Facile synthesis and biological activities of novel fluorine-containing pyrido[4,3-d]pyrimidines

Fourteen novel 3-substituted-5-methyl-4-methylene-7-alkylsulfanyl-3,4-dihydro-pyrido[4,3-d]pyrimidine-8-carbonitriles 4a-n were synthesized via a facile regioselective cyclization process. The structures of compounds 4a-n were confirmed by IR, 1H NMR, MS and elemental analysis. Some compounds possess good herbicidal activity, especially when the fluorine atom was introduced to the para position of substituents on pyrimidine ring. And some compounds show moderate fungicidal activities as well, and the introduction of fluorine has negative effect on the antifungal activities.