GB812245A - A substituted benzoic acid and salts and esters thereof - Google Patents

Abstract

The invention comprises: (i) compounds of the general formula: <FORM:0812245/IV (b)/1> where R is hydrogen, a pharmacologically acceptable cation or a hydrocarbon radical containing 1 to 9 carbon atoms; an ester of 3,5 - di - n - propyl - 4 - hydroxy benzoic acid, wherein the hydrocarbon radical of the ester group contains 1 to 9 carbon atoms; (ii) a process for the preparation of compounds of the general formula (I) wherein (a) an ester of 3,5 - diallyl - 4 - hydroxybenzoic acid is hydrogenated in the presence of a hydrogenation catalyst to produce the corresponding ester of 3,5-di-n-propyl-4-hydroxybenzoic acid which is then reacted with an allyl halide in the presence of an alkali to produce the corresponding ester of 3,5-di-n-propyl-4-allyloxy-benzoic acid and if desired this is saponified to produce the acid, or (b) an ester of 3,5-di-n-propyl-4-hydroxybenzoic acid is saponified and acidified to produce the free acid which is then reacted with an allyl halide in the presence of an alkali to produce allyl-3,5-di-n-propyl-4-allyloxybenzoate, and this is hydrolysed to produce 3,5 - di - n - propyl - 4 - allyloxybenzoic acid; and (iii) a process for the manufacture of an ester of 3,5 - di - n - propyl - 4 - hydroxy-benzoic wherein an ester of 3,5 - diallyl - 4 - hydroxy-benzoic acid is hydrogenated in the presence of a hydrogenation catalyst. In examples: (1) ethyl 3,5-diallyl-4-hydroxy-benzoate is hydrogenated in the presence of platinum dioxide catalyst to give ethyl 3,5-di-n - propyl - 4 - hydroxybenzoate; (2) ethyl 3.5 - di - n - propyl - 4 - hydroxybenzoate is treated with allylbromide to give ethyl 3,5-di-n-propyl-4-allyloxybenzoate; (3) ethyl 3,5-di-n - propyl - 4 - allyloxybenzoate is saponified with potassium hydroxide and on acidification yields 3,5 - n - propyl - 4 - allyloxybenzoic acid. In place of the ethyl ester used as starting material in (1) the methyl, isopropyl, n-butyl, n-hexyl, n-octyl cyclopentyl, cyclohexyl, benzyl, allyl, phenethyl, or cinnamyl esters may be used to yield the corresponding saturated esters, in the case of the allyl and cinnamyl esters, the n-propyl and 3-phenylpropyl benzoates being formed respectively. Further, these products may be used as alternative starting materials in (2) and (3) to yield the correspondsaturated esters of 3,5-di-n-propyl-4-alloxy-benzoic acid and the same free acid as in (3). The free acid formed in (3) either as such or by first converting it into the acid chloride or bromide may be esterified with methyl, ethyl, isopropyl, n-butyl, n-hexyl, n-octyl, cyclopentyl, cyclohexyl, benzyl, allyl, phenethyl or cinnamyl alcohol to form the corresponding esters, or the free acid itself may be reacted with sodium or potassium hydroxides, calcium oxide, sodium carbonate, aluminium oxide, ammonia, or substituted ammonium compounds, such as methyl-, ethyl-, and dimethylamines to form the corresponding salts of the acid.