A. Maqestiau, J. V. Eynde
1987
Citations
0
Influential Citations
6
Citations
Journal
Tetrahedron
Abstract
Abstract Treatment of ethyl (heteroalkylidene)aminopyrazole-4-carboxylates with hydrazine hydrate generally provides a ready synthetic route to 5-amino-4, 5-dihydropyrazolo [3,4-d] pyrimidin-4-ones, although ethyl 5-[(dimethylamino) alkylidene]aminopyrazole-4-carboxylates are unreactive. On the other hand, reactions between aminopyrazole-4-carboxhydrazides and orthoesters or amide acetal are more versatile : we observed formation of isomeric 2-pyrazolyl-1,3,4-oxadiazoles, as major compounds, either from triethyl orthoacetate and 1-methyl-5-aminopyrazole-4-carboxhydrazide or from dimethylacetamide dimethyl acetal and various heterocyclic precursors. The ring closure mechanism is discussed.