DE923868C - Process for the preparation of thiazolone cyanine dyes - Google Patents

Description

(WiGBl. P. 175)

ISSUED FEBRUARY 21, 1955

p 29337 IVd 122 e D

The invention relates to a process for the preparation of thiazolone cyanine dyes, which for sensitizing halogen silver emulsions and used as intermediates in the manufacture of trinuclear cyanine dyes can.

EiS has been found to contain thiazolone cyanine dyes can be obtained by adding a substituted thioamide of the type described below is condensed with a haloacetic or dihaloacetic acid or with an α-halopropionic acid. The condensation can be caused by simply melting together of the reaction components or by taking them to a temperature of 5 to 6o minutes in my suitable solvent 75 to 120 ° can be heated. The obtained dyes are represented by the following general formula marked:

R. r c

A ₁ -

O = C, C = CH-C = (CH-CH) _m _ ₁ =:

R ₉

in A ₁ the remainder of a heterocyclic nitrogen-containing ring of the type customary in cyanine dyes, such as, for example, oxazole, thiazole, selenazole and their polycyclic homologues, such as those of the benzene, naphthalene, acenaphthene and anthracene series, pyridine and its polycyclic homologues, such as quinoline and a- or /? - naphthoquinolines, indolenines, benzimidazoles, diazines, such as pyrimidines and quinazolines, thiazolines and selenazolines.

The polycyclic compounds - these series can also be in the carbocyclic rings one or more groups, such as alkyl, for example methyl, ethyl and the like, or aryl, such as Phenyl, or amino, hydroxy, or alkoxy, such as methoxy or ethoxy or the like, and methylenedioxy groups or be replaced by halogen, such as chlorine, bromine or iodine atoms.

Ot means ι or 2, R means hydrogen or a halogen, such as chlorine, bromine or iodine, or a methyl group, R ₂ means an alkyl, allyl, aryl or aralkyl group, such as methyl, ethyl, propyl, phenyl, naphthyl, Tolyl, benzyl and the like, R ₃ means an alkyl or aralkyl group or substituted groups of this kind such as methyl, ethyl, propyl, butyl, oxyethyl, ethoxyethyl, naphthylmethyl, benzyl and the like., And X means an acid residue such as Chloride, bromide, iodide or alkyl sulfate or alkyl p-toctol sulfonate or perchlorate.

The preparation of the substituted thioamides is carried out according to the method of Schneider and coworkers (Ber. D. Chem. Ges. 57, pp. 522 to 532), which consists in using a heterocyclic quaternary ammonium salt of the type commonly used for cyanine dye synthesis and in a- or /? - position to the ring nitrogen atom contains a reactive methyl group, is condensed with an alkyl, allyl, aryl or aralkyl ester of isothiocyanic acid in the presence of a base such as triethylamine or pyridine. The reaction probably works according to the following equation:

= (CH- CH) _m _ ₁ = C-CH ₃ + R ₂ NCS-

A ₁ -

SH

N - (CH = CH) _mx- C = CH-C + HX j \ N

R ₃ 1

in the A ₁ , m, R ₂ , i? ₃ and X have the meaning given above.

2 Methylbenzothiazoläthjödid, - - 2 Methylbenzoxazolätihjodid - 2 Methylbenzoeelenazolmeth / iodide, 2-Methylpyridinäthtjodid, 2-Methyldhinolinäthjodid, 2-Methylthiazolinäthjodid, 2-methyl a- or ^ u -naphthotbiiazoläthjodM: As typical examples of heterocyclic quaternary ammonium salts, the following may be gemannt. like

The inferring compounds are examples of more suitable Isothiocyanic acid ester: methyl, ethyl, butyl, isoamyl or isopropyl ester, Phenyl, o-tolyl or xenyl ester, allyl or benzyl ester. Phethyl isoselenocyanate can also be used will.

