Oxazoline-carbene system

In addition to palladium catalysts, Co(OAc)2 shows a catalytic activity for the arylation of heterocycles, including thiazole, oxazole, imidazole, benzothiazole, benzoxazole, and benzimidazole.78 As shown in Scheme 6, the catalytic system Co(OAc)2/9/Cs2C03 gives G5 phenylated thiazole, while the bimetallic system Co(OAc)2/CuI/9/Cs2C03 furnishes the G2 phenylated thiazole. The rhodium-catalyzed reaction of heterocycles such as benzimidazoles, benzoxazole, dihydroquinazoline, and oxazoline provides the arylation product with the aid of [RhCl(coe)]2/PCy3 catalyst.79 The intermediacy of an isolable A-heterocyle carbene complex is proposed. 

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