Thiols were effectively oxidized into disulfides by reacting with hydrogen peroxide in the presence of a catalytic amount of iodide ion or iodine.The controlled oxidative coupling of thiols to disulfides is important in organic synthesis, and a wide range of methods have been developed for this transformation. 1 Thiols are among the functional groups which can be easily over oxidized, therefore, extensive studies have been carried out for their controlled oxidation with molecular oxygen, 2 peroxide, 3 metal oxidants, 4 halogens and derivatives, 5 sulfoxide, 6 and N-oxide. 7 In particular, the methods of oxidative coupling of disulfides with halogens such as I 2 , 5a I 2 /HI, 5b and Br 2 /KHCO 3 5c were carried out under mild reaction conditions, and gave the disulfides in good yields. However, these reactions require a stoichiometric amount of oxidants and long reaction times. Oae and co-workers developed the oxidative coupling of thiols to disulfides by dimethyl sulfoxide in the presence of a catalytic amount of molecular iodine. 5b Although this reaction affords the products in high yield under very mild reaction conditions, there are still some problems such as the requirement of a long reaction time and the production of foulsmelling dimethyl sulfide as a waste product.To develop an environmentally benign oxidative coupling of thiols, we planned to use hydrogen peroxide as a cooxidant for the oxidation of thiols with molecular iodine, because the iodide ion (iodoanion) is easily oxidized to molecular iodine by hydrogen peroxide.Hydrogen peroxide itself can oxidize thiols to the corresponding disulfides; however, alkaline conditions were required. 3a Recently, Bégué et al. reported that disulfides can be efficiently prepared from thiols using 30% hydrogen peroxide in fluoroalcohols at ambient temperature under neutral conditions. 3b Although this method provides the desired compounds in high yields in most cases, fluoroalcohols are expensive for industrial use. Furthermore, the thiols, which are less soluble in the fluoroalcohols, produced the desired disulfides in poor yields. In this paper, we describe a method for the oxidation of thiols 1 to disulfides 2 using 30% hydrogen peroxide catalyzed by iodide ion (Scheme 1). Scheme 1

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Cu(In,Ga)Se2 thin films with high Ga content were fabricated by sequential evaporation from CuGaSe2 and CuInSe2 ternary compounds (CuGaSe2/(CuGaSe2+CuInSe2) = 0.8) for photovoltaic device applications. XRF analysis showed that the Cu:In:Ga:Se atomic ratio in all thin films was consistent with the amounts of the evaporating materials. The Ga/(In+Ga) mole ratio in the thin films was within the range from 0.61 to 0.88. XRD studies showed that the prepared thin films had a chalcopyrite Cu(In,Ga)Se2 structure. The best solar cell using Cu(In,Ga)Se2 thin film prepared at CuGaSe2/(CuGaSe2 + CuInSe2) = 0.8 demonstrated Voc = 496 mV, Isc = 27.57 mA/cm2, FF = 0.508 and efficiency = 6.95% without AR‐coating. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Polysulfides P 0425A Mild and Environmentally Benign Oxidation of Thiols to Disulfides. -Oxidative coupling of various thiols can be achieved in excellent yields under conditions A) in Et-O-Ac within a short time. Only the bulky substrate (If) requires 24 h and is formed in a low yield. In water as the solvent, the yields of the products remain high but an essentially longer reaction time is necessary with exception of cysteine (III). -(KIRIHARA*, M.; ASAI, Y.; OGAWA, S.; NOGUCHI, T.; HATANO, A.; HIRAI, Y.; Synthesis 2007, 21, 3286-3289; Dep. Mater. Sci., Shizuoka Inst. Sci. Technol., Fukuroi, Shizuoka 437, Japan; Eng.) -Mais 12-062