A novel, convenient and chemoselective procedure for oxidizing sulfides to sulfoxides with 30% aqueous H 2 O 2 in phenol at room temperature is described. The procedure is very simple and no strict conditions were required for the selective conversion without affecting the functional groups even including the highly reactive aldehyde group. The reactions proceeded very quickly in excellent yields. Some experimental evidences are presented describing the role of the solvent.The oxidation of sulfides to sulfoxides has been the aim of considerable research due to the importance of sulfoxides as useful intermediates in various chemically and biologically significant molecules. 1,2 There are several reagents available for this key transformation 3 . Unfortunately, most of these reagents are not satisfactory because they are either harmful or expensive, and a simple procedure is not easily available because of the over oxidation of sulfoxides to sulfones. Despite careful control of the reaction temperature, reaction time and the relative amount of oxidants, it is difficult to avoid completely such over oxidation.Aqueous hydrogen peroxide has attracted great attention as oxidation reagent because of its low cost of production and transportation, effective-oxygen content and the formation of only harmless water as by-product. These obvious advantages have spurred the development of useful procedures for H 2 O 2 oxidation of sulfides, including the use of a wide range of catalysts based on metals or semimetals such as H 2 WO 4 4 and H 3 PW 12 O 40 + [(C 8 H 17 ) 4 N]Br. 5 However, organic, nonmetal compounds capable of activating H 2 O 2 for the oxidation of sulfides to sulfoxides is rather limited. The most prominent example was 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). 6 The group of Bégué successively transformed the sulfides to sulfoxides with complete selectivity in HFIP. But the HFIP is poisonous, expensive, and volatile which severely restricted its use in organic synthesis especially in practical organic synthesis, and in our repeated study we found that some reactive functional groups were easily oxidized in the reaction. Drabowiczr 7 reported a selective method for the oxidation of sulfides to sulfoxides by aqueous 30% H 2 O 2 in methanol, but it was found that the reaction time was extremely long and some other functional groups were also easily destroyed. Thus, it is desirable to develop a medium for the selective and convenient oxidation of sulfides to sulfoxides by aqueous H 2 O 2 without affecting other functional groups.In an extended experiment, the oxidation of methyl phenyl sulfide by using aqueous 30% H 2 O 2 was attempted in different solvents. When the reaction was carried out in propan-2-ol and cyclohexanol, unreacted sulfide could be detected even after one day. When acetic acid was adopted as the reaction medium, although the oxidation reaction was enhanced, a mixture of sulfoxide and sulfone was obtained. Eventually, the reaction was carried out in trifluoroacetic acid, and it was found that the ...