Remarkable Dependence of Diastereoselectivity on Anhydrous or Aqueous Solvent in the Indium Hydride Promoted Reudctive Aldol Reaction of #alpha#,#beta#-Unsaturated Ketones

摘要

Dichloroindium hydride generated by the transmetallation between tributyltin hydride and indium trichloride predominantly reduced #alpha#,#beta#-unsaturated ketones (enones) with 1,4-selectively even in the presence of aldehydes. Under anhydrous conditions, the successive aldol reaction between the resulting enolates and the remaining aldehydes proceeded with high anti-selectivity. The stereo-chemistry was dramatically reversed to be syn-selective by the use of water and methanol as an additive and solvent, respectively.