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Synfacts 2006(3): 0205-0205  
DOI: 10.1055/s-2006-931961
Synthesis of Heterocycles
© Georg Thieme Verlag Stuttgart · New York

Synthesis of α-Carbolines

Contributor(s): Victor Snieckus, Till Vogel
K. Tanaka, M. Kitamura, K. Narasaka*
University of Tokyo, Japan
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Publikationsdatum:
21. Februar 2006 (online)

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Significance

A synthesis of α-carbolines 3 by copper-catalyzed radical cyclization of β-(3-indolyl) ketone O-pentafluorobenzoyloximes and carbonates 1 is described. Although the previously used (Y. Koganemaru, K. Kitamura, K. Narasaka Chem. Lett. 2002, 784-785) CuBr×SMe2 can be applied as catalyst, elementary Cu gave surprisingly better results in dichloroethane and with N,N¢,N¢,N¢¢,N¢¢-pentamethyldiethylenetriamine (PMEDTA) as an additive. A radical mechanism involving generation of a Cu(I) species by a redox reaction between Cu and solvent is proposed. Dihydrocarboline 2 is readily oxidized to carboline 3 by treatment with chloranil at ambient temperature.