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Keywords
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Disulfide, ionic liquid, oxidation, sonochemistry, thiol, L-cysteine
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Abstract
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An ultrasound-assisted method with specific characteristics of green chemistry for aerobic oxidative coupling of thiols to disulfides is presented. In this method, a readily available ionic liquid catalyzed the aerobic oxidative coupling of thiols to disulfides in water as a green solvent under ultrasonic irradiation at room temperature. In this novel sonocatalysis/ionic liquid protocol, aromatic thiols having both electron-donating and electron-withdrawing substituents, alkyl thiols and cysteine, were cleanly converted to the corresponding disulfides in excellent yields. This methodology uses 1,3-dimethyl imidazolium methyl sulfate (DiMIM-CH3SO4) ionic liquid as a recyclable catalyst and aerobic oxygen as an oxidative agent. This protocol has the advantages of high yields, short reaction times, lower cost, environmentally friendly reaction media, easy isolation of products, convenient procedure and recoverability of catalyst.
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