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Download fileGallium Bromide-Promoted Dearomative Indole Insertion in 3‑Indolylmethanols: Chemoselective and (Z/E)‑Selective Synthesis of 3,3′-Bisindole Derivatives
journal contribution
posted on 2016-10-28, 00:00 authored by Cong-Shuai Wang, Tao Fan, Hong-Hao Zhang, Can Li, Yang Shen, Guang-Jian Mei, Feng ShiGallium 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.