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Updated: Sep 24, 2025

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Transition metal-free functionalization of 2-oxindoles via sequential aldol and reductive aldol reactions using
Sivaparwathi Golla1, Swathi Jalagam1, Soumya Poshala1
1Department of Chemistry, National Institute of Technology Warangal, Warangal, Telangana-506004, India. harikokatla@nitw.ac.in.
Abstract:
A sequential one-pot classical aldol, transition-metal and hydride-free reductive aldol reaction is reported here for C(sp3)- H functionalization of 2-oxindoles using the multifaceted reagent rongalite. Here, rongalite functions as a hydride-free reducing agent and double C1 unit donor. This protocol enables the synthesis of a wide range of 3-methylindoline-2-ones and 3-(hydroxymethyl)-3-methylindolin-2-ones from 2-oxindoles (65-95% yields), which are the synthetic precursors for many natural products. Some of the important aspects of this synthetic approach include one-pot methylation and hydroxymethylation, low-cost rongalite (ca. $0.03 per 1 g), mild reaction conditions and applicability to gram-scale synthesis.
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