Direct Synthesis of Dibenzotropones from o -Alkynylaryl Nitriles via Pd(II)-Catalyzed Cascade Reaction

Abstract Herein, we report a one-step Pd(II)-catalyzed strategy for the synthesis of synthetically challenging and medicinally important functionalized dibenzotropone scaffolds from readily accessible o-alkynylaryl nitriles and electron-rich aryl boronic acids. The cascade process involves regioselective 1,2-syn-carbopalladation, 1,4-palladium migration, unusual cis–trans isomerization of o-aryl-palladium species and intramolecular cyclization. Electronic tuning of aryl boronic acids enables the difficult cis–trans isomerization process. The protocol features good substrate scope with optimal functional group tolerance and is supported by control experiments and DFT studies elucidating the reaction mechanism and regioselectivity.