Process for the preparation of tetrachloropyrimidine

Process for the preparation of tetrachloropyrimidine, characterized in that compounds of the formula ##STR1## wherein R = a radical which can be split off under the reaction conditions and PA1 R' = optionally substituted lower allyl radical, are reacted with chlorine or agents which release chlorine, preferably at temperatures from 0.degree. to 150.degree. C and using more than 7.5 mols of chlorine, preferably 8 to 9 mols of chlorine.

The present invention relates to a new process for the preparation of 
tetrachloropyrimidine. 
The process is characterised in that (2-cyanoethyl)-dithiocarbamic acid 
esters of the formula 
##STR2## 
wherein R denotes a radical which can be split off under the reaction 
conditions and 
R' denotes an optionally substituted lower alkyl radical, are reacted with 
chlorine or compounds which release chlorine, if appropriate mixed with an 
inert diluent. The reaction is carried out, for example, at temperatures 
from 0.degree.-150.degree. C. with more than 7.5 mols of chlorine, 
preferably 8 to 9 mols of chlorine, and especially 9 mols of chlorine. 
In a preferred embodiment, the chlorination is carried out at temperatures 
from about 40.degree. C. to about 70.degree. C. until the evolution of HCl 
has virtually ended and the mixture is then further heated to temperatures 
from 70.degree. to 130.degree. C. A further preferred embodiment consists 
in carrying out the chlorination at temperatures from about 40.degree. to 
130.degree. C. 
Suitable radicals R which can be split off under the reaction conditions 
are, in particular, lower alkyl, preferably C.sub.1 -C.sub.4 -alkyl, such 
as methyl, ethyl, propyl or butyl, and furthermore, lower alkenyl, 
especially C.sub.2 -C.sub.4 -alkenyl, such as allyl, it being possible for 
these groups also to be substituted, for example by chlorine, C.sub.1 
-C.sub.4 -alkoxy or optionally substituted phenyl. 
Suitable radicals of this type are, for example, chloroethyl, methoxyethyl, 
benzyl, phenylethyl, chloropropyl, dichloropropyl and methoxypropyl. 
Methyl is particularly preferred. 
Suitable optionally substituted lower alkyl radicals R' are, preferably, 
C.sub.1 -C.sub.4 -alkyl, such as methyl, ethyl, propyl and butyl, it being 
possible for these groups also to be substituted, for example by chlorine, 
C.sub.1 -C.sub.4 -alkoxy or optionally substituted phenyl. 
Suitable radicals of this type are, for example, chloroethyl, methoxyethyl, 
benzyl and phenethyl. 
Methyl is particularly preferred. 
In addition to chlorine, all the customary chlorinating agents which can 
split off chlorine under the reaction conditions are, of course, suitable. 
Examples which may be mentioned are: sulphur dichloride, sulphuryl chloride 
and phosphorus pentachloride. 
Although the starting compounds of the formula (I) are not known, they can 
be easily prepared according to the instructions in the literature for the 
preparation of dialkyldithiocaramic acid alkyl esters (for example J. 
Chem. Soc. 1944, page 151) by initially reacting, according to the 
following equation 
##STR3## 
cyanoethylated amines (II), in which R has the meaning given above, with 
carbon disulphide in aqueous sodium hydroxide solution to give the 
dithiocarbamates of the formula (III), which are then converted, by 
alkylation, into the esters of the formula (I), for example with 
(substituted) alkyl halides, sulphonic acid alkyl esters or dialkyl 
sulphates, for example with dimethyl sulphate, according to the following 
equation: 
##STR4## 
The cyanoethylated amines (II) are obtained, for example, according to the 
following equation 
##STR5## 
by subjecting primary amines (IV), in which R has the abovementioned 
meaning, to an addition reaction with acrylonitrile; (compare, for 
example, J. Am. Chem Soc. 66, 725 (1944); J. Am Chem. Soc. 68, 1217 
(1946); J. Am. Chem. Soc. 78, 2573 (1956); and J. Heterocyclic Chem. 1, 
260 (1964). 
(2-Cyanoethyl)-dithiocarbamic acid esters of the formula (I) which are 
suitable for the process according to the invention are, for example: 
(2-cyanoethyl)-methyl-dithiocarbamic acid methyl ester, 
(2-cyanoethyl)-ethyl-dithiocarbamic acid methyl ester, 
(2-cyanoethyl)-methyl-dithiocarbamic acid ethyl ester, 
(2-cyanoethyl)-ethyl-dithiocarbamic acid ethyl ester, 
(2-cyanoethyl)-methyl-dithiocarbamic acid propyl ester, 
(2-cyanoethyl)-methyl-dithiocarbamic acid butyl ester, 
(2-cyanoethyl)-methyl-dithiocarbamic acid chloroethyl ester, 
(2-cyanoethyl)-butyl-dithiocarbamic acid benzyl ester, 
(2-cyanoethyl)-butyl-dithiocarbamic acid methyl ester, 
(2-cyanoethyl)-benzyldithiocarbamic acid methyl ester and 
(2-cyanoethyl)-benzyl-dithiocarbamic acid benzyl ester. 
Diluents which are inert under the reaction conditions are all sovents 
which are stable towards chlorine, for example chlorinated aliphatic and 
aromatic hydrocarbons, such as methylene chloride, chloroform, carbon 
tetrachloride, 1,1,2,2-tetrachloroethane, tetrachloroethylene, 
1,1,2,3,3-pentachloropropane, hexachlorocyclopentadiene, 
octachlorocyclopentene and 1,2,4-trichlorobenzene, chlorinated pyrimidines 
and phosphorus oxychloride. In general, 0.5 to 20, preferably 1 to 10, 
parts by volume of diluent are used per part by weight of (I). 
In the case where the chlorinating agent is a liquid under the reaction 
conditions, such as, for example, sulphur dichloride or sulphuryl 
chloride, the additional use of an inert diluent can be omitted. 
If chlorine is used as the chlorinating agent, the reaction initially 
proceeds strongly exothermically. Thus, it is appropriate - especially 
when larger batches are used - not to carry out the chlorination with an 
excess of chlorine until the exothermic reaction has subsided. After the 
strongly exothermic first chlorination phase has subsided, the 
chlorination is appropriately carried out with an excess of chlorine 
(recognisable by the greenish colour of the chlorination off-gas) in order 
to end the reaction as rapidly as possible. 
If other chlorinating agents are used, for example SCl.sub.2, it can be 
appropriate to employ an excess from the beginning. 
In detail, the process is carried out by initially mixing a 
(2-cyanoethyl-dithiocarbamic acid ester of the formula (I), especially 
(2-cyanoethyl)-methyl-dithiocarbamic acid methyl ester, with one of the 
diluents mentioned, for example chloroform, at room temperature and then 
adding the chlorinating agent. External cooling and metering of the 
chlorinating agent are matched with one another so that the initially 
strongly exothermic reaction does not become too violent. 
Chlorination is preferably carried out at about 40.degree. to 70.degree. C. 
until the evolution of HCl has virtually ended. 
If the chlorination is carried out in the absence of an inert diluent using 
a chlorinating agent which is liquid under the reaction conditions, such 
as, for example, sulphur dichloride, it is advisable initially to 
introduce the latter and to meter in the starting material (I) in portions 
at a temperature at which it reacts with the chlorinating agent as rapidly 
as possible, that is to say, for example, between 40.degree. and 
70.degree. C., preferably 50.degree. and 60.degree. C. 
A particularly favourable embodiment of the process consists in initially 
carrying out the chlorination at about 40.degree. to 70.degree. C. until 
the evolution of HCl has virtually ended and then heating the mixture to 
temperatures up to about 100.degree. C., and in particular appropriately 
until the evolution of HCl, which starts again, has virtually ended. 
Tetrachloropyrimidine is suitable as a reactive component for the 
preparation of reactive dyestuffs (compare, for example, Belgian Patent 
Specification No. 578,933).

