Compounds of the formula ##STR1## wherein n is 1 to 5 and the/each X is hydrogen, halogen, cyano, nitro, optionally substituted alkyl or alkoxy alkenyloxy, alkynyloxy, haloalkylthio, alkenylthio or alkynylthio;m is 0 or 1 to 3 and the/each Y is halogen, alkyl or haloalkyl;Z is oxygen or sulphur;andR.sup.1 and R.sup.2 each, independently, is hydrogen, alkyl optionally substituted by halogen, hydroxy, cyano, alkoxy, alkylthio, alkoxycarbonyl, or mono- or di-alkylamino, alkenyl, alkynyl, hydroxy, alkoxy, alkenyloxy, alkynyloxy, alkoxycarbonyl, amino, mono- or di-alkylamino, alkoxycarbonylamino, arylamino, dialkylcarbamoyl, cycloalkyl, or optionally substituted cycloalkylalkyl;orR.sup.1 and R.sup.2 together form an alkylene chain optionally interrupted by oxygen, sulphur or --NR--, R being hydrogen or alkyl;are herbicides.