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Paper | Regular issue | Vol 38, No. 9, 1994, pp.2081-2089
Published online, 1st January, 1970
DOI: 10.3987/COM-94-6811
Pyridazines, 71. A Novel Type of 1,2-Diazine Æ 1,2-Diazole Ring Contraction

Gottfried Heinisch, Barbara Matuszczak,* and Kurt Mereiter

*Institute of Pharmaceutical Chemistry, University of Innsbruck, Innrain 52a, A-6020 Innsbruck, Austria


Reaction of the 3,6-dichloro-4-pyridazinecarboxamide derivative (2) with sodium hydride in dimethylformamide does not afford a pyridazino[3,4-b][1,5]benzodiazepine system (3) but results in a ring transformation to give the quinoxalinyl-substituted pyrazole derivative (4). The structure of this unexpected reaction product could be elucidated by means of a crystal structure determination; a mechanistic interpretation of this novel type of a pyridazine → pyrazole ring contraction is proposed.