Copper-Catalyzed Selective Oxidative Cross-Coupling of Tryptophols and Tryptamines To Access Heterocyclic 3a,3a'-Bisindolines.

The first example of cyclization cross-coupling of tryptophols and tryptamines has been realized by copper catalysis with air or oxone as the terminal oxidant, resulting in the direct construction of a new class of heterocyclic 3a,3a'-bisindolines in moderate to good yields with high chemoselectivities. A series of mechanistic control experiments were also conducted, indicating that the copper catalyst selectively coordinates with the nitrogen moiety of the tryptamine to initiate the oxidation, and a nucleophilic-alkylation process is proposed for the carbon-carbon bond-forming in the reaction. The novel synthetic strategies and molecular skeletons outlined in this work provide new ideas and concepts for the design of other useful reaction and potential drugs.