CS235421B1 - Process for preparing 2,5-dialkoxychlorobenzenes - Google Patents

Abstract

A process for the preparation of 2,5-dialkoxychlorobenzenes, where the alkoxyl contains 1 to 5 carbons, corresponding to 2,5-dialkoxybenzenes with sulfuryl chloride in a melt of 2,5-dialkoxybenzenes in the presence of sulfur trichloride as a catalyst. 2,5-dialkoxychlorobenzenes are intermediates for the production of components of diazotype materials used in reprography.

Description

The present invention relates to a process for the preparation of 2,5-dialkoxychlorobenzenes by chlorination of 1,4-dieloxybenzenes of chloride · sulfuryl in the melt without the presence of solvents, catalysed with potassium chloride. 2,5-Diskoxychlorobenzenes are important intermediates for the production of components of diazotypic materials used in reprography.

According to the literature, much attention has not been paid to the preparation of these substances. A reference to the preparation of 2,5-dibutoxychlorobenzene is disclosed in U.S. Pat. 3,028,240 in connection with other analogous compounds. Said process consists in chlorination of the corresponding dialkoxybenzene with sulfuryl chloride in a 50% excess without additional conditions.

A disadvantage of this process is that the excess sulfuryl chloride causes the pre-chlorination of the starting 4-dialkoxybenzene to the undesired and longer synthetically unusable dichloro-derivative. The reduction of the excess chlorinating agent allows the procedure of MS. No. 229183, according to which chlorination is carried out in solvents in the presence of sulfur trichloride as a catalyst.

A further improvement of the basic process for chlorination of 4-alkoxybenzenes with sulfuryl chloride is provided by the process of the present invention, which makes it possible to carry out chlorination without solvent.

The dialkoxychlorobenzenes of the general formula I have been found

Cl 1 where R is an alkyl of 1 to 5 carbons can be prepared by chlorination of 1,4-dialkoxybenzene of formula II

Wherein R is as defined above by treating sulfuryl chloride in a 1,4-dialkoxybenzene melt heated above the melting point in the presence of 0.1 to 2% sulfur trichloride as a catalyst. The reaction proceeds at a temperature of 40 to 75 ° C, preferably at 40 to 50 ° C, at the end of the chlorination at 40 to 20 ° C, using sulfuryl chloride in an amount of 100 to 30% of theory based on the amount of starting material.

By performing chlorination in the melt of 1,4-dialkoxybenzene with the exclusion of solvent and in the presence of sulfur trichloride as a catalyst, the reaction temperature is reduced, the reaction time and the treatment time of the chlorination product are reduced. Production technology will be simplified, equipment capacity will be increased, solvent recovery problems will be eliminated, and hygiene and environmental performance will be improved.

The process according to the invention is explained in more detail in the following examples.

Example,

The reaction vessel was charged with 133.4 g 1,4-dibutoxybenzene and melted at 60 ° C. 0.89 g of sulfur trichloride are added to the resulting melt, the melt is cooled to 45 [deg.] C., and 1/3 of the total amount of 89 g of sulfuryl chloride is metered in with vigorous stirring over 0.5 h. The resulting waste gases are absorbed in alkaline absorption. The temperature of the reaction mixture is maintained at 45 ° C for one hour. The remaining sulfuryl chloride is continuously metered in over 2 h and after a further 0.5 h the reaction is complete. The chlorination product cooled to 25 ° C is neutralized with 100 ml of 10% sodium carbonate solution, the excess alkalinity is removed by washing with 2 times 100 ml of water and the separated product is sclerated with g of powdered activated carbon. For further use, 147.6 g of a liquid chlorination product are obtained by filtration:

9.5% unreacted 1,4-dibutoxybenzene, 78.1% 2,5-dibutoxychlorobenzene, 12.2% 2,5-dibutoxy-1,4-diohlorobenzene and 0.2% higher chloro derivatives. The total yield of chromatographically pure 2,5-dibutoxy-chlorobenzene 115.2 g corresponds to 74.8% of theory to the starting 1,4-dibutoxybenzene.

