Diastereoselective construction of continuous all-carbon quaternary centers via intramolecular oxidative coupling reaction

Construction of continuous all-carbon quaternary centers via intramolecular oxidative coupling was described. Intramolecular oxidative coupling of bisoxindole linked by diol derived from d-tartaric acid diastereoselectively produced C1 or C2 isomers of the annulation product. The selectivity was realized by judiciously choosing base and solvent employed in the reaction. As key intermediates for the synthesis of cyclotryptamine alkaloids, the resulting bisoxindole should be applicable to the total syntheses of complex indole alkaloids with continuous all-carbon quaternary centers.