The condensation reaction between the substituted - Thioaimide and a haloacetic acid, dihaloacetic acid or with a α-halopropionic acid of the following formula:

R ₅ -CX ₁

O = C

OH

in which R ₄ denotes hydrogen or a methyl group, R ₅ denotes hydrogen or halogen, such as chlorine, bromine or iodine, and X ₁ denotes a halogen in the sense of R ₅ , by simply heating the reaction components in a bomb or a sealed tube to a temperature of 100 to I2O °. The reaction can also be carried out by heating the reaction components in the presence of an alcohol or an acetic acid or an acetic anhydride for a few minutes under reflux or on the steam bath. It is preferable to work in such a way that the reaction components are heated to a temperature between 75 to 120 minutes in the presence of methyl, ethyl, propyl, isopropyl, butyl, amyl or isobutyl alcohol and the like, or acetic acid or acetic anhydride ^{0 can be} heated. The reaction that occurs using haloacetic acid is likely to go as follows:

H ₂ C-X ₁

HS

-A ₁ -

O = C + ^ C-CH = C- (CH = CH) _m - N

In '■ I -

OH IR ₃

R,

H ₂ C

O = CC = CH-C = (CH-CH) _TO = N

+ H ₂ O

The following examples describe the preparation of some of the substituted thioamides, which, as described later, becomes thiiazolone cyanine dyes are processed.

example 1

a- (3-Ethylbenzothiazolylidene) tfeioacetanilide

A mixture of 60 g of 2-methylbenzothiazole and 100 g of ethyl p-toluenesulfonate was gradually increasing 195 °, at which temperature an exothermic

mixed reaction occurred and the mixture was held ^{at 195 0 for 5 minutes.} After cooling to 100 °, the product was poured into a solution of 85 ecm phenyl isothiocyanate in 250 ecm pyridine. The resulting mixture was stirred and heated to 120 ° for 10 minutes, cooled to room temperature and diluted with 1 l of ice water. After decanting the water from the heavy oil, rewashing with 0.5 l of water and decanting the water, the oil was triturated with 200 ecm of methanol until it solidified. This solid crude product was boiled with 300 ecm isopropanol, filtered and dried in an oven at So °. Ale yield was 96.5 g of an orange-yellow product were obtained, which melts at 195 ^0th Another 12.5 kg was obtained by concentrating and cooling the mother liquor. The total yield was 109 g.
Example 2

CH ₃ O

C = CH-C

^: N

CHo

go (3-methyl-6-methoxybenzothiazolylidene) -thio-

acetanilide

12.5 g of 2-methyl-6-methoxybenzothiazole methyl ptoluenesulfonate were dissolved in 20 ecm of methanol. 6 ecm of phenyl isothiocyanate and 4 ecm of triethylamine were then added and the mixture was left to stand for 12 hours. Furthermore, 60 ecm of water were then added and the mixture was stirred through. The water was drawn off from the heavy oil and the oil was boiled with 50 ecm of methanol. After cooling, the product was filtered off and washed with methanol. The yield was 6.45 g of a yellow solid with a melting point of 199 to 200 ⁰ .

Example 3

CH ₃
j
CH ₃ - '\ C-CH ₃ SH

"C = CH-C

C ₂ H,

(i-Ethyl-3, 3, 5-trimethylindoleninyliidene) thioacetanilide.

12.5 g of 2, 3, 3, 5-tetramethylindolenine ethiodide were dissolved in 20 ecm of methanol, whereupon the solution was 4 ecm of triethylamine and 6 ecm of phenyl isothiocyanate and the mixture was left to stand for 48 hours. Thereon .60 ecm of ether were added and the batch was cooled in an ice bath. A small amount of the as The starting product used Äthjodidsakes was removed by filtration and the filtrate on the Steam bath evaporated. Remained as the end product 6.9 g as a thick orange residue.

Example 4

\ / ^SH

C = CH- C

CH 2 CH = CH ₂

(S-ÄthylbenzothiazolylidenJ-N-allylthioacetamid y, y ecm AMylisothiocyanat and 25.07 g of 2-Methylbenzothiazoläthyl - ρ - were toluolsulfonai with 35 cc of pyridine 10 minutes heated to 120 ⁰ After passing stirring the mixture with water and decantation, followed by stirring. Ether and decanting, the solid residue was filtered off and dried at 80 ° The yield was 3.5 g of dark crystals.

Example 5
Se

C = CH-C

C ₂ H ₅

(3-Ethyl-5-methoxybenzoselenazolylidene) thioacetanilide

3 ecm of phenyl isothiocyanate and 7.1 g of 2-methyl-5-methoxyselenazole ethiodide in 15 ecm of pyridine were boiled for 5 minutes. After cooling, 35 ecm of ether were added. The mixture was then stirred and set aside for 1 hour. A precipitate formed which was filtered off and washed with water. The solid residue was boiled with 50 ecm isopropanol, cooled to room temperature, filtered and dried at 80 °. The yield was 4.19 g; Melting point 233 to 234 ⁰ .

