Revisiting the Betti synthesis : using a cheap, readily-available, recyclable clay catalyst in solventless conditions

Abstract

One‐pot multicomponent reactions have gained significant importance in recent years because they are usually more selective, simple, efficient, atom‐economic and green than their multistep counterparts. The Betti synthesis involves the combination of aldehydes, amines and 2‐naphthol to form compounds which can serve as catalysts or as biologically active compounds. In this study, Montmorillonite K30 was used as a heterogeneous catalyst for the Betti reaction at 60 0C in relatively short reaction times. Positively, it is cheap, readily and commercially available and requires no preparation, it can be used in neat conditions whilst minimizing excess reagent amounts. Most importantly, it is fully recoverable and can be recycled up to 5 times. In reactions involving secondary aliphatic amines, very good to excellent results were obtained whilst primary ones including benzylamine gave appreciable yields. In addition, the heteroaromatic aldehyde 4‐pyridinecarboxaldehyde and the polyaromatic aldehyde 1‐naphthaldehyde also gave encouraging results.