

Synthesis of Borylcyclopropanes by Chromium-Promoted Cyclopropanation of Unactivated Alkenes

Co-reporter:Masahito Murai, Chisato Mizuta, Ryuji Taniguchi, and Kazuhiko Takai

Organic Letters November 17, 2017 Volume 19(Issue 22) pp:6104-6104

Publication Date(Web):October 30, 2017

DOI:10.1021/acs.orglett.7b02956

The combination of diiodomethylboronate ester, CrCl2 with TMEDA promoted borylcyclopropanation of unactivated alkenes under mild conditions. Compared with the typical Simmons–Smith cyclopropanation, the current protocol offers the following advantages: (1) the reaction proceeds stereoselectively with disubstituted alkenes even without hydroxy or alkoxy groups; (2) both electron-rich and electron-deficient alkenes can be applicable; and (3) the reaction does not require potentially flammable alkylzinc. These unique reactivity features result from the steric and electronic nature of the gem-dichromiomethane intermediates.

Iridium-catalysed hydrosilylation of cyclopropanes via regioselective carbon–carbon bond cleavage

Co-reporter:Masahito Murai;Atsushi Nishiyama;Naoki Nishinaka;Haruka Morita

Chemical Communications 2017 vol. 53(Issue 66) pp:9281-9284

Publication Date(Web):2017/08/15

DOI:10.1039/C7CC04296E

While cyclopropanes have been explored as synthetically valuable building blocks, their transformation without conjugated substituents or directly substituted heteroatoms remains challenging. The current study describes the iridium-catalysed ring-opening hydrosilylation of cyclopropanes. A nitrogen-based directing group was found to control the reactivity of iridium active species as well as the regiochemistry of carbon–carbon bond cleavage and hydrosilylation.

Rhenium-Catalyzed Construction of Polycyclic Hydrocarbon Frameworks by a Unique Cyclization of 1,n-Diynes Initiated by 1,1-Difunctionalization with Carbon Nucleophiles

Co-reporter:Dr. Masahito Murai;Erika Uemura;Shunsuke Hori; Dr. Kazuhiko Takai

Angewandte Chemie International Edition 2017 Volume 56(Issue 21) pp:5862-5866

Publication Date(Web):2017/05/15

DOI:10.1002/anie.201701159

AbstractA regioselective cyclization of 1,n-diynes under rhenium catalysis was developed on the basis of a rare type of 1,1-difunctionalization of terminal alkynes with carbon nucleophiles, followed by sequential addition reactions of the resulting alkenylrhenium species. The reaction provides an efficient approach to the synthesis of complex cyclopentane-fused bi- and tricycles and spirocycles, which are useful building blocks for the construction of essential frameworks of biologically active compounds as well as functional materials, from simple starting materials by the formation of up to six new carbon–carbon bonds in a single step. The reaction proceeds under neutral conditions and does not require external ligands or additives. The key to this reactivity is the unique activation mode of the rhenium carbonyl complex, which prefers to interact with heteroatoms in polar carbon–heteroatom bonds as well as nonpolar carbon–carbon unsaturated π bonds.

Rhenium-Catalyzed Construction of Polycyclic Hydrocarbon Frameworks by a Unique Cyclization of 1,n-Diynes Initiated by 1,1-Difunctionalization with Carbon Nucleophiles

Co-reporter:Dr. Masahito Murai;Erika Uemura;Shunsuke Hori; Dr. Kazuhiko Takai

Angewandte Chemie 2017 Volume 129(Issue 21) pp:5956-5960

Publication Date(Web):2017/05/15

DOI:10.1002/ange.201701159

Synthesis of Linear Allylsilanes via Molybdenum-Catalyzed Regioselective Hydrosilylation of Allenes

Co-reporter:Sobi Asako, Sae Ishikawa, and Kazuhiko Takai

ACS Catalysis 2016 Volume 6(Issue 5) pp:3387

Publication Date(Web):April 14, 2016

DOI:10.1021/acscatal.6b00627

A simple molybdenum-based catalytic system for hydrosilylation of allenes has been developed. The reactions of mono- and disubstituted allenes with secondary and tertiary silanes proceeded smoothly and selectively to afford linear allylsilanes. The origin of the unprecedented linear selectivity was investigated by density functional theory studies to reveal that the reaction consists of the following steps: (1) concerted hydromolybdation/Si–H oxidative addition from a Mo(CO)4/allene/silane adduct to form (π-allyl)molybdenum, (2) allyl rotation from the initially formed (π-allyl)molybdenum to a thermodynamically more stable isomer, and (3) reductive elimination at the less-hindered allyl carbon to afford a linear allylsilane.Keywords: allenes; allyl rotation; density functional theory; hydrosilylation; linear allylsilanes; molybdenum

Synthesis and Properties of Sila[n]helicenes via Dehydrogenative Silylation of C–H Bonds under Rhodium Catalysis

Co-reporter:Masahito Murai, Ryo Okada, Atsushi Nishiyama, and Kazuhiko Takai

Organic Letters 2016 Volume 18(Issue 17) pp:4380-4383

Publication Date(Web):August 11, 2016

DOI:10.1021/acs.orglett.6b02134

Use of a rhodium catalyst with (R)-(S)-BPPFA ligand allows efficient synthesis of sila[n]helicenes via dehydrogenative silylation of C–H bonds. By selecting the proper ligands, the current method provides the ability to prepare unsymmetrical sila[n]helicene derivatives without any oxidants. The resulting sila[6]helicene is a rare example of a five-membered ring-fused [6]helicene, which was isolated as a single pure enantiomer without substituents on the terminal benzene rings.

Rhenium-Catalyzed anti-Markovnikov Addition Reaction of Methanetricarboxylates to Unactivated Terminal Acetylenes

Co-reporter:Shunsuke Hori; Masahito Murai

Journal of the American Chemical Society 2015 Volume 137(Issue 4) pp:1452-1457

Publication Date(Web):January 6, 2015

DOI:10.1021/ja5090755

A novel anti-Markovnikov addition reaction of methanetricarboxylates with terminal acetylenes under neutral conditions was achieved using a rhenium complex. This transformation represents a rare example of intermolecular anti-Markovnikov addition of carbon nucleophiles to unactivated terminal acetylenes. 1,3-Diesters having bulky substituents at the active methylene carbon are also applicable as substrates to provide anti-Markovnikov adducts as single regio- and stereoisomers. Preliminary mechanistic studies imply that the rhenium vinylidene species is the key intermediate in the current catalytic cycle.

