Molybdenum-catalyzed deoxygenative heterocyclization of 2-nitroazobenzenes: a novel strategy for catalytic synthesis of 2-aryl-2 H -benzo[ d ][1,2,3]triazoles.

A novel strategy for the catalytic synthesis of 2-aryl-2 H -benzo[ d ][1,2,3]triazoles bearing a wide range of functional groups in good to excellent yields by non-noble molybdenum-catalyzed deoxygenative heterocyclization of 2-nitroazobenzenes is described. The salient features of the transformation include the use of readily available substrates, valuable products and ease of scale-up. The mechanistic study indicates that the reaction occurred via double deoxygenation by the Mo(VI)/Mo(IV) catalytic cycle from 2-nitroazobenzene, through the formation of 2-aryl-2 H -benzo[ d ][1,2,3]triazole- N 1 -oxide or nitrene intermediates.