Stereoselective ring opening of dimethyl 5-aryl-2,3-dihydro-3,3-dimethyl-1- oxo-1H,5H-pyrazolo[1,2-a]pyrazole-6,7-dicarb oxylates with hydrazine hydrate. Synthesis of rel-(4′R,5′S)-3-[5-aryl-3,4-bis(hydrazino-carbonyl)]-4, 5-dihyd ro-1H-pyrazol-1-yl)-3-methylbutano-hydrazides

Abstract

Reactions of dimethyl 5-aryl-2,3-dihydro-3,3-dimethyl-1-oxo-1H,5H- pyrazolo[1,2-a]pyrazole-6,7-dicarboxylates 3a-e with excess of hydrazine hydrate gave propanohydrazides 5a-e in 70-99% yields. The ring opening of pyrazolo[1,2-a]pyrazole-6,7-dicarboxylates 3a-e proceeded stereoselectively, furnishing the rel-(4′R,5′S)-isomers of 3-[5-aryl-3,4- bis(hydrazinocarbonyl)-4,5-dihydro-1H-pyrazol-1-yl)-3-methyl-butanohydrazides 5a-e. The X-ray structure of 5a was determined.