Patent GB-594559-A (GB)
Title: Improvements in the manufacture of intermediates and photographic sensitising dyes made therefrom
IPC: C09B23/02
Filed: 1945-03-01
Abstract: Dye intermediates of the general formula <FORM:0594559/IV/1> (wherein Q represents a sulphur or selenium atom, R a substituted or unsubstituted pyrryl group, preferably attached in the 2-position, R1 a hydrogen atom, an alkyl group, an aralkyl group or an aryl group, substituted (e.g. p-chlorophenyl) or unsubstituted, and R2 an alkyl, aralkyl or aryl group or an amino or substituted amino group) are manufactured by heating a thiomide or a selenoamide with a formula <FORM:0594559/IV/2> advantageously in a solvent, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, or isobutyl alcohol, and in the presence of alkalis, e.g. alkali metal carbonate or bicarbonate. Specified thioamides and selenoamides are thioacetamide, selenoacetamide, thiourea, selenourea, phenylthiourea, thiopropionamide, thiobenzamide, methylthiourea, benzylthiourea and thiophenylacetamide.  Specified halogenated ketones are 2-chloracetyl-, 2-bromoacetyl- and 2-iodoacetyl-pyrrole, 2 - (a  - chloropropionyl) - pyrrole, 2-(phenyl-chloroacetyl)-pyrrole and 2-(a -chloro-b  - phenylpropionyl) - pyrrole.  The resulting pyrrylthiazole or pyrrylselenazole compounds may be quaternated by heating with alkyl or aralkyl esters of inorganic or arylsulphonic acids, e.g. alkyl halides, such as ethyl, and n-propyl iodide, n-propyl, isobutyl and n-butyl bromide or n-butyl chloride, alkyl arylsulphonates, such as methyl and ethyl p-toluenesulphonate or methyl benzenesulphonate, aralkyl halides, such as benzyl bromide or chloride, or dialkyl sulphates, such as dimethyl or diethylsulphate. The anion of the resulting salts may be changed and a less soluble quaternary salt produced by treating an alcoholic or aqueous solution of the more soluble quaternary salt with an aqueous metal salt; e.g. the quaternary iodides, bromides, perchlorates or rhodanates may be obtained by the action of the corresponding sodium or potassium salts on the quaternary chlorides, p-toluenesulphonates or alkylsulphates. Methine or polymethine dyes are obtained by treating a compound of the foregoing general formula or its quaternary salt, wherein R2 represents methyl, by any method known to be capable of converting a heterocyclic nitrogen base or its quaternary salt, having a methyl group in the a -position to the nitrogen atom, into such a dye. Thus, monomethinecyanine dyes are obtained by condensing a quaternary salt of the type described with a cyclammonium quaternary salt having in the a - or g -position to the quaternary nitrogen atom a thioether or a selenoether group, e.g. a methylthio, ethylthio, benzylthio, phenylthio or ethyl selino group.  Symmetrical trimethinecyanine dyes are obtained by condensing a quaternary salt of the type described, wherein R represents methyl, with an ortho ester of a carboxylic acid (e.g. a trialkyl orthoformate) or by condensing not substantially less than two molecular proportions of a quaternary salt of the type described, wherein R2 represents methyl, with one molecular proportion of a diarylformamidine, an alkyl isoformanilide or an alkyl isothioformanilide, specified reagents being diphenylformamidine, ethyl isoformanilide and methyl isothioformanilide.  A b -arylaminovinyl derivative is obtained when in the latter condensation substantially equimolecular proportions of the reactants are used.  The b -arylaminovinyl or b -acylarylamidovinyl derivatives can be condensed with cyclammonium quaternary salts containing a reactive methyl group to furnish carbocyanine dyes, specified reagents being 2-methylbenzthiazole ethiodide, 2-methyl-4-(21-furyl)-thiazole metho-p-toluenesulphonate, 2 - methylbenzoxazole ethiodide, quinaldine ethiodide, lyridine ethiodide, or 2-methyl-4-(21-pyrryl)-thiazole quaternary salts.  