Iridium-Catalyzed Dehydrogenative Silylation of Azulenes Based on Regioselective C–H Bond Activation

Co-reporter:Masahito Murai, Keishi Takami, Hirotaka Takeshima, and Kazuhiko Takai

Organic Letters 2015 Volume 17(Issue 7) pp:1798-1801

Publication Date(Web):March 24, 2015

DOI:10.1021/acs.orglett.5b00575

Use of an iridium catalyst allowed the efficient dehydrogenative functionalization of C–H bonds of azulenes with the production of hydrogen as the sole byproduct. The reaction occurred with excellent chemo- and regioselectivities to provide 2-silylazulenes even without any directing groups. Effective conjugation through the 2-position of the azulene ring was demonstrated by the unique stimuli-responsiveness against an acid–base reaction.

Transition-Metal-Catalyzed Facile Access to 3,11-Dialkylfulminenes for Transistor Applications

Co-reporter:Masahito Murai, Hiroyuki Maekawa, Shino Hamao, Yoshihiro Kubozono, David Roy, and Kazuhiko Takai

Organic Letters 2015 Volume 17(Issue 3) pp:708-711

Publication Date(Web):January 29, 2015

DOI:10.1021/ol503723j

Novel [6]phenacenes (fulminenes) with two long alkyl chains at the axis positions were synthesized. This short synthesis comprises the following three steps: (1) ruthenium-catalyzed direct C–H bond arylation; (2) conversion of directing groups by Wittig reaction; and (3) bismuth- or gold-catalyzed cyclization of vinyl ether. Organic field-effect transistor devices fabricated with a thin film of 3,11-di(tetradecyl)fulminene exhibited typical p-channel normally-off properties.

Rhodium-Catalyzed Synthesis of Benzosilolometallocenes via the Dehydrogenative Silylation of C(sp2)–H Bonds

Co-reporter:Masahito Murai, Koji Matsumoto, Yutaro Takeuchi, and Kazuhiko Takai

Organic Letters 2015 Volume 17(Issue 12) pp:3102-3105

Publication Date(Web):June 10, 2015

DOI:10.1021/acs.orglett.5b01373

Use of a rhodium catalyst with electron-rich and bulky chiral diphosphine ligands having C2-symmetry allowed efficient dehydrogenative silylation of the C(sp2)–H bond of ferrocenes leading to chiral benzosiloloferrocenes. The substrate scope was expanded to hydrogermane and hydrosilanes having a ruthenocene backbone, which resulted in a new approach to benzosilole- and benzogermole-fused metallocenes.

Stereospecific Deoxygenation of Aliphatic Epoxides to Alkenes under Rhenium Catalysis

Co-reporter:Takuya Nakagiri, Masahito Murai, and Kazuhiko Takai

Organic Letters 2015 Volume 17(Issue 13) pp:3346-3349

Publication Date(Web):June 12, 2015

DOI:10.1021/acs.orglett.5b01583

The combination of a catalytic amount of Re2O7 and triphenyl phosphite as a reductant is effective for the deoxygenation of unactivated aliphatic epoxides to alkenes. The reaction proceeds stereospecifically with variously substituted epoxides under neutral conditions and is compatible with various functional groups. Protection and deprotection of a double bond functionality using an epoxide are shown as an example of the current rhenium-catalyzed deoxygenation protocol. The effect of reductants for the stereoselectivity has also been studied, indicating that the use of electron-deficient phosphines or phosphites is the key for the stereospecific deoxygenation.

Acceleration Effects of Phosphine Ligands on the Rhodium-Catalyzed Dehydrogenative Silylation and Germylation of Unactivated C(sp3)–H Bonds

Co-reporter:Masahito Murai, Hirotaka Takeshima, Haruka Morita, Yoichiro Kuninobu, and Kazuhiko Takai

The Journal of Organic Chemistry 2015 Volume 80(Issue 11) pp:5407-5414

Publication Date(Web):May 11, 2015

DOI:10.1021/acs.joc.5b00920

The current work describes the marked rate of acceleration caused by phosphine ligands on the rhodium-catalyzed dehydrogenative silylation and germylation of unactivated C(sp3)–H bonds. The reactivity was affected by the steric and electronic nature of the phosphine ligands. The use of the bulky and electron-rich diphosphine ligand (R)-DTBM-SEGPHOS was highly effective to yield the dehydrogenative silylation products selectively in the presence of a hydrogen acceptor. An appropriate choice of C2-symmetric chiral diphosphine ligand enables the asymmetric dehydrogenative silylation via the enantioselective desymmetrization of the C(sp3)–H bond. The unprecedented catalytic germylation of C(sp3)–H bonds with dehydrogenation was also examined with the combination of the rhodium complex and a wide bite angle diphosphine ligand to provide the corresponding 2,3-dihydrobenzo[b]germoles in good yield.

Iridium-Catalyzed Intermolecular Dehydrogenative Silylation of Polycyclic Aromatic Compounds without Directing Groups

Co-reporter:Dr. Masahito Murai;Keishi Takami ;Dr. Kazuhiko Takai

Chemistry - A European Journal 2015 Volume 21( Issue 12) pp:4566-4570

Publication Date(Web):

DOI:10.1002/chem.201406508

Abstract

This study describes the iridium-catalyzed intermolecular dehydrogenative silylation of C(sp²)H bonds of polycyclic aromatic compounds without directing groups. The reaction produced various arylsilanes through both SiH and CH bond activation, with hydrogen as the sole byproduct. Reactivity was affected by the electronic nature of the aromatic compounds, and silylation of electron-deficient and polycyclic aromatic compounds proceeded efficiently. Site-selectivity was controlled predominantly by steric factors. Therefore, the current functionalization proceeded with opposite chemo- and site-selectivity compared to that observed for general electrophilic functionalization of aromatic compounds.

