Eiji Shirakawa

The palladium–iminophosphine catalyst for the reactions of organostannanes ☆

Abstract A palladium complex coordinated by an iminophosphine ligand was found to be a remarkably active catalyst for the coupling of organostannanes with aryl halides. The mechanistic studies show that the reaction of an alkynylstannane proceeds through an unprecedented catalytic cycle which involves an oxidative addition of the organostannane to the Pd(0)–iminophosphine complex. The catalyst was demonstrated to be also useful for the carbostannylation of alkynes and the homocoupling reaction of organostannanes.

Friedel–Crafts alkenylation of arenes using alkynes catalysed by metal trifluoromethanesulfonates

Metal trifluoromethanesulfonates [M(OTf)n; M = Sc, Zr, In] catalyse the Friedel–Crafts alkenylation of arenes using alkynes, including internal alkynes, to give, through an alkenyl cation intermediate, 1,1-diarylalkenes in high to excellent yields.

Palladium-iminophosphine-catalyzed homocoupling of alkynylstannanes and other organostannanes using allyl acetate or air as an oxidant

Abstract A palladium–iminophosphine complex was found to catalyze the homocoupling reaction of alkynylstannanes using allyl acetate as an oxidant, whereas aryl- and alkenylstannanes were oxidatively homocoupled with air.

Stereospecific formation of optically active trialkylsilyllithiums and their configurational stability

Optically active trialkylsilyllithiums, (R)-(n-butyl)methylphenylsilyllithium (63% ee) and (S)-methyl(1-naphthyl)phenylsilyllithium (96% ee), were prepared by cleavage of the siliconsilicon bond of (R)-1-(n-butyl)-1-methyl-1-phenyl-2,2-diphenyl-2-methyldisilane with lithium metal, or the silicontin bond of (S)-methyl(1-naphthyl)phenylsilyltrimethylstannane with methyllithium, respectively. Optical purity of the silyllithiums was evaluated as corresponding silanes by HPLC on optically active stationary phase after hydrolysis. The formation of silyllithium was found to be highly stereospecific (>94, >99% retention, respectively). (S)-Methyl(1-naphthyl)phenylsilyllithium is configurationally stable for at least 1 h at −78°C in tetrahydrofuran.

Indium triflate-catalysed double addition of heterocyclic arenes to alkynes

Indium triflate was found to be a prominent catalyst for addition of heterocyclic arenes to alkynes to afford 2:1 adducts, where two heterocyclic arenes regioselectively attacked the same carbon atom of alkynes.

Synthesis of functionalized alkenes by transition metal-catalyzed carbostannylations of alkynes and dienes followed by cross-coupling reactions

Transition metal-catalyzed carbostannylation of alkynes and 1,2-dienes provides alkenylstannanes having an alkynyl, alkenyl or acyl group with or without conjugation. The alkenylstannanes are transformed to various unsaturated compounds with diverse functionalized structures through palladium-catalyzed cross-coupling reactions with organic electrophiles.

Palladium-catalysed dimerization of vinylarenes using indium triflate as an effective co-catalyst

A palladium-indium triflate catalyst was found to be much more active for the dimerization of vinylarenes compared with generally used cationic palladium(II) catalysts.

Palladium–iminophosphine-catalysed carbostannylation of arynes: synthesis of ortho-substituted arylstannanes

Arynes were found to insert into a carbon-tin bond of alkynyl- and vinylstannanes in the presence of a catalytic amount of a palladium-iminophosphine complex to afford ortho-substituted arylstannanes, which were convertible into a wide variety of 1,2-disubstituted arenes via carbon-carbon bond forming reactions.

Synthesis of polycyclic compounds utilizing the nickel-catalysed alkynylstannylation of 1,2-dienes

Polycyclic compounds having linearly-fused six-membered rings can be readily prepared by various modes of cyclization from dienediynes, which were synthesized through the nickel-catalysed alkynylstannylation of 1,2-dienes followed by the palladium-catalysed oxidative homocoupling of the resulting alkenylstannanes.

Diphenylphosphinophenolate: a ligand for the palladium-catalysed silylation of aryl halides activating simultaneously both palladium and silicon

Diphenylphosphinophenolate was found to be an effective ligand for the palladium-catalysed silylation of aryl halides, activating not only palladium but also silicon of a disilane, where aryl bromides and iodides having such substituents as methyl, methoxy, amino, ethoxycarbonyl, trifluoromethyl, formyl or phenyl are applicable to the reaction with hexamethyldisilane to give the corresponding trimethylsilylarenes.