ZrCl4 or ZrOCl2 under neat conditions: optimized green alternatives for the Biginelli reaction

Biginelli reactions were performed using either ZrCl4 or ZrOCl2·8H2O as catalysts under neat conditions. Shorter reaction time than most of the classical methods was required when ZrCl4 was used. In general, 3,4-dihydropyrimidin-2(1H)-ones and thioxo-3,4-dihydropyrimidin-2(1H)-ones were obtained under neat conditions in moderate to good yields and good purity without using harmful solvents in the work up.