An eco-friendly catalytic route for synthesis of 4-amino-pyrazolo[3,4-d]pyrimidine derivatives by Keggin heteropolyacids under classical heating and microwave irradiation

Various solid acid catalysts such as HY-zeolite, silica-supported sulfuric acid, H3PW12O40, H3PMo12O40, and H3PW12O40/SiO2 have been used for the synthesis of 4-amino–pyrazolo[3,4-d]pyrimidine derivatives from the reaction of 1-substituted-5-amino-4-cyano-pyrazoles and formamid under classical heating and microwave irradiation. The microwave-solid acid combination, leads to a nice and convenient catalytic synthesis of 4-amino-pyrazolo[3,4-d]pyrimidines with much reduced reaction times compared to traditional conditions. Among the above catalysts, heteropolyacid, H3PW12O40 showed the best catalytic activity in term of yields and reaction times.

Graphical abstractReaction of 5-amino-1-phenyl-H-pyrazolo-4-carbonitrile 1(a-e) with formamid was carried out over various solid acid catalysts under reflux and thermal conditions and the results are compared with results of conventional acid catalysts. Among the catalysts studied, heteropolyacids showed higher activities than the conventional acids. Figure optionsDownload full-size imageDownload as PowerPoint slide