Example 5a
O

C = CH-C

SH

(3-Ethyl-4,5-diphenyloxazolylidene) thioacetanilide

A mixture of 7.8 g of 2-methyl-4, 5-diphenyIoxazoläthjodid, 2.7 g phenyl isothioeyanate, 10 g pyridine and 2 g of triethylamine were dissolved with gentle heating and the resulting solution in Leave room temperature to itself for 10 days. The reaction mixture was with 150 ecm of water diluted and stirred until the product solidified. The material was washed with Purified water and ground with isopropyl alcohol. The yield was 2.7 g; Melting point at 144 to 145 °.

Example 5b

CH ₃ -I
CH "-

C = CH-C

C ₂ H ₅

3 "ethyl-5,6-dimethylbenzoxazolylidene) -fhioacetanilide

A mixture of 31.7 g of 2, 5, 6-Trimethylbenzoxazoläthjodid, 13.5 g Phenylisothioeyanat, ^l 7> 9g Py ^r ~ idin and 10.1 g of triethylamine was gently warmed until the solution -and stirred. After the mixture had stood at 25 ° for 10 days, it was diluted with 300 ecm of water and washed with water by decanting. The semi-solid product obtained was dissolved in the smallest possible amount of hot isopropyl alcohol and, after cooling, 3 volumes of ether were added. The light yellow solid material was dried at 80 °. The yield was ng; Melting point 172 to 175 ⁰ .

Example 6

SH

C = CH-C

C ₂ H ₅

Example 7

(3-Ethylbenzothiazolylidene) -thioacet-o-toluide

This procedure corresponds essentially to that of Example 1 with the difference that 6 g of 2-methylbenzothiazole, 10 g of ethyl p-toluenesulfonate and 8.5 ecm of o-tolyl isothiocyanate were used. The yield was 6.22 g of a solid product with a melting point of 198 to 200 ^° . CH ₃ O

SH

C = CH-C

N ''

C ₂ H ₅

(3-Ethyl-6-methoxy <ben'Zothiazolylidene) -thioacet-o-naphthalide

5.2 g 2 - Meithyli-6 -mieiihoxybeinizothiazoläthy 1-ptoktolsulfonat and 2.2 g of a-naphthylisothiocyanate in 12 ecm of pyridine were heated to ι io ° for 10 minutes while stirring. After cooling to room temperature and cooling with ice water, the solid body was treated with 20 ecm of methanol and filtered. The residue was with 25 ecm isopropanol boiled, cooled, filtered and dried at 80 °. The yield was 1.9 g; Melting point 200 to 2io °.

Example 8

S .SH

\ / so

C = CH-C

C, H ₅

'N

(3-Ä & yliben'zothiazolyHden) -N-ethylthioacetamide

6 g of 2-Methylbenizofhiazoläthjodid, 2 ecm Äthylisothiocyanat, 10 cc pyridine and 1 cc of triethylamine were refluxed for 20 minutes (140 Wachsbaidtsmperatur ^0). After the mixture was poured into 400 ecm of water, it was set aside for 48 hours. A red, rubbery solid material deposited. This product was filtered off and triturated with isopropanol. The red crystals obtained were filtered, dried at 8o ° to give a yield of i, S g of melting point 126-136 ^0th

CH, - '

Example 9
S.

C = CH-C

SH

^ N

CH ₃

(3, 6-Dimethylbenzothiazolylidene) thioacetanilide

20 g phenyl isothiocyanate, 38.8 g 2-methylbenzothiazole methosulfate and 40 ecm of pyridine were refluxed ι Sturade and the mixture poured in water. After standing, the water was removed by decantation and the

solid residue boiled with isopropanol. The j A mixture of 17 g of 2-methylbenzoselenazole mixture was cooled, filtered and dried at 80 °. The yield was 25.85 g; the melting point 188 to 190 ⁰ .

Example 10

CH ₃ 0—

C = CH-C

⁴ N '
C,

SH

(3-ethyl-6-methoxybenzothiazolylidene) -thioacetyl-naphthalide

5 g of 2-methyl-6-methoxybenzothiiazolimethyl ptoluenesulfonate, 2 g of β- naphthyl isothiocyanate and 12 ecm of pyridine were heated together to 10 minutes with stirring. This mixture was poured into ice water and stirred until a sticky solid had formed. The water was removed by decanting, the solid body was treated with 20 ecm of methanol and filtered off. The residue was boiled with isopropanol, cooled, filtered off and dried at 80 °; the yield was 1.4 g of a solid with a melting point of 167 to 169 ⁰ .

