3 - Iranian Journal of Organic Chemistry 2 (2009) 80-83 80...

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Unformatted text preview: Iranian Journal of Organic Chemistry 2 (2009) 80-83 80 Solvent-free synthesis of bis(indolyl)methanes catalyzed by CAN Majid M. Heravi, * Khadijeh Bakhtiari, * and Azadeh Fatehi Department of Chemistry, School of Sciences, Azzahra University, Vanak, Tehran, Iran Abstract: Indoles and carbonyl compounds undergo a rapid electrophilic substitution reaction in the presence of a catalytic amount of CAN, under solvent-free conditions, to afford the corresponding bis(indolyl)methanes in excellent yields. Keywords: Bis(indolyl)methanes; Solvent-free conditions; Ceric ammonium nitrate; CAN Introduction Indole fragments are featured wide variety of pharmacologically and biologically active compounds [1]. Bis(indolyl)methanes are common components of bioactive metabolites of terrestrial and marine origin [2]. A few bioactive members of these compounds like Vibrindole-A and others have also been isolated from natural sources [3] and are generally found to be of pharmaceutical interest in a variety of therapeutic areas [1]. These compounds have received considerable attention over the past years due to their wide occurrence in various natural products possessing biological activity [2b,4] and usefulness for drug design [1]. Bis(indolyl)methanes are most active cruciferous substances for promoting beneficial estrogen metabolism and inducing apoptosis in human cancer cells [5]. A simple and direct method for the synthesis of bis(indolyl)methanes is the reaction of indole with aldehydes. A wide variety of reaction conditions have been published for the synthesis of bis(indolyl)methane derivatives in solution, on solid phase and under solvent-free conditions. Several catalyst including lanthanide triflate [6] Dy(OTf) 3 [7], InCl 3 [8], PPh 3- HClO 4 [9], montmorilonite K-10 [10], NBS [11], I 2 [12], KHSO 4 [13], RE(PFO) 3 [14], InF 3 [15], ZrOCl 2 [16], ZrCl 4 [17] and acidic ionic liquid [18] were found to promote the reaction. However, there are always some drawbacks with these procedures such as long reaction times, high catalyst loading, and use of an additional ultrasound or microwave oven. Therefore, the development of more efficient and green methods for the preparation of these *Corresponding author. Fax: +(98) 2188041344; E-mail: [email protected]; [email protected] kinds of compounds is still an active ongoing research area. Recently, ceric ammonium nitrate, CAN, has been introduced as a mild and efficient catalyst for various organic transformations [19]. The reaction of indoles with carbonyl compounds catalyzed by CAN which afford the bisindolymethane derivatives has been reported recently. However, the reactions must be reported recently....
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3 - Iranian Journal of Organic Chemistry 2 (2009) 80-83 80...

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