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Unexpected Reaction Course of 3‐Amino‐5‐aryl‐1 H ‐pyrazoles with Dialkyl Dicyanofumarates
Author(s) -
Ali Korany A.,
Ragab Eman A.,
Mlostoń Grzegorz,
Celeda Małgorzata,
Linden Anthony,
Heimgartner Heinz
Publication year - 2013
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.201200633
Subject(s) - chemistry , aryl , pyrimidine , nucleophile , medicinal chemistry , pyridine , boiling , stereochemistry , michael reaction , organic chemistry , catalysis , alkyl
On treatment of 3‐amino‐5‐aryl‐1 H ‐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‐1 H ‐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 NH 2 group, and subsequent HCN elimination and cyclization. The structures of the products have been established by X‐ray crystallography.