GB990466A - Process for the preparation of bis-azolyl-thiophene derivatives - Google Patents

Abstract

The invention comprises tetrahydro thiophene derivatives of the general formula <FORM:0990466/C2/1> in which A represents the residue of an o-phenylene radical which is unsubstituted or substituted by a halogen atom, an alkoxy or alkyl group with at most 4 carbon atoms, or a phenyl group and X is an oxygen atom, a sulphur atom or the group <FORM:0990466/C2/2> in which R is a hydrogen atom, or an alkyl, alkenyl or hydroxyalkyl group with at most 4 carbon atoms, and also the acid addition salts of those compounds in which X is <FORM:0990466/C2/3> These compounds may be prepared by reacting an aminobenzene of formula <FORM:0990466/C2/4> an addition salt thereof, at an elevated temperature with tetrahydrothiophene-2,5-dicarboxylic acid or with a functional derivative thereof, e.g. an ester or an acid dihalide. The reaction is preferably carried out in the presence of a dehydration catalyst, e.g. boric acid, sulphonic acids of the benzene series, polyphosphoric acids and zinc chloride. Alternatively the reactants may be heated in an aqueous mineral acid. The tetrahydrothiophene derivatives of the general formula given above may be converted to the corresponding thiophene compounds by treating with a dehydrogenating agent at elevated temperature. Suitable dehydrogenating agents are, for example, compounds of divalent mercury such as the acetate or oxide; potassium permanganate; manganese dioxide; copper oxide or sulphate; hydrogen peroxide; selenium dioxide; platinum oxide; ferric salts such as the sulphate and chloride; nitro compounds such as nitrobenzene or a mixture of nitrobenzene and quinoline; air mixed with quinoline; finely divided nickel, copper, platinum or palladium; bromine, chlorine phosphorus pentachloride, sulphuryl chloride, thionyl chloride and sulphur chlorides. The dehydrogenating agents are preferably used in the presence of solvents.