Synthesis, characterization and corrosion inhibition of Pyrazolo[1,5-a][1,8]naphthyridine, Pyrazolo[1,5-a]pyridine and Pyrazolo[1,5-a]pyrimidine derivatives, quantum chemical approach

Abstract

The behavior of 3-amino-5-cyanomethyl-1H-pyrazole-4-carbonitrile 1 towards some electrophiles such as arylidens, enamines is reported to afford pyrazolo[1,5-a][1,8]naphthyridine derivative 4, pyrazolo[1,5-a]pyridine derivatives 8, 10 and pyrazolo[1,5-a]pyrimidine derivatives 12a,b and 14. Also, reaction of pyrazole 1 with DMFDMA afforded enamine 16 which reacts with hydrazine hydrate and malononitrile to give tricyclic compound 17 and pyrazolo[1,5-a]pyrimidine derivative 18 respectively. The inhibition effect of tested compounds at 1.0 M H2SO4 was investigated by Potentiodynamic polarization. The data revealed that, as the concentration of inhibitors increased from 100 to 500 ppm the inhibition efficiencies increased. The sequence of the inhibition efficiencies increased for the tested compounds arranged as 4, 12b, 8, 14, 10 and 12a respectively. Quantum chemical calculation gives approval to the experimental data and the theoretical data is good agreement with experimental data.