Regioselective synthesis and bioactivity of new 5‐amino‐6‐arylamino‐pyrazolo[3,4‐ d ]‐pyrimidin‐4(5 H )‐one derivatives

A novel approach to regioselective synthesis of new 5‐amino‐6‐arylamino‐1 H ‐pyrazolo[3,4‐ d ]pyrimidin‐4(5 H )‐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, 1 H NMR, MS, elemental analysis) and the results of preliminary bioassay indicated that compounds 5 and 6 possess high antifungal activity against Botrytis cinerea Pers and Sclerotinia sclerotiorum , and compound 5h showed 100, 96.4, and 90.2% inhibitory rate to Botrytis cinerea Pers , Pyricularia oryzae, and Sclerotinia sclerotiorum at the concentration of 50 mg/L. The antifungal activities of compound 6 were generally higher than those of compound 5 . J. Heterocyclic Chem., (2009).