Oxidative coupling strategies for the synthesis of indole alkaloids

Direct bond formation between two C-H bonds is most challenging but imperative for efficient organic synthesis. Recently, significant progress has been made in direct functionalization of indole through oxidative coupling reactions with other nucleophiles such as enolates and phenols. Both intermolecular and intramolecular coupling reactions can be conducted under the action of base/oxidants or oxidants alone. Coupling typically occurs at the 3-position of indole moiety due to intrinsic nucleophilicity at this position. Coupling at the 2- or 4-position of the indole moiety has been observed for some special substrates. These coupling reactions provide powerful tools for quickly establishing the core structures of a number of indole alkaloids.