Production of compounds of the cyanine type

Cyanine compounds are prepared by reacting a heterocyclic nitrogen base having a thioether group in the a - or g - position to the nitrogen, with an alkyl salt and with a quaternary ammonium salt of a heterocyclic nitrogen compound having a reactive methyl group. Thus the a - or lambdamercaptan of a heterocyclic nitrogen base is first alkylated or aralkylated to form the thioether and this is then converted to the quaternary salt and reacted with the quaternary ammonium salt of a heterocyclic nitrogen compound having a reactive methyl group. A neutral solvent such as alcohol and an acid-binding agent such as sodium acetate is advantageously employed in such process, or the solvent may also be an acid-binding agent (pyridine). Alternatively a mixture of a heterocyclic nitrogen base having a reactive methyl group, a heterocyclic nitrogen base having a reactive thioether group in the a - or g - position to the nitrogen atom and the salt required to form the quaternary salts of these bases, is heated together, if necessary in the presence of a solvent and an acid-binding agent (pyridine may act in both capacities). Thioethers may be prepared by alkylation of the mercapto bodies derived from thiazoles, thiazolines, oxazoles, oxazolines, selenazoles, selenazolines, quinolines, indolenines, and pyridines and they may contain substituents such as hydroxy, alkoxy, halogen alkyl, aryl, aralkyl, amino or substituted amino; they are converted to quaternary ammonium salts by heating with an alkyl salt and these may be condensed with quaternary ammonium salts of the foregoing heterocyclic bases having a reactive methyl substituent in a - or g -position to the nitrogen atom. The cheapness of production, good yields and the purity of the products are mentioned as advantages of the process. In examples: (1) 1-methylmercaptobenzthiazole ethiodide is condensed with quinaldine ethochloride to give 1 .2-diethyl-thiopseudocyanine iodide, 2-methyl-b -naphthoxazole ethiodide to give 2.2 -diethyl-3 .4 -thiobenzoxacyanine iodide, 2.3.3-trimethylindolenine methiodide to give 2-ethyl-1 .3 .3 -trimethylthioindocyanine iodide, 1-methylbenzthiazole ethochloride to give 2.2 -diethylthiocyanine iodide, 2.4-dimethylquinoline methiodide to give 1.4-dimethyl-2 -ethylthiopseudocyanine iodide, lepidine methiodide to give 2-ethyl-1 -methylthioisocyanine iodide, a -picoline ethiodide to give 1.2 -dimethylpyridothiopseudocyanine iodide, 1-methyl-5.6-benzbenzthiazole ethiodide to give 2.2 -diethyl