Process for the manufacture of aromatic nitriles

A process for the manufacture of aromatic nitriles by reacting an aromatic halogen compound with formamide and the anhydride of a monocarboxylic acid in the presence of a copper catalyst and an acid-binding agent. Particularly applicable to replacement of halogen ortho to the azo linkage of an azo dyestuff by cyano.

This invention relates to a chemical process and more particularly to a 
process for the manufacture of aromatic nitriles. 
A number of methods for the preparation of aromatic nitriles is known, but 
particularly useful is the replacement of an aryl halogen atom by the 
cyano group, for example, by the action of cuprous cyanide at an elevated 
temperature, with or without an organic base (e.g. pyridine) as a promoter 
or solvent. 
However, this method has the disadvantage that it involves the preparation 
and handling of a metal cyanide, with consequent toxicity and effluent 
disposal problems. 
It has now been found that an aryl halogen atom can be replaced by the 
cyano group without the use of cyanide group-containing intermediates. 
According to the present invention there is provided a process for the 
manufacture of aromatic nitriles which comprises reacting an aromatic 
halide which is a chlorine, bromine or iodine compound with formamide and 
the anhydride of a monocarboxylic acid in the presence of a copper 
catalyst and an acid-binding agent. 
The amounts of formamide and carboxylic acid anhydride which are used may 
be from 2 to 20 mols per mol of the aromatic halide. It is preferred to 
use approximately 4 mols of each of these reactants per mol of the 
aromatic halide. 
The acid-binding agent may be used in an amount of 2 to 10, preferably 
approximately 3 mols, per mol of the aromatic halide. 
The copper catalyst may be used in an amount of 0.01 to 1.0 mols, 
preferably 0.1 mole, per mol of the aromatic halide. 
Examples of the anhydrides of monocarboxylic acids which may be used in the 
above process are acetic anhydride, propionic anhydride and benzoic 
anhydride. 
Examples of the copper catalysts which may be used are metallic copper, 
copper (I) chloride, copper (I) bromide, copper (I) iodide, copper (II) 
chloride and copper (II) acetate. The preferred catalyst is copper (I) 
iodide. Metallic copper may be used in the form of, for example, wire or 
copper bronze. 
Examples of the acid-binding agents which may be used are sodium acetate, 
potassium acetate, sodium benzoate, sodium carbonate and sodium hydroxide. 
Organic acid-binding agents, for example, imidazole, pyridine and 
triethylamine may also be used but are less effective. 
The reaction is preferably carried out in the presence of a non-hydroxylic 
solvent, for example, n-butyl acetate, iso-butyl acetate or nitrobenzene. 
The amount of solvent which is used is not critical, but should be 
sufficient to ensure that the reaction mixture is readily stirrable. 
A reaction temperature of at least 75.degree. C. is necessary for the 
reaction to proceed at an acceptable rate, and temperatures from 
75.degree. to 120.degree. C. are generally satisfactory. 
The reaction may be applied, for example, to the replacement of the 
aromatic halogen atom or atoms by the cyano group in a compound of the 
structure: 
##STR1## 
wherein W represents a chlorine, bromine or iodine atom and in which the 
aromatic nuclei may carry other substituents including chlorine, bromine 
or iodine atoms ortho to the azo linkage. 
Thus, the reaction is particularly useful when applied to azo dyestuffs. 
For example, in the case in which the aromatic halogen compound is an azo 
dyestuff of the formula: 
##STR2## 
wherein 
X and Y each independently represent a hydrogen atom, a halogen atom or a 
lower alkyl, lower alkoxy, cyano, nitro, sulphone, optionally substituted 
sulphamoyl, optionally substituted carbamoyl or alkoxycarbonyl group; 
Z represents a hydrogen atom or a lower alkyl, lower alkoxy, lower 
alkylamino or NR.sup.2 CO.T group in which R.sup.2 represents a hydrogen 
atom or a lower alkyl group and T represents a hydrocarbon radical, an 
amino group or a group --NHQ or --OQ in which Q represents a hydrocarbon 
radical; 
U represents a hydrogen atom, a halogen atom or a lower alkyl, lower 
alkoxy, sulphone or nitro group, provided that U is not a sulphone or 
nitro group when either of X and Y is a nitro, sulphone or optionally 
substituted sulphamoyl group; 
V represents a hydrogen atom, a halogen atom or a lower alkyl or lower 
alkoxy group; 
R represents a hydrogen atom or an optionally substituted hydrocarbon 
group; 
R.sup.1 represents an optionally substituted hydrocarbon group; and 
W represents a chlorine, bromine or iodine atom, the latter is replaced by 
the cyano group when the azo dyestuff is reacted with formamide and the 
anhydride of a monocarboxylic acid in the presence of a copper catalyst 
and an acid-binding agent according to the process of the present 
invention. If Y is also a chlorine, bromine or iodine atom this too may be 
replaced by cyano. 
