A compound of the formula ##STR40## wherein R.sub.1 ' is hydrogen;
- C.sub.1-4 alkyl;
- C.sub.1-4 alkyl monosubstituted by fluoro, bromo, chloro, hydroxy, (C.sub.1-4 alkyl)carbonyl, C.sub.1-4 alkoxy, cyano, thiocyano, phenoxy, (C.sub.1-4 alkoxy)carbonyl, phenoxycarbonyl, (C.sub.1-4 alkoxy)ethoxycarbonyl, carbamoyl, (C.sub.1-4 alkyl)carbamoyl, di-(C.sub.1-4 alkyl)carbamoyl, phenylcarbamoyl, N-C.sub.1-4 alkyl-N-phenylcarbamoyl, benzoyl, (C.sub.1-4 alkyl)carbonyloxy, phenylsulfonyl, C.sub.1-4 alkylsulfonyl, sulfamoyl, C.sub.1-4 alkylsulfamoyl, di-C.sub.1-4 alkylsulfamoyl, phenylsulfamoyl, N-C.sub.1-4 alkyl-N-phenylsulfamoyl, phenyl or substituted phenyl having 1 or 2 substituents each of which is independently chloro, bromo, nitro, cyano, trifluoromethyl, C.sub.1-4 alkyl or C.sub.1-4 alkoxy;
- C.sub.2-4 alkenyl;
- C.sub.2-4 alkenyl monosubstituted by chloro, bromo or phenyl;
- phenyl or substituted phenyl having 1 to 3 substituents each of which is independently C.sub.1-4 alkyl, C.sub.1-4 alkoxy, chloro, bromo, nitro, cyano (maximum of two), trifluoromethyl (maximum of two), (C.sub.1-4 alkoxy)carbonyl (maximum of two), formyl (maximum of one), (C.sub.1-4 alkyl)carbonyl (maximum of one), carbamoyl (maximum of one), (C.sub.1-4 alkyl)carbamoyl (maximum of one), di-(C.sub.1-4 alkyl)carbamoyl (maximum of one), C.sub.1-4 alkylsulfonyl (maximum of one), phenylsulfonyl (maximum of one), sulfamoyl (maximum of one), C.sub.1-4 alkylsulfamoyl (maximum of one), di-C.sub.1-4 alkylsulfamoyl (maximum of one) or phenylsulfamoyl (maximum of one),
- R.sub.2 ' is cyano, thiocyano, nitro, --COOM, (C.sub.1-4 alkyl)carbonyl, benzoyl, (C.sub.1-4 alkoxy)carbonyl, (C.sub.1-4 alkoxy)ethoxycarbonyl, phenoxycarbonyl, carbamoyl, (C.sub.1-4 alkyl)carbamoyl, di-(C.sub.1-4 alkyl)carbamoyl, phenylcarbamoyl, C.sub.1-4 alkylsulfonyl, phenylsulfonyl, sulfamoyl, C.sub.1-4 alkylsulfamoyl, di-C.sub.1-4 alkylsulfamoyl or phenylsulfamoyl, wherein M is hydrogen or a non-chromophoric cation,
- each of R.sub.3 and R.sub.4 is independently hydrogen;
- C.sub.1-8 alkyl;
- C.sub.1-8 alkyl monosubstituted by hydroxy, chloro, bromo, cyano, thiocyano, (C.sub.1-4 alkyl)carbonyl, (C.sub.1-4 alkoxy)carbonyl, formyloxy, (C.sub.1-4 alkyl)carbonyloxy, (C.sub.1-4 chloroalkyl)carbonyloxy, (C.sub.1-4 bromoalkyl)carbonyloxy, (C.sub.1-4 alkoxy)carbonyloxy, (C.sub.1-4 alkoxy)(C.sub.1-4 alkoxy)carbonyl, allyloxycarbonyl, chloroallyloxycarbonyl, bromoallyloxycarbonyl, C.sub.2-4 alkenyloxy, C.sub.2-4 chloroalkenyloxy, C.sub.2-4 bromoalkenyloxy, C.sub.2-4 alkynyloxy, benzoyloxy, C.sub.1-4 alkoxy, phenyl, phenoxy, phenyl(C.sub.1-4 alkoxy), (C.sub.1-4 alkyl)carbamoyl, di-(C.sub.1-4 alkyl)carbamoyl, (C.sub.1-4 alkyl)carbamoyloxy, di-(C.sub.1-4 alkyl)carbamoyloxy, phenylcarbamoyl, phenylcarbamoyloxy, phthalimidyl, saccharinyl-2, pyridyl or benzothiazolyl-2-mercapto;
- (C.sub.1-4 -alkoxy)C.sub.1-4 alkyl the C.sub.1-4 alkoxy moiety of which is monosubstituted by hydroxy, chloro, bromo, cyano, C.sub.1-4 alkoxy, (C.sub.1-4 alkoxy)carbonyl, (C.sub.1-4 alkoxy)carbonyloxy or (C.sub.1-4 alkyl)carbonyloxy;
- 2-hydroxy-3-propynyloxypropyl;
- 2-(C.sub.1-4 alkyl)carbonyloxy-3-propynyloxypropyl;
- 2-hydroxy-3-allyloxypropyl;
- 2-(C.sub.1-4 alkyl)carbonyloxy-3-allyloxypropyl;
- C.sub.2-4 alkenyl;
- C.sub.2-4 alkenyl monosubstituted by phenyl, chloro or bromo;
- C.sub.2-4 alkynyl;
- C.sub.5-7 cycloalkyl;
- C.sub.5-7 cycloalkyl substituted by 1 to 3 methyl groups;
- phenyl or substituted phenyl having 1 to 3 substituents each of which is independently chloro, bromo, methyl or C.sub.1-2 alkoxy, with the provisos that at least one of R.sub.3 and R.sub.4 is other than C.sub.5-7 cycloalkyl, C.sub.5-7 cycloalkyl substituted by 1 to 3 methyl groups, phenyl or substituted phenyl and that at least one of R.sub.3 and R.sub.4 is other than hydrogen,
- R.sub.5 is hydrogen, chloro, bromo, C.sub.1-2 alkyl, C.sub.1-2 alkoxy or phenoxy, and
- R.sub.6 is hydrogen;
- C.sub.1-2 alkyl;
- C.sub.1-2 alkoxy;
- cyano;
- formamido;
- (C.sub.1-4 alkyl)carbonylamino;
- (C.sub.1-4 alkyl)carbonylamino the C.sub.1-4 alkyl moiety of which is monosubstituted by hydroxy, chloro, bromo, C.sub.1-4 alkoxy, phenyl or phenoxy;
- benzamido;
- (C.sub.2-4 alkenyl)carbonylamino;
- aminocarbonylamino;
- (C.sub.1-4 alkyl)aminocarbonylamino;
- (C.sub.1-4 alkoxy)carbonylamino;
- (C.sub.1-4 alkoxy)carbonylamino the C.sub.1-4 alkoxy moiety of which is monosubstituted by C.sub.1-4 alkoxy or phenyl;
- C.sub.1-2 alkylsulfonylamino;
- phenylsulfonylamino;
- di-C.sub.1-2 alkylaminosulfonylamino;
- chloro;
- bromo or phenoxy, with the proviso that R.sub.6 is other than chloro, bromo or phenoxy when R.sub.5 is chloro, bromo or phenoxy,
- with the proviso that the molecule is free of metallizable groups and ##STR41## radicals.