Manufacture of sensitizing dyestuffs

519,895. Sensitizing dyes. KENDALL, J. D. Oct. 6, 1938, No. 29021. Sample furnished. [Class 2 (iii)] [Also in Group XX] Unsymmetrical sensitizing dyes for photographic emulsions are made by reacting together, in the presence of a strongly basic substance, a heterocyclic nitrogen compound containing in oc- or #- position to the nitrogen atom an external reactive methyl, methylene or mono-substituted methyl or methylene group, an ortho ester of a monocarboxylic, acid and a five-membered heterocyclic keto-methylene compound containing the grouping -NR-COCH2-(R=a hydrogen atoin or' hydrocarbon radicle) in the heterocyclic ring. The strongly basic substance may be an organic base such as piperidine, or di- or tri-ethylamine, or other bases as strong as or stronger than ammonia, e.g., caustic soda or sodium ethoxide, may be used. The heterocyclic nitrogen compound containing the external methyl or methylene group is preferably employed as a quaternary salt, although the corresponding base, e.g., 2- methylene-1:3:3-trimethylindoline, may be used. Specified compounds are thiazoles, oxazoles, selenazoles, thiazolines, oxazolines, selenazolines, pyridines, quinolines, indolenines, and diazines or diazoles, e.g., pyrimidine, thiodiazoles and quinazolines, and the corresponding polycyclic, compounds, e.g., benz-, naphtha-; and anthra-thiazoles. The quaternary salts may be formed with alkyl halides, sulphates or nitrates, or alkyl-p-toluene sulphonates. As keto-methylene compounds containing the group -NR-CO-OH2- are specified rhodamines, pyrazolones, hydantoins, thiohydantoins and oxindoles. As ortho esters; ethyl or methyl orthoformic, orthoacetic and orthopropionic esters are specified. In examples, dyestuffs are made from (1) 2:3:3-trimethylindoenine methiodide, ethyl orthoformate and (a) 1-phenyl-3- methyl-5-pyrazolone, (b) 1-#-naphthyl-3-methy1-5-pyrazolone, (c) 1-phenyl-3-furyl-5-pyrazolone, and (d) 1-#-naphthyl-3-furyl-5-pyrazolone ; (2) 2:3:3-trimethylindolenine methiodide, 1-phenyl-3-methyl-5-pyrazolone, and (a) ethyl orthoacetate and (b) ethyl orthopropionate ; (3) 1-methylbenzthiazole, methyl or ethyl p-toluene sulphonate, ethyl orthoformate. orthoacetate or orthopropionate and (a) 1- phenyl-3-methyl-5-pyrazolone, (b) N-methylrhodanine, (c) N-ethyl-rhodanine, (d) N-methyloxa-rhodenine, (e) thiohydantoin, and (f) N-methyl- or ethyl-oxindole ; (4) lepidine- or quinaldine-methiodide, ethyl orthoformate and 1-phenyl-3-methyl-5-pyrazolone; (5) 1-methylbenzoxazol