Patented Dec. 17,‘ 1946 r 2,412,815 a UNITED STATES PATENT’OFFICE 2,412,815 , DICARBOCYANINE DYES John David Kendall and Harry Derek Edwards, Ilford, England, assignors to Ilford Limited, Ilford, England, a British company No Drawing. Application Decemberv 17, 1943, ?e11~19a;l3No. 514,667. In Great Britain January 4 Claims. 1 (Cl. 260-240) ‘ 2 This invention relates to the production of dicarbocyanine dyes and particularly to the pro- ‘ to compounds of general Formula D by treating them with a sodium alkyl mercaptide and an duction of symmetrical dicarbocyanine dyes which are useful as optical sensitisers for silver alkyl mercaptan under pressure. . Beta-alkyl-thio acrolein di-alkyl mercaptals can be made by treating a compound of Formula , halide photographic emulsions. 5 In co-pending application Serial No. 514,666 A in which the groups R are alkyl groups with ?led December 17, 1943, corresponding to British alkyl mercaptan in the presence of a basic con application No. 14/43, there is described the production of compounds of the general Formula I: densing ‘agent under pressure. According to the present invention, symmetri XRl 10 cal carbocyanine dyestuffs are obtained by con densing a compound of general Formula I with an alkyl or aralkyl quaternary salt of a hetero-. XRl cyclic nitrogen compound containing a reactive where the groups R1 represent alkyl groups and methylene group (which term includes a methyl preferably ethyl groups, and the groups X are 15 or mono-substituted methyl group) substituted R‘s_OH=CH_Cé ' (I) both oxygen atoms or both sulphur atoms. Com- in the iii-position t0 the quaternary heterocyclic pounds of the general Formula I can be made, nitrogen atOm- as described in the aforesaid application by treating with an alkyl mercaptan, in the presence of The course of the reaction is believed to be as follows: V ‘ ‘ - I\ | \ IXRI \\ $2 FWD-n} §“1'1“-'F'§1§i'~c11=on-c : + Etc-62 ' TDD“: lib/L4"""" '3 lXR / R/ \A N=~=é~Q Rs l I :1 a | I /I '5 """""""" ‘f ?e ...... lei ' :"D"1 1,“ R2 r"D"1 N-—-(5=C-CH=CH—OH=C~—C a 1'\I\+ HA + men + zitlxn Re (n) A an acid condensing agent, a compound of one of In the foregoing formulae R2 and R3 represent the Formulae A, B. C‘, 01‘ D: "D alkyl or aralkyl groups, R3 may also be an une SR saturated aliphatic group, e. g. allyl, or a sub OHzCEFC? (A * stituted alkyl group, e. g. hydroxyalkyl, D rep ) resents the residue of a heterocyclic nitrogen nucleus and A represents an acid radicle. SR OR -» 40 CH:CH_C? — (B) 0R - . . . taming the necessary reactive methylene (or methyl or mono-substituted methyl) group de on r rived from the following heterocyclic nitrogen RO_CE=C;I_C§ (C 40 compounds: substituted and unsubstituted thia ) OR OR RS_CH=CH_C§ _ . . . zoles,th1azol1nes, oxazoles, oxazolmes, selenazoles, selenazolines, pyridine, quinoline, indolenine, di azines (e. g. pyrimidine and the diazines de (D) OR ‘ Examples of heterocyclic nitrogen compounds which may be employed are quaternary salts con _ or by treating with an alkyl mercaptan in the presence of a baslc condensing agent under PresSure, a Compound of Formula A. scribed in British patent speci?cation No. 425, 50 609), thiodiazoles and quinazoline and the cor responding substituted and unsubstituted. poly cyclic compounds such as the benzthiazoles, 'naphthathiazoles and anthrathiazoles and the v__ corresponding polycyclic oxazoles and selenazoles. C'qmpounds 0f the general Formula A may be M iSuch heterocyclic compounds‘ may contain sub obtamed by brommatmg acrolein and treating stituent groups in the benzene nuclei, e. g. alkyl, the product with an alkyl mercaptan followed by heating with an. alkali to remove bromine. Compounds of general Formula B may be converted‘ aryl, amino, hydroxy and alkoxy groups or halo gen atoms. The quaternary salts may be derived from vari 2,412,815 3 of triethylamine was then added, andlthe reac ous organic or inorganic acids,vfor example, they may be chlorides, bromides, iodides, alkyl sul tion mixture stirred. The boiling was fooiotinued for 5 minutes, and the reaction mixture was then allowed to cool. The dye was precipitated from solution by the addition of ether, and ?ltered o?. phates, p-toluene sulphonates or perchlorates. ' In carrying out the condensation using a com— pound of general Formula I where X is oxygen, it is generally convenient to heat the reagents together in the presence of albase and a solvent; pyridine is excellent in serving both purposes. When carrying out the condensation using a compound of general Formula I where X is sul 10 phur, however, it is preferred to heat the re agents together in the presence of a solvent and Recrystallisation from methyl alcohol yielded the dye as blue crystals with a bronze re?ex M. pt. 238° C. with decomposition. The dye had the structural formula: 4 a substance which will combine with alkyl mer captan split off during the reaction (a suitable medium is acetic anhydride which serves both 15 purposes) and to ?nish oil the reaction by add ing a‘ base and heating for a further period. The following examples illustrate the inven tion: - I EXAMPLE IV Preparation of 3:3'-dimethyl-thiazolino ' 20 dicarbocyanine iodide EXAMPLE I V1.12 gms. of 2-methyl thiazoline methiodide, , : Preparation of 2':2'-diethyl thiadicar ‘ ' - 1.0 gm. of ,B-ethyl-thio-acrolein-mercaptal, and bocyanine iodide 3.05 gms. of lemethylbenzthiazole ethiodide, 1.11 gms. of ?