Metal-Free Selective Air-Oxidation of Sulfides to Sulfoxides Using 2,2′-Azobis-(2,4-dimethyl-4-methoxyvaleronitrile) (V-70) and Isobutyraldehyde

Abstract

Selective oxidation of sulfides to sulfoxides using ‘air’ was achieved using a combination of 2,2′-azobis-(2,4-dimethyl-4-methoxyvaleronitrile) (a radical initiator) and isobutyraldehyde (a co-oxidant). Various sulfides were successfully converted into their corresponding sulfoxides using this method. This approach promotes a sustainable oxidation process by excluding harmful oxidants, such as peroxides and metal reagents.

Key words

air - oxidation - V-70 - radicals - sulfoxide

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• 14 General Procedure: Under air atmosphere, V-70 (12.3 mg, 0.04 mmol, 20 mol%) was added to a suspension of sulfide (0.2 mmol, 1.0 equiv) and isobutyraldehyde (18.3 µL, 0.2 mmol, 1.0 equiv) in EtOAc (2 mL) and the mixture was stirred at room temperature. Upon completion, the reaction mixture was diluted with EtOAc and washed with sat. NaHCO₃ aq. and brine. The organic layer was dried over Na₂SO₄, filtered, and concentrated under reduced pressure. The conversion was determined by ¹H NMR analysis of the crude product.
• 15 Analytical data for sulfoxides are provided in the Supporting Information.