Enantioselective synthesis of indoles through catalytic indolization

A variety of chiral indole-containing functional molecules are of great importance in chemistry and medicine. These compounds have traditionally been prepared by enantioselective functionalization of simple indole substrates. Although diverse indolization methods are established for the construction of indoles, achieving enantioselectivity directly in these transformations remained elusive until the past decade or so. In this review, we summarize various catalytic indolization strategies for the enantioselective construction of chiral substituted indoles or novel indole-based backbones bearing an axial or helical chirality. The cyclization of 2-alkynylanilines either in a direct atroposelective fashion or in cascade with another enantiodetermining transformation will be described. Subsequently, the development of enantioselective Fischer indolization, Doyle indolization, and chiral indole synthesis via a formal cycloaddition will also be reviewed.