Reactions of methyl 2-(benzyloxycarbonyl)amino-3-dimethylaminopropenoate and related compounds with hydrazines. Regiospecific synthesis of 1-substituted-4-amino-substituted-1H-pyrazol-5-(2H)-ones †

In this paper the regiospecific transformations of methyl 2-(benzyloxycarbonyl)amino-3-dimethylaminopropenoate (1) with hydrazine, alkyl-, aryl- and heteroaryl-substituted hydrazines via the corresponding hydrazones 12-16 into pyrazoles 17-25 are described. Heteroaryl-substitued hydrazones 13-16 afforded by oxidation with bromine or lead tetraacetate the corresponding substituted (1,2,4-triazolo[4,3-b]pyridazin-3-yl)glycinates 27-30. Alkyl 2-(2,2-disubstituted-1-ethenyl)amino-3-dimethylaminopropenoates 31-33 gave with hydrazines alkyl 2-[2,2-(disubstituted)ethenyl]amino-3-heteroarylhydrazonopropanoates 40-48 and 2-alkyl 2,3-bis((hetero)arylhydrazono)propanoates 51-55.