N‐Heterocyclic Carbene‐Catalyzed Formal [6+2] Annulation Reaction via Cross‐Conjugated Aza‐Trienolate Intermediates
作者:Kuruva Balanna、Krishnaprasad Madica、Subrata Mukherjee、Arghya Ghosh、Thomas Poisson、Tatiana Besset、Garima Jindal、Akkattu T. Biju
DOI:10.1002/chem.201905177
日期:2020.1.16
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
N-杂环卡宾(NHC)在有机催化中的不同反应性是由于可能存在不同作用方式的缘故。尽管已知与NHC结合的烯酸酯和二烯酸酯,但相关的与NHC结合的交叉偶联的氮杂三烯酸酯仍然难以捉摸。在这里,我们证明了NHC催化的含氮杂环醛与[α,α,α-三氟苯乙酮]的正式[6 + 2]环化反应,导致形成通用的吡咯并恶唑酮(29个例子)。催化生成的交叉共轭氮杂三烯酸酯(氮杂富烯型)与亲电子酮进行平稳的[6 + 2]环合,在温和条件下以中等至良好的收率得到产物。还提供了有关该机制的初步DFT研究。