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Fused pyridine derivativesR 0450 DOI: 10.1002/chin.201030162

Ionic Liquid-Coordinated Ytterbium(III) Sulfonate Catalyzed Michael Addition of Indoles to Electron-Deficient Nitroolefins. — The title catalyst shows high activ-ity in the Michael addition of indoles (I) to nitroolefins (II). Its recycling procedure is very simple and can be carried out without extraction with water. The catalyst is reused five times without any loss of activity. The synthetic potential of the present transfor-mation is demonstrated by the straightforward conversion of (III) into tryptamines (IV) which can be directly subjected to Pictet-Spengler cyclization with benzaldehyde (V) to give the tetrahydro-β-carbolines (VI). The Pictet—Spengler cyclization is performed in a mixture of a Broensted acidic ionic liquid and a conventional ionic liquid since the reaction proceeds much faster than in organic solvent. Moreover, the Broensted acidic ionic liquid is much less corrosive. — (SHEN, W.; WANG*, L.; TANG, J.; QIAN, Z.; TONG, X.; Chin. J. Chem. 28 (2010) 3, 443-448; Lab. Adv. Mater., Inst. Fine Chem., East China Univ. Sci. Technol., Shanghai 200237, Peop. Rep. China; Eng.) —H. Hoennerscheid

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