When a mixture of 4-chloro-1-phenyl-1H-pyrazolo[3, 4-d]pyrimidine (9), aromatic aldehyde (5), sodium hydride, and a catalytic amount of 1, 3-dimethylbenzimidazolium iodide (4) in tetrahydrofuran was refluxed, the nucleophilic aroylation occurred, resulting in the formation of the aryl 1-phenyl-1H-pyrazolo[3, 4-d]pyrimidin-4-yl ketones (11).Similar reaction of 4-chloro-1-methyl-1H-pyrazolo[3, 4-d]pyrimidine (10) gave the corresponding aryl 1-methyl-1H-pyrazolo[3, 4-d]pyrimidin-4-yl ketones (12) in moderate yields. Use of dimethylformamide or dimethyl sulfoxide in the above reaction reduced the necessary reaction time and reaction temperature. A plausible reaction pathway for the formation of the ketones 11 and 12 involving the catalytic action of 4 is proposed.