GB762575A - Omega [3-(1,2-dithiolanyl)] aliphatic acids, salts and esters and the preparation thereof - Google Patents

Abstract

The invention comprises omega [3-(1,2-dithiolanyl)] aliphatic acids of the general formula <FORM:0762575/IV(b)/1> in which n is from 2 to 6, and their salts and esters. The acids may be prepared by oxidizing a dithiol acid of the formula CH2(SH).CH2.CH(SH).(CH2)n.COOH e.g. using iodine in potassium iodide solution or air in the presence of ferric iron. The dithiol acids (II) may be prepared by refluxing an omega thiol-hydroxy acid of the formula CH2(SH).CH2.CH(OH).(CH2)nCOOH with excess thiourea and a halogen acid, and hydrolysing the intermediate thiouronium salts with, for example, sodium hydroxide, followed by acidification. The thiolhydroxy acid (III) may be prepared by reducing an omega-acetylthioketoester of the formula CH3.CO.S.CH2.CH2.CO.(CH2)n.COOR in which R is alkyl, with a metallic hydride reducing agent such as sodium borohydride or lithium aluminium hydride and hydrolysing the products. The acetylthioketoester (IV) may be obtained by reacting an unsaturated ketoester of the formula CH2=CH.CO.(CH2)n.COOR with thioacetic acid. The unsaturated ketoester (V) may be obtained by dehydrohalogenating a b -halogen-substituted ketoester of the formula X.CH2.CH2.CO.(CH2)n.COOR, where X is halogen, for example by distillation at reduced pressure. The halogen-substituted ketoester may be prepared by reacting an ester halide ROOC.(CH2)nCOX with ethylene in the presence of a metallic halide catalyst, preferably aluminium chloride. The reaction may be effected by bubbling ethylene through a solution of aluminium chloride in the acid chloride, or by adding the acid chloride to a suspension of aluminium chloride in a solvent through which ethylene is passed. Salts of the new products (I) are prepared by neutralization with alkali. Esters are obtained by heating the acid (I) with an alcohol in the presence of an esterifying catalyst or by reacting with diazomethane or diphenyl diazomethane to give the methyl and benzhydryl ester respectively. The novel acids, salts and esters are useful as oxidation inhibitors and growth supporting factors for certain micro-organisms. The 1, 2-dithiolanyl ring may be oxidized with t.-butyl hydroperoxide resulting in addition of one atom of oxygen to the disulphide ring whereas treatment with hydrogen peroxide results in two oxygen atoms being attached to the ring on either or both sulphur atoms. A detailed example is given of the synthesis of omega-[3-(1,2-dithiolanyl)]-valeric acid starting from ethyl adipyl-chloride and by way of the intermediates D 7,6-keto-octenoate, 8-thiol-6-hydroxyoctanoic acid and 6,8-dithioloctanoic acid. Ethyl succinyl chloride and ethyl glutaryl chloride are mentioned as starting materials for acids of formula (I) where n is 2 and 3 respectively.