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Unexpected reaction course of 3-Amino-5-aryl-1H-pyrazoles with Dialkyl Dicyanofumarates


Ali, Korany A; Ragab, Eman A; Mloston, Grzegorz; Celeda, Malgorzata; Linden, Anthony; Heimgartner, Heinz (2013). Unexpected reaction course of 3-Amino-5-aryl-1H-pyrazoles with Dialkyl Dicyanofumarates. Helvetica Chimica Acta, 96(4):633-643.

Abstract

On treatment of 3-amino-5-aryl-1H-pyrazoles 1 with dialkyl dicyanofumarates (=(E)-but-2-enedioates) 4 in boiling 1,2-dichloroethane, two competitive reactions occurred leading to 3-aryl-5-cyano-6,7-dihydro-6-oxo-1H-pyrazolo[3,4-b]pyridine-4-carboxylates 10 and 7-amino-2-arylpyrazolo[1,5-a]pyrimidine-5,6-dicarboxylates 11. In DMF at room temperature, as well as at 100°, only compounds 10 were isolated. The formation of the major products of type 10 was rationalized via Michael addition of 1 as a C(4)-nucleophile onto 4, followed by HCN elimination and lactamization. On the other hand, the minor products 11 result from a Michael addition of 1 onto 4 via the NH2 group, and subsequent HCN
elimination and cyclization. The structures of the products have been established by X-ray crystallography.

Abstract

On treatment of 3-amino-5-aryl-1H-pyrazoles 1 with dialkyl dicyanofumarates (=(E)-but-2-enedioates) 4 in boiling 1,2-dichloroethane, two competitive reactions occurred leading to 3-aryl-5-cyano-6,7-dihydro-6-oxo-1H-pyrazolo[3,4-b]pyridine-4-carboxylates 10 and 7-amino-2-arylpyrazolo[1,5-a]pyrimidine-5,6-dicarboxylates 11. In DMF at room temperature, as well as at 100°, only compounds 10 were isolated. The formation of the major products of type 10 was rationalized via Michael addition of 1 as a C(4)-nucleophile onto 4, followed by HCN elimination and lactamization. On the other hand, the minor products 11 result from a Michael addition of 1 onto 4 via the NH2 group, and subsequent HCN
elimination and cyclization. The structures of the products have been established by X-ray crystallography.

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Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:April 2013
Deposited On:17 Apr 2013 08:36
Last Modified:05 Apr 2016 16:44
Publisher:Wiley-Blackwell
ISSN:0018-019X
Funders:Faculty of Chemistry, University of Lodz
Publisher DOI:https://doi.org/10.1002/hlca.201200633

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