Magnesium Bromide and Magnesium Chloride Hexahydrate Catalyzed One-Pot Synthesis of Dihydropyrimidines via Biginelli Reaction under Solvent-Free Conditions

Biologically important 12 new important 3,4-dihydropyrimidin-2-(1H)-ones (-thiones) were synthesized with in one-pot three-component Biginelli reaction from the corresponding aromatic aldehydes (5-methyl-2-thiophenecarboxaldehyde and 2-chloro-5-nitrobenzaldehyde), -keto esters (ethylacetoacetate, allylacetoacetate, and t-butylacetoacetate), and urea/thiourea in the presence of catalytic amount of magnesium bromide and magnesium chloride hexahydrate as nontoxic, inexpensive, and easily available catalysts under solvent-free conditions at 80 and 100 degrees C. Compared with the catalyst-free three-component Biginelli reaction conditions, this method consistently has the advantage of short reaction time (45100 min) and good to excellent yields (7591%).