With reference to the above-defined formula (II): 
Examples of the lower alkyl groups represented by R.sup.2, X, Y, Z, U and V 
are methyl, ethyl, n-propyl, isopropyl and n-butyl. 
Examples of the lower alkoxy groups represented by X, Y, Z, U and V are 
methoxy and ethoxy. 
Examples of the hydrocarbon radicals represented by T and Q are aryl 
radicals, preferably the phenyl radical, and alkyl radicals, preferably 
lower alkyl radicals and particularly the methyl or ethyl radical. 
An example of a lower alkylamino radical represented by Z is the 
methylamino radical. 
Examples of the halogen atoms represented by X, Y, U and V are chlorine and 
bromine atoms. 
Examples of sulphone groups represented by X, Y and U are methylsulphonyl 
and ethylsulphonyl. 
Examples of substituted sulphamoyl groups represented by X and Y are 
N-methylaminosulphonyl, N,N-dimethylaminosulphonyl, N-ethylaminosulphonyl 
and N,N-diethylaminosulphonyl. 
Examples of substituted carbamoyl groups represented by X and Y are 
N-methylaminocarbonyl, N,N-dimethylaminocarbonyl, N-ethylaminocarbonyl and 
N,N-diethylaminocarbonyl. 
The alkoxycarbonyl groups represented by X and Y are preferably lower 
alkoxycarbonyl groups, examples of which are methoxycarbonyl, 
ethoxycarbonyl and n-butoxycarbonyl. 
The optionally substituted hydrocarbon groups represented by R and R.sup.1 
may be optionally substituted alkyl, cycloalkyl, aralkyl or aryl groups. 
It is preferred that R and R.sup.1 are optionally substituted alkyl groups 
and especially optionally substituted lower alkyl groups. 
Examples of optionally substituted hydrocarbon groups represented by R and 
R.sup.1 are methyl, ethyl, n-propyl, iso-propyl, n-butyl, cyclohexyl, 
benzyl, .beta.-phenylethyl, phenyl, 2-hydroxyethyl, 2-acetoxyethyl, 
2-(methoxycarbonyl)ethyl and 2-(ethoxycarbonyl) ethyl. 
In this specification the terms "lower alkyl" and "lower alkoxy" mean alkyl 
and alkoxy groups respectively which contain from 1 to 4 carbon atoms. 
Preferred conditions for the conversion of an azo compound of formula (II) 
in which W is bromine into the corresponding compound in which W is cyano 
involve the reaction of 1 mol of (II) (W=Br), 4 mols of formamide, 4 mols 
of acetic anhydride, 3 mols of anhydrous sodium acetate and 0.1 mole of 
copper (I) iodide in approximately 20 mols of n-butyl acetate as solvent, 
the mixture being stirred at approximately 110.degree. C. until the 
reaction is complete. The reaction time if from 30 minutes to 24 hours 
depending upon the substituents which are present in the azo compound of 
formula (II). The product (II) (W=CN) is obtained essentially free from by 
products and usually does not require purification. Yields of 90% or even 
higher may be obtained. 
The o-cyanoazo compounds obtained by the process of the present invention 
are dyestuffs useful for the colouration of synthetic textile materials, 
especially aromatic polyester textile materials. The dyestuffs in the form 
of aqueous dispersions may be applied to such textile materials by dyeing, 
padding or printing methods and give orange to violet shades.

The invention is illustrated but not limited by the following Examples in 
which parts and percentages are by weight. 
EXAMPLE 1 
2-Bromo-4,6-dinitro-2'-acetylamino-4'-(N,N-diethylamino) azobenzene (479 
parts), copper (I) iodide (19 parts), anhydrous sodium acetate (246 
parts), formamide (180 parts), acetic anhydride (408 parts) and n-butyl 
acetate (2190 parts) are mixed together and heated, with stirring, to 
110.degree. C. during 15 minutes. The temperature is maintained at 
110.degree. for 30 to 50 minutes, when a solid is suddenly precipitated 
from the reaction mixture, indicating completion of the reaction. The 
mixture is allowed to cool to room temperature and the product is 
collected, washed with ethanol to remove residual n-butyl acetate and 
dried. 2-Cyano-4,6-dinitro-2'-acetylamino-4'-(N,N-diethylamino)azobenzene 
is obtained in 88% yield and requires no purification. 
