A compound of formula (I): ##STR1## or a salt, enamine or the like, acylate, sulphonate, carbamate or ether derivative thereof; wherein X, X.sup.1 and X.sup.2 are independently oxygen or sulphur, R.sup.1 is an optionally substituted heterocyclic or cycloalkyl group, and Y is an optionally substituted C.sub.2 -C.sub.4 alkylene group which is optionally interposed by an oxygen atom, a group ##STR2## a group ##STR3## or an optionally mono-substituted nitrogen atom, wherein p is 0, 1 or 2, s is 0 or 1 and R.sup.b is alkyl or alkoxy; provided that when X, X.sup.1 and X.sup.2 are oxygen, R.sup.1 is not pyridyl or pyrimidinyl. Processes for the preparation of these compounds and herbicidal compositions containing them are also described and claimed.