Synthesis of Aminopyridazines from Aminocyclopropenylium Salts and Diazomethyl Compounds [1] |
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Authors: | Heinrich Heydt Philipp Eisenbarth Karin Feith Klaus Urgast Gerhard Maas Manfred Regitz |
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Affiliation: | Fachbereich Chemie der Universität Kaiserslautem, Erwin-Schrödinger-Strasse, D-6750 Kaiserslautem, FRG |
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Abstract: | Amino-substituted cyclopropenylium salts ( 11a,b ) react with diazomethyl compounds ( 12a-i ) in dichloromethane or acetonitrile in the presence of a base (ethyldiisopropylamine, 1,5-diazabicyclo[4.3.0] non-5-ene) to form 4-aminopyridazines ( 13a-i ) specifically. The reaction is interpreted in terms of an initial electrophilic diazoalkane substitution to give diazomethylcyclopropenes ( 11 + 12 → 14 ) which undergo a [1.5]-cyclisation to form the betaines 16 which, in turn, isomerise with opening of the bridging bond to give the aminopyridazines 13 . In a similar manner, the tris[amino] cyclopropenylium salts 8a,b and 10a-c are converted to the 3,4,5-tris[amino]-pyridazines ( 21a-k ) by treatment with diazomethyl compounds ( 12a, c-f ). |
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