NHC Catalysis for Umpolung Pyridinium Alkylation via deoxy‐Breslow Intermediates

Umpolung NHC (N-heterocyclic carbene) 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 pyridiniums 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.