Highly Chemo- and Enantioselective Cross-Benzoin Reaction of Aliphatic Aldehydes and α-Ketoesters

An electron-deficient, valine-derived triazolium salt is shown to catalyze a highly chemo- and enantioselective cross-benzoin reaction between aliphatic aldehydes and alpha-ketoesters. This methodology represents the first high yielding and highly enantioselective intermolecular cross-benzoin reaction using an organocatalyst (up to 94% ee). Further diastereoselective reduction of the products gives access to densely oxygenated compounds with high chemo- and diastereoselectivity.