Synthesis and biological activity of 4‐methylene‐pyrido[4,3‐d]pyrimidines

Fifteen novel 3‐substituted‐5‐methyl‐4‐methylene‐7‐alkylsulfanyl‐3,4‐dihydro‐pyrido[4,3‐d]pyrimidine‐8‐carbonitriles 5a , 5b , 5c , 5d , 5f , 5g , 5h , 5i , 5j , 5k , 5l , 5m , 5n , 5o , were synthesized via a facile annulation process in which formation of the pyrimidine ring proceeded smoothly by the regioselective attack of a formamidate group on a neighboring carbonyl group instead of a cyano group. Bioassay results indicated that these compounds showed significant herbicidal activity at a dose of 100 μg/mL on the roots of oil rape and barnyard grass. In addition , some of these compounds displayed fungicidal activity. J. Heterocyclic Chem., (2009).