Isolation and Structural Characterization of Geminal Di(iodozincio)methane Complexes Stabilized with Nitrogen Ligands

Co-reporter:Yusuke Nishida; Naoki Hosokawa; Masahito Murai

Journal of the American Chemical Society 2014 Volume 137(Issue 1) pp:114-117

Publication Date(Web):December 24, 2014

DOI:10.1021/ja5114535

Treatment of gem-di(iodozincio)methane with pyridine or diamine derivatives resulted in the isolation of a storable gem-di(iodozincio)methane species. Use of the sterically bulky bipyridine ligand gave a gem-di(iodozincio)methane complex, which allowed the first X-ray structural analysis of such species. This work represents a rare example of the isolation of an organometallic reactive species in Schlenk equilibrium and thus provides new insight into the design of efficient and storable organometallic reagents. The isolated gem-di(iodozincio)methane complexes serve as effective methylene dianion synthons for olefination of carbonyl compounds.

Rhodium-Catalyzed Dehydrogenative Germylation of C–H Bonds: New Entry to Unsymmetrically Functionalized 9-Germafluorenes

Co-reporter:Masahito Murai, Koji Matsumoto, Ryo Okada, and Kazuhiko Takai

Organic Letters 2014 Volume 16(Issue 24) pp:6492-6495

Publication Date(Web):December 10, 2014

DOI:10.1021/ol503355q

Rhodium-catalyzed dehydrogenative germylation leading to unsymmetrically functionalized 9-germafluorenes via Ge–H and C–H bond activation is described. Despite the significant achievements made in dehydrogenative functionalization of C–H bonds, only a limited number of examples with the fourth-row atom–H bonds have been reported. The current method enabled the synthesis of various 9-germafluorene derivatives, including tetracyclic as well as donor–acceptor substituted germoles, which may be useful for electronic device applications.

Bismuth-Catalyzed Synthesis of Polycyclic Aromatic Hydrocarbons (PAHs) with a Phenanthrene Backbone via Cyclization and Aromatization of 2-(2-Arylphenyl)vinyl Ethers

Co-reporter:Masahito Murai, Naoki Hosokawa, David Roy, and Kazuhiko Takai

Organic Letters 2014 Volume 16(Issue 16) pp:4134-4137

Publication Date(Web):July 30, 2014

DOI:10.1021/ol5018273

The reaction of 2-(2-arylphenyl)vinyl ethers in the presence of a catalytic amount of bismuth(III) triflate gave substituted phenanthrenes in excellent yields under mild reaction conditions. The reaction was also applied to the construction of other polycyclic aromatic hydrocarbons (PAHs), such as chrysene, helicene, and pyrene having a phenanthrene backbone, via regioselective cyclization. This method has the advantages of easy availability of the cyclization precursors, operational simplicity, and high reaction efficiency.

Bismuth(III)-Catalyzed Dehydrative Etherification and Thioetherification of Phenolic Hydroxy Groups

Co-reporter:Masahito Murai, Kazuki Origuchi, and Kazuhiko Takai

Organic Letters 2014 Volume 16(Issue 14) pp:3828-3831

Publication Date(Web):July 9, 2014

DOI:10.1021/ol501744g

Use of a bismuth catalyst allowed efficient dehydrative substitution of phenolic hydroxy groups with alcohols and thiols to form C–O and C–S bonds. The reaction required equimolar amounts of two readily available substrates that generated H2O as the only byproduct. The relatively mild reaction conditions were compatible with the functional groups selected, and provided excellent chemoselectivity.

Rhenium-Catalyzed Synthesis of 2H-1,2-Oxaphosphorin 2-Oxides via the Regio- and Stereoselective Addition Reaction of β-Keto Phosphonates with Alkynes

Co-reporter:Masahito Murai, Masahiro Nakamura, and Kazuhiko Takai

Organic Letters 2014 Volume 16(Issue 21) pp:5784-5787

Publication Date(Web):October 24, 2014

DOI:10.1021/ol502859w

Treatment of β-keto phosphonates (Horner–Wadsworth–Emmons reagents) with terminal alkynes in the presence of a rhenium catalyst gave 2H-1,2-oxaphosphorin 2-oxides with various substitution patterns. The reaction proceeds via two consecutive processes: cleavage of a carbon–carbon σ-bond of the β-keto phosphonate with insertion of the alkyne in a regio- and stereoselective manner, followed by cyclization of the resulting δ-phosphonyl α,β-unsaturated ketone yielding the 2H-1,2-oxaphosphorin 2-oxide. Horner–Wadsworth–Emmons reagents were found to add to nonpolar unsaturated compounds under neutral conditions.

Rhodium-Catalyzed Intramolecular Silylation of Unactivated C(sp3)–H Bonds

Co-reporter:Yoichiro Kuninobu, Takahiro Nakahara, Hirotaka Takeshima, and Kazuhiko Takai

Organic Letters 2013 Volume 15(Issue 2) pp:426-428

Publication Date(Web):January 10, 2013

DOI:10.1021/ol303353m

The treatment of a variety of hydrosilanes, each incorporating a benzylic C(sp3)–H bond, with a rhodium catalyst resulted in intramolecular dehydrogenative silylation. This silylation reaction was found to occur at typically unreactive C(sp3)–H bonds located at terminal positions on alkyl chains. Interestingly, the rhodium catalyst also promoted regioselective silylation at a site internal to an alkyl chain.

