Patent GB-810381-A (GB)
Title: Improvements in ester synthesis
IPC: C08G63/85
Filed: 1955-06-20
Abstract: A carboxylic ester is obtained by reacting a material having at least one acyloxy group with a compound having at least one complementary ester-forming group in the presence of an organo-tin compound having at least one carbon atom attached directly to a tin atom by a carbon to tin bond and in an amount from 0.01 to 5.0 per cent based on the weight of said material having at least one acyloxy group.  The material having at least one acyloxy group comprises carboxylic acids, anhydrides thereof, esters thereof and polyesters thereof and the compounds having at least one complementary ester-forming group comprise alcohols, carboxylic acids, anhydrides thereof, esters thereof and polyesters thereof.  The process is applicable to (1) direct esterification of a carboxylic acid with an alcohol; (2) alcoholysis between esters and alcohols; (3) acidolysis between esters and carboxylic acids; (4) ester interchange reactions; and (5) reaction between carboxylic anhydrides and alcohols.  A long list of suitable starting materials is given including saturated and unsaturated mono- and polycarboxylic acids, mono- and poly-hydric alcohols, anhydrides of dibasic carboxylic acids, esters of mono-carboxylic acids with mono- and poly-hydric alcohols and of polycarboxylic acids with monohydric alcohols (see Group IV (b)). The organo-tin compounds used as catalysts may be: (1) compounds in which at least one hydrocarbon group is attached directly to a tin atom, e.g. di-, tri- or tetra-methyl tin or trimethyl tin hydride; (2) compounds having a hydrocarbon radical attached to a tin atom and tin to tin bonds, e.g. hexamethylditin; (3) compounds having hydrocarbon radicals attached to a tin atom and oxygen to tin bonds, e.g. dimethyltin oxide, triacetyltin hydroxide, di-(trimethyltin) oxide, methylstannic acid, trimethyltin acetate, dimethyltin diacetate, di-p-chlorophenyltin dimaleate, monomethoxy dimethyltin laurate, polystannacediol compounds including polystannane-diol-esters, ethers and ether esters; and (4) and (5) compounds having hydrocarbon radicals attached to a tin atom and tin to halogen bonds or tin to sulphur bonds, e.g. trimethyltin chloride, dimethyltin dichloride, monomethyltin trichloride, dimethyltin sulphide, and methyltin triethylmercaptide.  Several other examples of each class of organotin compounds are given.  The ester-forming reaction may be carried out in conventional manner and it is usually desirable to use elevated temperature, especially reflux temperature. The reaction may be carried out under reduced pressure or in the presence of an organic diluent which is insoluble in and distils with one or more of the reaction products at temperatures less than their normal boiling points, or superheated steam or an inert gas, e.g. nitrogen, may be passed through the reaction mixture to strip the products therefrom.  The examples given include the production of polyesters by heating a mixture of butanediol-1,3, adipic acid and a small proportion of lauric acid in one or two stages in the presence of dibutyl tin oxide as catalyst (in one example zinc chloride is used as catalyst in the first stage and dibutyltin oxide is added in the second stage) and the production of a polyester by heating a mixture of dimethyl terephthalate, ethylene glycol, dibutyl tin oxide, antimony trioxide and triphenyl phosphite at 185-190 DEG  C. for 2 hours with continuous removal of methyl alcohol and then heating the mixture for 3 hours at 280-285 DEG  C. under reduced pressure with continuous removal of ethylene glycol.ALSO:A carboxylic ester is obtained by reacting a material having at least one acyloxy group with a compound having at least one complementary ester-forming group in the presence of an organo-tin compound having at least one carbon atom attached directly to a tin atom by a carbon to tin bond and in an amount from 0.01 to 5 per cent based on the weight of said material having at least one acyloxy group.  The material having at least one acyloxy group comprises carboxylic acids, anhydrides thereof, esters thereof and polyesters thereof and the compounds having at least one complementary ester forming group comprise alcohols, carboxylic acids, anhydrides thereof, esters thereof and polyesters thereof. The process is applicable to the following types of ester-forming reactions: (1) direct esterification of a carboxylic acid with an alcohol; (2) alcoholysis between esters and alcohols; (3) acidolysis between esters and carboxylic acids; (4) ester interchange reactions; and (5) reaction between carboxylic acid anhydrides and alcohols.  