Cobalt-Catalyzed C(sp2)-H Allylation of Biphenyl Amines with Unbiased Terminal Olefins
Unactivated olefins usually react poorly in conventional alkenylation reactions. Their introduction via C-H activation is limited to aromatic acids. Herein, we disclose a C-H functionalization protocol of aromatic amines with unactivated olefins, which shows exclusive allylic selectivity for the distal ring of the biphenyl system by exploiting a readily available cobalt(II) catalyst. The allylation proceeds smoothly involving a broad set of unbiased olefins and biaryls, giving access to the functionalization of the biphenyl scaffold.
Metal-Oxidant-Free Cobalt-Catalyzed C(sp2)-H Carbonylation of ortho-Arylanilines: An Approach toward Free (NH)-Phenanthridinones
A traceless directing group assisted Co-catalyzed C(sp2)-H carbonylation of ortho-arylanilines for the synthesis of free (NH)-phenanthridinones in metal-based-oxidant-free fashion was accomplished. This protocol employs diisopropyl azodicarboxylate as the CO source and oxygen as the sole oxidant, and provides good yields with various functional tolerance. The methodology has been applied for the total synthesis of PARP inhibitor PJ-34. Furthermore, the kinetic isotopic effect experiments reveal the C-H bond cleavage probably occurred in the rate-determining step.
Synthesis of carbazoles by copper-catalyzed intramolecular C-H/N-H coupling
A Cu-catalyzed intramolecular C-H amination for the synthesis of carbazoles has been developed. The key to success is the installation of the picolinamide-based directing group, which is spontaneously removed after the coupling event. The Cu catalysis proceeded smoothly under Pd- and I(III)-free conditions, and its mild oxidation aptitude enables the rapid and concise construction of heteroatom-incorporated carbazole core π-systems.