One-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones using CuBr2 as catalyst.

A simple, efficient procedure and improved conditions have been found to carry out the Biginelli reaction for the synthesis of 3,4-dihydropyrimidin-2(1H)-one derivatives. This synthesis was performed using CuBr2 as the catalyst in ethanol solution. The optimum conditions were as follows: the molar ratio of aldehyde to alpha,beta-diketone to urea or thiourea is 1:1:1:0.5, the molar ratio of catalyst to aldehyde is 25%, and the reaction time is 4 h. Under the above conditions, the highest yield of dihydropyrimidinones was up to 95%. Compared with the classical Biginelli reaction conditions, this new method has the advantage of excellent yields and short reaction times.