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Ring Closure Reactions of 4-Chloro-5-hydroxyalkylamino-6-nitro-3(2H)- pyridazinones: Synthesis of Novel Pyridazino-Fused Ring Systems
1 , 1 , 2 , 3 , 3 , * 1
1  Institute of Organic Chemistry, Semmelweis University, 1092 Budapest, Hõgyes Endre utca 7, Hungary
2  Institute of Pharmaceutical Chemistry, University of Szeged, 6720 Szeged, Eötvös utca 7, Hungary
3  Department of Theoretical Chemistry, Eötvös Lóránd University, 1117 Budapest, Pázmány Péter sétány 1, Hungary

Abstract: Cyclization of the title compounds may occur in various ways (e.g., with the participation of C-6 or C-4 atom of the pyridazinone ring) to form differently fused pyridazino ring systems. The regiochemistry was found to be particularly dependent on the length of the side chain: from the hydroxyethylamino derivatives pyridazino[3,4-b]oxazines, and from hydroxypropylamino derivatives pyridazino[3,4-b]oxazepine and pyridazino[4,5-b]oxazepine systems were formed.
Keywords: 4-chloro-5-hydroxyalkylamino-6-nitro-3(2H)-pyridazinone; pyridazino[3,4-b] oxazepines; pyridazino[4,5-b]oxazepines.