JPS6284038A - Production of bromoacetal compound - Google Patents

Abstract

PURPOSE:To obtain the titled compound useful as an intermediate for the production of organic fine chemicals such as agricultural chemicals, etc., stably in high yield without producing HBr and H2O2 as by-products, by reacting vinyl acetate with bromine and a lower alcohol in the presence of a dehydration agent. CONSTITUTION:The objective bromoacetal compound can be produced by reacting 1mol of vinyl acetate with preferably 0.5-5mol of bromine and preferably 0.5-20mol of a lower alcohol such as methanol in the presence of a dehydration agent preferably at -30-+100 deg.C, especially -20-+60 deg.C. The dehydration agent is an alkaline earth metal halide or sulfate, etc., such as CaCl2, MgCl2, MgSO4, BaCl2, etc. EFFECT:The hydrolysis of bromoacetal compounds during the reaction can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing bromoacetals useful as intermediate raw materials for organic fine chemical products such as agricultural chemicals.

[Conventional technology]

A well-known method for synthesizing bromoacetals is a method in which vinyl acetate is reacted with bromine and alcohol.

This method is illustrated by the following chemical reaction formula.

OHM-CHOAC+Brt+RO)! -4Brc%0
R(OR)*+ACOR14O-1-HBr An example of a synthesis report using this method is Org.

5ynth, DI, 123.1955 and Russian Patent No. 282308 (1970).

Org, gynth,, II, f25, 1955
According to 2006, Brl was dropped into a mixed solution of vinyl acetate and alcohol, followed by acetalization, and the reaction solution was poured into water, followed by alkali washing, extraction, and distillation.
The bromoacetal is obtained with a yield of ~63%.

On the other hand, according to Russian Patent No. 282508, the addition reaction solution obtained after adding BrH to vinyl acetate in a dichloromethane solvent is added to an alcohol solution to perform acetalization, and then an aqueous solution of NaHOOs is added dropwise to the reaction solution K. After neutralization, extraction-distillation separation was performed to obtain bromoacetal with a yield of 90%.

However, when the present inventors carried out a follow-up test of the method of the Russian patent, the desired product could only be obtained with a yield of 47%.

[Problem that the invention seeks to solve]

As described above, the method of producing bromoacetal from vinyl acetate, Br₂, and alcohol has a problem in that the yield is low and the stability of the reaction is low. The main reason for this is that HBr, H, and O are produced as by-products in this method, as shown in the reaction formula above.
This is thought to be because the bromoacetal produced by HBr and El,0 is hydrolyzed.

[Means for solving problems]

The present inventors conducted intensive studies to solve the above-mentioned problems, and as a result, discovered that the above-mentioned reaction could be carried out in the presence of a dehydrating agent, and the present invention was completed. ,
A method for producing bromoacetals by reacting vinyl acetate with bromine and a lower alcohol, which is characterized in that the reaction is carried out in the presence of a dehydrating agent.

The present invention will be explained in detail below.

There are the following two methods for reacting vinyl acetate with bromine and lower alcohol in the present invention.

1) A method in which Br2 is dropped into a solution of vinyl acetate and alcohol in the presence of a dehydrating agent and reacted at a predetermined temperature.

2) A method in which an adduct of vinyl acetate and Brl is generated in advance and then reacted with alcohol at a predetermined temperature in the presence of a dehydrating agent. In this case, a dehydrating agent may be added from the stage of producing the adduct.

Alcohols used in the present invention include methanol, ethanol, n-propanol, 1-propatool, n-
Butanol, etc. are used.

As a dehydrating agent, CaCl2, MgCl2, M
Alkaline earth metal halides and sulfates such as gEjO4 and BaC/2 can be used.

The reaction conditions for both methods 1) and 2) are as follows.

The amount of Br used is 11.0% per mole of vinyl acetate.
It is preferable to use 5 to 5 moles, and more preferably 8 to 1.5 moles. The alcohol is preferably used in a proportion of 5 to 20 moles, more preferably 1.0 to 10 moles, per mole of vinyl acetate. Further, the dehydrating agent is preferably used in a ratio of L5 to 100 mol per 1 mol of vinyl acetate;
．． More preferably, it is used in a proportion of 0 to 20 moles.

The reaction is preferably carried out at a temperature within the range of -50°C to 1 on°C, more preferably at a temperature within the range of -20°C to 60°C.

The reaction products are C atffi, cHct from the reaction solution.
, .

halogenated hydrocarbons such as oar4, ethyl ether,
An ether such as n-butyl-n-propyl ether can be extracted with an aromatic hydrocarbon such as benzene, toluene, or xylene, and after the extraction solvent is distilled off, it can be separated by distillation or the like.

Vinyl acetate & 60f (CLl
12.82 (α40 mol) of methanol and Br, I
S 36 f (CL n 96 mol) was added dropwise to the dropping funnel at an internal temperature of 22 to 25° C. over 50 minutes. Br
After dropping t m, the reaction temperature was maintained at 25°C and the change over time in the amount of bromoacetal produced was observed by Go analysis.
, 9r (α[194 mol), but Br2 dropwise addition 90
After minutes, it decreased to 11,5y (o, n 6 a mole).

Br was added dropwise under the same conditions as in Examples and Comparative Examples, and after the completion of Bry K, 11.1 t (o, 1 o mol) of calcium chloride was added. After dropping 1 drop of Br, the reaction temperature was maintained at 25°C and we looked at the change in the amount of bromoacetal produced over time (by aa analysis), and found that 60 minutes after dropping 2 drops of Er2, bromoacetal was produced faid 15.2 y (9 moles of CL).
1 & 2f (0,096 mol) after 120 minutes and 24 hours
Even after the yield was 16.2f(Q, (196 mol) vs. Br
2) It was 1on%. By adding CaOZ2 in this way, the hydrolysis of promoacetal during the reaction was almost suppressed.

Claims (1)

[Claims] 1. A method for producing bromoacetals by reacting vinyl acetate with bromine and a lower alcohol, characterized in that the reaction is carried out in the presence of a dehydrating agent.