HU202836B - Process for selective chlorinating 2-chloro-5-(trichloro-methyl)-pyridine at the 3 position - Google Patents

Abstract

According to the invention, 2-chloro-5- (trichloromethyl) pyridine is reacted in the liquid phase with an appropriate amount of chlorine at elevated pressure and at elevated temperature using a ferric chloride catalyst or without the use of a catalyst. EN 202 836 B Scope of the description: 4 pages without drawing -1-

Description

The present invention relates to a process for the selective chlorination of 2-chloro-5- (trichloromethyl) pyridine at the 3-position to a 2,3-dichloro-5- (trichloromethyl) pyridine in a liquid phase chlorination reaction.

A2,3-dichloro-5- (trichloromethyl) pyridine is a known compound, agrochemicals such as 2- [4- (3-chloro-5- (trifluoromethyl)) - 2-pyridine-N-oxy] phenoxypropionic acid and derivatives thereof. The preparation of 2,3-dichloro-5- (trichloromethyl) pyridine according to known procedures is usually carried out in the presence of a catalyst in a liquid phase chlorination reaction. No. 4,331,811. For example, the process described in U.S. Pat. No. 4,123,125 discloses the use of tungsten, molybdenum and ruthenium catalysts.

According to the process of the present invention, 2-chloro-5-trichloromethylpyridine is selectively chlorinated at the 3-position by either 2-chloro-5- (trichloromethyl) pyridine or optionally chlorinated β-picolines and pyridines. a mixture of chloro-5- (trichloromethyl) pyridine in the liquid phase with 1 to 15 molar equivalents of chlorine and optionally

3-10 molar equivalents of hydrogen chloride at a pressure of 446-6996 kPa, 60-180 ° C, optionally in the presence of an iron (III) chloride catalyst, and if desired, the resulting 2,3-dichloro-5- (trichloro) methyl) pyridine is isolated from the mixture containing at least 2.8: 1 ratio of 2,6-dichloro-3- (trichloromethyl) pyridine to 2,3-dichloro-5- (trichloromethyl) pyridine.

One of the advantages of the process according to the invention is that it does not require the use of a catalyst, thus saving the cost of purchasing the catalyst and the cost of the catalyst removal step.

Unexpectedly, it has been found that 2-chloro-5- (trichloromethyl) pyridine is reacted with chlorine gas in a liquid phase at elevated temperature and pressure to afford the product, which is selectively chlorinated at the 3-position of the pyridine ring without the use of a catalyst. (trichloromethyl) pyridine. In addition, avoiding the use of a catalyst reduces tar formation in the reaction vessel. It has also been found that at appropriate temperature and pressure conditions, while maintaining the desired selectivity, an iron catalyst such as FeCl 3 can be used.

In the process of the invention, chlorine gas is introduced into liquid 2-chloro-5- (trichloromethyl) pyridine at elevated temperature and pressure. Optionally, a solvent such as a chlorinated hydrocarbon can be used, but preferably the reaction is carried out without the use of a solvent. The chlorine gas reagent is used in an amount sufficient to selectively chlorinate the starting pyridine derivative at the 3-position. The chlorine gas is generally used in an amount of at least equimolar to the 2-chloro-5- (trichloromethyl) pyridine used. An excess of chlorine gas up to 15 molar equivalents relative to the starting pyridine derivative is desirable. The most appropriate ratio of chlorine gas is influenced by factors such as reaction temperature, pressure, reaction volume, etc. This ratio can be determined by one skilled in the art.

A critical element of the process of the invention is the temperature and pressure used. The reaction temperature is 60-180 ° C, the preferred temperature is 120-170 ° C, more preferably 140-160 ° C, the most preferred reaction temperature is 150 ° C. The reaction is preferably carried out at atmospheric pressure of 446-6996 kPa. Higher pressure may be applied, but not economically feasible. The reaction is preferably carried out at a pressure of 791 to 2170 kPa, more preferably 1480 kPa.

It has further been found that the conversion is improved by the continuous addition of hydrogen chloride to the reaction mixture.

Unexpectedly, it has been found that using the specific temperature and pressure conditions in the process of the invention produces the desired selectivity of 2,3-dichloro-5- (trichloromethyl) pyridine, whether or not it is present in the reaction mixture. iron present or absent. Accordingly, the process of the invention can be carried out in an iron reactor, optionally using a FeG ₃ catalyst. Optionally, up to or equal to 3% by weight FeCl ₃ catalyst is used.

