General procedure for the synthesis of 7-methyl-4(3H)-quinazolinone from 2-amino-4-methylbenzamide (1, 4.0 mmol) and compound (CAS: 77287-34-4, 2, 6.0 mmol): a mixture of 2-amino-4-methylbenzamide (1), formamide (2), Yb(OTf)3 (0.20 mmol, 5.0 mol%) and a mixture of homotrimethylbenzene (5.0 mL) were placed in a 20 mL Pyrex flask, the unit was equipped with a magnetic stir bar and a reflux condenser, and the reaction was carried out under argon protection. The reaction mixture was stirred at 120-165 °C (oil bath temperature) for 6 hours. After completion of the reaction, the mixture was cooled to room temperature and analyzed by GLC, GC-MS (EI) and LC-MS (ESI). After removal of homotrimethylbenzene by evaporation under vacuum, the product (3) was purified by recrystallization from methanol/hexane and/or silica gel medium pressure column chromatography (eluent: ethyl acetate/hexane = 50/50 to 100% ethyl acetate. For 3j, eluent: methanol/chloroform = 50/50). The structures of the products were confirmed by 1H NMR (400 MHz) and 13C NMR (100 MHz, DMSO-d6). The analytical and spectral data of compounds 3a-e, 3f, 3g, 3h and 3j were in agreement with literature reports. The product 3i was characterized as follows.