The structure of the compound was confirmed by the identity of its n.m.r. 
spectrum with that of authentic material. 
EXAMPLE 2 
2-Bromo-4-nitro-4'-(N,N-diethylamino)azobenzene (1.9 parts), copper (I) 
iodide (0.95 parts), anhydrous sodium acetate (1.2 parts), formamide (1.8 
parts), acetic anhydride (2.0 parts) and n-butyl acetate (44 parts) are 
mixed together and heated, with stirring, to 110.degree. C. during 15 
minutes. The temperatures is maintained at 110.degree. C. for 31/2 hours 
when reaction is adjudged complete by thin layer chromatography. The 
solvent is removed at 80.degree. C. under reduced pressure and the residue 
is slurried in water (250 parts), collected and dried. 
2-Cyano-4-nitro-4'-(N,N-diethylamino)azobenzene is obtained in 75% yield 
and requires no purification. 
When the 1.9 parts of 2-bromo-4-nitro-4'-(N,N-diethylamino) azobenzene 
employed in Example 2 are replaced by an equivalent amount of one of the 
azo compounds listed in Table 1, the corresponding o-cyanodiarylazo 
compound is obtained. The symbols W, X, U, Y, Z, V, R and R.sup.1 in Table 
1 have the same significance as in the foregoing Formula II. The shade 
obtained when an aqueous dispersion of the dyestuff is applied to aromatic 
polyester textile material is given in the final column of the table. 
In the case of Examples 16 to 18, both bromine atoms ortho to the azo 
linkage are replaced by cyano. 
Table 1 
__________________________________________________________________________ 
Example 
No. W X Cl Y Z V R R.sup.1 Shade 
__________________________________________________________________________ 
3 Cl 
NO.sub.2 
H NO.sub.2 
NHCOCH.sub.3 
H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Blue 
4 Br 
NO.sub.2 
H NO.sub.2 
H H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Blue 
5 Br 
NO.sub.2 
H NO.sub.2 
NHCOCH.sub.3 
H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Blue 
6 Br 
NO.sub.2 
H NO.sub.2 
N(CH.sub.3)(COCH.sub.3) 
H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Blue 
7 Br 
NO.sub.2 
H NO.sub.2 
NHCH.sub.3 
H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Blue 
8 Br 
NO.sub.2 
H H NHCOCH.sub.3 
H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Violet 
9 Br 
NO.sub.2 
H H N(CH.sub.3)(COCH.sub.3) 
H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Violet 
10 Br 
H NO.sub.2 
H H H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Red 
11 Br 
H NO.sub.2 
H NHCOCH.sub.3 
H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Bluish-red 
12 Br 
H NO.sub.2 
H N(CH.sub.3)(COCH.sub.3) 
H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Bluish-red 
13 Br 
H H H H H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Orange 
14 Br 
H H H NHCOCH.sub.3 
H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Orange 
15 Br 
H H H N(CH.sub.3)(COCH.sub.3) 
H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Orange 
16 Br 
NO.sub.2 
H Br H H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Blue 
17 Br 
NO.sub.2 
H Br NHCOCH.sub.3 
H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Blue 
18 Br 
NO.sub.2 
H Br N(CH.sub.3)(COCH.sub.3) 
H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Blue 
19 Br 
CH.sub.3 
H NO.sub.2 
NHCOCH.sub.3 
H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Rubine 
20 Br 
CH.sub.3 
H H NHCOCH.sub.3 
H C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
Orange 
21 Br 
NO.sub.2 
H H H H C.sub.2 H.sub.4 OCOCH.sub.3 
C.sub.2 H.sub.4 OCOCH.sub.3 
Rubine 
22 Br 
NO.sub.2 
H H CH.sub.3 H C.sub.2 H.sub.4 OCOCH.sub.3 
C.sub.2 H.sub.4 OCOCH.sub.3 
Rubine 
__________________________________________________________________________ 
EXAMPLE 23 
2-Bromo-4,6-dinitro-2'-acetylamino-4'-(N,N-diethylamino)azobenzene (2.4 
parts), copper (I) iodide (0.95 parts), anhydrous sodium acetate (1.2 
parts), formamide (1.8 parts), propionic anhydride (2.6 parts) and n-butyl 
acetate (44 parts) are mixed together are heated, with stirring, to 
110.degree. C. during 15 minutes. The temperature is maintained for 30 
minutes when reaction is adjudged complete by thin layer chromatography. 
