Production of esters

摘要

Acyclic esters are prepared by reacting an oxidising agent with a cyclic ether containing at least five carbon atoms and having the general formula wherein R and R1 represent hydrogen atoms or C1-20 alkyl groups and n is an integer from 0 to 3, at least one R1 being a hydrogen atom and when n is 0 or 1, at least one R1 being an alkyl group, the reaction being effected under mild oxidation conditions whereby the cyclic ether is converted into the corresponding peroxide, reacting the peroxide with a reducing agent whereby ring fission and reduction are effected and separating from the product a resulting acyclic ester. The oxidising agent may be air, oxygen, ozone-containing gas, hydrogen peroxide, chlorine water, sodium hypochlorite or selenium dioxide. Temperatures may range from -10 DEG C. to the boiling point of the reaction mixture. Preferably, oxygen is used with an oxidation catalyst such as copper, cobalt, manganese or vanadium or a salt thereof. Solvents and elevated pressures may be used. The reducing agent may be ferrous sulphatic, sodium sulphite, sodium and an alcohol, sodium hydrosulphite, iron and HCl or hydrogen and a hydrogenation catalyst. The oxidation and reduction may be effected in a single stage using an oxidising agent and a reducing agent together e.g., ferrous sulphate and hydrogen peroxide or oxygen. In addition to the esters, minor amounts of alcohols, glycols, ketones, glycols and other oxygenated compounds are formed. In Examples: (1) 2:5-dimethyl tetrahydrofuran is partially peroxidised with air, the peroxide is decomposed with aqueous ferrous sulphate and the product is fractionated to recover sec.-butyl acetate, and some 2-pentanol and 2:5-hexanedione; (2) a mixture of 2-methyl-5-ethyl tetrahydrofuran, 2-propyl-tetrahydrofuran, 2:4-epoxy heptane and 3:4-epoxy heptane is similarly reacted yielding sec-butyl propionate, amyl acetate, n-propyl butyrate and n-butyl propionate and in addition hepten-4-one. Some dimerisation of the esters occurs such as of the sec-butyl acetate to a C8 diol diacetate. Numerous other cyclic ether starting materials are listed including 2:3:4:5-tetramethyl tetrahydrofuran, 2-methyl-5-undecyl tetrahydrofuran, tetrahydropyran, trimethyl tetrahydropyran, 1:3-epoxy-2,4,4-trimethyl pentane and 1:2-epoxy decane.