Chemoselective Reduction of Conjugated Indole-maleimides and Oxindole-esters via Zn/TiCl₄-Assisted Unified Approach

Abstract Chemoselective reduction of electron-deficient alkenes incorporated within structurally diverse heterocyclic frameworks, such as indole-tethered maleimide and oxindole-based unsaturated esters, is disclosed using a Zn/TiCl₄-catalyzed quick protocol (0 °C, 10 min). The reducing agent Zn/TiCl₄ offers a non-hydrogenative, metal-economical strategy that demonstrates excellent chemoselectivity and suggests potential applicability toward late-stage functionalization. The protocol exhibited broad substrate scope (32 examples), providing a route to access saturated analogs in excellent yields up to 95% and tolerance to other functional moieties: esters and amides.