Palladium-Catalyzed Ligand-Free Double Cyclization Reactions for the Synthesis of 3-(1'-Indolyl)-phthalides.

Indole and phthalide are privileged heterocyclic scaffolds in numerous natural products and bioactive molecules. The synthesis and biological evaluation of the compounds combining these two scaffolds have rarely been reported. Herein, we repot the first palladium-catalyzed ligand-free double cyclization reactions that enable efficient synthesis of 3-(1'-indolyl)-phthalides (42 examples, up to 96% yield) under mild conditions. Notably, only 1.0 mol % of catalyst loading is used, suggesting high efficiency. Late-stage elaborations give highly functionalized analogues.