Tamejiro Hiyama

How I came across the silicon-based cross-coupling reaction

Briefly reviewed are the historical background, motivation for invention, and salient features of the silicon-based cross-coupling reaction, now simply called Hiyama Coupling, in addition to recent progress.

Palladium-catalyzed cross-coupling reaction of organometalloids through activation with fluoride ion

Activation of organosilicon compounds with fluoride ion produces a transient pentacoordinate silicate, which is capable of transmetalation with a catalytic organopalladium complex and achieves cross-coupling reaction. Mono-, di- or trifluorosilanes can deliver alkenyl, aryl, or alkyl group, respectively. The reaction, characterized by high chemo- and stereoselectivity, was successfully applied to synthesis of HMG-CoA reductase inhibitor NK-104 and functionalized biaryls for liquid crystals. The stereochemical aspects are discussed.

Chromium(II) mediated threo selective synthesis of homoallyl alcohols

Abstract Remarkable threo selectivity is observed in the reaction of aldehydes with trans - and cis -1-bromo-2-butene with the aid of chromium(II) salts. Solvent effect as well as the synthetic application is discussed.

Geminal dimetalation of alkylidene-type carbenoids with silylboranes and diborons

Abstract A novel and efficient method for gem-dimetalation of carbenoids has been demonstrated. Treatment of alkylidene-type lithium carbenoids with such an interelement compound as silylborane or diboron to generate the corresponding borate complex, followed by warming to room temperature, induced migration of the silyl or boryl group from a negatively charged boron atom to the carbenoid carbon to afford 1-boryl-1-silyl-1-alkenes or 1,1-diboryl-1-alkenes in good yields. Carbon–carbon bond forming transformations of the gem-dimetalated compounds mediated by boron or silicon is also described.

NaOH-Promoted cross-coupling reactions of organosilicon compounds with organic halides: Practical routes to biaryls, alkenylarenes and conjugated dienes

Abstract The use of NaOH has been found to be extremely effective in promoting the palladium-catalyzed cross-coupling reactions of aryl and alkenylchlorosilanes with organic halides such as aryl bromides and chlorides under very mild conditions.

Stereoselective alternating copolymerization of carbon monoxide with alkenes

Abstract Stereoselective alternating copolymerization of carbon monoxide with various alkenes is reviewed. Using Pd(II) complexes of chiral ligands, completely alternating, isotactic, and enantioselective copolymerizations have been achieved from aliphatic 1-alkenes and from vinylarenes. Alternating copolymerization of carbon monoxide with other olefins are also described, such as functionalized ones, dienes, and allenes. Polymer conformation is mentioned briefly both in solid phase and in solution.

Preparation and carbonyl addition of γ,γ-difluoroallylsilanes

Abstract The reaction of 3,3,3-trifluoropropenes with disilane/tetrabutylammonium fluoride or silyllithium reagent gives γ,γ-difluoroallylsilanes which afford gem-difluoroallyl adducts of aldehydes and ketones with the aid of a catalyst such as potassium t-butoxide o r tris(diethylamino)sulfonium difluorotrimethylsilicate.

Synthetic and structural studies of [6]-, [7]- and [10]metacyclophanes

Abstract A new preparative sequence from 2,3-polymethylene-2-cyclopentenone 5 to 2,6-polymethylenebromobenzenes 3 (n = 6, 7, 10) and 2,6-polymethylenephenyllithiums 6 has been found. The reaction of 6 with various electrophiles produces a number of new compounds to disclose the unique reactivity of the aryl C-Li moiety surrounded by the polymethylene chain. Photolysis of 3a and 3b provides transannular products 8, 10 and 11 , all arising from the proximity between the aromatic bromine and the aliphatic hydrogen intraannularly opposed to be removed as HBr. Spectrometric study gives quantitative data of the dependence of the molecular geometry upon the chain length and the aromatic substituents. The energy barriers ΔG c ≠ of the conformational flipping are 17·4 kcal/mol (T c 76·5°) for [6]metacyclophane ( 7a ), 11·5 kcal/mol (T c −28°) for [7]metacyclophane ( 7b ), ·8 kcal/mol for [10]metacyclophane ( 7c ). The lower-energy process of the aliphatic chain in [6]metacyclophane derivatives is the pseudorotation with substituent-dependent barrier ΔG c ≠ 11·1 kcal/mol (T c −31·5°) for 7a , 12·4 kcal/mol (T c −4·5°) for 3a and 12·7 kcal/mol (T c 1·0°) for 12a . The rather large rotational barrier is attributed to the compressed structure of each system. The benzene ring distortion of the cyclophanes is deduced from the bathochromic shift of the B-band and the diamagnetic shift of the benzene proton signals in the PMR.

A novel C-C bond forming reaction of aryl- and alkenylsilanols. A halogen-free mizoroki-heck type reaction

Abstract When dimethyl(phenyl)silanol is subjected to on electron-deficient olefin in the presence of a stoichiometric amount of Pd(OAc)2, substitution of the CH bond of the olefin by a phenyl group on the silanol occurs in 52–86% yields. The reactions of several aryl- and alkenylsilanols with several olefins are also found to proceed in the system of 10 mol% of Pd(OAc)2, Cu(OAc)2 (3 mol), LiOAc (2 mol) to give the corresponding products in up to 69% yield.

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.