CS246644B1 - Preparation method of (2-chlor- 1,1,2-trifluorethyl)methylether - Google Patents

Abstract

Preparation method (2-chloro-1,1,2-trifluoroethyl) - the methyl ether of formula I CH3OCF2CHFC1 / 1 / is that 1,2-dichloro-1,1,2-tri- fluoroethane or in a mixture with 1,1,2-trichlorotrifluoroethane or chlorotrifluoroethylene and 1,1,2-trichlorotrifluoroethane alkaline hydroxide in methanol or to a solution of an alkali metal hydroxide, methanol and water.

Description

The invention relates to a process for preparing / 2-chloro-l, 1,2-trifluoro-ethyl / methyl ether of the formula X ₂ CH ₃ OCF chfci / 1 /

The ether of formula I is an intermediate of the synthesis of [2-chloro-1,1,2-trifluoroethyl] difluoromethyl ether, which is a major inhalation anesthetic as described in the literature: Terrell R. C.,

Summit N.J .: U.S. Pat. 3,469,011 (1969), C.A. 72, 3025 (1970) and Spinka A., Chem. and Industry 18, 475 (1977).

The ether of formula (I) is still prepared in technical practice by the base-catalyzed addition of methanol to chlorotrifluoroethylene, as reported in the literature: Hanford W. E., Rigby G. W.

U.S. Pat. No. 2,409,274 (1946), C.A. 41, 982 (1947) and Miller, W. T., Jr., Fager, E. W., Griswold, P. H., J. Am. Chem. Soo. 70, 431 (1948).

Chlorotrifluoroethylene is obtained from 1,1,2-trichlorotrifluoroethane with dehalogenated zinc.

Recently, a process for preparing the ether of formula I from trichlorotrifluoroethane and methanol is known, as disclosed in US Pat. No. 4,365,097, C.A. 99, 5203 (1983). Ethers of this type may also be prepared by the reaction of fluoro-haloalkanes with alkoxides as described in the literature: Tarrant p.

Young J. A., J. Am. Chem. Soc. 75, 932 (1953).

Another route to the synthesis of the above inhalational anesthetic is through the preparation of the (2-chloro-1,1,2-trifluoroethyl) methyl ether of formula CH ₃ OCF ₂ CHFC1.

Its essence lies in the fact that 1,2-dichloro-l, 1,2-trifluoroethane formula _CF2 C1CHFC1 introduced into an alkaline solution of methanol or methanol containing to 50% by weight. water, the amount of methanol and alkali used in the reaction mixture being greater than the stoichiometric amount.

In another aspect, the reaction is carried out using an alkali or calcium hydroxide. Further, 1,2-dichloro-1,1,2-trifluoroethane containing triohortrifluoroethane or trifluorotrichloroethane and triohortrifluoroethylene may be used.

In another aspect, the 1,2-dichloro-1,1,2-trifluoroethane is present in the liquid or gas phase. It is further desirable to carry out the reactions at temperatures of 20 to 50 ° C. After completion of the reaction, excess water was added to the reaction mixture, the organic layer was separated, dried and distilled.

The main advantage of the process according to the invention for the preparation of (2) chloro-1,1,2-trifluoroethyl (methyl ether) (1) in one reaction step is that it starts from waste which has not yet been used, yielding the same quality product as previously known. from full-value raw materials.

The starting 1,2-dichloro-1,1,2-trifluoroethane, which is eliminated in the production of chlorotrifluoroethylene and is also a by-product of the production of 1,1,2-triohortrifluoroethane, has so far found no application in technical practice.

The process according to the invention is described in more detail in several exemplary embodiments.

He did

76.5 g (0.5 mol) of 1,2-dichloro-1,1,2-trifluoroethane was introduced in gaseous form for 3 hours at a temperature of 40 to 45 ° C into a solution of 56 g (1 mol) of potassium hydroxide in 128 g (4 mol), i.e. 160 ml of methanol. After cooling to room temperature, water was added to the reaction mixture until the solid phase dissolved (120 mL). The organic layer was separated, washed with 2 x 20 mL of ice water, dried over CaCl 3. Distillation at atmospheric pressure gave 54.6 g (0.368 mol), i.e. 73.6% of the theoretical yield of (2-chloro-1,1,2-trifluoroethyl) methyl ether, m.p. Mp 68-70 ° C.

