Patent GB-734792-A (GB)
Title: Improvements in or relating to cyanine dyes
Inventor: KENDALL JOHN DAVID
IPC: C09B23/10
Filed: 1952-11-28
Abstract: Cyanine dyes are described which have one of the following two formul <FORM:0734792/IV (c)/1> or <FORM:0734792/IV (c)/2> wherein R1 and R2 are hydrocarbon group and may together form an aliphatic carbocyclic system, R3, R4 and R5 are alkyl groups, R6 is a hydrocarbon group or is linked through C and N to a carbon atom in D2, X is an anion, n is 0 or 1 and D1 and D2 complete 5- or 6-membered heterocyclic nuclei. They are parepared by condensing a compound of the formula <FORM:0734792/IV (c)/3> with a compound of the formula <FORM:0734792/IV (c)/4> or <FORM:0734792/IV (c)/5> in the presence of a base, and when using a strong base the starting materials must be substantially in equimolecular proportions.  In place of the iminazolenine quaternary salt of formula III the free base may be employed together with an equimolecular proportion of R3X, and in the case of the monomethine dyes of formula I the free base of the heterocyclic compound containing the methyl group may also be used together with two molecular proportions of R3X, in which case R5 is identical with R3.  R1 and R2 are preferably methyl or ethyl but they may be benzyl or phenyl or together form a cyclopentamethylene ring, R3 and R4 are preferably both methyl or both ethyl and R6 is preferably alkyl or phenyl.  D1 may complete a thiazole, benzthiazole, benzoxazole, benzselenazole, naphthathiazole, quinoline, indolenine or thiazoline nucleus, the carbocyclic rings of which may bear substituents such as alkyl, aryl, alkoxy or halogen. D2 may complete a rhodanine, pyrazole-5-one or thiazolidone nucleus, or together with R6 form a 2 : 3 - (benziminazo - 21 : 11) - 4 - thiazolidone nucleus. Specification 734,793 is referred to. According to the Provisional Specification the process of the invention yields dyes of the formula <FORM:0734792/IV (c)/6> and <FORM:0734792/IV (c)/7> wherein the symbols have the meanings given above but in addition R3 and R4 are any hydrocarbon groups and R5 may be aralkyl, hydroxyalkyl or carboxyalkyl.  Additional values of D1 specified are thiazoles, oxazoles, selenazoles and their benzene, naphthalene, acenaphthene and anthracene homologues, pyridine and its polycyclic homologues, diazines, diazoles, oxazolines, selenazolines and pyrazolenine.  Substituents specified are amino, hydroxy and methylene dioxy groups. Additional values of D2 specified are oxarhodanine, oxindoles, hydantoin, thiohydantoin, pseudohydantoin and pseudothiohydantoin.  It states that the 2-thioether group in compound III is unreactive and the 4-thioether group reactive.ALSO:5 : 5 - Dimethyl - 2 : 4 - dimethylthio - iminiazolenine is prepared by treating an aqueous sodium hydroxide solution of 5 : 5-dimethyldithiohydantoin with dimethyl sulphate, and extraction with ether.  The base is quaternized by refluxing with methyl iodide.  The following bases and their salts are prepared in a similar manner.  5 : 5-Diethyl, 5 : 5-cyclopentamethylene, 5 : 5-cyclotetramethylene, 5-benzyl-5-methyl, and 5 : 5 - diphenyl - 2 : 4 - dimethylthioiminazolenines and 5 : 5 - dimethyl - 2 : 4-diethylthio-iminazolenine.