N-Heterocyclic carbene-catalyzed umpolung of imines for the enantioselective synthesis of dihydroquinoxalines

TitleN-Heterocyclic carbene-catalyzed umpolung of imines for the enantioselective synthesis of dihydroquinoxalines
Publication TypeJournal Article
Year of Publication2019
AuthorsDas, TKanti, Ghosh, A, Balanna, K, Behera, P, Gonnade, RG, Marelli, UKiran, Das, AKumar, Biju, AT
JournalACS Catalysis
Volume9
Issue5
Pagination4065-4071
Date PublishedMAY
Type of ArticleArticle
ISSN2155-5435
Keywordsdihydroquinoxalines, imines, N-heterocyclic carbenes, organocatalysis, umpolung
Abstract

N-heterocyclic carbene (NHC) organocatalysis is widely employed for the umpolung of aldehydes and recently to the umpolung of Michael acceptors and aldimines. Described herein is the NHC-organocatalyzed umpolung of aldimines for the enantioselective synthesis of nitrogen heterocycles. The bisimines generated from the condensation of 1,2-phenylenediamines and salicylaldehydes undergo intramolecular cyclization in the presence of a chiral NHC catalyst, resulting in the formation of dihydroquinoxalines in moderate to good yields and er values. Detailed DFT studies shed light on the role of -OH groups in stabilizing the initially generated aza-Breslow intermediates via intramolecular hydrogen bonds. Preliminary photophysical studies on the synthesized dihydroquinoxalines revealed that these molecules can be used for the sensing of various acids and bases.

DOI10.1021/acscatal.9b00737
Type of Journal (Indian or Foreign)Foreign
Impact Factor (IF)11.384
Divison category: 
Center for Material Characterization (CMC)
Organic Chemistry

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