Direct Synthesis of Imines via Solid State Reactions of Carbamates with Aldehydes



Various solid carbamates were prepared from the reactions of liquid amines with carbon dioxide in an autoclave and these carbamates were used as stable, efficient alternatives for toxic liquid amines. Solid-state grinding of carbamates and aldehydes, using a mortar and pestle, produced imines as the sole products in greater than 97% yields. Complete conversions were generally accomplished within a day at 25 °C without using solvents or additives. Reaction rates were drastically enhanced upon increasing the reaction temperature. In contrast, reactions of aldehydes with liquid amines in the presence of solvent or in neat conditions afforded imines in moderate yields along with by-products.