GB2028361A - Process for the preparation of azo dyestuffs - Google Patents

Abstract

When ortho-halogenoazo dyestuffs are reacted with copper-I cyanide, cyanoazo dyestuffs with a low copper content are obtained if a mixture of 25-95 mol percent, preferably 30-80 mol per cent, of CuCN, relative to halogen to be replaced, and 5-75 mol per cent, preferably 20-70 mol per cent, of Zn(CN)2 is used.

Description

SPECIFICATION Process for the preparation of azo dyestuffs The invention relates to a process for the preparation of azo dyestuffs which have a low copper content and, in the diazo component, have at least one cyano group in the ortho-position relative to the azo bridge, by reacting corresponding orthohalogenoazo dyestuffs with metal cyanides in the presence of copper compounds.

The process is characterised in that a mixture of 25-95 mol per cent, preferably 30-80 mol per cent, of CuCN, relative to halogen to be replaced, and at least 5-75 mol per cent, preferably 20-70 mol per cent, of Zn(CN)2 is used, the copper cyanide being employed as such or as a bonded complex, or being prepared in the reaction medium from copper or copper-ll compounds in a manner which is in itself known.

Itis preferable to use previously prepared CuCN, a slight excess of Zn(CN)2 sometimes being advantageous.

The process is particularly suitable for the prepared tion of azo dyestuffs of the formula I

from corresponding halogenoazo dyestuffs of the formula II

wherein A denotes an aromatic-carbocyclic radical, pref erablyfrom the benzene or naphthalene series, a (benz)isothiazole radical or a pyrazole radical, X denotes a halogen substituent, preferably chlorine or bromine, which is in the o-position, in the radical A, relative to the azo group, n denotes 1 or 2, Ri denotes hydrogen, halogen, alkyl, cyano, OV or-COOW, R2 denotes hydrogen, alkyl, aralkyl, aryl or cyc loalkyl, R3 denotes hydrogen, alkyl, alkenyl or aralkyl, R4 denotes alkyl, V denotes alkyl, alkenyl, aralkyl oraryl and W denotes hydrogen orV, the alkyl, aralkyl, alkenyl, cycloalkyl and aryl radicals mentioned above in any connection being optionally substituted by non-ionic substituents customary in the chemistry of azo dyestuffs or by-COOH.

Bulky radicals are in those positions where they cause no steric hindrance, for example tert.-butyl is in the m-position or p-position of a phenyl radical.

By cycloalkyl there is preferably understood cyclohexyl, which is optionally monosubstituted by C1-C4-alkyl, OH, CN, halogen or C-C4-alkoxy.

Suitable aryl is, in particular, phenyl which is monosubstituted, disubstituted or trisubstituted by halogen, C1-C4-alkyl, C1-C4-alkoxy, nitro, cyclohexyl or phenyl, the last three radicals mentioned preferably only occurring once.

Suitable halogen is fluorine, chlorine, bromine or iodine, preferably bromine and chlorine.

Suitable alkenyl radicals have 2-6 C atoms.

Suitable alkyl and alkoxy radicals have 1-6 C atoms, it being possibleforthe alkyl radicals, in particular, to carry a further substituent, such as halogen, cyano, alkoxy, aryl, aryloxy, acyl or acyloxy, or such as those of the type indicated in the formulae below.

Dyestuffs of the formula Ill

and IV

can preferably be prepared by this new process. In these formulae, Denotes hydrogen or a group -NO2, -CN, -V, -OV, -CF2, -SO2V, -SO2CF3,

or -N=N-R7, wherein Re and R6 represent hydrogen or identical or dif 0 ferent substituents, which together can also be a constituent of a heterocyclic ring, and R, represents aryl or hetaryl, Z denotes hydrogen or substituents, amongst these preferably the groups -NO2, -CN, -V, -OV,

-Cl,-Br and-COV and 0 heterocyclic groups of the formula V, VI and VII

wherein R8 represents methyl or also, together with R9, a fused-on benzene ring, and R9 represents-CO2CH3 or-CO2C2Hs, 0 Z1 denotes hydrogen or substituents, amongst these preferably the groups -NO2, -CN, -V, -OV,

-Cl, -Br or-COV, and wherein Z and Z1 together can also form a fused-on isothiazole ring, R', denotes hydrogen, halogen, alkyl or alkoxy, R'2 denotes hydrogen, alkyl which is optionally substituted by a cyano, chlorine, bromine, -COCH =CH2, phenyl, -SO2CH =CH2, -CO2-alkyl, -OCO-al kyl, -OCO2-alkyl, -OCO2-phenyl, alkoxy, phenoxy, -OCONH-alkyl, -OCONH-phenyl, -OPO(OQ)2 or PO(OQ)2, -(C2H4O)-H or (C2H40)mCOQ, wherein mdenotes1,2,3,4Or5and Q denotes alkyl, alkenyl or phenyl, R'3 denotes hydrogen, cyclohexyl, phenyl or R'2 and R'4 denotes C,-C4-alkyl, optionally substituted by cyano, chlorine, bromine, carbamoyl, carboxyl or carbalkoxy.