Palladium-Catalyzed ortho-Selective CH Borylation of 2-Phenylpyridine and Its Derivatives at Room Temperature

Co-reporter:Dr. Yoichiro Kuninobu;Takashi Iwanaga;Tetsuya Omura;Dr. Kazuhiko Takai

Angewandte Chemie International Edition 2013 Volume 52( Issue 16) pp:4431-4434

Publication Date(Web):

DOI:10.1002/anie.201210328

Rhodium-Catalyzed Asymmetric Synthesis of Spirosilabifluorene Derivatives

Co-reporter:Dr. Yoichiro Kuninobu;Kanae Yamauchi;Naoya Tamura;Takayuki Seiki;Dr. Kazuhiko Takai

Angewandte Chemie International Edition 2013 Volume 52( Issue 5) pp:1520-1522

Publication Date(Web):

DOI:10.1002/anie.201207723

Rhenium-Catalyzed Regioselective Synthesis of Multisubstituted Pyridines from β-Enamino Ketones and Alkynes via C–C Bond Cleavage

Co-reporter:Shun-ichi Yamamoto, Kana Okamoto, Makiko Murakoso, Yoichiro Kuninobu, and Kazuhiko Takai

Organic Letters 2012 Volume 14(Issue 12) pp:3182-3185

Publication Date(Web):2017-2-22

DOI:10.1021/ol301273j

A new method is described for the regioselective synthesis of multisubstituted pyridine derivatives. Treatment of N-acetyl β-enamino ketones with alkynes in the presence of the rhenium catalyst, Re2(CO)10, gives multisubstituted pyridines regioselectively. In this reaction, the N-acetyl moieties are important for the selective formation of the multisubstituted pyridines. This reaction proceeds via insertion of alkynes into a carbon–carbon single bond of β-enamino ketones, intramolecular nucleophilic cyclization, and elimination of acetic acid.

Rhenium-Catalyzed Regio- and Stereoselective Synthesis of γ-Thio-α,β-unsaturated Ketones via Insertion of Terminal Alkynes into the C–S Bond

Co-reporter:Mitsumi Nishi, Yoichiro Kuninobu, and Kazuhiko Takai

Organic Letters 2012 Volume 14(Issue 23) pp:6116-6118

Publication Date(Web):November 12, 2012

DOI:10.1021/ol302810u

The reaction of α-thioketones and alkynes in the presence of a rhenium catalyst, [HRe(CO)4]n, gave γ-thio-α,β-unsaturated ketones in excellent yields. The alkynes were inserted into the carbon–sulfur bond of the α-thioketones, and isomerization of a double bond provided the products with high regio- and stereoselectivities. This reaction also proceeded in an intramolecular fashion.

Organic Reactions Catalyzed by Rhenium Carbonyl Complexes

Co-reporter:Yoichiro Kuninobu and Kazuhiko Takai

Chemical Reviews 2011 Volume 111(Issue 3) pp:1938

Publication Date(Web):November 23, 2010

DOI:10.1021/cr100241u

Rhenium-Catalyzed Regio- and Stereoselective Addition of Two Carbon Units to Terminal Alkynes via Carbon–Carbon Bond Cleavage of β-Keto Sulfones

Co-reporter:Yoichiro Kuninobu, Hironori Matsuzaki, Mitsumi Nishi, and Kazuhiko Takai

Organic Letters 2011 Volume 13(Issue 11) pp:2959-2961

Publication Date(Web):May 9, 2011

DOI:10.1021/ol2008507

Treatment of β-keto sulfones with terminal alkynes gave unsaturated δ-keto sulfones in good to excellent yields under rhenium catalysis. In this reaction, the insertion of the alkynes into the nonstrained carbon–carbon single bond between the α- and β-positions of the β-keto sulfones proceeded smoothly, and (Z)-isomers were produced with high regio- and stereoselectivities.

Rhenium-catalyzed allylation of C–H bonds of benzoic and acrylic acids

Co-reporter:Yoichiro Kuninobu, Kazuhiro Ohta and Kazuhiko Takai

Chemical Communications 2011 vol. 47(Issue 38) pp:10791-10793

Publication Date(Web):05 Sep 2011

DOI:10.1039/C1CC12359A

We have succeeded in the allylation of aromatic and olefinic C–H bonds of benzoic and acrylic acids using a rhenium catalyst, Re2(CO)10. In this reaction, isomerization of the introduced allyl group to the 1-propenyl group did not occur.

Rhenium-catalyzed insertion of terminal alkenes into a C(sp2)–H bond and successive transfer hydrogenation

Co-reporter:Yoichiro Kuninobu, Takahiro Nakahara, Peng Yu, Kazuhiko Takai

Journal of Organometallic Chemistry 2011 696(1) pp: 348-351

Publication Date(Web):

DOI:10.1016/j.jorganchem.2010.09.064

Palladium-Catalyzed Synthesis of Dibenzophosphole Oxides via Intramolecular Dehydrogenative Cyclization

Co-reporter:Yoichiro Kuninobu, Takuya Yoshida, and Kazuhiko Takai

The Journal of Organic Chemistry 2011 Volume 76(Issue 18) pp:7370-7376

Publication Date(Web):August 5, 2011

DOI:10.1021/jo201030j

Dibenzophosphole oxides were obtained from secondary hydrophosphine oxides with a biphenyl group by dehydrogenation via phosphine–hydrogen and carbon–hydrogen bond cleavage in the presence of a catalytic amount of palladium(II) acetate, Pd(OAc)2. By using this reaction, a ladder-type dibenzophosphole oxide could also be synthesized by double intramolecular dehydrogenative cyclization.

Indium-Catalyzed Construction of Polycyclic Aromatic Hydrocarbon Skeletons via Dehydration

Co-reporter:Yoichiro Kuninobu, Tomohiro Tatsuzaki, Takashi Matsuki, and Kazuhiko Takai

The Journal of Organic Chemistry 2011 Volume 76(Issue 17) pp:7005-7009

Publication Date(Web):July 18, 2011

DOI:10.1021/jo200861s

Polycyclic aromatic compounds can be synthesized from 2-benzylic- or 2-allylbenzaldehydes using a catalytic amount of In(III) or Re(I) complexes. By using this method, polycyclic aza-aromatic compounds can also be prepared efficiently. In these reactions, only water is formed as a side product.

Manganese-Catalyzed Cleavage of a CarbonCarbon Single Bond between Carbonyl Carbon and -Carbon Atoms of Ketones

Co-reporter:Dr. Yoichiro Kuninobu;Tadamasa Uesugi;Dr. Atsushi Kawata ;Dr. Kazuhiko Takai

Angewandte Chemie International Edition 2011 Volume 50( Issue 44) pp:10406-10408

Publication Date(Web):

DOI:10.1002/anie.201104704

Rhodium-Catalyzed Synthesis of Silafluorene Derivatives via Cleavage of Silicon−Hydrogen and Carbon−Hydrogen Bonds

Co-reporter:Tomonari Ureshino ; Takuya Yoshida ; Yoichiro Kuninobu

Journal of the American Chemical Society 2010 Volume 132(Issue 41) pp:14324-14326

Publication Date(Web):September 24, 2010

DOI:10.1021/ja107698p

The rhodium-catalyzed synthesis of silafluorenes from biphenylhydrosilanes is described. This highly efficient reaction proceeds via both Si−H and C−H bond activation, producing only H2 as a side product. Using this method, a ladder-type bis-silicon-bridged p-terphenyl could also be synthesized.

