One-Pot Acid-Promoted Synthesis of 6‑Aminopyrazolopyrimidines from 1H‑Pyrazol-5-yl‑N,N‑dimethylformamidines or 5‑Amino‑1H‑pyrazole-4-carbaldehydes with Cyanamide

A convenient and efficient one-pot acid-promoted synthesis of 6-aminopyrazolo­[3,4-d]­pyrimidine has been developed by treatment of 1H-pyrazol-5-yl-N,N-di­methyl­formamidines or 5-amino-1H-pyrazole-4-carbaldehydes with cyanamide (NH2CN) in an acid-mediated solution. This synthetic route involves four steps of deprotection, imination, the key acid-promoted heterocyclization, and aromatization. On the basis of optimized studies, methanesulfonylchloride is considered to be the best solvent. Furthermore, the microwave-assisted synthetic technique was also carried out to improve the major product 6-aminopyrazolo­[3,4-d]­pyrimidines in this method. Moreover, our proposed mechanism was confirmed in this study, which demonstrates that N-[(5-amino-1,3-diaryl-1H-pyrazol-4-yl)­methylene]­cyanamide is the intermediate.