Regiocontrolled synthesis of 3-substituted-6-trifluoromethyl-4(3H)-pyrimidinones

Direct reaction of a variety of N-monosubstituted benzamidines with 4,4,4-trifluoroacetoacetate esters substituted at the 2-position with methyl, ethyl or methoxy afforded moderate to good yields of herbicidal 3-substituted-6-trifluoromethyl-4(3H)-pyrimidinones. Lower yields were obtained with the corresponding 4,4-difluoroacetoacetate esters and the reaction failed with nonfluorinated β-ketoesters. In addition to benzamidines, 3- and 4-pyridylcarboxamidines reacted successfully. The reaction tolerated propyl, allyl, propargyl and phenyl substituents on the amidine nitrogen.