Synthesis of vinyl esters

Details Synthesis of vinyl esters Synthesis of vinyl esters

1996-02-28

1997-10-21

Ivy, C. Warren

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acid esters

560130, C07C 6714

Patent

active

056798334

DESCRIPTION:

BRIEF SUMMARY
This invention relates to the synthesis of vinyl esters derived from an alcohol which may be aliphatic or non-aliphatic (e.g., a phenol) and may be polyhydric. The invention is of particular value when the alcohol is sterically hindered due to the position of the hydroxyl group of the alcohol relative to a cyclic or other bulky group in the alcohol.
When the alcohol that is to provide the esterifying group is not sterically hindered (for instance when it is a straight chain aliphatic alcohol) it is relatively easy to form a vinyl ester by reaction of the alcohol with an ethylenically unsaturated carboxylic acid, for instance using an acidic catalyst. However this technique tends to be inadequate when the alcohol is sterically hindered.
One example of a valuable ester that is difficult to synthesise is benzoin acrylate. The hydroxyl group in benzoin is sterically hindered and the solubility of benzoin in many solvents is low. A synthesis of benzoin acrylate is described in Chemical Abstracts 40151K Volume 68 in which benzoin was dissolved in dimethyl aniline and chloroform and acryloyl chloride was added dropwise at below 10.degree. C. The recovery procedures involve distillation under reduced pressure and the addition of aqueous sulphuric acid with ice cooling. The use of acryloyl chloride as a reactant is undesirable because of difficulties associates with the manufacture, supply and storage of acryloyl chloride. For instance its initial synthesis is inconvenient to perform and the product tends to be unstable on storage.
A further disadvantage in the described process is that it requires the use of chloroform as part of the reaction medium. This may result in the end product containing trace amounts of chloroform. For some purposes, e.g., pharmaceutical purposes, even trace amounts of halogenated hydrocarbon impurities are considered undesirable.
Processes are described in JP-A-61/286346 and 61/286347 in which one mole of a particular sterically hindered alcohol is reacted with 0.9 to 1.25 moles .beta. chloropropionyl chloride per hydroxyl group at -10.degree. to 35.degree. C. in a polar organic solvent and in the presence of an aqueous solution of sodium hydroxide or potassium hydroxide. Temperatures of 0.degree. to 10.degree. C. are said to be especially preferred. It is stated that if the temperature is higher, there is hydrolysis of the chloropropionol chloride which causes a decline in yield, and there is hydrolysis of the end product.
Although the low temperatures are essential in this process for the reasons stated, they have undesirable disadvantages. The solubility of the alcohol at the low temperatures is less than it would be at higher temperatures. With alcohols such as benzoin, which tend to have a relatively low solubility in many solvents, the use of low temperatures necessarily limits the concentration of the alcohol that can be dissolved in the reaction mixture, and thus reduces the yield of vinyl ester that can be obtained from a given reaction vessel in a given reaction time (the pot yield). Further, the use of a low temperature necessarily results in a lower reaction rate.
One important object of the invention is to provide a more convenient and reliable synthesis of benzoin acrylate.
Another object of the invention is to provide a convenient synthesis for vinyl esters of alcohols in general, especially sterically hindered alcohols.
Another object is to provide such processes that can be performed in the absence of halocarbons.
Another object to devise a process for making vinyl esters of alcohols and which is convenient to perform and which is especially suitable for sterically hindered alcohols and which is capable of giving a good pot yield of the desired product.
In the invention, we make a vinyl ester of an alcohol by reaction of the alcohol with a 3-haloalkyl acid halide in a liquid reaction medium in which the alcohol is dissolved and through which a hydrogen halide acceptor is distributed, and in this process the liquid reaction medium is an anhydrous reaction medium and compr

REFERENCES:
patent: 2028012 (1936-01-01), Reid
patent: 2890241 (1959-06-01), Holmen
patent: 4068082 (1978-01-01), Stoffey

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