In the course of efforts to find novel compounds with improved crop safety in transplanted rice by the modification of 1-[1-(3,5-dichlorophenyl)-1-methylethyl]-4-methyl-3-phenyl-3-pyrrolin-2-one (1a), which was reported to have excellent herbicidal activity against paddy weeds, 2,3-dihydro-2-oxo-1H-pyrrole derivatives with a quaternary carbon atom having an alkoxycarbonyl group at the α-position of the cyclic amide were synthesized and examined. Among these compounds, methyl 1-[1-(3,5-dichlorophenyl)-1-methylethyl]-2,3-dihydro-4-methyl-2-oxo-3-phenyl-1H-pyrrole-3-carboxylate (2a) was not only active against Echinochloa oryzicola and Scirpus juncoides but also compatible with transplanted rice even in harsh conditions. On the basis of preliminary experimental results, it was thought that 2a would generate the corresponding 2-oxo-3-pyrrolin (1a) through the metabolic degradation of the methoxycarbonyl moiety. © Pesticide Science Society of Japan