Rhenium-Catalyzed Diastereoselective Synthesis of Aminoindanes via the Insertion of Allenes into a C−H Bond

Co-reporter:Yoichiro Kuninobu, Peng Yu, and Kazuhiko Takai

Organic Letters 2010 Volume 12(Issue 19) pp:4274-4276

Publication Date(Web):August 30, 2010

DOI:10.1021/ol101627x

Aminoindane derivatives were synthesized diastereoselectively by the treatment of aromatic imines with allenes in the presence of a catalytic amount of a rhenium complex, [HRe(CO)4]n. The allenes inserted into the aromatic C−H bonds.

Rhenium-Catalyzed Synthesis of Indenones by Novel Dehydrative Trimerization of Aryl Aldehydes via C−H Bond Activation

Co-reporter:Yoichiro Kuninobu, Takashi Matsuki and Kazuhiko Takai

Organic Letters 2010 Volume 12(Issue 13) pp:2948-2950

Publication Date(Web):June 7, 2010

DOI:10.1021/ol100947p

By heating aryl aldehydes with catalytic amounts of a rhenium complex, ReBr(CO)5, and N-phenylacetamide in toluene, indenone derivatives are obtained in good to excellent yields. This reaction proceeds via (1) the formation of an isobenzofuran derivative by the insertion of an aldehyde into the C−H bond of another aldehyde (C−H bond activation) and successive intramolecular nucleophilic cyclization, (2) nucleophilic addition of the formed isobenzofuran derivative to the third aldehyde, (3) isomerization, and (4) intramolecular aldol condensation.

Synthesis of Functionalized Pentacenes from Isobenzofurans Derived from C−H Bond Activation

Co-reporter:Yoichiro Kuninobu, Takayuki Seiki, Shunsuke Kanamaru, Yuta Nishina, and Kazuhiko Takai

Organic Letters 2010 Volume 12(Issue 22) pp:5287-5289

Publication Date(Web):October 20, 2010

DOI:10.1021/ol102349r

The synthesis of unsymmetric functionalized pentacenes from 1,4-anthraquinones and functionalized isobenzofurans, which were prepared by transformation via C−H bond activation, was successfully accomplished. Examples of the synthesis of pentacenes with functional groups at the 5-position are still rare. These obtained functionalized pentacenes are highly soluble in hexane, toluene, and THF.

Iron-catalyzed synthesis of glycine derivatives via carbon–nitrogen bond cleavage using diazoacetate

Co-reporter:Yoichiro Kuninobu, Mitsumi Nishi and Kazuhiko Takai

Chemical Communications 2010 vol. 46(Issue 46) pp:8860-8862

Publication Date(Web):21 Oct 2010

DOI:10.1039/C0CC03781H

Treatment of tertiary amines with diazoacetate in the presence of a catalytic amount of an iron salt, FeCl3, in ethanol gave glycine derivatives. In this reaction, a carbon–nitrogen single bond of the amine was cleaved.

Regioselective functionalization of alkanes by sequential dehydrogenation–hydrozirconation

Co-reporter:Yoichiro Kuninobu, Tomonari Ureshino, Shun-ichi Yamamoto and Kazuhiko Takai

Chemical Communications 2010 vol. 46(Issue 29) pp:5310-5312

Publication Date(Web):14 Jun 2010

DOI:10.1039/C0CC00243G

We have succeeded in formal regioselective functionalization of alkanes by iridium-catalyzed dehydrogenation, hydrozirconation of the resulting alkenes, and electrophilic reaction of the generated alkylzirconium intermediate.

Rhenium- and Manganese-Catalyzed Synthesis of Aromatic Compounds from 1,3-Dicarbonyl Compounds and Alkynes

Co-reporter:Yoichiro Kuninobu, Mitsumi Nishi, Atsushi Kawata, Hisatsugu Takata, Yumi Hanatani, Yudha S. Salprima, Aya Iwai and Kazuhiko Takai

The Journal of Organic Chemistry 2010 Volume 75(Issue 2) pp:334-341

Publication Date(Web):December 9, 2009

DOI:10.1021/jo902072q

We have succeeded in the development of three approaches to the synthesis of aromatic compounds from 1,3-dicarbonyl compounds and alkynes. The first approach is a manganese-catalyzed [2+2+2] cycloaddition between 1,3-dicarbonyl compounds, which have no substituents at the active methylene moiety, and terminal alkynes. This reaction proceeds with high regioselectivity when aryl acetylenes are employed as the alkyne component. The second approach is a rhenium- or manganese-catalyzed formal [2+1+2+1] cycloaddition between β-keto esters and two kinds of alkynes. In this reaction, the aromatic compounds are obtained by the following reaction sequence: (1) insertion of the first alkyne into a carbon−carbon single bond of a β-keto ester, (2) formation of 2-pyranones via intramolecular cyclization with the elimination of ethanol, and (3) Diels−Alder reaction between the formed 2-pyranone and the second alkyne. This reaction provides multisubstituted aromatic compounds in a regioselective manner. The third approach is a rhenium-catalyzed formal [2+2+1+1] cycloaddition reaction from two 1,3-diketones and one alkyne. In this reaction, the aromatic skeleton is constructed from three carbons of the first 1,3-diketone, two carbons of the alkyne, and one carbon of the second 1,3-diketone.

Rhenium-Catalyzed Regioselective Alkylation of Phenols

Co-reporter:Yoichiro Kuninobu ; Takashi Matsuki

Journal of the American Chemical Society 2009 Volume 131(Issue 29) pp:9914-9915

Publication Date(Web):July 1, 2009

DOI:10.1021/ja904360k

Treatment of phenol derivatives with terminal alkenes in the presence of a catalytic amount of a rhenium complex, Re2(CO)10, gave monoalkylated phenol derivatives in good to excellent yields. This reaction proceeds at the ortho- or para-position of phenols regioselectively.

