Tetrazole and Azido Derivatives of Pyrimidine: Synthesis, Mechanism, Thermal Behaviour & Steering of Azido–Tetrazole Equilibrium

A new family of pyrimidine modified tetrazole & azido derivatives (1-16) was developed using the conventional and nucleophilic substitution methods. The 1H-tetrazol-1-yl)pyrimidine (1-10) compounds were prepared via traditional cycloaddition and condensation method. The compounds tetrazolo[1,5-a]pyrimidine (11 a,12 a, and 13 a), azido-(1H-tetrazol-1-yl)pyrimidine (14 a and 15 a) and tetrazolo[1,5-c]pyrimidine (16 a) were synthesized by simultaneously introducing conventional and nucleophilic substitution approaches. The latter technique was easy to process and reduce the synthesis time. The factors (solvent, temperature, steric effect, electron-donating groups, and electron-withdrawing groups) were found responsible for steering the azido-tetrazole equilibrium in the compounds 11 a, 12 a, 13 a, and 16 a. All the prepared compounds were well characterized including single-crystal X-ray diffraction structures of 1, 3, 4, 6, 8, 10, 11 a, 12 a, 13 a, 14 a, 15 a, and 16 a. Thermal behaviour was investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The current work is significant to the development of a new class of pyrimidine modified tetrazole and azido derivatives in sense of easy reaction approach, good to excellent yields, safe process, and simple work-ups.