SH

Example 11

= CH-C

CH ₃

(i-Methyl-2-quinolylidene) thioacetanilide

A mixture of 50 g of quinaldine methyl p-toluenesulfonate, 25 g of phenyl isothiocyanate, 20 g of triethylamine and 80 ecm of pyridine was heated to the boil and left to stand overnight. The mixture was diluted with ether and a dark brown solid was deposited which was purified by washing with methanol. The yield was 21 g, the melting point 163 to 169 ⁰ .

Example 12

Se

^S N ''

CH ₃

SH

= CH-C

(3-methylbenzoselenazolylidene) -thioacetanilide methyl-p-toluenesulfonate, ng phenyl isothiocyanate and 20 ecm of pyridine was treated as in Example 11. 14 g of orange crystals were obtained.

Example 13

CH ₁ -CS

= CH-C

> —C

Ν '

SH

N /

(3-Ethyl-5-methyl-4-phenylthiazolylidene) thioacetanilide

A mixture of 10 g of 2,5-dimethyl-4-phenylthiazole and 10.5 g of ethyl p-toluenesulfonate was ^{melted at no 0 for} 10 minutes. The quaternary salt thus obtained was mixed with 9 g of phenyl isothiocyanate, 10 cm of pyridine and 2 g of molten sodium acetate. After 5 minutes heating at 175 ⁰ An orange-red color, was mixed and the product with 200 cc of water and washed by decanting developed. Crystals formed after stirring with 25 ecm of methanol. After filtering and washing with isopropanol and finally with ether 2 g of orange-colored crystals were obtained which melted at 146-147 ^0th

The following examples describe the preparation of thiazolone cyanine dyes from the substituted thioamides described above.

Example 14

S CH ₂

C-CH = C C = O

C ₂ H ₅

Br

A mixture of 25 g of (3-ethylbenzothiazolylidene) thioacetanilide (Example 1) and 25 g of bromoacetic acid were dissolved in 50 ecm of n-butanol. The mixture was cooled, stirred with ether, filtered and washed with ether. The residue was dried at 80 °, and 34.9 g of a solid were obtained. which melts at 231 to 236 ^0. A portion of this product weighing 10 g was converted from methanol

crystallized, and 7.7 g with a melting point of 233 to 234 ^{0 were} obtained as the finished dye.

Example 15

CH, 0

CH,

ν '

CH ₃

C-CH = C

Br

A mixture of 5 g of (3-methyl-6-methoxybenzothiazolylidene) thioacetanilide (example) and 5 g of bromoacetic acid in 10 ecm of n-butanol was heated on a steam bath with stirring for 15 minutes, whereby the solution took on a yellowish color. The mixture was treated with a small amount of ether, nitrated and washed with ether. The solid product was recrystallized from methanol to give 4.6 g of dye crystals of melting point 216-217 ^0th

CH

S-CH ₉

N-C = O.

Br

6.9 g of (i-ethyl-3, 3, 5-trimethylikidoleninylidene) thioacetanilide (Example 3) were heated to 105 to 10 minutes with 6.9 g of bromoacetic acid in 25 ecm of n-butanol for 10 minutes. The mixture was treated with ether and the ether layer decanted. The black liquid was made with isopropanol. stirred and filtered. The residue was uimkristallisiert from methanol to give 1.7 g of the desired dye with a melting point of 236-238 ^0th

\
C. example S-CH ₅ 0 S. / / = CH ₂ H ₅ = CH-C N
I. \ NC =
I. I.
C ₂ I.
CH ₂ CH =

Cl

A mixture of 3.5 g of (3-ethylbenzothiazolylidene) -N-allylthioacetamide (Example 4), 3.5 g of chloroacetic acid and 7 ecm of butanol was boiled for 3 minutes. After cooling, the product was precipitated with ether, and 4.3 g of crystals with a melting point of 227 to 230 ^{° were} obtained.

Example 18

CHoO

NS,

N-C = O

Br

A mixture of 4.11 g (3-ethyl-S-methoxy-benzoselenazolyliden) -thioacetanilid (example), bromoacetic acid and 4,11g 45 com n-butanol was heated for 20 minutes to 90 ⁰ and 10 minutes iio °. The thick slurry of greenish crystals was diluted with 3 volumes of ether and filtered and gave 5 g of a product with a melting point of 283 to 284 ⁰ .

Example 19

S-CH ₅ ,

C = CH-C

Br

4 g of (3-ethylbenzothiazolylidene) thioacet-o-toluide (Example 6), 4 g of bromoacetic acid and 8 ecm of n-butanol were treated as in Example 14 and gave 3.9 g of a thiazolone cyanine dye with a melting point of 240 to 241 ⁰ .

