Efficient functionalization of indole ring via regioselective lithiations

Abstract

This article reviews the regioselective lithiations of indole derivatives. The C-2 lithiation can be readily achieved by utilizing directed lithiation promoted by a protecting (directing) group on indole nitrogen. The C-3 lithiation has been carried out mainly by halogen-lithium exchange of N-protected 3-bromo (or iodo) indoles. The lithiation at the benzenoid portion of indole has been performed by several unique methods, which are designed by considering the specific properties of indole ring and N-protecting groups. These regioselective lithiations have been nicely applied for the short-step synthesis of a number of indole-containing natural products.