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  • Ruthenium‐Catalyzed meta‐Se...
    Li, Zhong‐Yuan; Li, Liang; Li, Qi‐Li; Jing, Kun; Xu, Hui; Wang, Guan‐Wu

    Chemistry : a European journal, March 8, 2017, Volume: 23, Issue: 14
    Journal Article

    The first example for the ruthenium‐catalyzed ligand‐directed meta‐selective C−H mono‐ and difluoromethylation is developed, affording a variety of new meta‐mono‐ and difluoromethylated 2‐phenylpyridines, 2‐phenylpyrimidines, and 1‐phenylpyrazoles in moderate‐to‐good yields. This new transformation exhibits broad substrate scope, good functional group tolerance, and high efficiency, and offers a practical approach to synthesize mono‐ and difluoromethylated arenes. Mechanistic studies indicate that a reaction pathway involving palladium‐initiated radical species is involved in the catalytic cycle. The new dual catalytic system consisting of compatible ruthenium(II) and palladium(0) complexes enables the key processes of C−H activation and mono‐/difluoromethyl‐radical formation to occur and achieves the meta‐selective functionalization efficiently. In addition, the present protocol can also be extended to non‐fluoromethylation. A meta approach to fluoromethylation: The first example for the ruthenium‐catalyzed ligand‐directed meta‐selective C−H mono‐ and difluoromethylation is developed, affording a variety of new meta‐mono‐ and difluoromethylated 2‐phenylpyridines, 2‐phenylpyrimidines, and 1‐phenylpyrazoles in moderate‐to‐good yields. This new transformation exhibits broad substrate scope, good functional group tolerance, and high efficiency, and offers a practical approach to synthesize mono‐ and difluoromethylated arenes.