Synthesis of 5-amino-4, 5-dihydropyrazolo [3,4-d] pyrimidin-4-ones and related isomeric systems. Part I. Synthesis and characterization of potential intermediates

Article abstract of DOI:10.1016/S0040-4020(01)83459-1

Reactions between aminopyrazole-4-carboxylic acids derivatives and orthoesters or amide acetals lead, in most cases, to the introduction of a heteroalkylidene moiety on the amino group of ethyl aminopyrazole-4-carboxylates and on the β-hydrazide nitrogen atom of aminopyrazole-4-carboxhydrazides. Several factors governing the course of these reactions are discussed.