GB637924A - Manufacture of tetrahydrothiophene derivatives - Google Patents

Abstract

Tetrahydrothiophene derivatives of the general formula <FORM:0637924/IV (b)/1> (wherein R represents a carboxylic acyl group, R1 hydrogen or alkyl and Y-N=an arylhydrazino radical) are manufactured by reacting an arylhydrazine with an alkyl ester of a 2 - (o - carboxybutylidene) - 3 - keto - 4 - acylamidotetrahydrothiophene, and, if desired, hydrolysing the product. The starting materials are obtainable by the process of Specification 637,923, and the products may be further converted as described in Specification 637,925, as a step in the synthesis of biotin. In examples, 2 - (41 - carbomethoxybutylidene) - 3 - keto - 4 - benzamidotetrahydrothiophene is refluxed in methanolic hydrochloric acid with (1) p-nitrophenylhydrazine and (2) 2 : 4-dinitrophenylhydrazine. Other 4-acylamido derivatives, e.g. the 4-acetamido or 4-propionamido compound, and other alkyl esters, e.g. the propyl ester, may be similarly treated. The Specification as open to inspection under Sect. 91 comprises also the manufacture of the corresponding aryl and aralkyl (e.g. benzyl) esters and of analogous compounds containing other o -carboxyalkylidene groups in place of the o -carboxybutylidene group, the manufacture of compounds in which Y-N= is a semicarbazido radical by using semicarbazide (or a salt thereof) instead of an acylhydrazine, and the subject-matter of Specification 606,192. This subject-matter does not appear in the Specification as accepted.