Brønsted Acid Catalyzed C3-Alkylation of 2-Indolylmethanols with Azlactones via an Umpolung Strategy

An efficient method for the synthesis of C3-alkylated indoles has been established via Brønsted acid catalyzed alkylation of 2-indolylmethanols with azlactones. The reaction exhibits broad substrate scope and delivers high yields (22 examples, up to 99% yield). This approach not only provides a new strategy for the direct synthesis of C3-alkylated indoles, but also represents a rarely reported alkylation between indole motifs and electron-rich synthons at the C3 position. This protocol serves as a good example of the application of the umpolung strategy in the synthesis of C3-alkylated indoles from 2-indolylmethanols.