Compounds of the formula: ##STR1## wherein R.sup.1 is H or alkyl; R.sup.2 and R.sup.3 are independently H, alkyl, aryl or substituted aryl; R.sup.4 is H or alkoxycarbonyl; R.sup.5 is H, acyl or a cation; and Z is thienyl or substituted thienyl.The compounds exhibit grass herbicide activity and are prepared via the reaction of the appropriately substituted cyclohexane-1,3-dione with the appropriate thienylmethoxyamine derivative and optionally acylating this product at the 3-hydroxy position or converting it to the cation salt.