Hirokazu Tsukamoto

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Organization: Tohoku University
Department: Graduate School of Pharmaceutical Sciences
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Co-reporter:Hirokazu Tsukamoto, Taishi Ikeda, and Takayuki Doi
The Journal of Organic Chemistry 2016 Volume 81(Issue 5) pp:1733-1745
Publication Date(Web):November 25, 2015
DOI:10.1021/acs.joc.5b02378
1,2-Bis(diphenylphosphino)ethane (dppe)-ligated palladium(II) complexes catalyze the annulation of internal alkynes with 2-(cyanomethyl)phenylboronates to provide 3,4-disubstituted-2-naphthalenamines in good yields. The annulation reaction proceeds under mild and neutral conditions and requires methanol as an essential solvent. In addition to symmetrical alkynes, unsymmetrical alkynes substituted by aryl, alkyl, and alkynyl groups participate in the annulation to afford the corresponding 2-naphthalenamines with electron-withdrawing sp2- and sp-carbons preferentially located at the C-3 position. Substituents including an alkyl or alkoxy group on the cyanomethyl moiety and a halogen atom on the benzene ring in the boronates are compatible with the reaction conditions. The annulation proceeds through the transmetalation of the palladium(II) complexes with the boronates and alkyne insertion followed by nucleophilic addition of the generated alkenylpalladium(II) species to the intramolecular cyano group. Stoichiometric reactions revealed that the methanol solvent was effective for both transmetalation and catalyst regeneration.
Co-reporter:Hirokazu Tsukamoto, Ayumu Kawase and Takayuki Doi  
Chemical Communications 2015 vol. 51(Issue 38) pp:8027-8030
Publication Date(Web):03 Apr 2015
DOI:10.1039/C5CC02176F
Palladium/chiral diphosphine-catalyzed umpolung cyclization of allylic acetate-aldehyde using formate as a terminal reductant affords cis-disubstituted pyrrolidine, tetrahydrofuran, and spiro carbocycle in high enantioselectivity. The formate does not cause allylpalladium reduction under the catalysis. The highly stereoselective cyclization would proceed through a cationic η1-allylpalladium ligated by diphosphine.
Co-reporter:Hirokazu Tsukamoto, Mitsugu Shiraishi, and Takayuki Doi
Organic Letters 2013 Volume 15(Issue 23) pp:5932-5935
Publication Date(Web):November 8, 2013
DOI:10.1021/ol402685g
Pd/P(c-C6H11)3-catalyzed alkynyliminium ion cyclization in the presence of organoboronic acids affords stereodefined N-alkyl-3-alkylidenepyrrolidines. The distinctive cis-selective addition of the boronic acids and the iminium ions across the alkyne would result from favored 5-exo- or 6-exo-dig cyclization through oxidative addition of the formaldiminium ions to Pd(0).
Co-reporter:Hirokazu Tsukamoto, Tomomi Uchiyama, Takamichi Suzuki and Yoshinori Kondo  
Organic & Biomolecular Chemistry 2008 vol. 6(Issue 16) pp:3005-3013
Publication Date(Web):27 Jun 2008
DOI:10.1039/B804991B
Allylic alcohols can be used directly for the palladium(0)-catalyzed allylation of aryl- and alkenylboronic acids with a wide variety of functional groups. A triphenylphosphine-ligated palladium catalyst turns out to be most effective for the cross-coupling reaction and its low loading (less than 1 mol%) leads to formation of the coupling product in high yield. The Lewis acidity of the organoboron reagents and poor leaving ability (high basicity) of the hydroxyl group are essential for the cross-coupling reaction. The reaction process is atom-economical and environmentally benign, because it needs neither preparation of allyl halides and esters nor addition of stoichiometric amounts of a base. Furthermore, allylic alcohols containing another unsaturated carbon–carbon bond undergo arylative cyclization reactions leading to cyclopentane formation.
Co-reporter:Hirokazu Tsukamoto Dr. ;Yoshinori Kondo Dr.
Angewandte Chemie International Edition 2008 Volume 47( Issue 26) pp:4851-4854
Publication Date(Web):
DOI:10.1002/anie.200800823
Co-reporter:Hirokazu Tsukamoto Dr. ;Yoshinori Kondo Dr.
Angewandte Chemie 2008 Volume 120( Issue 26) pp:4929-4932
Publication Date(Web):
DOI:10.1002/ange.200800823
Co-reporter:Hirokazu Tsukamoto, Masanori Sato and Yoshinori Kondo  
Chemical Communications 2004 (Issue 10) pp:1200-1201
Publication Date(Web):15 Apr 2004
DOI:10.1039/B402256D
Allyl alcohols can be directly used for the palladium-catalyzed allylation of aryl- and vinyl-boronic acids without the aid of a base.
Co-reporter:Hirokazu Tsukamoto, Tomomi Uchiyama, Takamichi Suzuki and Yoshinori Kondo
Organic & Biomolecular Chemistry 2008 - vol. 6(Issue 16) pp:NaN3013-3013
Publication Date(Web):2008/06/27
DOI:10.1039/B804991B
Allylic alcohols can be used directly for the palladium(0)-catalyzed allylation of aryl- and alkenylboronic acids with a wide variety of functional groups. A triphenylphosphine-ligated palladium catalyst turns out to be most effective for the cross-coupling reaction and its low loading (less than 1 mol%) leads to formation of the coupling product in high yield. The Lewis acidity of the organoboron reagents and poor leaving ability (high basicity) of the hydroxyl group are essential for the cross-coupling reaction. The reaction process is atom-economical and environmentally benign, because it needs neither preparation of allyl halides and esters nor addition of stoichiometric amounts of a base. Furthermore, allylic alcohols containing another unsaturated carbon–carbon bond undergo arylative cyclization reactions leading to cyclopentane formation.
Co-reporter:Hirokazu Tsukamoto, Ayumu Kawase and Takayuki Doi
Chemical Communications 2015 - vol. 51(Issue 38) pp:NaN8030-8030
Publication Date(Web):2015/04/03
DOI:10.1039/C5CC02176F
Palladium/chiral diphosphine-catalyzed umpolung cyclization of allylic acetate-aldehyde using formate as a terminal reductant affords cis-disubstituted pyrrolidine, tetrahydrofuran, and spiro carbocycle in high enantioselectivity. The formate does not cause allylpalladium reduction under the catalysis. The highly stereoselective cyclization would proceed through a cationic η1-allylpalladium ligated by diphosphine.
Benzeneacetonitrile, 4-chloro-2-iodo-
2-Naphthalenamine, 3,4-bis(4-methoxyphenyl)-
2-Naphthalenamine, 6,7-dimethoxy-3,4-diphenyl-
2-Naphthalenamine, 4-(3,3-dimethyl-1-butynyl)-3-(1,1-dimethylethyl)-
2-Naphthalenamine, 3-(1,1-dimethylethyl)-4-phenyl-
Benzeneacetonitrile, a-(acetyloxy)-2-iodo-
Acetaldehyde, [2-[[(1,1-dimethylethyl)dimethylsilyl]oxy]ethoxy]-
2-(2-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)acetonitrile
2-Oxazolidinone,3-[(1E)-1-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-2-methyl-1,3-butadienyl]-4-(1-methylethyl)-, (4S)-