Ultrasound accelerated solvent-free synthesis of ethyl 7-methyl-5-phenyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate through Biginelli reaction catalyzed by Amberlyst-15 - Dương, Công-Thắng; Luu, Xuan Thi (VNUHCM Journal of Advanced Research in Natural Sciences, 2020)