Direct Aldol Reactions Catalyzed by a Heterogeneous Guanidinium Salt/Proline System under Solvent-Free Conditions‡

The combined activity of (S)-proline and an achiral cocatalyst (a TBD-derived guanidinium salt) allow direct aldol reactions to be carried out with high diastereoselectivity and enantioselectivity under solvent-free conditions with a rather simple reaction setup where stirring is not required.