Synthesis and herbicidal activity of 1-aryl-2-phenyl-3-methyl-3-isopropyl-1,4,2-diazaphospholidin-5-one-2-oxides

A series of 1-aryl-2-phenyl-3-methyl-3-isopropyl-1, 4, 2-diazaphospholidin- 5-one-2-oxides(2a-2o)have been synthesized by the Mannich-type reaction of substituted phenyl ureas, phenyldichlorophosphine and 3-methyl-2-butanone, and their structures were confirmed by elemental analysis, NMR, IR and MS. On the basis of NMR analyses, we found that the cis-isomers, in which the b igger group isopropyl and the phenyl group linked with the phosphorus atom are at the opposite side, are generated preferably in the reaction. The res ults of preliminary bioassay show that compounds 2 possess an excellent her bicidal activity selectively against rape. The structure-herbicidal activit y relationship(SAR) has also been discussed. Their herbicidal activities fo r the same substituent at different positions and those for different subst ituents at the same position are compared.