Example 20

CH ₃ O

N-C = O

Br

A mixture of 1.5 g (3-Äfliyl-6-methoxybenzothiazolylidene) -thioacet-a-naphthalide (Example 7) was heated to 100 for 5 minutes with the same weight of bromoacetic acid in S ecm n-butanol. The yellow crystals that separated out on cooling weighed 0.75 g and melted between 201 and 203 ^° .

V ^S x

Example 21

NS"

C = CH-C
"N ^ NC = O

C ₂ H ₅

C ₂ H

₂ H ₅

Br

A mixture of 1.5 g (3-ethylbenzothiazolylidene) -N-ethylthioacetamide (Examples), 1.5 g of bromoacetic acid and 5 ecm acetic acid was heated to I20 ° for 5 minutes. After cooling down, that became Product precipitated with ether and dried; Yield 2.07g.

Example 22

S-CH ₂

CH ₃ O-

C = CH-C

* N-C = O

Br

A mixture of 1.3 g of (3-ethyl-δ-methoxybenzothiazolylidene) thioacet - /? - naphthalide (Example 10), 1.3 g of bromoacetic acid and 5 ecm of n-butanol was heated to 100 ° for 10 minutes. After precipitation with ether and recrystallization from n-propyl alcohol, 1.01 g of crystals with a melting point of 217 to 219 ^{0 were} obtained.

Example 23

CH ₈ -

C = CH-C

S-CH ₂

^ N-C = O

CH ₃

Br

A mixture of 20 g (3, 6-Dimetliylbenzofhiazolyliden) -thioacetanilide (Example 9), 20 g of bromoacetic acid and 25 ecm of n-butanol was 5 minutes heated to no °. The product was precipitated with ether and boiled with isopropanol cleaned. Yield 21.93 g; Melting point 230 to 231

Example 24

SS - CH ₂

C = CH-C

^ N ⁷ '\ [- C = O

C ₂ H ₅

Br A mixture of 0.65 g (3-ethyl-5-methyl-4-phenyl-thiazoly the Ii) -thioacetanilid (Example 13), 1.0 g of bromoacetic acid and 2 cc of acetic acid was heated to 115 ι hour ^0th The product was precipitated with ether and then washed with ether by decantation. The viscous product does not solidify and can be used directly in dye synthesis.

Example 25

Se

C = CH-C

S-CH ₉

N
CH.

N-C = O

Br

A mixture of 14 g of (3-methylbenzoselenazolylidene) thioacetanilide (Example 12), 5.7 g of bromoacetic acid and 10 ecm of n-butanol was heated on the steam bath for 5 minutes. The reaction mixture thickened and after diluting with ether the product was filtered and a yield of 13 was obtained; Melting point 266-272 ^0th

Example 26

S-CH ₂

CH-C

N-C = O

Br

A mixture of 5.5 g of (i-methyl-2-quinolylidene) thioacetanilide (Example 11) and the same weight of bromoacetic acid was in 50 ecm of n-butanol dissolved and heated to 100 ° for 10 minutes. When cooling down Yellow crystals formed which were filtered off and washed with ether. By recrystallization yellow crystals with a melting point of 212 ° were obtained from methanol.

Example 27

1 SC-CH ₃

C = CH-C

N-C = O

C ₂ H ₅

Cl

A mixture of 0.7 g of a-chloropropiomic acid, 0.7 g of the product from Example 1 and 15 ecm

923

n-Propyl alcohol was refluxed for ίο minutes). The product separated out on cooling and, after recrystallization from n-propyl alcohol, weighed 0.55 g; Melting point 198 to 199 ⁰ .

Example 28

H C-Cl

C = CH-C

^S N - C = O

Cl

A mixture of 0.75 g of dichloroacetic acid, 0.75 g of the product of Example 1 and 15 ml of n-propyl alcohol was treated as in Example 27 and gave 0.6 g of dye with a melting point of 197 to 198 ⁰ .

Example 29

S-CH ₉

C = CH-C

N-C = O

A mixture of 2.5 g (3-ethyl-4, 5-diphenyloxazolyliden) -thioacetanilid, 2.5 g of bromoacetic acid and 2.5 com acetic acid was heated for 30 minutes 9S ^0th After cooling, the product was precipitated with ether and converted into the iodide under reflux with 15 ecm of a saturated solution of sodium iodide in acetone. After cooling, an equal volume of ether was added and the light yellow crystals were filtered off and washed with ether. 1 g of dye with a melting point of 156 to 157 ^{° was} obtained.

