Biginelli reaction catalyzed by elemental bromine as a novel Lewis acid catalyst, under mild conditions

Abstract

In the present study, we discussed that, the elemental bromine is a highly efficient and selective homogeneous Lewis acid catalyst for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones. Biginelli three-component condensation was carried out by the reaction of an aromatic aldehyde, urea/thiourea, and methyl/ethyl acetoacetate in ethanol, to afford the desired product in high yields. The influence of reaction parameters including the solvent type and the bromine quantity on catalytic activity were also investigated. In addition, the quantum computations were employed to clarify the effect of the Lewis acid catalyst. The structure of the products was validated using the FT-IR, 1HNMR, and 13CNMR. Our procedure offered several advantages including, the mild reaction conditions, employing an inexpensive catalyst, and easy workup.