Experimental and theoretical study of the acylation reaction of aminopyrazoles with aryl and methoxymethyl substituents

Abstract As a result of the chain of transformations from 1,3-butanedione with aryl and methoxy substituents through nitrosation and cyclization with hydrazine, the corresponding nitrosopyrazoles and aminopyrazoles were synthesized. According to this scheme, eight new previously unknown compounds were obtained. Their structures were established by the methods of IR, UV, 1 H NMR, 13 C NMR spectroscopy and mass spectrometry. DFT method of quantum-chemical calculations showed that obtained aminopyrazoles can exist as two tautomers; it was also confirmed by NMR 1 H spectroscopy data. In the case of acylation, an isomer is formed, where aryl substituent takes place in the fifth, rather than in the third position of the pyrazole ring, as shown by the DFT calculations.