Example 30

P TX

C = CH-C

S-CH ₉

N-C = O

A mixture of 5 g (3-ethyl-5,6-dimethyl-benzoxazolylidene) thioacetanilide, 5 g bromoacetic acid and 5 ecm acetic acid was heated to 95 ° for 30 minutes. After cooling, the product was precipitated with ether. The semi-solid product was refluxed with 40 ecm of acetone containing 5 g of sodium iodide. After cooling, the slightly yellow product was filtered off and dried at 80 °. There were 3.5 g of a solid product were obtained, which melts above 290 ^0th

The above dye salts can be converted to other than halosake by the Halogensaliz with an aqueous or aqueous-alcoholic solution containing a sodium or potassium salt which contains perchloric or thiocyanic acid is treated,

The thiazolone cyanine dyes described above can act as sensitizers for silver halide emulsions: to be used. For the production of emulsions containing these dyes, the dye can be dissolved in methyl or ethyl alcohol and the alcoholic solution that Contains 3 to 50 mg of the dye, per liter of emulsion are added. The appropriate and economical For the person skilled in the art, concentration for a given emulsion results from the usual ones Preliminary searches and measurements! As used in technology for the production of emulsions will.

The thiazolone cyanine dyes have the further advantage that they can also be used in the production of light filters and protective layers against the formation of sound halos. In addition, the thiazolone cyanine dyes, which contain a methylene (= CH ₂ ) group in the 5-position of the thiazole nucleus, can be used as intermediates in the production of trinuclear cyanine dyes.

Claims (8)

PATENT APPLICATIONS: I. Process for the production of thiazolone cyanine dyes, characterized in that a compound of the general formula -A ₁ - N - (CH = _ _x -C = CH-C SH R, with a compound represented by the following formula R ₅ -CX ₁ OH is heated, wherein in the formulas A ₁ the remainder of a heterocyclic nitrogen-containing ring of the type customary in cyanine dyes, R _{2 is} alkyl, allyl, aryl or aralkyl groups, R _{3 is} alkyl or aralkyl groups, R _{4 is} hydrogen or a methyl group, R _{5 is} hydrogen or halogen, m is an integer from ι to 2 and X _{1 is} halogen (bromine, chlorine or Iodine) means. 2. The method according to claim i, characterized in that that a combination of the general formula ..A ₁ SH i C-CH = C with a compound of the following formula R ₄ R ₅ -CX ₁
O = C
OH is heated, where in the formulas A ₁ the remainder of a heterocyclic nitrogen-containing ring of the type customary in cyanine dyes, R ₂ alkyl, allyl, aryl or aralkyl groups, R ₃ alkyl or aralkyl groups, R ₄ hydrogen or a methyl group, R _{5 is} hydrogen or halogen and X _{1 is} halogen (bromine, chlorine or iodine). 3. The method according to claim 1 and 2, characterized characterized in that a compound of the general formula / "Ν / ^SH ■ C-CH = C in which A ₁ denotes the remainder of a heterocyclic nitrogen-containing ring of the type customary in cyanine dyes, R ₂ denotes alkyl, allyl, aryl or aralkyl groups and R ₃ denotes alkyl or aralkyl groups, is heated with bromoacetic acid or chloroacetic acid. 4. The method according to claim ϊ and 2, characterized characterized that a connection of the general formula SH C-CH = C "N" in which A ₁ denotes the remainder of a heterocyclic nitrogen-containing ring of the type customary in cyanine dyes, R ₂ denotes alkyl, allyl, aryl or aralkyl groups and R ₃ denotes alkyl or aralkyl groups, is heated with α-chloropropionic acid. 5. The method according to claim 1 and 2, characterized in that a compound of the formula S SH C = CH-C C ₂ H ₅ SH C = CH-C 'N heated with bromoacetic acid or chloroacetic acid. 6. The method according to claim 1 and 2, characterized in that a compound of the formula 95 is heated with α-chloropropionic acid. 7. The method according to claim 1 to 6, characterized in that the heating on the Steam bath is expediently carried out under reflux cooling. 8. The method according to claim 1 to 7, characterized in that the heating, preferably n-butanol, is carried out at a temperature between about 100 to 120 ⁰ expediently in the presence of an aliphatic · acid such as acetic acid, or an aliphatic alcohols. © 9591 2nd SS