Cobalt-catalyzed arylation of azole heteroarenes via direct C-H bond functionalization.
[reaction: see text] We herein report a new cobalt-catalyzed method for arylation of azole heteroarenes, including thiazole, oxazole, imidazole, benzothiazole, benzoxazole, and benzimidazole. The direct arylation of thiazole and oxazole was achieved both with iodo- and bromoarenes as the aryl donors in the presence of cobalt catalyst [Co(OAc)(2)/IMes] and cesium carbonate, while imidazole required the use of zinc oxide as the base. A complete reversal of arylation from C-5 to C-2 was accomplished using the bimetallic Co/Cu/IMes system. A direct comparison of the new cobalt method and the previously developed palladium protocol revealed significant differences, in terms of both chemical yield and selectivity.
D001393:Azoles / Q000737:chemistry*; D002384:Catalysis; D003035:Cobalt / Q000737:chemistry*; D006841:Hydrocarbons, Aromatic / Q000138:chemical synthesis* / Q000737:chemistry; D007093:Imidazoles / Q000737:chemistry; D010080:Oxazoles / Q000737:chemistry; D010165:Palladium / Q000737:chemistry
D001393:Azoles; D006841:Hydrocarbons, Aromatic; D007093:Imidazoles; D010080:Oxazoles; D003035:Cobalt; D010165:Palladium; C029899:imidazole