EXAMPLE 
50 g (0.288 mol) of (2-cyanoethyl)-methyl-dithiocarbamic acid methyl ester 
are dissolved in about 250 ml of chloroform in a 0.5 l three-necked flask 
which is provided with a thermometer, gas inlet tube, stirrer and reflux 
condenser. A vigorous stream of chlorine is passed in, whilst stirring, 
the initially strongly exothermic reaction being kept at a temperature 
between 40.degree. and 50.degree. C. by cooling with ice. After this first 
stage, which is the most strongly exothermic, has subsided, the stream of 
chlorine is reduced so that chlorine is always present in a slight excess 
(recognisable, for example, by the light green colour of the off-gas). The 
mixture is then subsequently heated for the first time, a reflux 
temperature of about 59.degree. C. being reached after about 1 hour from 
the start of chlorination, whilst passing in a further slight excess of a 
stream of chlorine. The reflux condenser is now replaced by a distillation 
device and sulphur dichloride and chloroform are distilled off in the 
slight stream of chlorine until the internal temperature reaches about 
100.degree. C. (reached after about 13/4 hours from the start of 
chlorination). 
The residue, which contains tetrachloropyrimidine is distilled in a 
waterpump vacuum almost quantitatively, until the temperature at which it 
passes over reaches 110.degree. C./12 mm Hg. According to analysis by gas 
chromatography, the distillate contains 60 g (corresponding to 95.5% of 
theory) of tetrachloropyrimidine, which can be obtained pure by fractional 
distillation at a boiling point 12 of 108.degree. to 110.degree. C. 
The starting material, that is to say (2-cyanoethyl)-methyl-dithiocarbamic 
acid methyl ester, was obtained as follows: 
Initially 420 g (5.0 mols) of 3-methylamino-propionitrile and then, in the 
course of about 10 minutes, 400 g (5.26 mols) of carbon disulphide are 
allowed to flow into a solution, cooled to 5.degree. C., of 203 g (5.07 
mols) of sodium hydroxide in 1,800 ml of water, whilst cooling externally 
with ice/water. The mixture is then subsequently stirred vigorously for 
about 1.5 hours, whilst cooling further in an ice bath, a virtually 
homogeneous phase being formed. 650 g (5.16 mols) of dimethyl sulphate are 
now added dropwise to the mixture, whilst cooling further with ice, at 
such a rate that the reaction temperature does not exceed about 30.degree. 
C. Thereafter, the oily layer which separates out is washed thoroughly 
with water, after which it solidifies to a colourless crystalline mass of 
pure (2-cyanoethyl)-methyl-dithiocarbamic acid methyl ester. The melting 
point, after filtering off and drying, is 45.degree. to 46.degree. C. The 
compound exhibits a characteristic IR spectrum having the following bands 
(in cm.sup.-1): 2,250, 1,490, 1,425, 1,380, 1,300, 1,250, 1,195, 1,100, 
1,030, 985, 955 and 755.