Yoshiaki Horiguchi

Me3SiCl/HMPA accelerated conjugate addition of catalytic copper reagent. Stereoselective synthesis of enol silyl ether of aldehyde

Abstract Copper-catalyzed conjugate addition of the Grignard reagents in the presence of Me 3 SiCl and HMPA proceeds in much higher yield than the reaction of conventional organocopper reagents and shows very good regio-, stereo-, and chemoselectivities.

Me3SiCl accelerated conjugate addition of stoichiometric organocopper reagents

Abstract Chlorotrimethylsilane, particularly if combined with hexamethylphosphoric triamide or 4-dimethylaminopyridine, strongly promote the conjugate addition of stoichiometric organocopper reagents.

Chlorosilane-accelerated conjugate addition of catalytic and stoichiometric organocopper reagents

Abstract Trialkylsilyl chlorides, particularly in combination with hexamethylphosphoramide or 4-dimethylaminopyridine, dramatically accelerates the conjugate addition of catalytic and stoichiometric organocopper reagents onto enones, enals, and enoates, in which very high degrees of stereo- and chemoselectivities were observed.

Formation and characterization of trichlorotitanium enolates

Abstract The reaction of enol silyl ethers with TiCl4 gives trichlorotitanium enolates, which are unique with their relatively electron deficient double bonds.

Does Me3SiCl activate conjugate addition of copper reagents as a Lewis acid

Abstract The role of Me 3 SiCl to accelerate the conjugate addition of organocopper reagents has been examined by comparison of the stereochemical results of reactions with 6- and 2,6-disubstituted cyclohexenones, and mechanism involving an initial coordination of the chlorosilane to enones has been proposed.

Double hydroxylation of enol silyl ethers. A single-step synthesis of α,α'-dihydroxy ketones

Abstract Oxidation of the more substituted regioisomer of the enol silyl ether of a methyl sec-alkyl ketone with 2 equiv of m-chloroperbenzoic acid in the presence of KHCO3 gives, after acidic workup, an α,α′-dihydroxylated ketone in high yield. Applications to the synthesis of adrenal hormones and an anthracycline model compound are also described.

Diastereoselective [3 + 2] cycloaddition of methyl 2-phenylthiocyclopropyl ketone with enol silyl ethers: Synthesis of functionalized cyclopentanes.

Abstract Dimethylaluminum chloride-mediated [3 + 2] cycloaddition of methyl 2-phenylthiocyclopropyl ketone and enol TBDPS or TIPS ethers proceeds highly diastereoselectively to afford functionalized cyclopentanes in good yields.

Stoichiometric generation of 3-siloxyallenyllithium and its reactions with electrophiles

Abstract A 3-( t -butyldimethylsiloxy)allenyllithium generated quantitatively from the 1-silylpropargyl alcohol can be used as a synthetic equivalent of α,β-unsaturated ketone having nucleophilic center at its β-position through transmetallation.

Synthetic studies of taxane carbon framework. A highly efficient eight-membered ring cyclization with complete stereocontrol

Abstract Cyclization reaction of 5-[2-(dimethoxymethyl)-6-methoxy]benzyl-2,4,4-trimethyl-3-(trimethylsilylmethyl)cyclohexenone 2 and 5-[2-(dimethoxymethyl)-6-methoxy]benzyl-2,6,6-trimethyl-3-(siloxy)-1-methylenecyclohex-2-ene 9 gave the corresponding endo tricarbocycle bearing of sp2 carbon on the bridge-head position. Phenylthio and methoxy derivatives of 9, e.g. 11 and 12, also underwent similar cyclization to afford the endo tricarbocyclic products 13 and 14 in high yields. Further, the stereochemistry of the substituents on 8-membered ring has been completely controlled in a desired manner in every case.

An enantioselective synthesis of the A-Ring fragment of taxol

Abstract A-Ring fragment of taxol (2), α-hydroxy aldehyde 1, was enantioselectively prepared by using asymmetric dihydroxylation of enol silyl ether of the parent aldehyde.