The present invention relates to a compound of formula (I) wherein: R1 is C1-C3alkoxy, C1-C2alkoxy-C1-C3alkoxy, C1-C2fluoroalkoxy, ethyl, n-propyl, n-butyl, cyclopropyl or ethynyl； R2 is hydrogen, ethyl, n-propyl, cyclopropyl, vinyl, ethynyl, C1-C3alkoxy, C1-C3fluoroalkyl, C1-C2fluoroalkoxy, C1-C2alkoxy-C1-C3alkoxy-, or C1fluoroalkoxy-C1-C3alkoxy-； provided that when R1 is ethyl, n-propyl, n-butyl, cyclopropyl or ethynyl, then R2 is hydrogen, ethyl, n-propyl, cyclopropyl, vinyl or ethynyl； and Y is O, S, S(O), S(O)2, N(C1-C2alkyl), N(C1-C2alkoxy), C(O), CR8R9 or —CR10R11CR12R13—； and G, R3, R4, R5 and R6 are as defined herein； wherein the compound of formula (I) is optionally present as an agrochemically acceptable salt thereof. These compounds are suitable for use as herbicides. The invention therefore also relates to a method of controlling weeds, especially grassy monocotyledonous weeds, in crops of useful plants, comprising applying a compound of formula (I), or a herbicidal composition comprising such a compound, to the plants or to the locus thereof.