Example 2

166 g of a mixture containing 92.7% of 1,2-dichloro-1,1,2-trifluoroethane and 7.3% of 1,1,2-triohortrifluoroethane, corresponding to 1.0 mol of ethane of formula II, were stirred with stirring dropwise over 3 hours to a solution of 60 g (1.06 mol) of potassium hydroxide in 160 ml (4 mol) of methanol. The temperature of the reaction mixture is between 22 and 40 ° C.

The reaction mixture was worked up as described in Example 1. 124 g of crude ether of formula I containing 7.8% trichlorotrifluoroethane were obtained. This corresponds to a 76% yield of pure ether of Formula I obtained from the mixture by rectification. T.v. it was 68-70 ° C.

Example 3

190 g of a mixture of 5 * halotrifluoroethylene, 75% 1,1,2-trichlorotrifluoroethane and 20% 1,2-dichloro-1,1,2-trifluoroethane corresponding to 0.082 mol of chlorotrifluoroethylene and 0.248 mol of ethane of formula II were added dropwise over 150 minutes at 40 to 46 ° C to a solution of 40 g (1 mol) of sodium hydroxide and 160 ml (4 mol) of methanol.

The reaction mixture was worked up as in Examples 1 and 2. 145 g of a mixture containing 74.4% trichlorotrifluoroethane and 25.6% ether of formula I were obtained. This corresponds to 63.6% of the theoretical yield of pure [2-chloro-1,2,2] -trifluoroethyl / methyl ether obtained from the mixture by rectification. Mp 68-70 ° C.

Example 4

112 g of a mixture consisting of 10% chlorotrifluoroethylene, 77.2% 1,1,2-trichlorotrifluoroethane and 12.8% 1,2-dichloro-1,2,2-trifluoroethane, i.e. 0.096 mol of halotrifluoroethylene and 0.094 mol of ethane of formula II was added dropwise to a suspension of 8 g (1.08 mol) of Ca (OH) in 50 ml of water and 160 ml (4 mol) of methanol over a period of 180 minutes with stirring at 35-44 ° C.

After cooling, 150 ml of a 10% aqueous ammonium chloride solution was added to the reaction mixture. After separation, the organic layer was washed with 2 x 20 mL of water and dried with CaCl 2. 84 g of a mixture of 79.4% of 1,1,2-trichlorotrifluoroethane and 20.6% of [2-chloro-1,1,2-trifluoroethyl] methyl ether were obtained, corresponding to 61.1% of the theoretical yield of the ether of formula I. The pure product was obtained from the mixture by rectification. Mp 68-70 ° C.

Example 5 g of a mixture of 7.3% 1,1,2-trichlorotrifluoroethane and 92.7% 1,2-dichloro-1,1,2-trifluoroethane corresponding to 0.243 mol of ethane of formula II was added dropwise with stirring over a period of 5 minutes. to a solution of 28 g (0.5 mol) of KOH in a mixture of 80 ml (2 mol) of methanol and 60 ml of water. The temperature was maintained between 40 and 44 ° C during the reaction.

The reaction mixture was worked up as in Examples 1-3. 23 g of a mixture containing 90.4% ether of formula I, 8% 1,1,2-trichlorotrifluoroethane and 1.6% unidentified material were obtained. This corresponds to 57.6% of theory. yield of (2-chloro-1,1,2-trifluoroethyl) methyl ether. This was isolated from the mixture by rectification. Mp 68-70 ° C.

Claims (5)

A process for the preparation of (2-chloro-1,1,2-trifluoroethyl) methyl ether of formula I CH ₃ OCF ₂ CHFC1 (1) characterized in that 1,2-dichloro-1,1,2-trifluoroethane of formula II CF _{2 (} CHCl 3/11) is introduced into an alkaline solution of methanol or methanol containing up to 50% by weight. water, the amount of methanol and alkali used in the reaction mixture being greater than the stoichiometric amount. 2. A process according to claim 1 wherein the reaction is carried out using an alkali or calcium hydroxide. 3. A process according to claim 1 or 2, wherein 1,2-dichloro-1,1,2-trifluoroethane containing trichlorotrifluoroethane or trichlorotrifluoroethane and chlorotrifluoroethylene is used. 4. A process according to any one of claims 1 to 3 wherein the 1,2-dichloro-1,1,2-trifluoroethane is introduced in the liquid or gas phase. 5. A process as claimed in any one of claims 1 to 4, wherein the reaction is carried out at temperatures of 20 to 50 ° C.