Cobalt-Catalyzed Effective Access to Quinoxalines with Insights in Annulation of Terminal Alkynes and o-Phenylenediamines.

A novel methodology for the annulation of terminal alkynes and o-phenylenediamines by using a combination of a cobalt catalyst and oxygen as a terminal oxidant is reported. This method shows wide substrate scope and good functional group tolerance and provides a wide range of quinoxalines in good to high yields. The method is demonstrated by its gram-scale and broad potential applications. Furthermore, this protocol serves as a powerful tool for the late-stage functionalization of various complex bioactive molecules and drugs to provide a new class of molecules containing two distinct bioactive molecules directly linked. Detailed mechanistic studies reveal that the current reaction goes through a novel mechanism different from the previously reported glyoxal mechanism.

Pd-Catalyzed Intramolecular Chemoselective C(sp2)-H and C(sp3)-H Activation of N-Alkyl- N-arylanthranilic Acids.

A controllable palladium-catalyzed intramolecular C-H activation of N-alkyl- N-arylanthranilic acids has been developed. The methodology allows selective synthesis of 1,2-dihydro-(4 H)-3,1-benzoxazin-4-ones and carbazoles from the same starting materials and palladium catalyst. The selectivity is controlled by the oxidant. Silver oxide promotes C(sp3)-H activation/C-O cyclization to provide 1,2-dihydro-(4 H)-3,1-benzoxazin-4-ones, while copper acetate contributes to C(sp2)-H activation/decarboxylative arylation to afford carbazoles. This protocol is demonstrated by its wide substrate scope and good functional group tolerance.