GB604217A - Improvements in or relating to cyanine dyestuffs and to photographic silver halide emulsions sensitised therewith - Google Patents

Abstract

Symmetrical cyanine dyes are prepared by condensing a cyclohexane 1 : 3-dione, a D 2 : 3-(3-alkylthio)-cyclohexenone (1) or a D 2 : 3-(3-aralkylthio)-cyclohexenone (1) with an alkyl or aralkyl quaternary salt of a thiazole or selenazole or polycyclic homologue, a thiazoline selenazoline, diazine, or diazole or with rhodanine or a N-hydrocarbon substituted derivative, or with an oxindole, pyrazole-5-one, hydantoin, thiohydantoin, pseudohydantoin, or pseudothiohydantoin by heating together in presence of a base, preferably in presence of a solvent for the reactants. The D 2 : 3-(3-alkylthio)-cyclohexenone (1) may be one of those of Specification 595,783. In examples, dyes are prepared (1) by fusing together D 2 : 3-(3-ethylthio-5 : 5-dimethyl)-cyclohexenone (1), 1-methylbenzthiazole, and methyl p-toluenesulphonate, and pyridine and refluxing, adding triethylamine and further refluxing, and pouring into aqueous KI solution; (2) as in (1), using ethyl p-toluenesulphonate; (3) as in (2), using 1-methyl-4-chlorobenzthiazole; (4) as in (2), using 1-methylbenzselenazole; (5) by fusing together 5 : 5-dimethylcyclohexane dione (1 : 3), 1 : 4-dimethylbenzthiazole and ethyl p-toluenesulphonate, adding pyridine and triethylamine and refluxing, and pouring into aqueous KI solution; (6) as in (2), using D 2 : 3 - (3 - ethylthio - 5 - methyl) - cyclohexenone (1); (7) as in (2), using D 2 : 3-(3-ethylthio-5-phenyl)-cyclohexenone (1); (8) as in (5), using 5-phenylcyclohexane dione (1 : 3); (9) by fusing together D 2 : 3-(3-ethylthio-5 : 5-dimethyl)-cyclohexenone (1) and 1-phenyl-3-methyl-5-pyrazolone, adding pyridine and refluxing, adding triethylamine and refluxing, and acidifying; (10) as in (9), using N-methylrhodanine; (11) as in (6), using 1-methyl-4-chlorobenzthiazole; and (12) as in (2) using D 2 : 3-(3-ethylthio)-cyclohexenone (1).