Example 2

155.6 g of 1,4-dibutoxybenzene are introduced into the reaction vessel and melted at 60-65 ° C. To the resulting melt was added 1.04 g of sulfur trichloride and the mixture was cooled to 45 ° C. With vigorous stirring, 1/3 of the total amount of 103.9 g of sulfuryl chloride is metered in over 0.5 h. The dosing is slowed and the temperature of the reaction mixture is lowered to 20-25 ° C to avoid crystallization. The remaining sulfuryl chloride is metered in over 2 to 3 hours and after 0.5 to 1 hour the reaction is complete. The liquid chlorination product is neutralized by stirring with 100 ml of 10% sodium carbonate solution and washed with 2 ml of 100 ml of water. The separated chlorination product was filtered by filtration with 0.8 g of pulverized charcoal. After filtration, 173 g of a liquid chlorination product was obtained for further use of the composition: 5.5% unreacted

1,4-dibutoxybenzene, 79.6% 2,5-dibutoxy-chlorobenzene, 14.8% 2,5-dibutoxy-1,4-dichlorobenzene and 0.1% higher chloro derivatives. Total yield 137.7 g pure chromatographically

2,5-dibutoxy-chlorobenzene corresponds to 76.6% of theory to the starting 1,4-dibutoxybenzene. Boiling point of 2,5-dibutoxy-chlorobenzene 150-152 ° C / 666 Pa.

Example 3

To a 0.5 L flask was charged 96 g 1,4-diethoxybenzene and melted by heating at 70-71 ° C. 0.9 g of sulfuryl chloride is added to the melt and 30 g of sulfuryl chloride are continuously metered in over 0.5 h. After 15 to 20 min, the temperature is gradually reduced to 60 ° C to avoid crystallization. After 1 h, an external cooling of 45-50 ° C was achieved with an additional 10 g of sulfuryl chloride being metered in. The temperature is maintained at 45-40 ° C for 3 h with the gradual addition of the remainder of 49.6 g of sulfuryl chloride. The reaction is terminated after 0.5 hours of cessation of the off-gas evolution. The chlorination product is neutralized with 100 [mu] l of a 10% sodium carbonate solution of 45 [deg.] C. and the excess alkalinity is washed with 2 times 100 ml of 45 [deg.] C. warm water. The separated organic product layer was sclerified through carberaffin. 103 g of chlorination product are obtained, from which a crystalline slurry precipitates at 20 DEG C. in 12 to 24 h

7.5 g of unreacted 1,4-diethoxybenzene and after filtration, 95.5 g of liquid crude 1,4-diethoxychlorobenzene are obtained. Unreacted 1,4-dietexybenzene was used to carry out further chlorination.

The total yield of chromatographically pure 2,5-diethoxychlorobenzene is 75% of theory starting from 1,4-diethoxybenzene.

Similarly, 2,5-dimethoxychlorobenzene, 2,5-dipropyloxychlorobenzene, 2,5-diisopropyloxychlorobenzene, 2,5-diisobutyloxychlorobenzene, 2,5-dipentyloxychlorobenzene, 2,5-dipentyloxychlorobenzene and other derivatives can be obtained from the corresponding 1,4-dialkoxybenzenes.

Claims (1)

A process for the preparation of dialkoxychlorobenzenes of formula (I) wherein R is C1 -C5 alkyl by chlorination of 1,4-dialkoxybenzenes of formula (11) wherein R is as defined above with sulfuryl chloride in the presence of sulfur trichloride catalyst, characterized in that chlorination is carried out in melt 1, 4-dialkoxybenzene at a temperature of 40 to 75 ° C, preferably at 40 to 45 ° C and at the end of the reaction at 40 to 20 ° C by treatment with sulfuryl chloride in an amount of 100 to 130% of theory calculated on the amount of starting material and % 0.1 to 2 wt. calculated on the amount of sulfuryl chloride.