Divergent Synthesis of [3,4]-Fused 3-Alkenyl-Oxindoles via Propargyl Alcohol-Triggered C(sp³)–H Functionalization

Abstract

[3,4]-Fused oxindoles are the core structures of the naturally occurring oxindole alkaloids, and the fused tricyclic structures have distinguished themselves with unique biological activities. Herein, we developed a synthetic strategy for divergent synthesis of diverse types of [3,4]-seven- or six-membered ring-fused 3-alkenyl-oxindoles incorporating benzazepine and significant building blocks from propargyl alcohols via the cascade nucleophilic substitution/site-selective hydride transfer/cyclization process unprecedentedly. In addition, a variety of nucleophiles, including H2O, were available for controllable construction of a wide range of conjugated alkenes, conjugated ketones, and allyl alcohols encompassing natural products and pharmaceutical motifs with the utilization of 4-amine substituted isatins and widespread terminal alkyne-derived propargyl alcohols. Furthermore, the synthetic utility of the methodology and mechanistic studies also were well presented.