Formal Synthesis of Olivacine via Indolylborate |
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| Authors: | Minoru Ishikura Norinobu Takahashi Koji Yamada Takumi Abe Reiko Yanada |
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| Institution: | 1. Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Ishikari‐Tobetsu, Hokkaido 061‐0293, Japan (phone/fax: +81‐133‐23‐1245);2. Faculty of Pharmaceutical Sciences, Hiroshima International University, 5‐1‐1 Hirokoshingai, Kure, Hiroshima 737‐0112, Japan |
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| Abstract: | Palladium‐catalyzed tandem cyclization–cross‐coupling reaction of indolylborate 2 and vinyl bromide 5 was successfully applied in a short formal synthesis of olivacine. The reaction of 2 with 5 in the presence of Pd(OAc)2 readily afforded three kinds of products, triene derivative 6 and vinylindole derivative 7 , along with a small amount of the piperidine derivative 8 (Scheme 2). On the other hand, the reactions of 2 with bromide 10 or 15 were also examined (Schemes 4 and 5), and their outcome markedly depended on the relative ease of ring closure as a function of ring size. Irradiation of 6 with a high‐pressure mercury lamp (→ 9 ; Scheme 2), followed by removal of the N‐(benzyloxy)carbonyl] group and subsequent oxidation afforded, after deprotection, pyridocarbazole 23 , and the conversion of 23 to olivacine is known (Scheme 6). |
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| Keywords: | Olivacine Palladium catalysis Borate indolyl‐ Tandem cyclization – cross‐coupling reaction |
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