Facile synthesis of tricyclic isoxazole-fused benzo[b]thiophene 1,1-dioxide derivatives via 1,3-dipolar cycloaddition

Abstract A facile and efficient [3+2] 1,3-dipolar cycloaddition reaction of nitrile oxides generated in situ from hydroximoyl chlorides with benzo[b]thiophene 1,1-dioxides has been achieved for rapid access to tricyclic isoxazole-fused benzo[b]thiophene 1,1-dioxide derivatives in excellent yields (up to 98%) with high diastereoselectivities (dr >19:1). The present process is characterized by mild reaction conditions and broad substrate scope. The conversion of the cycloadduct to other useful structure has also been achieved. The chemical structures of the typical compounds were confirmed by X-ray single-crystal structure analysis.