N-Heterocyclic Carbene-Catalyzed Umpolung of Imines for the Enantioselective Synthesis of Dihydroquinoxalines

Das, Tamal Kanti and Ghosh, Avik and Balanna, Kuruva and Behera, Pradipta and Gonnade, Rajesh G and Marelli, Udaya Kiran and Das, Abhijit Kumar and Biju, Akkattu T (2019) N-Heterocyclic Carbene-Catalyzed Umpolung of Imines for the Enantioselective Synthesis of Dihydroquinoxalines. In: ACS CATALYSIS, 9 (5). pp. 4065-4071.

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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.

Item Type:	Journal Article
Publication:	ACS CATALYSIS
Publisher:	AMER CHEMICAL SOC
Additional Information:	The copyright for this article belongs to AMER CHEMICAL SOC
Keywords:	N-heterocyclic carbenes; organocatalysis; umpolung; imines; dihydroquinoxalines
Department/Centre:	Division of Chemical Sciences > Organic Chemistry
Date Deposited:	20 Jun 2019 18:31
Last Modified:	21 Jun 2019 07:25
URI:	http://eprints.iisc.ac.in/id/eprint/62790

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