Rhenium-Catalyzed Formation of Bicyclo[3.3.1]nonene Frameworks by a Reaction of Cyclic β-Keto Esters with Terminal Alkynes

Co-reporter:Yoichiro Kuninobu, Junya Morita, Mitsumi Nishi, Atsushi Kawata and Kazuhiko Takai

Organic Letters 2009 Volume 11(Issue 12) pp:2535-2537

Publication Date(Web):May 20, 2009

DOI:10.1021/ol900772h

Treatment of cyclic β-keto esters with terminal alkynes in the presence of a catalytic amount of a rhenium complex, [ReBr(CO)3(thf)]2, gave bicyclo[3.3.1]nonene derivatives. The reaction conditions and yields of the bicyclo[3.3.1]nonenes were improved by the sequential use of tetrabutylammonium fluoride (TBAF) after the rhenium-catalyzed reactions.

Rhenium-Catalyzed Insertion of Nonpolar and Polar Unsaturated Molecules into an Olefinic C−H Bond

Co-reporter:Yoichiro Kuninobu, Yasuo Fujii, Takashi Matsuki, Yuta Nishina and Kazuhiko Takai

Organic Letters 2009 Volume 11(Issue 12) pp:2711-2714

Publication Date(Web):May 26, 2009

DOI:10.1021/ol900962v

Treatment of olefins bearing a directing group with α,β-unsaturated carbonyl compounds, alkynes, or aldehydes in the presence of a catalytic amount of a rhenium complex, [ReBr(CO)3(thf)]2 gave γ,δ-unsaturated carbonyl compounds, dienes, and allyl silyl ethers, respectively. This reaction proceeds via C−H bond activation, insertion of unsaturated molecules into the formed rhenium−carbon bond, and then reductive elimination (or transmetalation in the case of aldehydes).

Synthesis of Cp−Re Complexes via Olefinic C−H Activation and Successive Formation of Cyclopentadienes

Co-reporter:Yoichiro Kuninobu ; Yuta Nishina ; Takashi Matsuki

Journal of the American Chemical Society 2008 Volume 130(Issue 43) pp:14062-14063

Publication Date(Web):October 1, 2008

DOI:10.1021/ja805921f

Treatment of an α,β-unsaturated ketimine with an α,β-unsaturated carbonyl compound in the presence of a rhenium complex, Re2(CO)10, gave a cyclopentadienyl−rhenium complex. This reaction proceeds via rhenium-catalyzed C−H bond activation of an olefinic C−H bond, insertion of an α,β-unsaturated carbonyl compound into a Re−C bond of the alkenylrhenium intermediate, intramolecular nucleophilic cyclization, reductive elimination, elimination of aniline to give a cyclopentadiene derivative, followed by the formation of a cyclopentadienyl−rhenium complex from the cyclopentadiene derivative and the rhenium complex.

Rhenium- and manganese-catalyzed insertion of acetylenes into β-keto esters: synthesis of 2-pyranones

Co-reporter:Yoichiro Kuninobu, Atsushi Kawata, Mitsumi Nishi, Hisatsugu Takata and Kazuhiko Takai

Chemical Communications 2008 (Issue 47) pp:6360-6362

Publication Date(Web):24 Oct 2008

DOI:10.1039/B814694B

Rhenium- and manganese-catalyzed reactions between β-keto esters and acetylenes, followed by treatment with tetrabutylammonium fluoride, gave 2-pyranone derivatives regioselectively.

Rhenium-Catalyzed Synthesis of Stereodefined Cyclopentenes from -Ketoesters and Aliphatic Allenes

Co-reporter:Salprima YudhaS. Dr.;Yoichiro Kuninobu Dr. Dr.

Angewandte Chemie International Edition 2008 Volume 47( Issue 48) pp:9318-9321

Publication Date(Web):

DOI:10.1002/anie.200803350

Indium-Catalyzed Retro-Claisen Condensation

Co-reporter:Atsushi Kawata;Kazumi Takata;Yoichiro Kuninobu Dr. Dr.

Angewandte Chemie International Edition 2007 Volume 46(Issue 41) pp:

Publication Date(Web):4 SEP 2007

DOI:10.1002/anie.200702798

Retro-aldol reaction: Indium-catalyzed reaction of a 1,3-diketone with an alcohol proceeds under solvent-free conditions by nucleophilic attack of the alcohol on a carbonyl group of the 1,3-diketone and carbon–carbon bond cleavage by a retro-Claisen condensation to give an ester in high yield (see scheme). Using water and an amine as nucleophiles instead of an alcohol gave the corresponding carboxylic acid and amide.

Rhenium- and Gold-Catalyzed Coupling of Aromatic Aldehydes with Trimethyl(phenylethynyl)silane: Synthesis of Diethynylmethanes

Co-reporter:Yoichiro Kuninobu Dr.;Eri Ishii Dr.

Angewandte Chemie International Edition 2007 Volume 46(Issue 18) pp:

Publication Date(Web):23 MAR 2007

DOI:10.1002/anie.200700183

Very couply! Coupling reactions of propargyl or benzyl alcohols with allyl- or alkynylsilanes proceed efficiently using [{ReBr(CO)₃(thf)}₂] as catalyst. Additionally, diethynylmethane derivatives were obtained by the reaction of aromatic aldehydes with trimethyl(phenylethynyl)silane in the presence of both the rhenium complex and AuCl (see scheme).

Manganese-Catalyzed Insertion of Aldehydes into a CH Bond

Co-reporter:Yoichiro Kuninobu Dr.;Yuta Nishina;Takahiro Takeuchi Dr.

Angewandte Chemie International Edition 2007 Volume 46(Issue 34) pp:

Publication Date(Web):24 JUL 2007

DOI:10.1002/anie.200702256

Mn gets in the game: In the presence of a manganese catalyst and a stoichiometric amount of hydrosilane, aldehydes insert into CH bonds of aromatic rings of compounds with directing groups (see scheme). This first example of a manganese-catalyzed chemical transformation through CH bond activation gives silyl ethers in good to excellent yields and can also be applied to asymmetric transformation.

