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N‐Heterocyclic Carbene‐Catalyzed Formal [6+2] Annulation Reaction via Cross‐Conjugated Aza‐Trienolate Intermediates
Author(s) -
Balanna Kuruva,
Madica Krishnaprasad,
Mukherjee Subrata,
Ghosh Arghya,
Poisson Thomas,
Besset Tatiana,
Jindal Garima,
Biju Akkattu T.
Publication year - 2020
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.201905177
Subject(s) - annulation , conjugated system , chemistry , electrophile , carbene , organocatalysis , fulvene , catalysis , combinatorial chemistry , reactivity (psychology) , stereochemistry , organic chemistry , enantioselective synthesis , polymer , medicine , alternative medicine , pathology
The diverse reactivity of N‐heterocyclic carbenes (NHCs) in organocatalysis is due to the possibility of different modes of action. Although NHC‐bound enolates and dienolates are known, the related NHC‐bound cross‐conjugated aza‐trienolates remain elusive. Herein, we demonstrate the NHC‐catalyzed formal [6+2] annulation of nitrogen‐containing heterocyclic aldehydes with α,α,α‐trifluoroacetophenones leading to the formation of versatile pyrrolooxazolones (29 examples). The catalytically generated cross‐conjugated aza‐trienolates (aza‐fulvene type) underwent smooth [6+2] annulation with electrophilic ketones to afford the product in moderate to good yields under mild conditions. Preliminary DFT studies on the mechanism are also provided.