According to the invention, 2-chloro-5- (trichloromethyl) pyridine is generally introduced into the reactor in liquid form (at a temperature of about 53 ° C), heated to a temperature between 60 ° C and 180 ° C, and then introduced with chlorine gas. generally at a rate such that the pressure in the reactor is 203.4 kPa or more. The reaction is continued until sufficient

2,3-dichloro-5- (trichloromethyl) pyridine was not obtained. The progress of the reaction is monitored by periodically analyzing samples of the reaction mixture and exhaust gas by known methods. The reaction is stopped by cooling the reactor, eliminating the introduction of chlorine gas, and releasing the reactor overpressure. The resulting 2,3-dichloro-5- (trichloromethyl) pyridine product is then recovered from the reaction mixture by known separation and purification techniques, such as distillation, purification of the crystalline material or recrystallization from a solvent. One skilled in the art will recognize that there is a reaction time that results in a maximum product of 2,3-dichloro-5- (trichloromethyl) pyridine. The optimum reaction time is influenced by many factors, including the starting material used, pressure, temperature, the amount of reagents used, and the rate of chlorine gas feed. The optimum reaction time of the process according to the invention can be determined by monitoring the course of the reaction as described above for the particular operation.

In one embodiment of the process of the invention, substantially pure 2-chloro-5- (trichloromethyl) pyridine is reacted with chlorine gas at 150 ° C and 1480 kPa. The resulting 2,3-dichloro-5- (trichloromethyl) pyridine is distilled off from the reaction mixture.

Alternatively, a 2-chloro-5- (trichloromethyl) pyridine starting material may be used as a component of the mixture of chlorinated β-picolines and chlorinated pyridines. The mixture is the product of the vapor phase chlorination of β-picoline, which is used for the preparation of 2-chloro-5- (trichloromethyl) pyridine. Typically, the mixture contains the following ingredients:

Crowd%

2-Chloro-5- (trichloromethyl) pyridine 20-35

2.6- dichloro-5- (trichloromethyl) pyridine 30-40

2.3.6-Trichloropyridine 15-30 Other chlorinated β-picolines 10-25

Without isolating the 2-chloro-5- (trichloromethyl) pyridine, the described mixture is reacted with chlorine under the reaction conditions of the present invention.

EN 202 836 Β for the preparation of 23-dichloro-5- (trichloromethyl) pyridine. The resulting 2,3-dichloro-5- (trichloromethyl) pyridine is isolated from the reaction mixture in a known manner, for example by distillation, purification of the crystalline material, recrystallization from a solvent, or a combination of these methods.

The invention is illustrated by the following examples. The examples are not limiting.

As shown in the following tables, a number of experiments were performed. In each case, the starting material used is 2-chloro-5- (trichloromethyl) pyridine, which is introduced into the reactor, heated to the desired temperature, and introduced into the reactor via a submerged tube until a reaction pressure of 1480 kPa is achieved. Chlorine gas and, where applicable, hydrogen chloride are introduced at the required rate and the hydrogen chloride and excess chlorine in the exhaust gas are passed through a washer. Occasionally, the reaction mixture is sampled and the reaction is monitored.

Table I

Apélda number Quantity of starting material (g) tem- ture CC) chlorine gas current (G / hr) Reaction time (Hours) (THE) Product formation (% by weight) (B) (C) (D) other B / C ratio First 779.9 100 12.1 28.4 18 38.5 - 1.4 42.1 OO Second 701.5 125 22a 65.8 34.5 27.5 02 3.8 34.0 138 Third 691.9 150 21.9 27.5 46.3 30.0 1.7 2.5 19.5 18 4th 618.9 150 21.5 22 412 31.4 1.9 2.5 17.0 17 5th 781.8 150 12.8 44.5 28.4 49.5 2.1 3/5 16.5 24 6th 706.3 160 18.5 33.7 43.7 43.8 4.1 4.0 4.4 11 7th 703.6 175 23.6 332 37.1 41.1 14.5 5.7 1.6 2.8 'Eighth 706.1 200 31.9 18.2 21.3 24.7 39.7 8.1 62 0.6

Note: The procedures of Examples 1, 4, and 5 were performed in a Monel Metal Parr Reactor 11 equipped with a glass inner tube, a monel immersion and sample tube, and a heater.

The other exemplary procedures were performed in a 0.6 liter glass-coated Pfaudler drum sealed with Teflon * plate sealed with stainless steel flanges at both ends. The material for the chlorine inlet pipe, the sample pipe and the heater is tantalum.

