A facile synthesis and fungicidal activities of novel fluorine-containing pyrido[4,3-d]pyrimidin-4(3H)-ones

Sixteen novel 2-substituted-5,8,9-trimethyl-3-(4-fluoro-substituted)phenyl-thieno[3′,2′-5,6] pyrido[4,3-d]pyrimidin-4(3H)-ones 5a–5p were designed and have been successfully synthesized via tandem aza-Wittig and annulation reactions of the corresponding iminophosphorances 1, para-fluoro phenyl isocyanate, and substituted phenols or amines in 73–90% isolated yields. Their structures were clearly verified by IR, 1H NMR, EI-MS spectroscopy and elemental analysis, and in the case of compound 5a, analyzed by single-crystal X-ray diffraction further. The results of preliminary bioassay indicated that some compounds possess inhibition activities against Rhizoctonia solani and Botrytis cinereapers at a dosage of 50 mg/L.