3,5-[5-Arylisoxazol-3-yl(4,5-dichloroisothiazol-3-yl)]-substituted 1,2,4- and 1,3,4-oxadiazoles: synthesis, palladium complexes, and catalysis of Suzuki reactions in aqueous media

Abstract

A reaction sequence involving transformations of 5-(4-methylphenyl)isoxazole and 4,5-dichloroisothiazole derivatives containing an amidoxime group at position 3 allowed to synthesize the respective 3,5-isoxazolyl(isothiazolyl)-substituted 1,2,4-oxadiazoles. Selective recyclization of 4,5-dichloro-3-(1Н-tetrazol-5-yl)isothiazole and 5-(4-methylphenyl)-3-(1Н-tetrazol-5-yl)isoxazole gave 2,5-isoxazolyl-(isothiazolyl)-substituted 1,3,4-oxadiazoles. The obtained compounds combining three azole heterocycles in one molecule formed palladium complexes that showed high catalytic activity in Suzuki reactions in aqueous and aqueous alcohol media. The bimetallic reusable Pd/Fe catalyst obtained from palladium polyazole complex retained high catalytic activity after five uses.