Dye intermediates are obtained by condensing a quaternary salt of the type described, wherein R2 represents methyl, with a mixture of an alkyl orthoformate, e.g. triethyl orthoformate, and a primary or secondary aromatic amine, e.g. aniline or methyl aniline. Symmetrical or unsymmetrical trimethinecyanine dyes are obtained by condensing a b -arylamino-vinyl compound of general formula <FORM:0594559/IV/3> wherein R, R1 and Q have the meanings assigned above, R3 represents alkyl or aralkyl, Ar represents aryl and X represents an anion, or its acylation product, or a b -arylaminovinyl compound of general formula <FORM:0594559/IV/4> wherein R5 represents hydrogen or alkyl, the other symbols being as above-defined, with a cyclammonium quaternary salt having, in the a - or g -position to the quaternary nitrogen atom, an alkyl (e.g. a methyl) group, which may be of the type herein described, or, e.g. 2-methylbenzthiazole ethiodide, 2-methyl benzoxazole ethiodide, quinaldine ethiodide, lepidine ethiodide or 2-methyl-4-(21-furyl)-thiazole metho-p-toluenesulphonate, condensation being advantageously effected in presence of an acid-binding agent, e.g. pyridine or triethylamine. The b -arylaminovinyl or b -acylarylamidovinyl derivatives may also be condensed with heterocyclic compounds containing a ketomethylene group to obtain merocarbocyanine dyes; thus condensation can be effected with rhodanine, 3 - ethyl - rhodanine, 3 - phenyl -rhodanine, 3-ethyl-2 : 4-oxazoledione, 2-thiohydantoin or 1 : p 3-diphenylthiohydantoin, preferably in presence of an acid-binding agent.  Polymethine dyes are obtained by condensing a b -arylaminovinyl compound as of the general formul  shown above, with a ketomethylene heterocyclic compound containing in the ring the grouping <FORM:0594559/IV/5> (wherein A represents an oxygen or sulphur atom, a carbonyl group or a -NR4- group, R4 representing hydrogen, alkyl, aralkyl or aryl), advantageously in presence of an acid-binding agent, e.g. a tertiary amine, such as a trialkylamine, e.g. triethyl-, tripropyl- or tributyl-amine, or an alkali metal carbonate, e.g. sodium or potassium carbonate.  In examples: (1) thiourea, 2-chloroacetylpyrrole and ethanol are heated under reflux to obtain 2-amino-4-(21-pyrryl)-thiazole hydrochloride, from which the base is liberated by aqueous sodium bicarbonate; (2) thioacetamide, 2-chloroacetyl-pyrrole and ethanol are heated under reflux with anhydrous potassium carbonate, producing 2-methyl-4-(21-pyrryl)-thiazole; 2-methyl-4-(21-pyrryl)-selenazole is similarly obtained from selenoacetamide, 2-ethyl-4-(21-pyrryl)-thiazole from thiopropionamide and 2-phenyl-4-(21-pyrryl)-thiazole from thiobenzamide; (3) 2-methyl - 4 - (21 - pyrryl) - thiazole and ethyl p-toluenesulphonate are heated together to form 2-methyl-3-(21-pyrryl)-thiazole etho-p-toluenesulphonate; (4) 2-methyl-4-(21-pyrryl)-thiazo etho-p-toluenesulphonate, 2-ethylthioquinoline etho - p - toluenesulphonate, triethylamine and ethanol are boiled together and poured into hot aqueous potassium iodide to isolate crude [2-(1-ethylquinoline)] - [2 - { 4 - (21 - pyrryl) - 3 - ethyl thiazole)]-methinecyanine iodide; (5) 2-methyl-4-(21-pyrryl)-thiazole etho-p-toluenesulphonate, 2-ethylthiobenzthiazole etho - p - toluenesulphonate, triethylamine and ethanol are treated with hot aqueous potassium iodide as in (4) to isolate crude [2-(3-ethylbenzthiazole)]-[2- { 4-(21-pyrryl)-3-ethylthiazole } ]-methinecyanine iodide; (6) 2-methyl-4-(21-pyrryl)-thiazole and ethyl p-toluenesulphonate are heated together and the product, in pyridine, is treated with ethyl orthoformate, prior to refluxing and pouring into hot aqueous potassium iodide to isolate bis - 2 - [4 - (21-pyrryl) - 3 - ethylthiazole]-trimethinecyanine iodide; similarly, bis-2-[3-methyl - 4 - (21 - pyrryl) - thiazole] - trimethine -cyanine iodide is obtained from 2-methyl-4-(2 pyrryl) - thiazole metho - p - toluenesulphonate and bis - 2 - [3 - propyl - 4 - (21 - pyrryl) - thiazole]-trimethinecyanine iodide from 2-methyl-4-(21-pyrryl) - thiazole propio - p - toluenesulphonate.  Specifications 344,409, 537,961 and 594,558 are referred to.  2 - Chloroacetylpyrrole is obtainable from pyrrole and chloroacetonitrile or from pyrrole magnesium bromide and chloroacetyl chloride.