Dyestuffs of the formula VIII

can particularly preferably be prepared by this new process. In this formula, R'2 denotes hydrogen, or C1-C5-alkyl which is optionally substituted by a phenyl, -CN, -CO2 alkyl. -OCO-alkyl, (C,-C4)-OCO2-alkyl (C,- C4)-OCOrphenyl, alkoxy (C,-C4), phenoxy, CONH-alkyl (C1-C4) or-OCONH-phenyl, R'3 denotes cyclohexyl, phenyl or R'2 and R'4 denotes C,-C4-alkyl, optionally substituted by cyano, carbamoyl, carboxyl or carbalkoxy.

Suitable solvents are all the solvents hitherto described for the replacement of halogen by cyano.

Possible solvents in this case are polar protic solvents, such as monoalkyl ethers of ethylene glycol or diethylene glycol, and above all polar aprotic solvents, such as, for example, carboxylic acid amides and lactams, optionally alkylated on the nitrogen, dialkylsulphoxides, trialkyl phosphates, hexaalkylphosphoricacid triamides and carboxylic acid nitriles.

Examples which may be mentioned are: glycol monomethyl ether, glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, tet ramethylurea, dimethylsulphoxide, tetramethylene sulphone, triethyl phosphate, hexamethylphos phoric acid triamide and acetonitrile. Water can also be used. The reaction temperature is in general bet ween 20 and 220"C, temperatures between 20 and 1500C being preferred.

When the reaction has ended, the reaction pro ducts can, if necessary, be precipitated by polar sol vents. Suitable solvents for this are highly volatile, organic solvents, such as acetone and chloroform, but in particular water, and especially polar, protic solvents, such as lower alcohols with 14 carbon atoms.

A particular variant of the process according to the invention is characterised in that a mixture of 25-95 mol %, preferably 30-80 mol %, of a cyanide-free copper compound and an equivalent amount (that is to say 100 mol %) of zinc cyanide (or a slight excess) is used. The mol percents relate to the halogen to be replaced. Examples ofsuitable copper compounds are CuBr, CuCI, Cul and Cu2O.

The new process makes it possible to prepare dyestuffs with a low copper content in a reproducible manner.

Moreover, the solvent or solvent mixture, such as, for example, dimethylformamide/methanol, which is obtained in the filtrate from the cyanoazo dyestuff can easily be recovered or separated by distillation.

Example I 45 g of zinc cyanide and 40 g of copper cyanide are added to a suspension of 322 g of 3 - methyl - 4 (2', 6' - dibromo - 4' - nitrophenyl - azo) - N - butyl - N - acetoxyethylaniline in 600 ml of N - methyl - pyrrolidone. The mixture is heated to 80"C, this temperature is maintained for 30 minutes and the temperature is then raised to 105"C and kept at 105"C for a further one hour. After cooling the mixture to room temperature, 700 ml of methanol and 88 g of sublimed iron-lll chloride are introduced. The mixture is stirred for 6 hours, 350 ml of water are added and the mixture is stirred for a further 12 hours. Thereafter, the dyestuff is filtered off and washed with 300 ml of methanol, 800 ml of 10% strength hydrochloric acid and 2 1 of water. Ater drying, 220 g of the corresponding dicyano dyestuff with a copper content of < 0.3 /O result.

Using exclusively CuCN and carrying out the decoppering analogously results in a considerably higher copper content.

Example 2 Instead of the abovementioned amounts of cyanide,54.4 of copper cyanide and 35.6 g of zinc cyanide are employed in the same batch. Analogous working up gives 225 g of the dicyano dyestuff with a copper content of < 0.3%.

The dyestuffs listed in the table which follows can be obtained in good yield using an analogous or similar procedure.

% of Cu-l % ofZn(CN)2 compound relative to halogen to be replaced

aJ & OH 50 50 "Cz"40" 50 50 c oeN- H 40 60 N r \cnS 40 60 CN SN/C2ZHH5 60 40 CHZCHSOzCH3 80 80 3 7 20 OdZCHzCO2Od3 FN 4 30 70 CN CH3

Claims (8)

1. A process for the production of an azo dyestuff which, in the diazo component, has at least one cyano group in the ortho-position relative to the azo bridge, comprising reacting a corresponding orthohalogenoazo dyestuff with a mixture of 25 to 95 mol per cent of cyanide radical as copper-l-cyanide, relative to halogen to be replaced, and 75 to 5 mol per cent of cyanide radical as Zn(CN)2 such that sum of cyanide radicals is at least 100 mol per cent, the copper cyanide being employed as such or as a bonded complex, or being prepared in the reaction medium from a copper or copper-ll compound.

2. A process according to Claim 1, in which the mixture is of 30 to 80 mol per cent of copper cyanide, relative to the halogen to be replaced, and 70 to 20 mol per cent of Zn(CN)2.

3. A process according to Claim 1 or 2, in which copper-l-cyanide which has been previously prepared is used in the presence of a slight excess of Zn(CN)2.

4. A process according to Claim 1 in which the copper-l-cyanide is prepared in the reaction medium by mixing 25 to 95 mol per cent of cyanide-free copper compound and at least 100 mol per cent of cyanide radical as zinc cyanide.

5. A process according to any of the foregoing claims in which the reaction is carried out in polar aprotic solvents.

6. A process according to any of the foregoing claims in which the reaction is cattied out at temperatures between 20 and 1500C.

7. A process according to Claim 1 when carried out substantially as described in any one of the Examples.

8. An azo dyestuff according to Claim 1 when produced by the process of any of the foregoing claims.