Compounding Example 5 (A): 2-Chloro-5- (trichloromethyl) pyridine (B): 2,3-dichloro-5- (trichloromethyl) pyridine (Example 5) C): 2,6-Dichloro-5- (trichloromethyl) pyridine (D): 2,3,6-Trichloro-5- (trichloromethyl) pyridine

Π. spreadsheet

Apélda number Quantity of starting material (s) tem- ture CC) Chlorine- gas current (G / hr) Tbmeg% FeCl ₃ Reaction- time (Hours) Product formation (% by weight) (THE) (B) (C) (D) other B / C gold 9th 772.1 150 26.4 0.29 45 26.9 62.1 1.5 32 6.3 41 10th 747.4 150 9.9 1.5 48 13.0 78.1 1.3 2.9 4.7 60 11th 724.6 150 6.1 3.0 43 11.3 83.5 0.85 1.5 2.9 98 12 '. 605 200 16.5 2.9 18 20.9 38.2 17.5 6.4 17.0 2.2

'Comparative example

Compounds (A), (B), (C) and (D) are listed in Table I below.

ΙΠ. spreadsheet

Apélda number Amount of starting material <g) tem- ture CC) Chlorine- gas current (G / hr) HCl current (g / h) TSmeg% FeCl ₃ Reaction time (Hours) Product formation (% by weight) (THE) (B) (C) (D) Other B / C ratio 13th 940.5 150 11.9 16.9 0 48 25.7 71.8 - 1.8 0.7 OO 14th 891.2 175 8a 23.8 0 48 29.8 59.7 6.9 3.7 - 9 15th 903.9 150 19.3 9.3 3.0 49 18.5 78.9-1.4 12 OO 16th 956.6 125 18a 10.3 3.0 49 13.3 83.7 - 0.4 2.6 OO

Compounds (A), (B), (C) and (D) are listed in Table I below.

HU 202 836 Β

In a similar procedure, under different pressure and temperature conditions, as described above, 2-chloro-5- (trichloromethyl) pyridine is reacted with an appropriate amount of chlorine to provide 2,3-dichloro-5- (trichloro) methyl) pyridine The desired product is removed from the reaction mixture by distillation.

In another embodiment of the process of the invention, 2,3-dichloro-5- (trichloromethyl) pyridine is prepared by a continuous recycle process. The essence of this process is the distillation of 2,3-dichloro-5- (trichloromethyl) pyridine by selective chlorination of 2-chloro-5- (trichloromethyl) pyridine at elevated temperature and pressure as described above. and the unreacted 2-chloro-5- (trichloromethyl) pyridine is recycled in a known manner.

Claims (9)

PATENT CLAIMS 1. Procedure For the selective chlorination of 2-chloro-5- (trichloromethyl) pyridine at the 3-position, characterized in that 2-chloro-5- (trichloromethyl) pyridine or optionally chlorinated β-picolines and 2-chloro-pyridines A mixture of 5- (trichloromethyl) pyridine in the liquid phase is reacted with 1-15 molar equivalents of chlorine and optionally 3 to 10 molar equivalents of hydrogen chloride at a pressure of 446-6996 kPa at 60-180 ° C, optionally as an iron (III) chloride catalyst. in the presence of, and optionally obtained from, a mixture containing at least 2.8: 1 of 2,3-dichloro-5- (trichloromethyl) pyridine relative to 2,6-dichloro-3- (trichloromethyl) pyridine the 2,3-dichloro-5- (trichloromethyl) pyridine is isolated. 2. The process of claim 1 wherein the amount of chlorine is greater than 1 molar equivalent. A process according to claim 2, wherein the pressure is at least 190 kPa and the temperature is 100 ° C. The process according to claim 3, wherein the pressure is 1480 kPa and the temperature is 140-180 ° C. The process of claim 4, wherein the temperature is 150 'C. 6. Process according to any one of claims 1 to 4, characterized in that the 2,3-dichloro-5- (trichloromethyl) pyridine is isolated from the reaction mixture. 7. Process according to any one of claims 1 to 20, characterized in that a 2-chloro-5- (trichloromethyl) pyridine-containing mixture of chlorinated β-picolines and chlorinated pyridines obtained by vaporization of β-picoline is used as starting material. 8. A process according to any one of claims 1 to 4, wherein hydrogen chloride is continuously added to the reaction mixture. 9. The process according to any one of claims 1 to 3, wherein the iron (III) chloride catalyst is used.