Kei Takeda

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Organization: Hiroshima University

Department: 1 Graduate School of Medical Sciences

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Chemicals
References

Enantiodivergent Deprotonation/Acylation of -Amino Nitriles

Co-reporter:Dr. Michiko Sasaki;Tomo Takegawa;Kunihiro Sakamoto;Yuri Kotomori;Dr. Yuko Otani;Dr. Tomohiko Ohwada;Dr. Masatoshi Kawahata;Dr. Kentaro Yamaguchi;Dr. Kei Takeda

Angewandte Chemie International Edition 2013 Volume 52( Issue 49) pp:12956-12960

Publication Date(Web):

DOI:10.1002/anie.201306443

Chirality transfer in Brook rearrangement-mediated SE2′ solvolytic protonation and its use in estimation of the propensity for racemization of the α-lithiocarbanions of the substituents

Co-reporter:Michiko Sasaki, Misato Fujiwara, Yuri Kotomori, Masatoshi Kawahata, Kentaro Yamaguchi, Kei Takeda

Tetrahedron 2013 69(29) pp: 5823-5828

Publication Date(Web):

DOI:10.1016/j.tet.2013.05.043

Enantioselective trapping of an α-chiral carbanion of acyclic nitrile by a carbon electrophile

Co-reporter:Michiko Sasaki, Tomo Takegawa, Hidaka Ikemoto, Masatoshi Kawahata, Kentaro Yamaguchi and Kei Takeda

Chemical Communications 2012 vol. 48(Issue 23) pp:2897-2899

Publication Date(Web):30 Jan 2012

DOI:10.1039/C2CC00082B

An α-chiral nitrile carbanion generated by deprotonation of enantioenriched O-carbamoyl cyanohydrin was trapped in situ with ethyl cyanoformate to give the corresponding ester derivative in 92% yield and 90:10 er, providing the first example of trapping of an α-chiral acyclic nitrile carbanion that has been considered to be very configurationally labile.

Steric Course of the Electrophilic Substitution of a Lithiocarbanion Generated from (S,E)-1-Phenylbut-2-en-1-yl Diisopropylcarbamate and Solvent Effects

Co-reporter:Hidaka Ikemoto;Michiko Sasaki;Masatoshi Kawahata;Kentaro Yamaguchi

European Journal of Organic Chemistry 2011 Volume 2011( Issue 32) pp:6553-6557

Publication Date(Web):

DOI:10.1002/ejoc.201100970

Abstract

The effects of electrophiles and solvents on the stereochemistry of electrophilic substitution of a lithiocarbanion generated from (S,E)-1-phenylbut-2-en-1-yl diisopropylcarbamate were examined using various acids and carbon electrophiles. The stereochemical outcomes were influenced by the relative ability of the electrophiles and solvents to coordinate to lithium.

Enantioselective Synthesis of Siloxyallenes from Alkynoylsilanes by Reduction and a Brook Rearrangement and Their Subsequent Trapping in a [4+2] Cycloaddition

Co-reporter:Dr. Michiko Sasaki;Yasuhiro Kondo;Dr. Masatoshi Kawahata;Dr. Kentaro Yamaguchi;Dr. Kei Takeda

Angewandte Chemie 2011 Volume 123( Issue 28) pp:6499-6502

Publication Date(Web):

DOI:10.1002/ange.201102430

Enantioselective Synthesis of Siloxyallenes from Alkynoylsilanes by Reduction and a Brook Rearrangement and Their Subsequent Trapping in a [4+2] Cycloaddition

Co-reporter:Dr. Michiko Sasaki;Yasuhiro Kondo;Dr. Masatoshi Kawahata;Dr. Kentaro Yamaguchi;Dr. Kei Takeda

Angewandte Chemie International Edition 2011 Volume 50( Issue 28) pp:6375-6378

Publication Date(Web):

DOI:10.1002/anie.201102430

Solvent Effects on the Steric Course of the [2,3]-Wittig Rearrangement of (S,E)-[3-(Allyloxy)prop-1-ene-1,3-diyl]dibenzene and Derivatives

Co-reporter:Hidaka Ikemoto;Michiko Sasaki

European Journal of Organic Chemistry 2010 Volume 2010( Issue 34) pp:6643-6650

Publication Date(Web):

DOI:10.1002/ejoc.201001061

Abstract

The effect of solvents and additives on the steric course of [2,3]-Wittig rearrangement of the chiral 1,3-diphenyl-1-propenyloxy-2-propen-1-yl carbanion and its derivatives wasexamined on the basis of chirality transfer in intramolecular trapping.

[2,3]-Wittig Rearrangement of Enantiomerically Enriched 3-Substituted 1-Propenyloxy-1-phenyl-2-propen-1-yl Carbanions: Effect of Heteroatoms and Conjugating Groups on Planarization of an -Oxy-Benzylcarbanion through a Double Bond

Co-reporter:Michiko Sasaki Dr.;Hidaka Ikemoto;Masatoshi Kawahata Dr.;Kentaro Yamaguchi Dr.

Chemistry - A European Journal 2009 Volume 15( Issue 18) pp:4663-4666

Publication Date(Web):

DOI:10.1002/chem.200802322

Stereoselective SE2 Protonation of -Hydroxyallylsilanes Mediated by a Brook Rearrangement

Co-reporter:Michiko Sasaki Dr.;Yuri Shirakawa;Masatoshi Kawahata Dr.;Kentaro Yamaguchi Dr. Dr.

Chemistry - A European Journal 2009 Volume 15( Issue 14) pp:3363-3366

Publication Date(Web):

DOI:10.1002/chem.200802499

Chirality Transfer from Epoxide to Carbanion: Base-Induced Alkylation of O-Carbamoyl Cyanohydrins of -Silyl-,-epoxy Aldehyde

Co-reporter:Michiko Sasaki;Eiji Kawanishi;Yuri Shirakawa;Masatoshi Kawahata;Hyuma Masu;Kentaro Yamaguchi

European Journal of Organic Chemistry 2008 Volume 2008( Issue 18) pp:3061-3064

Publication Date(Web):

DOI:10.1002/ejoc.200800300

Abstract

Enantioselective C–C bond formation at an α-position of a nitrile group with an external electrophile can be realized, although in modest ee, with the aid of both the concerted process of an epoxysilane rearrangement and a carbamoyl group. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Enantioselective trapping of an α-chiral carbanion of acyclic nitrile by a carbon electrophile

Co-reporter:Michiko Sasaki, Tomo Takegawa, Hidaka Ikemoto, Masatoshi Kawahata, Kentaro Yamaguchi and Kei Takeda

Chemical Communications 2012 - vol. 48(Issue 23) pp:NaN2899-2899

Publication Date(Web):2012/01/30

DOI:10.1039/C2CC00082B