SU1097601A1 - Process for preparing 1,1-dimethoxy-2-bromoethane - Google Patents

Abstract

1, THE WAY OF OBTAINING 1,1-DIMETOXI-2-BROMETHANE by reacting vinyl acetate with bromine at a temperature of (- 5) -

Description

The invention relates to a process for the preparation of 1,1-dimethoxy-2-bromoethane, which is used as an intermediate in the preparation of drugs.

A method is known for producing 1 1-dimethoxy-2-bromoethane by treating a methanolic solution of vinyl acetate with a solution of bromine in chloroform at (-) O ° C. The yield of the desired product is 46% l. . .

The disadvantage of this method is the low yield of the desired product and the need to carry out the process at a low temperature, which is achieved by cooling with a dry ice-acetone mixture.

The closest to the proposed method is to obtain 151 dimethoxy-2-bromoethane, reacting vinyl acetate with bromine in CC1 at a temperature below 10 ° C for 20 minutes, then the mixture is added to methanol at 0-10 ° C and maintained at ambient temperature for 2 days, after which the reaction mixture is washed with water and the desired product is distilled under reduced pressure. The yield of the technical target product is 83% 2.

The disadvantage of this method is the relatively low yield of the target product and the long duration of the process.

The purpose of the invention is to increase the yield of the target product.

The goal is achieved by the fact that according to the method of obtaining 1,1-dimethoxy-2-bromoethane by reacting vinyl acetate with bromine in chlorine-containing hydrocarbon at a temperature of (- 5) - (0) ° C, the process is carried out in the presence of catalyst 1, taken the amount of 0.00020, 0005% by weight of the original vinyl acetate, and after adding the reaction mixture to methanol, the temperature is raised to 30-40 ° C.

It is preferable to conduct the process in fistom methylene as a solvent.

Example 1 (control).

87.5 ml of methylene chloride are added to 50 g of vinyl acetate, the mass is cooled to –5 ° C, and at this temperature the mixture of 30 ml of bromine and 52.5 mi of methylene chloride is poured over 20 minutes.

The resulting mass is added in 1.5 hours to 203.5 ml of methanol, cooled to 0 ° C. Then the reaction mixture is held at 4 hours. Upon termination of the reaction, 550 ml of 3% sodium bicarbonate solution are added to the reaction mass, stirred, settled, and the aqueous layer is separated from the organic. The upper aqueous methanol layer is extracted 2 more times with 85 ml of methylene chloride. Solvent is removed from the combined extract at vapor temperature. 78.95 g (80.43%) of technical 1,1-dimethoxy-2-bromoethane are obtained, distilled, and a fraction of C / 16 mm Hg is collected. Art. The yield of the target product is 72.6 g (73.98%), 1.44550. Example 2 (control).

To 50 g of vinyl acetate is added

87.5 ml of methylene chloride, cooled to -5 ° C and at this temperature, a mixture of 30 MP of bromine and 52.5 ml of methylene chloride, cooled to 0 ° C, is added over a period of 20 minutes.

The resulting mass is added in 1.5 hours to 203.5 ml of methanol cooled to 0 ° C. The reaction mixture is then kept at 30 ° C for 4 hours. Then, it is treated as in Example 1. 73.2 g (74.6%) are obtained. target product p 1.4450.

Example 3. 87.5 ml of chloride are added to 50 g of vinyl acetate.

methylene, 0.00015 g added

(0.0003%) iodine, cooled to, a mixture of 30 MP of bromine and 52.5 ml of methylene chloride, cooled to C, is poured in at 20 ° C for 20 minutes,

then to the resulting mass is added over f, 5 hours to 203.5 ml of methanol, cooled to O CI. The mass is heated to 30 ° C and kept constant for 4 hours while stirring.

temperature

It is further treated in the same way as Example 1. 88.4 g (90.1%) of technical 1,1-dimethoxy-2-bromoethane are obtained, distilled, and a fraction of 4849% / 16 mm Hg is collected. The yield of the target product is 84.9 g (86.5%) HD 1.4450.

The data in examples 4-9 are presented in the table.

Thus, as can be seen from the above examples, the proposed method allows to increase the yield of technical 1,1-dimethoxy 2-bromoethane

3 10976014

up to 90.1-96.89% versus 83. It is known that this is the duration of the process to the method and get a clean target up to 8 hours versus 52 by lime product with a yield of 86.3-87.72%. When, in a new way.

Claims (2)

1. METHOD FOR PRODUCING 1,1-DIMETOXY-2-BR0METHANE by reacting vinyl acetate with bromine at a temperature of (- 5) - (0) ⁰ C in a chlorine-containing hydrocarbon medium, followed by adding the reaction mixture to methanol and raising the temperature, characterized in that that, in order to increase the yield of the target product, the process is carried out in the presence of catalyst 1 ₂ taken in an amount of 0.0002-0.0005% by weight of the starting vinyl acetate and after adding the reaction mixture to methanol, the temperature is increased to 30-40 C. 2. The method of pop. 1, characterized in that as the chlorine-containing hydrocarbon, methylene chloride is used.