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Updated: May 31, 2026

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Revisiting keteniminium salts: more than the nitrogen analogs of ketenes
Claire Madelaine1, Viviana Valerio, Nuno Maulide
1Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany.
Abstract:
Keteniminium salts are powerful electrophilic heterocumulene reagents well-known for their selectivity and stereocontrol in [2+2] cycloadditions to olefins and carbonyl derivatives. Furthermore, they are readily accessible from stable and simple precursors under a variety of different conditions. Herein, we present the chemistry of keteniminium salts with the hindsight of time, describe preparation methods, recent [2+2] chemistry, mechanistic studies, and assorted applications that significantly extend the scope of utility of these unique electrophilic heterocumulenes.
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