Direct Base-Assisted C‒H Cyclonickelation of 6-Phenyl-2,2′-bipyridine

Titelangaben

Vogt, Nicolas ; Sivchik, Vasily ; Sandleben, Aaron ; Hörner, Gerald ; Klein, Axel:
Direct Base-Assisted C‒H Cyclonickelation of 6-Phenyl-2,2′-bipyridine.
In: Molecules. Bd. 25 (2020) Heft 4 . - No. 997.
ISSN 1420-3049
DOI: https://doi.org/10.3390/molecules25040997

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Abstract

The organonickel complexes [Ni(Phbpy)X] (X = Br, OAc, CN) were obtained for the first time in a direct base-assisted arene C(sp2)–H cyclometalation reaction from the rather unreactive precursor materials NiX2 and HPhbpy (6-phenyl-2,2′-bipyridine) or from the versatile precursor [Ni(HPhbpy)Br2]2. Different from previously necessary C‒Br oxidative addition at Ni(0), an extended scan of reaction conditions allowed quantitative access to the title compound from Ni(II) on synthetically useful timescales through base-assisted C‒H activation in nonpolar media at elevated temperature. Optimisation of the reaction conditions (various bases, solvents, methods) identified 1:2 mixtures of acetate and carbonate as unrivalled synergetic base pairs in the optimum protocol that holds promise as a readily usable and easily tuneable access to a wide range of direct nickelation products. While for the base-assisted C‒H metalation of the noble metals Ru, Ir, Rh, or Pd, this acetate/carbonate method has been established for a few years, our study represents the leap into the world of the base metals of the 3d series.