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ＣＨ ＿ Ｎ Ｅ５ＥOxone (3.5 mol%) was found to be an effective catalyst for the condensation reactions ofindoles with aldehydes to afford bis-indolylmethanes in good to excellent yields within 10–30 min. The method is simple and economic. The catalyst is found to berecyclable.# 2009 Zhi Qiang Du. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.口ＨＥＭ ＿ ＣＡ Ｌliquids [15–17]. Thus, there is still scope to develop simple and practical method for the synthesis of bis-indolylmethanes.Oxone (2KHSO5ÁKHSO4ÁK2SO4), a strong and commercially available reagent, has been used for many organictransformations [18]. Herein, we report a rapid and convenient procedure for the preparation of bis-indolylmethanesusing a catalytic amount of oxone in methanol at room temperature (Scheme 1).Ｌ Ｅ Ｔ Ｔ ＥＲ ５doi:10.1016/j.cclet.2009.06.021Synthesis of bis-indolylmethanes catalyzed by oxoneCai Li Zhang, Zhi Qiang Du*Department ofChemistry, Zhejiang University, Hangzhou 310027, ChinaReceived 3 April 2009AbstractKeywords: Indole; Aldehyde; Bis-indolylmethane; OxoneBis-indolylmethanes [1] are important derivatives ofindole and inhibit the proliferation ofbreast tumor cell [2,3].Therefore, their syntheses have received an increasing attention. Several methods have been reported in the literaturefor the synthesis ofbis-indolylmethanes. Protic acids [4] and Lewis acids [5,6] are known to promote these reactions.However, these procedures suffered from some limitations when several substrates are sensitive to protic acids. Mostrecently, a great effort has been made to find mild and clean procedure in the synthesis of bis-indolylmethanes andsome catalytic systems have been developed, such as LiClO4[7], NH4Cl [8], Zeolite [9] under solvent free conditions;Fe(DS)3[10], Zr(DS)4[11], NaBArF4[12], SDS [13], HMTAB [14] in aqueous medium; and Dy(OTf)3[15], In(OTf)3[16] and La(PFO)3[17] in ionic liquids. However, some ofthese methods suffered from some drawbacks such as hightemperature [7,8,15], long reaction time [9,16,17], low yields [9,13], causing toxic wastes [7,12] and expensive ionic1. ExperimentalTo optimize the stoichiometry ofoxone with indole and aldehyde required for the reaction, 1,2-dimethylindole andp-methoxybenzaldehyde were taken as model, several experiments were examined with different ratios ofoxone, thebest result was obtained by the molar ratio 1:2:0.035 for p-methoxybenzaldehyde, 1,2-dimethylindole, and oxone. Towww.elsevier.com/locate/ccletAvailable online at www.sciencedirect.comChinese Chemical Letters 20 (2009) 1411–1414* Corresponding author.E-mail address: duzq@zju.edu.cn (Z.Q. Du).1001-8417/$ –see front matter # 2009 Zhi Qiang Du. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.万方数据