Origin of the diastereoselection in the indium-mediated addition of haloallylic sulfones to aldehydes

Abstract

The R 1 substituents at C(2) of the haloallylic sulfones 1 play a pivotal role in controlling the diastereoselectivity of the indium-mediated addition reaction to benzaldehyde to produce the homoallylic alcohols 3. The R 1 Me group of 1 prefers the chair form in the In-coordinated six-membered cyclic transition state to give anti-3a, and the R 1 Ph group of 1 favors the twist boat form to give syn-3n, both in a high 13:1 selectivity.