Ultrasound‐Promoted Catalyst‐Free Synthesis of 2,2′‐(1,4‐Phenylene)bis[1‐acetyl‐1,2‐dihydro‐4H‐3,1‐benzoxazin‐4‐one] Derivatives

Abstract A convenient approach to 2,2′‐(1,4‐phenylene)bis[1‐acetyl‐1,2‐dihydro‐4 H ‐3,1‐benzoxazin‐4‐one] derivatives 4 was explored employing the one‐pot condensation of anthranilic acids (=2‐aminobenzoic acids) 1 with terephthalaldehyde (=benzene‐1,4‐dicarboxaldehyde; 2 ) under ultrasound‐irradiation conditions ( Scheme 1 ). The reactions proceeded smoothly in the presence of excess Ac 2 O in the absence of any other catalyst and solvent to afford the respective products in high yields.