Iodine-Catalyzed, Stereo- and Regioselective Synthesis of 4-Arylidine-4H-benzo[d][1,3]oxazines and their Applications for the Synthesis of Quinazoline 3-Oxides

4-Benzylidene-2-aryl-4H-benzo[d][1,3]oxazines have been synthesized with high stereoselectivity and regioselectivities from 2-alkynylbenzamides in the presence of a catalytic amount of I-2. In the reaction mechanism, iodine plays a key role in two different aspects as a catalyst, such as to activate the alkyne with the iodinium donor which triggers the cascade, and then as a proper acid source to facilitate catalyst recovery. The benzoxazines have been exploited as potential substrates for the synthesis of quinazoline 3-oxide derivatives directly in one step.