A novel approach to regioselective synthesis of new 5‐amino‐6‐arylamino‐1H‐pyrazolo[3,4‐d]pyrimidin‐4(5H)‐one 5 derivatives via a tandem aza‐wittig and annulation reaction of iminophosphorance 2, aromatic isocyanates and hydrazine in 69.6–94.7% isolated yields is reported. The compound 5 reacted with triethyl orthoformate to give compound 6 in good yield (65.8–82.8%). Their structure was clearly confirmed by spectroscopy data (IR, 1H NMR, MS, elemental analysis) and the results of preliminary bioassay indicated that compounds 5 and 6...
