The present invention relates to a compound of formula (I): wherein: X is methyl or chlorine; R1 is fluorine or bromine; R2 is ethynyl, C1-C3alkoxy, C1-C3haloalkoxy, or C1-C3alkoxy-C1-C3alkoxy-; and Q is a pyran-3,5-dione-4-yl, a thiopyran-3,5-dione-4-yl, a piperidine-3,5-dione-4-yl, a cyclohexane-1,3,5-trione-2-yl, a cyclohexane-1,3-dione-2-yl, a cycloheptane-1,3-dione-2-yl, in which each cyclic dione is bridged by alkanediyl, or a derivative thereof (e.g. an enol ketone tautomer derivative thereof), wherein Q is further defined herein; and wherein the compound of formula (I) is optionally present as an agrochemically acceptable salt thereof. Preferably, X is methyl; and/or R1 is fluorine; and/or R2 is —O—R2A, wherein R2A is methyl, ethyl, trifluoromethyl, difluoromethyl, trifluoroethyl, or —CH2CH2OCH3. 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 weeds and/or to the plants and/or to the locus thereof.