N-Heterocyclic carbene-catalyzed umpolung of imines for the enantioselective synthesis of dihydroquinoxalines
Title | N-Heterocyclic carbene-catalyzed umpolung of imines for the enantioselective synthesis of dihydroquinoxalines |
Publication Type | Journal Article |
Year of Publication | 2019 |
Authors | Das, TKanti, Ghosh, A, Balanna, K, Behera, P, Gonnade, RG, Marelli, UKiran, Das, AKumar, Biju, AT |
Journal | ACS Catalysis |
Volume | 9 |
Issue | 5 |
Pagination | 4065-4071 |
Date Published | MAY |
Type of Article | Article |
ISSN | 2155-5435 |
Keywords | dihydroquinoxalines, 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. |
DOI | 10.1021/acscatal.9b00737 |
Type of Journal (Indian or Foreign) | Foreign |
Impact Factor (IF) | 11.384 |
Add new comment