Borane-Catalyzed Enantioselective α-Alkylation of Unactivated 2-Alkylbenzoxazoles with Electron-Deficient Olefins.

Chiral borane-catalyzed reactions have recently emerged as a powerful tool for the enantioselective production of chiral scaffolds. In this study, we demonstrated for the first time that a chiral bisborane catalyst can be used for the α-functionalization of 2-alkylazaarenes; specifically, we accomplished unprecedented highly enantioselective α-alkylation of unactivated 2-alkylbenzoxazoles with electron-deficient olefins. The strong Lewis acidity and the steric bulk of the bisborane catalyst were essential to the observed reactivity and selectivity.

Diiodomethane-Mediated Generation of -Aryliminium Ions and Subsequent [4 + 2] Cycloadditions with Olefins.

Herein, we report a method for in situ generation of -aryliminium ions via reactions of ,-dimethylanilines with diiodomethane. We used the method to prepare tetrahydroquinolines via one-pot three-component reactions between ,-dimethylanilines, diiodomethane, and olefins. This transformation involves initial reaction of the aniline with diiodomethane to form an iodomethylammonium salt, which undergoes fragmentation accompanied by elimination of methyl iodide to give an -aryliminium ion, which is trapped by the olefin via [4 + 2] cycloaddition to give the final product.

Metal-Oxidant-Free Cobalt-Catalyzed C(sp)-H Carbonylation of ortho-Arylanilines: An Approach toward Free ( NH)-Phenanthridinones.

A traceless directing group assisted Co-catalyzed C(sp)-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.