Silver(I)-Catalyzed Regioselective Synthesis of Triazole Fused-1,5-Benzoxazocinones

Abstract

An efficient and regioselective synthesis of novel 1,2,3-triazole-fused-1,5-benzoxazocinones through intramolecular cyclization of substituted ethynyl triazoyl benzoic acids was explored. A crucial precursor 5-iodo-1,2,3-triazole benzoate was obtained from substituted 2-azido benzoic acid esters in a single step through a Copper-Catalyzed Azide-Alkyne Cycloaddition (CuAAC) reaction using a CuI/NBS catalytic system. A carbon carbon triple bond was installed through a Sonogashira coupling reaction by various terminal alkynes. Finally, the 1,4,5-substituted ethynyl triazoyl benzoic acids were cyclized by a AgOTf-mediated intramolecular cyclization to afford 8-endo-dig 1,2,3-triazole-fused-1,5-benzoxazocinones exclusively.