Compounds of formula I: ##STR1## where n is 0 or an integer from 1 to 5; X is halogen, nitro or cyano, or C.sub.1-10 hydrocarbyl or C.sub.1-10 hydrocarbyloxy, either of which may be substituted with one or more halogen atoms; Y is CH.sub.2, O or S; and R.sup.1 and R.sup.2 independently represent hydrogen, C.sub.1-6 alkyl, C.sub.1-6 haloalkyl, C.sub.2-6 alkenyl, C.sub.2-6 alkynyl or halogen; Processes for the preparation of compounds of formula I, herbicidal compositions and methods utilising them are also disclosed.