GB378455A - Improvements in sensitising photographic emulsions - Google Patents

Abstract

Cyclammonium polymethine dyes.--The Specification as open to inspection under Sect. 91 (3) (a) relates to the production of cyanine dyes from a condensation product of a m -methylnaphthothiazole and to the use of such dyes in sensitizing photographic emulsions. The dyes comprised by the Specification include the thiocarbocyanines, the thio-pseudocyanines and thioisocyanines derived from a m -methylnaphthothiazole, and the following examples are given: (1) 1-Methyl-a -naphthothiazole is condensed with ethyl-p-toluenesulphonate and the product condensed with 2 mols. of ethyl orthoformate; addition of ammonium bromide precipitates the dyestuff 2 , 2<1>-diethyl-5 : 6 : 5<1> : 6<1>-dibenzothiocarbocyanine bromide: (2) 1-methyl-a -naphthothiazole is condensed with allyl iodide and the quaternary salt condensed with ethyl orthoformate to give 2 : 2<1>-diallyl-5 : 6 : 5<1> : 6<1>-dibenzothiocarbocyanine iodide: (3) 2-methyl-b -naphthothiazole ethyl-p-toluenesulphonate is condensed with 2 mols. of triethyl orthoacetate; on addition of ammonium bromide 8-methyl-2 : 2<1>-diethyl-3 : 4 : 3<1> : 4<1>-dibenzothiocarbocyanine bromide is obtained: (4) trimethyl orthopropionate is employed in (3) instead of triethyl orthoacetate, and potassium iodide then added to give 2 : 2<1> : 8-triethyl-3 : 4 : 3<1> : 4<1>-dibenzothiocarbocyanine iodide: (5) 2-methyl-b -naphthothiazole is condensed with methyl-p-toluenesulphonate and the product condensed with 2 mols. of methyldiethyl-orthoisocaproate to give 2 : 2<1>-dimethyl-8-isoamyl-3 : 4 : 3<1> : 4<1>-dibenzothiocarbocyanine on precipitation with potassium iodide: (6) 1-methyl-a -naphthothiazole ethyl-p-toluenesulphonate is condensed with one molecular proportion of quinoline ethiodide in presence of caustic potash to give 1<1> : 2-diethyl-5 : 6-benzthioisocyanine iodide; by starting with 2-methyl-b -naphthothiazole 1<1> : 2-diethyl-3 : 4-benzthioisocyanine iodide is obtained: (7) 2-methyl-b -naphthothiazole ethyl-p-toluenesulphonate is treated with potassium iodide and the product condensed with 2-iodoquinoline ethiodide in presence of caustic potash to give 1<1> : 2-diethyl-3 : 4-benzthio-pseudocyanine iodide; by starting with 1-methyl-a -naphthothiazole ethiodide 1<1> : 2-diethyl-5 : 6-benzthio-pseudocyanine iodide is obtained. Substituted quinolines and substituted m -methylnaphthothiazoles may be employed in the above processes and other alkyl orthoacid esters for preparing 8-substituted dibenzthiocarbocyanines. This subject-matter does not appear in the Specification as accepted.