The carboxylic acids which may be used include mono- and poly-carboxylic acids which may be saturated or unsaturated and several such acids including hydroxy-acids are specified, typical examples being acetic, caprylic, lauric, palmitic, malonic, adipic, sebacic, pentadecane-1,15-dicarboxylic acid, tricarballylic, acrylic, methacrylic, tiglic, oleic, maleic, fumaric, citraconic, itaconic, aconitic, cyclopropane carboxylic, cyclopentane carboxylic, 1,3-cyclobutane dicarboxylic, 1,2,3,4,5,6 - cyclohexane hexacarboxylic, 1 - cyclohexene - 1 - carboxylic, 1,3 - cyclohexadiene - 1,4 - dicarboxylic, benzoic, alpha- and beta-naphthoic, o-, m-, and p-methyl (or ethyl) benzoic, benzene-1,2-dicarboxylic acid, terephthalic acid, benzene-1,2,4-tricarboxylic acid, benzene-1,2,4,5-tetracarboxylic acid, phenylacetic, cinnamic, hydroxyacetic, and beta-hydroxyvaleric acids.  Specified dibasic acid anhydrides are those of succinic, glutaric, adipic, pimelic, maleic, mesaconic, citraconic, itaconic, and phthalic acids.  The alcohols include mono- and polyhydric alcohols and several such alcohols are specified, typical examples being: methyl, ethyl, isopropyl, tert.-butyl, lauryl, stearyl and allyl alcohols, ethylene glycol, pentamethylene glycol, glycerol, pentaerythritol, 2,4-octadiene-1,8-diol benzyl, and triphenylethyl alcohols, o, m and p-phenylenediethyl alcohol and 1,3,5-tri-(ethylol) benzene. Specified esters which may be used include esters of monocarboxylic acids and mono- and polyhydric alcohols and several such esters are specified including methyl acetate, ethyl laurate, vinyl acetate, vinyl benzoate, methyl methacrylate, isopropenyl isobutyrate (or benzoate), ethyl cyclohexoate, ethyl hydroxyacetate, vinyl beta-hydroxypropionate, ethylene 1,2-diacetate, ethylidene diacetate, ethylene 1,2-dipalmitate, ethylene 1,2-diacrylate (or methacrylate), ethylene 1,2-dibenzoate, 2,4 - hexadiene - 1,6 - diacetate, pentaerythritol tetraacetate, glyceryl diacetate (dibenzoate or dipalmitate) and glyceryl triacetate (trioleate or tribenzoate). There may also be used esters of polycarboxylic acids and monohydric alcohols, e.g. dimethyl malonate (or succinate), dimethyl cyclopropane-1,1-dicarboxylate, dimethyl cyclohexane - 1,4 - dicarboxylate, diethyl (or dioctyl maleate, dimethyl (or diethyl) fumarate, dimethyl glutaconate (or citraconate) and dimethyl terephthalate.  Several classes of organo-tin compounds which may be used are specified and several examples of each class are given.  The specified classes with typical examples of each class are: (1) those having hydrocarbon radicals attached to a tin atom, e.g. dimethyl tin, dioctyl tin, dicyclohexyl tin, diphenyl tin, dibenzyl tin, trimethyl (or triphenyl) tin, tetramethyl (tetracyclohexyl- or tetraphenyl) tin, dimethyl dicyclohexyl tin, triphenyl stannyl methane and organo-tin hydrides, e.g. trimethyl tin hydride; (2) compounds having hydrocarbon radicals attached to a tin atom and tin to tin bonds, e.g. hexamethylditin, hexacyclohexylditin and hexaphenylditin; (3) compounds having hydrocarbon radicals attached to a tin atom and oxygen to tin bonds, e.g. dimethyltin oxide, dicyclohexyltin oxide, diphenyltin oxide, dibenzyltin oxide, trimethyl (tricyclohexyl or triphenyl) tin hydroxide, di-(trimethyltin) oxide, di-(tricyclohexyltin) oxide, di-(triphenyltin) oxide, methyl stannic acid, cyclohexyl-(phenyl or tolyl) stannic acid, trimethyltin acetate, triphenyltin oleate, tricyclohexyl tin propionate, tributyltin phthalate, tridodecyltin maleate, dimethyltin diacetate, dioctyltin dicyclohexoate, di-p-chlorophenyltin dimaleate, polystannanediol compounds consisting of a plurality of R2SnO groups linked to each other through the oxygen atoms wherein R is an aliphatic, alicyclic or aromatic hydrocarbon group, polystannanediol esters wherein one or both terminal hydroxyl groups are substituted by carboxylic acid radicals, e.g. the polystannanediol esters disclosed in U.S.A.  Specification 2,628,211, polystannanediol ethers in which one or both hydrogen atoms of the terminal hydroxy groups are substituted by aliphatic, alicyclic or aromatic radicals, e.g. those disclosed in U.S.A. Specification 2,626,953, polystannanediol ether esters wherein one of the terminal hydroxyl groups is substituted by a carboxylic acid radical and the hydrogen atom of the other terminal hydroxyl group is substituted by aliphatic, alicyclic, or aromatic radicals, e.g. those disclosed in U.S.A.  Specification 2,631,990; monohydrocarbon tin compounds such as methyltin triacetate, phenyltin tristearate and cyclohexyltin trimalonate and dihydrocarbon tin compounds such as monomethoxy dimethyltin laurate, monoethoxy dibenzyltin allylmaleate and monoethoxy diphenyltin butyl itaconate.  A fourth class of organo-tin compounds that may be used are those having hydrocarbon radicals attached to a tin atom and tin to halogen bonds, e.g. trimethyltin chloride, methylcyclohexylphenyltin chloride, dimethyltin dichloride and ditolyltin diiodide.  Another class of organo-tin compounds are those having hydrocarbon radicals attached to a tin atom and tin to sulphur bonds, e.g. dimethyltin sulphide, dicyclohexyltin sulphide, methyltin triethylmercaptide and diethyltin diphenylmercaptide.  The esterforming reaction in the presence of the organot