STEREOSELECTIVE ALDOL CONDENSATIONS OF ORGANOTIN REAGENTS WITH ALDEHYDES

Article abstract of DOI:10.1016/0040-4020(84)80016-2

The reaction of the enolstannanes of cyclohexanone or propiophenone with various aldehydes under kinetic control (-78 deg C) gave predominately the threo aldols, diastereoselectivity as high as 95:5 being achived.At higher temperatures (+45 deg C) predominate erythro selectivity was observed.The enolstannane of propiophenone exists as an equilibrium mixture of O-Sn (probably the E-isomer) and C-Sn derivatives.Reaction at -78 deg C takes place rapidly with the O-Sn enolate, further reaction requiring isomerization of the C-Sn to the O-Sn enolate.The Pd catalyzed condensation of cyanomethyltributyltin with reactive aldehydes, such as nitrobenzaldehydes, took place at ambient temperatures in polar solvents to give high yields of condensation products.No reaction occured with aldehydes such as benzaldehyde.Only low stereoselectivity (10-34percent ee) was observed when (-)DIOP or (-)BPPM were utilized as chiral phosphine ligands.