Enantioselective Direct Aldol Reactions of Achiral Ketones with Racemic Enolizable α-Substituted Aldehydes: Scope and Limitations

Aldol reactions of racemic enolizable dioxolan-protected α-substituted-β-ketoaldehydes with representative achiral ketones catalyzed by proline or 5-(2-pyrrolidine-2-yl)-1H-tetrazole in wet DMSO proceed with dynamic kinetic resolution (or via DYKAT with an α-substituted-β-alkoxyaldehyde) to give adducts with high dr and ee.