The molecular structure and chemical reactivities of the condensation products of o-substituted benzylidenacetylacetone with hydrazine dihydrochloride

Reaction of o-nitrobenzylideneacetylacetone (1a) with hydrazine dihydrochloride in methanol gave 4-(α-methoxy-o-nitrobenzyl)-3,5-dimethylpyrazole hydrochloride (4a), whose structure was unambigously confirmed by an X-ray crystallographic analysis, via 4-(o-nitrobenzylidene)-3,5-dimethylisopyrazole (2a). Compound 2a was synthesized by condensation of 1a with hydrazine dihydrochloride in acetonitrile. Analogously the corresponding o-chloro derivatives (2b, 4b) were obtained. These were converted to N-methyl (6b) and N-acetyl (7a,b) derivatives and the behaviors on bromination and pyrolysis were investigated.