The mixture is cooled to room temperature and poured into petroleum ether 
(boiling range 60-80.degree. C.) (400 parts). The precipitate is 
collected, washed with petroleum ether (100 parts) and dried. 
2-cyano-4,6-dinitro-2'-acetylamino-4'-(N,N-diethylamino)azobenzene is 
obtained in 83.5% yield. 
EXAMPLE 24 
When the 2.6 parts of propionic anhydride employed in Example 23 are 
replaced by 4.3 parts of benzoic anhydride, reaction goes to completion in 
10 minutes at 110.degree. C. to give 
2-cyano-4,6-dinitro-2'-acetylamino-4'-(N,N-diethylamino) azobenzene in 72% 
yield. 
EXAMPLE 25 
2-Bromo-4,6-dinitro-2'-acetylamino-4'-(N,N-diethylamino) azobenzene (2.4 
parts), copper (I) iodide (0.95 parts), anhydrous potassium acetate (1.5 
parts), formamide (1.8 parts), acetic anhydride (2.0 parts) and n-butyl 
acetate (44 parts) are mixed together and heated, with stirring, to 
110.degree. C. during 15 minutes. The temperature is maintained at 
110.degree. C. for 2 hours when reaction is complete. The mixture is 
cooled to room temperature and poured into petroleum ether (boiling range 
60-80.degree. C.) (400 parts). The precipitate is collected, washed with 
petroleum ether (100 parts) and dried. 
2-Cyano-4,6-dinitro-2'-acetylamino-4'-(N,N-diethylamino)azobenzene is 
obtained in 95% yield. 
EXAMPLE 26 
When the 1.5 parts of anhydrous potassium acetate employed in Example 25 
are replaced by 1.59 parts of anhydrous sodium carbonate, reaction goes to 
completion in 3 hours at 110.degree. C. to give 
2-cyano-4,6-dinitro-2'-acetylamino-4'-(N,N-diethylamino)azobenzene in 71% 
yield. 
EXAMPLE 27 
When the 1.5 parts of anhydrous potassium acetate employed in Example 25 
are replaced by 1.5 parts of triethylamine, reaction goes to completion 
after 21/2 hours at 110.degree. C. 
EXAMPLE 28 
2-Bromo-4,6-dinitro-2'-acetylamino-4'-(N,N-diethylamino)azobenzene (2.4 
parts), copper (II) chloride (0.67 parts), anhydrous sodium acetate (1.2 
parts), formamide (1.8 parts), acetic anhydride (2.0 parts) and n-butyl 
acetate (44 parts) are mixed together and heated, with stirring, to 
110.degree. C. during 15 minutes. The temperature is maintained for 5 
hours after which time the reaction is complete. The mixture is cooled to 
room temperature and poured into petroleum-ether (boiling range 
60-80.degree.) (400 parts). The precipitate is collected, washed with 
petroleum-ether (100 parts) and dried. 
2-Cyano-4,6-dinitro-2'-acetylamino-4'-(N,N-diethylamino)azobenzene is 
obtained in 96% yield. 
When the 0.67 parts of copper (II) chloride employed in Example 28 are 
replaced by an equivalent amount of the copper catalysts listed in column 
2 Table 2, 
2-cyano-4,6-dinitro-2'-acetylamino-4'-(N,N-diethylamino)azobenzene is 
obtained in the yields shown in column 4 Table 2. 
Table 2 
______________________________________ 
Example Time Yield 
No. Catalyst (hours) (%) 
______________________________________ 
29 Cu BRONZE 3 66 
30 Cu WIRE 3 77 
31 Cu.sup.I Br 3 76 
32 Cu.sup.I Cl 3 77 
33 Cu.sup.I I 13/4 92 
34 (CH.sub.3 COO).sub.2 Cu . H.sub.2 O 
5 78 
35 CuCN 5 10 
36 NO CATALYST 24 0 
______________________________________ 
EXAMPLE 37 
When the 44 parts of n-butyl acetate employed in Example 5 are replaced by 
44 parts of iso-butyl acetate, reaction is complete after 21/2 hours at 
110.degree. C. giving 
2-cyano-4,6-dinitro-2'-acetylamino-4'-(N,N-diethylamino)azobenzene in 88% 
yield. 
EXAMPLE 38 
When the 44 parts of n-butyl acetate employed in Example 5 are replaced by 
60 parts of nitrobenzene, reaction is complete after 11/2 hours at 
110.degree. C. giving 
2-cyano-4,6-dinitro-2'-acetylamino-4'-(N,N-diethylamino)azobenzene in 87% 
yield.