Selenium‐Sulfur analogs. 6. Selenoisosteres of levamisole

Abstract

A series of three new isosteres of levamisole was prepared by the substitution of the phenyl ring by the thienyl and selenienyl moieties and of the thiazole group by selenazole. The physiochemical properties and infrared spectra of the sulfur‐ and selenium‐containing analogs were very similar. Differentiation was mostapparent in the nuclear magnetic resonance spectra where the α‐ and β‐protons of the selenienyl compounds were shifted downfield relative to those of the corresponding thienyl compounds. With deuterated thiofluoroacetic acid as the solvent, a more rapid exchange was observed for the α‐proton of the selenienyl ring of compounds 17 and 18 compared to that observed for compound 16.