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Updated: Oct 5, 2025

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
NHC Catalysis for Umpolung Pyridinium Alkylation via Deoxy-Breslow Intermediates
Terence Wu1, Matthew R Tatton2, Michael F Greaney1
1School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
Abstract:
Umpolung N-heterocyclic carbene (NHC) catalysis of non-aldehyde substrates offers new pathways for C-C bond formation, but has proven challenging to develop in terms of viable substrate classes. Here, we demonstrate that pyridinium ions can undergo NHC addition and subsequent intramolecular C-C bond formation through a deoxy-Breslow intermediate. The alkylation demonstrates, for the first time, that deoxy-Breslow intermediates are viable for catalytic umpolung of areniums.
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