The Synthesis of 1,3,4-Thiadiazoles, 1,3,4-Selenadiazoles and Pyrazolo[3,4-d]pyrimidine Derivatives: Utility of hydrazonoyl bromide and DFT study

Abstract

1,3,4-Selenadiazoles and 1,3,4-thiadiazolese, were synthesized from the reaction of hydrazonoyl bromide with potassium thiocyanate and potassium selenocyanate, respectively. Also, treatment of hydrazonoyl bromide with malononitrile gave pyrazole-4-carbonitrile derivatives which reacted with formic acid, and formamide to produce the respective pyrazolo[3,4-d]pyrimidines. Elemental analyses, alternative synthesis procedures, and spectrum data were used to confirm the structures of the novel compounds. We studied the 1,3-dipolar cycloaddition reaction mechanism of these reactions using the density functional theory (DFT) method at the B3LYP/6–311++G** level of theory. The product formation was explained experimentally by calculations involving natural bond orbitals (NBO) and frontier molecular orbitals (FMO). The results of this study are consistent with the proposed experimental mechanism.