CS217995B2 - Method of making the ester of the 2-chloracetovinegar acid - Google Patents

Abstract

1. Process for the production of 2-chloroacetoacetic esters, characterized in converting diketene at temperatures of from +10 to -40 degrees C in the presence of chlorinated aliphatic hydrocarbons as solvent by using hydrogen chloride into the acetoacetic chloride, forming the 2-chloroacetoacetic chloride by introducing of chlorine at temperature of from +10 to -40 degrees C, and converting the 2-chloroacetoacetic chloride by adding of alcohols having from 1 to 4 carbon atoms at temperatures of from +10 to -40 degrees C into the corresponding esters.

Description

The present invention relates to a process for the preparation of 2-chloroacetic acid esters. Esters of 2-chloroacetacetic acid can be used to produce coumarilic acid derivatives, which are known as intermediates for the production of plant protection products. Esters of 2-chloroacetacetic acid also represent intermediates for pharmaceutical preparations such as Cimetidine.

The processes known to date are based on acetic acid esters which are chlorinated with either sulfuryl chloride or chlorine.

Although chlorination with sulfuryl chloride proceeds with high reactivity in good yield (93-97%), it has the disadvantage that the SO2 and HCl gases produced in the reaction must be separated and sulfur dioxide must be converted to sulfuryl chloride by a special process.

When chlorinating acetic acid esters with chlorine, relatively good selectivities and yields can be obtained if the reaction is carried out continuously (DE-OS No. 2 709 138).

The object of the invention is a simple and efficient method. According to the invention, this is achieved by starting from diketene, which is converted at a temperature of +10 to -40 ° C in the presence of a chlorinated aliphatic hydrocarbon as solvent by converting HCl into acetic acid chloride by introducing chlorine at temperatures of +10 to -40 ° C. The 2-chloroacetic acid chloride is formed at 40 ° C and is converted into the corresponding ester by the addition of C 1 -C 4 alcohols.

Chlorination can be carried out in the presence of acid catalysts such as Lewis acids, for example PCl 3, FeCl 3, inorganic acids, for example sulfuric acid, perchloric acid, or strong organic carboxylic acids, for example acetic acid, trifluoroacetic acid, p-toluenesulfonic acid. These acids are added in a catalytic amount, preferably 0.1 to 20 mol%, based on the diketene charged.

Aliphatic hydrocarbons such as carbon tetrachloride, ethyl chloride, dichloroethane, etc., preferably methylene chloride, are used as solvents. Suitably, 200 to 1000 g of solvent are added per mole of diketene. The molar ratio of HCl to diketene in the first stage may vary considerably, conveniently. per mole of diketene uses 1.1 to 10 moles, preferably 1.95 to 6.5 moles of HCl.

For chlorination in the second stage, preferably 0.9 to 1.1 mol of chlorine is used per mole of acetic acid chloride.

In order to produce the desired esters, the 2-chloroacetic acid chloride is reacted in the third step with an appropriate alcohol having 1 to 4 carbon atoms. Such alcohols are methanol, ethyl alcohol, propyl alcohol, butylalkphol.

The alcohol is added in a stoichiometric amount. In many cases, it may be expedient to use a slight excess, preferably 0.1 to 0.3 mol.

A particularly preferred embodiment of the process according to the invention is that all three steps can be carried out in the same reaction medium and in the same reaction vessel without having to isolate any of the intermediates.

Example 1

In a 500 ml double-jacketed flask equipped with a compressed air inlet, a thermometer, a frit gas inlet, a reflux condenser and a cryostat, dissolve 50.45 g (0.6 mol) of diketene in 300 ml of methylene chloride and cool to -20 ° C. After addition of 0.11 mol%. H2SO4, based on diketene, and 43.8 g (1.2 moles) of hydrogen chloride based on diketene, after stirring for 3.5 hours, 42.5 g (0.6 moles) of chlorine were introduced over 35 minutes and stirred for an additional 30 minutes . 27.6 g (0.6 mol) of absolute ethanol are then added dropwise at -20 to -10 ° C and stirred for 15 minutes.

Then · se. the solvent was evaporated on a rotary evaporator. There was obtained 98.7 g of ethyl 2-chloroacetate having a content of 83.4% by weight. · · _

Examples 1 to 2

The table below shows the results of further experiments.

Catalyst a% based on diketene Solvent Molar ratio ‘HCl / diketene Temperature ° C Yield in% of 2-chloroacetic acid ester based on diketene 2 0.1 CH2Cl2 1.95 —20 88.4 H2SO4 300 ml (ethyl ester) 3 0.1 CH2Cl2 1.95 0 86.0 H2SO4 300 ml [inethy lesser] 4 - CH2Cl2 2.00 0 83.0 300 ml (príopyiilertiea ’) 5 0.1 CC14 , 6.3 —40 83.0 'CHsCOOH 300 iml (methyl ester) 6 10.0 CH2Cl2 2.1 —20 87.4 PC13 300 ml (ethyl ester)

Claims (3)

Process for the preparation of 2-chloroacetottic esters, characterized in that diketene at temperatures of +10 to -40 ° C in the presence of chlorinated aliphatic hydrocarbons having 1 to 2 carbon atoms as solvent is converted with hydrogen chloride into acetic acid chloride, mole of diketene 1.1 to 10 moles of hydrogen chloride, acetic acid chloride is converted to 2-chloroacetoic acid chloride by the introduction of chlorine at temperatures of +10 to -40 ° C, preferably 0.9 to 1.1 moles per mole of acetacetic acid chloride chlorine, 2-chloroacetyl chloride is converted into the corresponding 2-chloroacetic acid ester at temperatures from +10 to -40 ° C by treatment with C 1 -C 4 alcohols. 2. Process according to claim 1, characterized in that the chlorination is carried out in the presence of acid catalysts. 3. The process according to claim 1, wherein the solvent is methylene chloride.