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.

Keywords

Chemoselective reduction - Indole-maleimide - Oxindole-ester - Zn-TiCl₄ - Electron-deficient alkenes - Late-stage functionalization

Publication History

Received: 14 October 2025

Accepted after revision: 12 November 2025

Article published online:
09 December 2025

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