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, 10min). 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 (32examples), providing a route to access saturated analogs in excellent yields up to 95% and tolerance to other functional moieties: esters and amides. © 2025. Thieme. All rights reserved.