-ethyl-thio acrolein diethyl acetal and_15 vccs. of pyridine were mixed and boiled gently under re?ux for 15 minutes. The reaction 15 ccs. of acetic anhydride were‘ boiled gently To the solution was added 0.35 r under re?ux. ' cc. of triethylamine and the heating continued for six minutes. The reaction mixture was al lowed to cool, lixiviated with petroleum ether, the petroleum ether decanted off, and the residue mixture was then poured into an aqueous solution of potassium iodide. The dye was precipitated and was ?ltered off, and washed with ethyl alco 30 diluted'with ether. The precipitated dyestu? ' was ‘filtered off and washed with ethyl alcohol, hol and ether. Recrystallisation from methyl al water, ethyl alcohol again and ?nally ether, and cohol solution yielded the dye as green needles. was obtained as silvery crystals. M. pt. 202? C. M. pt. 248° C. with decomposition. The dye had with decomposition. The dye had the structural the structural formula: 35 S S N/ 6.11. '40 EXAMPLE II As already stated, the dyestuffs obtained by the process of this invention are valuable sensi Preparation of 1 :1'-diethyl 2:2"-quinodi- ' carbocyanine iodide 45 ‘tisers for photographic silver halide emulsions. Thus, for example, the dyestufi of Example IV 1.5 gms. of quinaldine ethiodide, 0.6 gm. of ,8 ‘supra incorporated in a silver iodobromide emul ethyl thio acrolein diethyl mercaptal and 10 cos. sion, extends the sensitivity to about 6200 A. with of acetic anhydride were boiled gently under re ?ux until partly in solution. 0.7 cc. of triethyl amine was then added and the heating continued for IO-minutes. The reaction mixture was cooled a maximum sensitivity at about 5750 A. What‘ we and the dye precipitated by dilution with ether. The . dye had the structural formula: ' LCH—~CH=OH—CH=CH \N 02115 v I’ ' ' V ._ carbocyanine iodide _ . ‘ XR1 where the groups R1 are alkyl groups and the groups X are the same and selected from the 60 class consisting of oxygen and sulphur atoms, with a compound selected from the class con sisting of alkyl and aralkyl quaternary salts of heterocyclic nitrogen compounds containing a re active methylene group in a-position to the qua ternary heterocyclic‘ nitrogenatom of the type 65 usual in the cyanine dye art. _ 2. Process for the production of dicarbocyanine dyes which comprises condensing a compound or EXAMPLE III Preparation of 1 :1'-dimethyl-indodi V the general formula: The liquors were decanted through a ?lter and the residue lixiviated with water. The dye was ?ltered off and washed well with ethyl alcohol and ether,’ being thus obtained as green crystals with a bronze re?ex. M. pt. 245° C. (with de composition), and giving a turquoise blue solu tion in alcohol. claim is: 1. Process for the production of dicarbocyanine dyes which comprises condensing a compound of the general formula: ' - - ' 70 > ‘1.5 gms. of 2:3:3 trimethyl indolenine methi odide, 0.6 gm. of B-ethyl-thio-acrolein-mercaptal and 10 ccs. of acetic anhydride were boiled gent where the groups R1 are lower alkyl groups and. ly under re?ux until partly in solution. 0.7 cc. the groups X are the same and selected ‘from 5 2,412,815 the class consisting of oxygen and sulphur atoms, with a compound selected from the class con sisting of alkyl and aralkyl quaternary salts of heterocyclic nitrogen compounds containing a re active methylene group in a-position to the qua-. ternary heterocyclic nitrogen atom of the type usual in the cyanine dye art. ' 3. Process for the production of dicarbocyanine dyes which comprises condensing ,B-ethyl-thio 6 4. Process for the production of dicarbocyanine dyes which comprises condensing B-ethyl-thio acrolein dialkyl mercaptal with a compound se lected from the class consisting of alkyl and aralkyl quarternary salts of heterocyclic nitro gen compounds containing a reactive methylene group in u-position to the quarternary hetero cyclic nitrogen atom of the type usual in the cyanine dye art, by heating the reagents to acrolein dialkyl acetal, with a compound selected 10 gether in the presence of a solvent and a sub from the class consisting of alkyl and aralkyl stance which will combine with the alkyl mercap quarternary salts of heterocyclic nitrogen com tan split oiT during the reaction, and then add pounds containing a reactive methylene group in ing a base and continuing to heat the reagents a-IJOSitiOIl to the quaternary heterocyclic nitro gen atom of the type usual in the cyanine dye art, in the presence of a base and a solvent for the reactants. for a further period. JOHN DAVID KENDALL. HARRY DEREK EDWARDS.