Synthesis of 2-Tetrazolyl-Substituted 3-Acylpyrroles via a Sequential Ugi-Azide/Ag-Catalyzed Oxidative Cycloisomerization Reaction.

A new efficient Ag-catalyed cascade cycloisomerization/aerobic oxidation reaction of a Ugi-azide adduct for the preparation of 3-acylpyrroles using molecular oxygen as the terminal oxidant has been developed. A series of 2-tetrazolyl-substituted 3-acylpyrroles were obtained in 62-89% yields from readily available enynals 1, primary amines 2, isocyanides 3, and trimethylsilyl azide 4 in the presence of a catalytic amount of AgNO3 and DMAP under an O2 atmosphere.