Synthesis,structure, and properties of pyrazolo[4,3-b]quinuclidine derivatives

It was shown by means of ¹H and ¹³C NMR spectroscopy that the reaction of 2-arylmethylene-3-oxoquinuclidines with hydrazine hydrate gives 4a-hydroxy-7-aryl-4a,5,7,7a-tetrahydropyrazolo4,3-b]quinuclidines, which are stable in the crystalline state but undergo dehydration to the corresponding 7-aryl-6H-7,7a-dihydropyrazolo4,3-b]quinuclidines in solutions. The latter undergo cleavage to 3-(4-piperidyl)-5-arylpyrazoles when they are heated in an alkaline medium.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1248–1256, September, 1985.