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- Title
Temporary Intramolecular Generation of Pyridine Carbenes in Metal-Free Three-Component CH Bond Functionalisation/Aryl-Transfer Reactions.
- Authors
Nawaz, Faisal; Mohanan, Kishor; Charles, Laurence; Rajzmann, Michel; Bonne, Damien; Chuzel, Olivier; Rodriguez, Jean; Coquerel, Yoann
- Abstract
Nucleophilic addition of pyridines to benzyne generates zwitterionic adducts that evolve by a rapid intramolecular proton shift to produce the corresponding pyridine carbenes, N-phenyl pyrid-2-ylidenes. In the presence of electrophilic ketones (isatin derivatives), the pyridylidenes can further react by an original bis-arylation reaction of the carbonyl compounds involving a formal pyridine CH bond functionalisation. The overall transformation is an unprecedented three-component reaction featuring a carbene intermediate. The mechanism of this transformation was examined in detail by using both experimental and theoretical approaches. It was found that the generation of N-phenyl pyrid-2-ylidene from pyridine and benzyne is energetically favoured, and that the corresponding carbene dimer can also form easily. Under the three-component reaction conditions, the pyridylidene preferentially adds to the ketone group of the isatin derivative to produce a zwitterionic adduct amenable to an intramolecular aryl transfer reaction by a concerted nucleophilic aromatic substitution. This peculiar reactivity for a carbene was compared to possibly competitive known reactions of stable carbenes with carbonyl compounds, and the reaction was found to be under thermodynamic control. The reported method of generation of N-phenyl pyrid-2-ylidenes and their reactivity with carbonyl compounds unlock new perspectives in organic synthesis.
- Subjects
NUCLEOPHILIC addition (Chemistry); PYRIDINE synthesis; CARBENE synthesis; ARYLATION; AROMATIC compounds spectra; PHENYL compounds; KETONE synthesis
- Publication
Chemistry - A European Journal, 2013, Vol 19, Issue 51, p17578
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.201303359