Regiochemical and mechanistic studies of the addition of tin hydride and oxide to substituted ketenes

Article abstract of DOI:10.1016/0022-328X(90)80213-J

The reactions of aryl-substituted ketenes with tri-n-butyltin hydride give rise to O-bound tin enolates.With unsymmetrically-substituted methyl phenyl ketene this process exhibits little or no stereoselectivity.The kinetic mixture consists of virtually equal proportions of E and Z enolate isomers, which then equilibrates to a 71/29 Z/E mixture under thermodynamic control.Mechanistic studies are not consistent with either radical or polar mechanisms, and a concerted pathway with differential rates of bond formation is proposed.With dimethyl ketene a similar reactiongives a vinyl ester enolate, which preasumably results from an initially-formed aldehyde enolate.Finally, the reaction of diphenyl ketene with tri-n-butyltin oxide results in a tin carboxylate which adopts a polymeric structure in the solid state.