Gallium Bromide-Promoted Dearomative Indole Insertion in 3-Indolylmethanols: Chemoselective and (Z/E)-Selective Synthesis of 3,3′-Bisindole Derivatives

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• 作者：Cong-Shuai Wang ; Tao Fan ; Hong-Hao Zhang ; Can Li ; Yang Shen ; Guang-Jian Mei ; Feng Shi
• 刊名：Journal of Organic Chemistry
• 出版年：2016
• 出版时间：December 2, 2016
• 年：2016
• 卷：81
• 期：23
• 页码：11734-11742
• 全文大小：555K
• ISSN：1520-6904

文摘

Gallium bromide (GaBr₃)-promoted dearomative indole insertion in 3-indolylmethanols has been established, which chemoselectively constructs a biologically important 3,3′-bisindole framework bearing an all-carbon quaternary center in high yields and excellent (Z)-selectivities (up to 99% yield, all >95:5 Z/E). The reaction pathway was suggested to include a tandem sequence of Michael addition/C–C bond cleavage/nucleophilic addition, wherein the strong acidity of GaBr₃ played a crucial role in the key step of C–C bond cleavage. This reaction not only provides a new strategy for dearomatization of indoles, but also represents a new reaction category for 3-indolylmethanols, which involves a rarely reported late-stage C–C bond cleavage of 3-indolylmethanol derivatives. In addition, this approach also offers an efficient method for the synthesis of biologically important 3,3′-bisindole derivatives.