N¹-Substituted quinazolinone alkaloids hold significant research value in drug discovery. An efficient approach for the synthesis of 1-methyl-2-phenyl-2,3-dihydroquinazolin-4(1H)-one and its derivatives was developed. Using o-methylamino-benzamide and benzaldehyde derivatives as starting materials, racemic phosphoric acid as the catalyst, and 4 Å molecular sieves as a desiccant, the reaction proceeded at 120 ℃ for 24 h. Twenty-six target products were prepared with yields ranging from 57% to 98%. The structures of all compounds were characterized by ¹H NMR, ¹³C NMR, HRMS and single crystal X-ray diffraction analysis. Moreover, the synthesis of chiral target products was achieved when using chiral phosphoric acid as the catalyst. In summary, this method features readily accessible starting materials, cost-effectiveness, high efficiency, and good functional-group tolerance, offering a practical and efficient strategy for synthesizing N¹-substituted quinazolinone alkaloids.

Key words: quinazolinone, racemic phosphoric acid, chiral phosphoric acid