Compounds of formula (I): ##STR1## (wherein: R.sup.1 is optionally substituted alkyl, cycloalkyl, optionally substituted alkoxy, or optionally substituted alkylthio; R.sup.2 is hydrogen, optionally substituted alkyl, cycloalkyl, optionally substituted alkenyl, optionally substituted alkynyl or a group of formula --YR.sup.7 ; R.sup.3 is optionally substituted alkyl, cycloalkyl, optionally substituted alkoxy group, optionally substituted alkenyl, optionally substituted alkynyl, halogen, nitro or a group of formula --COR.sup.8, wherein R.sup.8 is hydrogen, alkyl, cycloalkyl or alkoxy; R.sup.4 and R.sup.5 are each hydrogen atom or alkyl; R.sup.6 is optionally substituted alkyl, cycloalkyl, optionally substituted alkoxy group, optionally substituted alkenyl, optionally substituted alkynyl, halogen, nitro, or a group of formula --COR.sup.8, as defined above; A, Q and X are each oxygen or sulfur; Y is a group of formula --CO--, --COO--, --CH.sub.2 O--, --CH.sub.2 S--, --CH.sub.2 CH.sub.2 O--, --CH.sub.2 CH.sub.2 S--, --CH.sub.2 CO--, --CH.sub.2 COO--, --CH(Me)COO--, --CH.sub.2 CH.sub.2 CO--, --CH.sub.2 OCO--, CH.sub.2 OCOO-- and --CH.sub.2 CH.sub.2 OCO--; R.sup.7 is optionally substituted alkyl group, cycloalkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted aryl, optionally substituted aralkyl, or an optionally substituted heterocycle; and m and n are each an integer from 0 to 4; and herbicidally acceptable addition salts thereof) are useful as herbicides.