Expeditious Synthesis\nof Highly Functional 4‑Trifluoromethyl-Substituted\nOxazoles Enabled by Cobalt(II) Metalloradical Catalysis

A synthetic strategy for the catalytic cycloaddition\nof α-trifluoromethyl-α-diazoketones\nwith nitriles has been achieved based on cobalt(II) metalloradical\ncatalysis. The easily accessible starting materials, cost-effective\ncatalyst, and experimental simplicity rendered this protocol a robust\nand practical approach to construct diverse functionalized 4-CF<sub>3</sub>-substituted oxazoles with high efficiency. A wide substrate\nscope of both α-trifluoromethylated diazoketones and nitriles\nis amenable to this catalytic system. The high level of functional\ngroup tolerance of this protocol provides several opportunities for\nprecise late-stage modifications of bioactive and drug-like molecules.\nMechanistic experiments and spectroscopic investigations confirm the\nradical nature of the reaction and reveal the involvement of both\nmonocarbene and biscarbene radical intermediates during the catalytic\nprocess.