Manganese-Catalyzed Insertion of Aldehydes into a CH Bond

Co-reporter:Yoichiro Kuninobu Dr.;Yuta Nishina;Takahiro Takeuchi Dr.

Angewandte Chemie 2007 Volume 119(Issue 34) pp:

Publication Date(Web):24 JUL 2007

DOI:10.1002/ange.200702256

Mn kommt ins Spiel: In Gegenwart eines Mangankatalysators und einer stöchiometrischen Menge Hydrosilan inserieren Aldehyde in Aryl-C-H-Bindungen von Verbindungen mit dirigierenden Gruppen (siehe Schema). Diese erste mangankatalysierte C-H-Aktivierung liefert Silylether in guten bis hervorragenden Ausbeuten und kann auch auf asymmetrische Umwandlungen angewendet werden.

Rhenium- and Gold-Catalyzed Coupling of Aromatic Aldehydes with Trimethyl(phenylethynyl)silane: Synthesis of Diethynylmethanes

Co-reporter:Yoichiro Kuninobu Dr.;Eri Ishii Dr.

Angewandte Chemie 2007 Volume 119(Issue 18) pp:

Publication Date(Web):23 MAR 2007

DOI:10.1002/ange.200700183

Kupplungskünstler: Katalytische Kupplungen zwischen Propargyl- oder Benzylalkoholen und Allyl- oder Alkinylsilanen gelingen effizient mit [{ReBr(CO)₃(thf)}₂]. In Gegenwart dieses Rheniumkomplexes und von AuCl wurden durch die Reaktion von Arylaldehyden mit Trimethyl(phenylethinyl)silan auch Diethinylmethan-Derivate erhalten (siehe Schema).

Indium-Catalyzed Retro-Claisen Condensation

Co-reporter:Atsushi Kawata;Kazumi Takata;Yoichiro Kuninobu Dr. Dr.

Angewandte Chemie 2007 Volume 119(Issue 41) pp:

Publication Date(Web):4 SEP 2007

DOI:10.1002/ange.200702798

Retroaldolreaktion: Die Indium-katalysierte Reaktion eines 1,3-Diketons mit einem Alkohol verläuft lösungsmittelfrei über einen nucleophilen Angriff des Alkohols an die Carbonylgruppe des 1,3-Diketons sowie eine C-C-Bindungsspaltung durch eine Retro-Claisen-Kondensation und liefert einen Ester in hoher Ausbeute (siehe Schema). Mit Wasser oder einem Amin als Nucleophil erhält man eine Carbonsäure bzw. ein Amid.

Isocyanate acting as a carbonyl precursor: pyridyl group-assisted formation of 4H-pyrido[1,2-a]pyrimidin-4-ones from ketimines and isocyanates

Co-reporter:Yoichiro Kuninobu, Shuhei Nishimura and Kazuhiko Takai

Organic & Biomolecular Chemistry 2006 vol. 4(Issue 2) pp:203-205

Publication Date(Web):13 Dec 2005

DOI:10.1039/B516916J

By the reactions of ketimines bearing a pyridyl or a picolyl group on a nitrogen atom of the imine moiety with tosylisocyanate, 4H-pyrido[1,2-a]pyrimidin-4-one derivatives could be obtained in quantitative yields. In these reactions, tosylisocyanate acts as a carbonyl precursor. The pyridyl or picolyl group is a key functional group because it is not only the constituent structure of the 4H-pyrido[1,2-a]pyrimidin-4-one framework but also the promoter of the formation of a ketene intermediate.

Rhenium- and Aniline-Catalyzed One-Pot Annulation of Aromatic Ketones and α,β-Unsaturated Esters Initiated by CH Bond Activation

Co-reporter:Yoichiro Kuninobu Dr.;Yuta Nishina;Makoto Shouho Dr.

Angewandte Chemie 2006 Volume 118(Issue 17) pp:

Publication Date(Web):23 MAR 2006

DOI:10.1002/ange.200503627

Einer der Reaktionsschritte der rheniumkatalysierten Umsetzung von aromatischen Ketiminen mit Ethylacrylat, die in guten Ausbeuten die Indenderivate ergibt, ist eine C-H-Aktivierung. Die Indenderivate sind auch aus aromatischen Ketonen und α,β-ungesättigten Estern in Gegenwart eines Rheniumkomplex-Katalysators und p-Anisidin erhältlich (siehe Schema).

Rhenium- and Aniline-Catalyzed One-Pot Annulation of Aromatic Ketones and α,β-Unsaturated Esters Initiated by CH Bond Activation

Co-reporter:Yoichiro Kuninobu Dr.;Yuta Nishina;Makoto Shouho Dr.

Angewandte Chemie International Edition 2006 Volume 45(Issue 17) pp:

Publication Date(Web):23 MAR 2006

DOI:10.1002/anie.200503627

Several reaction steps, including CH activation, lead to indene derivatives in good yields in the rhenium-catalyzed reaction of aromatic ketimines and ethyl acrylate. Indene derivatives can also be obtained by the reactions of aromatic ketones with α,β-unsaturated esters in the presence of a catalytic rhenium complex and p-anisidine (see scheme).

Cross-pinacol-type coupling reactions between α,β-unsaturated ketones and aldehydes with low-valent metals

Co-reporter:Ryotaro Morita;Hiroshi Matsushita;Chika Toratsu

Chirality 2003 Volume 15(Issue 1) pp:17-23

Publication Date(Web):20 NOV 2002

DOI:10.1002/chir.10148

Treatment of an α,β-unsaturated ketone and an aldehyde with chromium(II) chloride and R₃SiCl in DMF gives cross-pinacol-type coupling products, 1,2-diols selectively. The anti/syn ratios of the produced 1,2-diols are shown to depend on the reaction temperature: At lower temperatures, the anti adduct is produced selectively, but at higher temperatures, the anti/syn ratios gradually decrease. When a combination of manganese and a catalytic amount of lead are used instead of chromium(II), 1,6-diketone, a dimer of the α,β-unsaturated ketone, is produced selectively. Chirality 15:17–23, 2003. © 2002 Wiley-Liss, Inc.

