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N‐Heterocyclic Carbenes as Key Intermediates in the Synthesis of Fused, Mesoionic, Tricyclic Heterocycles
Author(s) -
Benaissa Idir,
Pallova Lenka,
Morantin MarieEmilie,
Lafitte Thomas,
Huynh Mathieu,
Barthes Cécile,
Vendier Laure,
Lugan Noël,
Bastin Stéphanie,
César Vincent
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201903242
Subject(s) - mesoionic , chemistry , pyridinium , moiety , carbene , nucleophile , cationic polymerization , combinatorial chemistry , malonate , nucleophilic aromatic substitution , nucleophilic substitution , bicyclic molecule , stereochemistry , medicinal chemistry , organic chemistry , catalysis
Coupling between 5‐bromoimidazo[1,5‐ a ]pyridinium salts and malonate or arylacetate esters leads to a facile and straightforward access to the new mesoionic, fused, tricyclic system of imidazo[2,1,5‐ cd ]indolizinium‐3‐olate. Mechanistic studies show that the reaction pathway consists of nucleophilic aromatic substitution on the cationic, bicyclic heterocycle by an enolate‐type moiety and in the nucleophilic attack of a transient free N‐heterocyclic carbene (NHC) species on the ester group; the relative order of these two steps depends on the nature of the starting ester. This work highlights the valuable implementation of free NHC species as key intermediates in synthetic chemistry, beyond their classical use as stabilizing ligands or organocatalysts.