GB964001A - Improvements in and relating to the production of unsaturated esters - Google Patents

Abstract

Carboxylic esters of unsaturated alcohols are made by contacting an alpha-olefine with a palladium salt, either under substantially anhydrous conditions or in the presence of a minor amount, as hereafter defined, of water in the presence of a carboxylic acid, carboxylate ions, a redose system and molecular oxygen. "Minor amount" of water means an amount which is small in comparison with the total amount of liquid constituents of the reaction mixture. The redox system may comprise a salt of copper and/ or iron, preferably the chloride(s), or a copper carboxylate, preferably the ester of which it is the object to produce. Para-benzoquinone, duroquinone, or 2-ethyl anthraquinone may be used as redox system, palladous chloride, bromide or carboxylate, preferably acetate as the palladium salt. Ethylene is prefered as the alpha-olefine, however C3 to C20 aliphatic alpha olefins, which may also be aryl substituted, specifically styrene may also be employed. An alkali metal halide, e.g. lithium or sodium chloride may be present in the reaction mixture. The carboxylic acid may be aliphatic monocarboxylic e.g. acetic, propianic, n-hexanoic, aromatic monocarboxylic, e.g. benzoic or a monoester of a dicarboxylic acid, e.g. ethylhydrogen phthalate, an aliphatic dicarboxylic acid e.g. adipic, an aromatic dicarboxylic acid e.g. terephthalic acid. The carboxylate ions may be provided by an alkali metal e.g. sodium, potassium or lithium carboxylate, preferably corresponding to the carboxylic acid and preferably made in situ. Molecular oxygen in the form of pure oxygen or air may be used, the olefin being introduced into the reaction in admixture therewith: The water content of the reaction mixture is preferably kept to a minimum . The reaction is improved by adding thereto one or more of urea, acetamide methyl or dimethyl acetamide, dimethyl formamide, acetonitrile, benzonitrile, dimethyl sulphoxide, or esters of the acid corresponding to the ester being produced, e.g. benzyl acetate. Reaction temperatures in the range 50 DEG to 180 DEG C. and atmospheric and 10 ats are preferred. Numerous examples also illustrate various mechanical methods of practically carrying out the invention. In the synthesis of vinyl acetate, acetaldelyde, ethylidene diacetate and ethyleneglycol diacetate are by products.