Reactions of coordinated geminal dichromium reagents with aldehydes: stereoselective formation of (Z)-2-chloroalk-2-en-1-ols

Co-reporter:Kazuhiko Takai, Ryo Kokumai and Takahumi Nobunaka

Chemical Communications 2001 (Issue 12) pp:1128-1129

Publication Date(Web):31 May 2001

DOI:10.1039/B102387J

Treatment of a carbonate ester of 2,2,2-trichloroethanol derivative with CrCl2–DMF in THF gives a β-carbonate-coordinated geminal dichromium species, which adds to an aldehyde and eliminates an acyloxychromium group to afford a (Z)-2-chloroalk-2-en-1-ol stereoselectively.

Stereoselective Cross Pinacol-Type Coupling between α,β-Unsaturated Ketones and Aldehydes Mediated by Chromium(II) and R3SiCl

Co-reporter:Kazuhiko Takai Dr.;Ryotaro Morita;Chika Toratsu

Angewandte Chemie 2001 Volume 113(Issue 6) pp:

Publication Date(Web):14 MAR 2001

DOI:10.1002/1521-3757(20010316)113:6<1150::AID-ANGE11500>3.0.CO;2-V

Cross-Coupling Reactions between α,β-Unsaturated Ketones and Aldehydes with CrCl2: Aldol Condensation and Cyclopropanol Formation

Co-reporter:Chika Toratsu;Takafumi Fujii;Takuma Suzuki Dr.

Angewandte Chemie 2000 Volume 112(Issue 15) pp:

Publication Date(Web):2 AUG 2000

DOI:10.1002/1521-3757(20000804)112:15<2837::AID-ANGE2837>3.0.CO;2-6

Drei-Komponenten-Kupplung von Alkyliodiden, 1,3-Dienen und Carbonylverbindungen durch aufeinanderfolgende Bildung von radikalischen und anionischen Spezies mit CrCl2

Co-reporter:Kazuhiko Takai;Naoto Matsukawa;Akira Takahashi;Takafumi Fujii

Angewandte Chemie 1998 Volume 110(Issue 1‐2) pp:

Publication Date(Web):12 MAR 1999

DOI:10.1002/(SICI)1521-3757(19980116)110:1/2<160::AID-ANGE160>3.0.CO;2-7

Als mildes Reduktionsmittel ist Chrom(II) in der Lage, zwischen Alkyliodiden, Alkylradikalen und Allylradikalen zu diskriminieren: Das Alkylradikal ist in Gegenwart von Cr^II so langlebig, daß es mit einem 1,3-Dien reagieren kann, und das dabei entstehende Allylradikal bildet nach rascher Einelektronenreduktion eine Allylchrom(II)-Spezies, die an einen Aldehyd unter Bildung des Drei-Komponenten-Produkts addiert [siehe z. B. Gl. (a)].

Three-Component Coupling Reactions of Alkyl Iodides, 1,3-Dienes, and Carbonyl Compounds by Sequential Generation of Radical and Anionic Species with CrCl2

Co-reporter:Kazuhiko Takai;Naoto Matsukawa;Akira Takahashi;Takafumi Fujii

Angewandte Chemie International Edition 1998 Volume 37(Issue 1‐2) pp:

Publication Date(Web):17 DEC 1998

DOI:10.1002/(SICI)1521-3773(19980202)37:1/2<152::AID-ANIE152>3.0.CO;2-8

The mild reductant chromium(II) chloride can discriminate between alkyl iodides, alkyl radicals, and allylic radicals. In the presence of Cr^II the alkyl radical is so long-lived that it can undergo intermolecular addition to a 1,3-diene. Rapid one-electron reduction of the formed allylic radical results in an allylic chromium(II) species, which adds to an aldehyde to afford a three-component coupling product [see, for example, Eq. (a)].

Regioselective functionalization of alkanes by sequential dehydrogenation–hydrozirconation

Co-reporter:Yoichiro Kuninobu, Tomonari Ureshino, Shun-ichi Yamamoto and Kazuhiko Takai

Chemical Communications 2010 - vol. 46(Issue 29) pp:NaN5312-5312

Publication Date(Web):2010/06/14

DOI:10.1039/C0CC00243G

Generation of chromioenamines by reduction of O-acetyloximes with chromium(II) and their application

Co-reporter:Kazuhiko Takai, Noriko Katsura and Yuji Kunisada

Chemical Communications 2001(Issue 18) pp:NaN1725-1725

Publication Date(Web):2001/08/13

DOI:10.1039/B105357B

Chromioenamines can be generated by treatment of O-acetyloximes with chromium(II) via two steps of one-electron reduction and successive isomerization, and the species react with aldehydes to give γ-amino alcohols after reduction with LiAlH4.

Rhenium- and manganese-catalyzed insertion of acetylenes into β-keto esters: synthesis of 2-pyranones

Co-reporter:Yoichiro Kuninobu, Atsushi Kawata, Mitsumi Nishi, Hisatsugu Takata and Kazuhiko Takai

Chemical Communications 2008(Issue 47) pp:NaN6362-6362

Publication Date(Web):2008/10/24

DOI:10.1039/B814694B

Rhenium- and manganese-catalyzed reactions between β-keto esters and acetylenes, followed by treatment with tetrabutylammonium fluoride, gave 2-pyranone derivatives regioselectively.

Rhenium-catalyzed allylation of C–H bonds of benzoic and acrylic acids

Co-reporter:Yoichiro Kuninobu, Kazuhiro Ohta and Kazuhiko Takai

Chemical Communications 2011 - vol. 47(Issue 38) pp:NaN10793-10793

Publication Date(Web):2011/09/05

DOI:10.1039/C1CC12359A

Iron-catalyzed synthesis of glycine derivatives via carbon–nitrogen bond cleavage using diazoacetate

Co-reporter:Yoichiro Kuninobu, Mitsumi Nishi and Kazuhiko Takai

Chemical Communications 2010 - vol. 46(Issue 46) pp:NaN8862-8862

Publication Date(Web):2010/10/21

DOI:10.1039/C0CC03781H