Influence of a remote sulfinyl group on L-proline-catalyzed direct asymmetric aldol addition of acetone

In recent years, notable results have been achieved in the asymmetric direct aldol addition of ketones to aldehydes by employing secondary amines as organocatalysts. Although several functionalized ketones have been used as nucleophiles, the influence of a chiral group on the aromatic aldehydes on the reactivity is still poorly explored. The aldehyde 1, easily accessible in racemic and enantiomerically enriched form, seemed to be the ideal substrate to explore this aspect in the L-proline catalyzed aldol addition of acetone. Interesting aspects, such as 1,4-asymmetric induction by the remote sulfinyl group of the aldehyde but also the stereochemical control and kinetic resolution of the racemic substrate by the chiral organocatalyst were examined. Finally, an unexpected stereoselective retro-aldol reaction catalyzed by L-proline was pointed out.