A convenient and efficient one-pot acid-promoted synthesis of 6-aminopyrazolo[3,4-]pyrimidine has been developed by treatment of 1-pyrazol-5-yl-,-dimethylformamidines or 5-amino-1-pyrazole-4-carbaldehydes with cyanamide (NHC≡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-]pyrimidines in this method. Moreover, our proposed mechanism was confirmed in this study, which demonstrates that -[(5-amino-1,3-diaryl-1-pyrazol-4-yl)methylene]cyanamide is the intermediate.
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