Solvent-free Imino-Aldol Three-component Couplings on a Conveniently-prepared and Reusable Phosphoric Acid-Silica Gel Support

A new solvent-free procedure for the synthesis of (beta)-amino carbonyl compounds in generally moderate to excellent yields has been developed. Three-component Mannich-type couplings between aldehydes (aromatic, aliphatic, alicyclic, and heterocyclic), aromatic amines and silyl enol equivalents proceeded smoothly on a conveniently prepared and reusable phosphoric acid-silica gel solid support.