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

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.