Three-carbon homologation of diorganozincs with lithiated acetylenic epoxides.

Reaction of dialkylzincs with lithiated acetylenic epoxides is described to give zincates that undergo a 1,2-metallate rearrangement by an anti-S(N)2' pathway. This rearrangement occurs with the transfer of an alkyl or a silyl group affording allenylzinc intermediates. Allenic and/or homopropargylic alcohols are obtained upon hydrolysis. Quenching the reaction mixture with aldehydes or ketones is shown to give access to 2-alkynyl-1,3-diols in a stereoselective manner.

Synthesis of 2-hydroxymethyl ketones by ruthenium hydride-catalyzed cross-coupling reaction of alpha,beta-unsaturated aldehydes with primary alcohols.

The cross-coupling reaction of alpha,beta-unsaturated aldehydes with primary alcohols to give 2-hydroxymethyl ketones was achieved using RuHCl(CO)(PPh(3))(3) as a catalyst. This atom-economical reaction is likely to proceed via the hydroruthenation of alpha,beta-unsaturated aldehydes followed by an aldol reaction of the resultant enolates with aldehydes to give alpha-formylated ketones, which undergo transfer hydrogenation with primary alcohols leading to alpha-hydroxymethyl ketones. The reduction step can generate aldehydes, participating in the next catalytic cycle.

Double deprotonation of acetylenic oxiranes: synthesis of allenic ketones through Dilithio Ynenolates.

[reaction: see text] The double deprotonation of acetylenic oxiranes gives allenic ketones through the 1,2-H or 1,2-Ar shift on the transient oxiranyl dianion intermediates. The resulting dilithium ynenolates give allenic ketones upon hydrolysis or can be quenched with various electrophiles.