Herbicidal isoxazole and 2-cyano-1,3-dione compounds

A compound of formula (Ia), (Ib) or (Ic):

• ##STR29## wherein:
• R is hydrogen or --CO.sub.2 R.sup.3 ;
• R.sup.1 is:
• straight- or branched-chain alkyl having up to six carbon atoms which is unsubstituted or is substituted by one or more halogen;
• or
• cycloalkyl having from three to six ring carbon atoms which is unsubstituted or which has one or more substituents selected from the group consisting of R.sup.4 and halogen;
• R.sup.2 is:
• halogen;
• straight- or branched-chain alkyl having up to six carbon atoms which is substituted by one or more --OR.sup.5 ;
• cycloalkyl having from three to six carbon atoms;
• or
• a member selected from the group consisting of nitro, cyano, --CO.sub.2 R.sup.5, --NR.sup.5 R.sup.6, --S(O).sub.p R.sup.7, --O(CH.sub.2).sub.m OR.sup.5, --COR.sup.5, --N(R.sup.8)SO.sub.2 R.sup.7, --OR.sup.7, --OH, --OSO.sub.2 R.sup.7, --(CR.sub.9 R.sup.10).sub.t SO.sub.q R.sup.7a, --CONR.sup.5 R.sup.6, --N(R.sup.8)--C(Z).dbd.Y, --(CR.sup.9 R.sup.10)NR.sup.8 R.sup.11 and R.sup.4 ;
• n is zero or an integer from one to three;
• when n is greater than one, then the groups R.sup.2 are the same or different;
• m is one, two or three;
• p is zero, one or two;
• q is zero, one or two;
• t is an integer from one to four;
• R.sup.3 is:
• straight- or branched-chain alkyl having up to six carbon atoms which is unsubstituted or which has one or more substituents selected from the group consisting of halogen, --OR.sup.5, --CO.sub.2 R.sup.5, --S(O).sub.p R.sup.7, phenyl and cyano;
• or
• phenyl which is unsubstituted or which has one or more substituents selected from the group consisting of halogen, --OR.sup.5 and R.sup.4 ;
• R.sup.4 is straight- or branched-chain alkyl, alkenyl or alkynyl having up to six carbon atoms which is unsubstituted or is substituted by one or more halogen;
• R.sup.5 and R.sup.6, which are the same or different, are each hydrogen or R.sup.4 ;
• R.sup.7 and R.sup.7a independently are R.sup.4, cycloalkyl having from three to six ring carbon atoms, or --(CH.sub.2).sub.w -phenyl wherein phenyl is unsubstituted or is substituted by from one to five R.sup.12 which are the same or different;
• w is zero or one;
• R.sup.8 is:
• hydrogen;
• straight- or branched-chain alkyl, alkenyl or alkynyl having up to ten carbon atoms which is unsubstituted or is substituted by one or more halogen;
• cycloalkyl having from three to six ring carbon atoms;
• --(CH.sub.2).sub.w -phenyl wherein phenyl is unsubstituted or is substituted by from one to five R.sup.12 which are the same or different;
• or
• --OR.sup.13 ;
• R.sup.9 and R.sup.10 independently are hydrogen or straight- or branched-chain alkyl having up to six carbon atoms which is unsubstituted or is substituted by one or more halogen;
• R.sup.11 is --S(O).sub.q R.sup.7 or --C(Z).dbd.Y;
• R.sup.12 is:
• halogen;
• straight- or branched-chain alkyl having up to three carbon atoms which is unsubstituted or is substituted by one or more halogen;
• or
• a member selected from the group consisting of nitro, cyano, --S(O).sub.p R.sup.3 and --OR.sup.5 ;
• Y is oxygen or sulphur;
• Z is R.sup.4, --NR.sup.8 R.sup.13, --NR.sup.8 --NR.sup.13 R.sup.14, --SR.sup.7 or --OR.sup.7 ;
• and
• R.sup.13 and R.sup.14 independently are R.sup.8
• or when the compound has formula (Ic), an enolic tautomeric form thereof;
• or an agriculturally acceptable salt or metal complex thereof.