Selectivities in the formation of pyridines and pyrimidines by ammonia-induced cyclocondensations of vinamidiniums

Balasubrahmanyam, Natarajan S and Jeyashri, Bommuswamy and Namboothiri, Irishi Narayanan N (1994) Selectivities in the formation of pyridines and pyrimidines by ammonia-induced cyclocondensations of vinamidiniums. In: Tetrahedron, 50 (27). pp. 8127-8142.

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Abstract

Arylvinamidines (2-, 3- or 4-aryl-4-(N,N-dimethyl)amino-1-azabuta-1,3-dienes), generated from 1,1,5,5-tetramethyl-2- or -3-phenyl-1,5-diazapentadienium salts, cyclocondense orientation-specifically under two regioselections forming 1-4' + 4-3' and 1-2' + 4-1' bonds on exposure to ammonia. The initial cyclates aromatise eliminatively to give mixtures of diarylpyridines and arylpyrimidines. The 2-arylvinamidines do not participate as 2-centre reactants and their 4-aryl isomers not as 4-centre reactants in the cyclocondensations which appear to be stepwise and not concerted. Reasons for the selective participation appear to be that the required eliminations from the initial cyclates are disfavoured in the first case and that a geometric factor prevents cyclate-formation in the second.

Item Type:	Journal Article
Publication:	Tetrahedron
Publisher:	Elsevier science
Additional Information:	Copyright of this article belongs to Elsevier science.
Department/Centre:	Division of Chemical Sciences > Organic Chemistry
Date Deposited:	11 Apr 2011 10:22
Last Modified:	11 Apr 2011 10:22
URI:	http://eprints.iisc.ac.in/id/eprint/36799

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