Heterocyclic oxy-phenoxyacetic acid derivatives and their use as herbicides

A heterocyclic oxy-phenoxyacetic acid derivative of the formula:

• ##STR79## wherein R.sup.1 and R.sup.2 are each hydrogen or lower alkyl and R.sup.3 is --NR.sup.4 R.sup.5, or --OR.sup.7 wherein R.sup.4 and R.sup.5 are each hydrogen or lower alkyl or, when taken together with the adjacent nitrogen atom, represent a piperidino group, a morpholino group, a thiamorpholino group or a piperazino group, which groups are unsubstituted or are substituted by one or two lower alkyl groups;
• R.sup.6 is lower cycloalkyl, phenyl, pyridyl, piperidino or morpholino, or a group of the formula:
• --NR.sup.8 R.sup.9 wherein R.sup.8 and R.sup.9 are each hydrogen or lower alkyl or, when taken together, represent a lower alkylidene group;
• and R.sup.7 is hydrogen, lower alkyl, phenyl(lower)alkyl, phenoxy(lower)alkyl, halo (lower)alkyl, hydroxy(lower)alkyl or lower alkoxy(lower)alkyl or an agriculturally acceptable salt thereof.