Unexpected Reaction Course of 3‐Amino‐5‐aryl‐1H‐pyrazoles with Dialkyl Dicyanofumarates |
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| Authors: | Korany A. Ali Eman A. Ragab Grzegorz Mlostoń Małgorzata Celeda Anthony Linden Heinz Heimgartner |
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| Affiliation: | 1. Applied Organic Chemistry Department, National Research Centre, Dokki, Cairo‐12622, Egypt;2. Chemistry Department, Faculty of Science, Cairo University, Cairo‐12613, Egypt;3. University of ?ód?, Department of Organic and Applied Chemistry, Tamka 12, PL 91‐403 ?ód?, (phone: +48‐42‐6355761;4. fax: +48‐42‐6655162);5. Institute of Organic Chemistry, University of Zürich, Winterthurerstrasse 190, CH‐8057 Zürich, (phone: +41‐44‐6354282;6. fax: +41‐44‐6356812) |
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| 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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| Keywords: | Pyrazolo[3,4‐b]pyridine‐4‐carboxylates Pyrazolo[1,5‐a]pyrimidine‐5,6‐dicarboxylates Michael addition Lactamization X‐Ray crystallography |
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