Synthesis, annulation, and heterofunctionalization of 4-hydrazinylpyrazolo[1,5-a]pyrazines

4-Hydrazinylpyrazolo[1,5-a] pyrazines were obtained by reactions of 4-chloropyrazolo[1,5-a] pyrazines with hydrazine hydrate and further combined with compounds having one reactive site (triethyl orthoformate, acetic anhydride, ethyl chloroformate, phenyl isothiocyanate, hydrazoic acid) or two reactive sites (diethyl oxalate), forming the respective derivatives containing fused 1,2,4-triazole, tetrazole, or 1,2,4-triazine rings. The reactions with acetylacetone and ethoxymethylene derivatives of malononitrile or ethyl cyanoacetate were used to synthesize 4-(1-pyrazolyl)-substituted pyrazolo[1,5-a] pyrazines.