Synthesis of 5-Substituted 3-Amino-1H-Pyrazole-4-Carbonitriles as Precursors for Microwave Assisted Regiospecific Syntheses of Pyrazolo15-aPyrimidines

摘要

A simple route to 3-oxoalkanonitrile >5, a precursor of the title compounds is described. Reaction of enaminones >2 with hydroxylamine hydrochloride in ethanol yielded aldoximes >3 that were converted readily into >5 in basic medium. This method has been successfully applied with a number of substrates and resulted in excellent yields of the products. Reacting >5 with trichloroacetonitrile afforded 3-amino-2-aroyl-4,4,4-trichloro-2-butenenitriles >6 that condensed with hydrazines to yield 3-amino-1H-pyrazole-4-carbonitrile derivatives >8. Substituted pyrazolo[1,5-a]pyridmidines have been prepared with regioselective condensation reactions of >8 with nonsymmetrical dielectrophiles. The structures of compounds obtained were deduced based on ¹H-NMR, ¹H-¹⁵N HMBC- measurements.