Watanabe indole synthesis applications

Scheme 2 Applications of the Watanabe-Cenini-Soderberg Indole Synthesis...

Murakami, Y, Watanabe, T, Takahashi, H., Yokoo, H., Nakazawa, Y, Koshimizu, M., Adachi, N., Kurita, M., Yoshino, T, Inagaki, T., Ohishi, M., Watanabe, M., Tani, M., and Yokoyama, Y. (1998) Fischer indolization of 2-sulfonyloxyphenylhydrazones a new and practical approach for preparing 7-oxygenated indoles and application to the first synthesis of eudistomin A. Tetrahedron, 54,45-64. 

Several investigators have developed the reductive cyclization of o-nitrostyrenes into an efficient synthesis of indoles. Thus, research by the groups of Watanabe [480], Soderberg [481], and Cenini [482] have established this reductive Pd-catalyzed TV-het-eroannulation reaction as a viable and powerful route to simple indoles and fused indoles (411) as shown below. In addition, Soderberg has shown the application of this method to carbazolones [481d], natural p-carbolines [481e], and the carbazole alkaloid murrayaquinone A [48If]. Ohta described the related Pd-catalyzed cyclization of o-aminophenethyl alcohol to indole in 78% yield [483]. 

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