One-pot synthesis of quinazolin-4(3 H )-ones and fused quinazolinones by a palladium-catalyzed domino process

Abstract An efficient one-pot synthesis of quinazolin-4(3 H )-ones, benzoimidazo[2,1- b ]quinazolin-12(6 H )-ones and imidazo[2,1- b ]quinazolin-5(1 H )-ones via a palladium-catalyzed domino process has been developed. The Pd-catalyzed reactions of 2-azidobenzamides 1 with isocyanides 2 produced quinazolin-4(3 H )-ones 4  at room temperature by a domino Pd-catalyzed cross-coupling/carbodiimide-mediated cyclization. However, as 2-azido- N -(2-bromophenyl)benzamides 1 were used under heating condition in the presence of Cs 2 CO 3 , the benzoimidazo[2,1- b ]quinazolin-12(6 H )-ones 5 were directly obtained by twice Pd-catalyzed domino cyclization. A domino reogioselective 5 -exo-dig intramolecular cyclization reaction of alkynyl-containing azides 6 with isocyanides 2 generated imidazo[2,1- b ]quinazolin-5(1 H )-ones 9 in 74–93% yields in the presence of catalyst Pd(PPh 3 ) 4 and K 2 CO 3 .