Solvent-free synthesis of β-amino carbonyl compounds via direct Mannich reaction catalyzed by a quaternary phosphonium salt.

Quaternary phosphonium salts, as organophosphorus compounds, play an essential role in organic synthesis, pharmaceuticals, and natural product chemistry. 1,2-Ethanediylbis(triphenylphosphonium) dibromide was prepared and characterized by 1H NMR, 13C NMR, and 31P NMR and used as an efficient catalyst for the preparation of β-amino carbonyl compounds under solvent-free conditions at room temperature via a multicomponent Mannich reaction. To evaluate the efficiency of our method, benzaldehyde, aniline derivatives, and aliphatic, aromatic and cyclic ketones were reacted in the presence of the synthesized quaternary phosphonium salt, yielding satisfactory results in both cases. This approach demonstrated multiple advantages, including short reaction times, high yields, simple product separation, the use of a low-cost catalyst, and reduced waste, enabling the synthesis of several β-amino carbonyl derivatives, which were structurally confirmed.