The synthesis of 3-substituted 4(3H)-quinazolinones from anthranilic acid, orthoesters, and amines in the presence of ceric ammonium nitrate has been studied. The reaction occurred in a few minutes at room temperature under solvent-free conditions and in excellent yields. The probable conversion mechanism has been discussed.One of the most frequently encountered heterocyclic compounds in medicinal chemistry is 4(3H)-quinazolinone, which exhibits interesting pharmacological activities. A series of methods has been developed previously for the synthesis of 3-substituted 4(3H)-quinazolinones from anthranilic acid, orthoesters, and amines in the presence of various catalysts [1][2][3][4][5][6][7][8]. The drawbacks of these methods are expensive catalyst, high temperature (60-80 o C), long reaction time (20 h), etc. In addition, anilines having strong electron-withdrawing substituents, e.g., Cl and NO 2 , gave generally no products at room temperature in previous reports. Hence, it was of interest to develop a more universal method for the synthesis of these products.During the course of our studies towards the development of green catalytic processes, we found that ceric ammonium nitrate (CAN) as an inexpensive and commercially available catalyst can efficiently catalyze one-pot synthesis of 3-substituted 4(3H)-quinazolinones 4 via triple-component condensation of anthranilic acid 1, orthoesters 2, and amines 3 (Scheme 1). The reaction was carried out under solvent-free conditions at room temperature. The triple-component interaction has been studied in the present work with the aim of extending the scope of reactants and of clarifying the mechanism.First, a blank experiment with anthranilic acid, triethyl orthoformate, and aniline in the absence of a catalyst was investigated. The result showed that only 5% product was obtained after 1 h. Then the scope and limitations of the condensation of anthranilic acid 1, triethyl or trimethyl orthoformate 2, and different substituted arylamines or alkylamine 3 catalyzed by CAN were studied; the results are shown in Table 1. All the reactions proceeded smoothly at room temperature. Both triethyl orthoformate and trimethyl orthoformate