Cobalt-Catalyzed Formation of Grignard Reagents <i>via</i> C–O or C–S Bond Activation
Ewa Pietrasiak, Seongmin Ha, Seungwon Jeon, Jongheon Jeong, Jiyeon Lee, Jongcheol Seo, Eunsung Lee
Abstract
C(aryl)–OMe bond functionalization catalyzed by cobalt(II) chloride in combination with a nacnac-type ligand and magnesium as a reductant is reported. Borylation and benzoylation of aryl methoxides are demonstrated, and C(aryl)–SMe bond borylation can be achieved under similar conditions. This is the first example of achieving these transformations using cobalt catalysis. Mechanistic studies suggest that a Grignard reagent is generated as an intermediate in a rare example of a magnesiation via a C–O bond activation reaction. Indeed, an organomagnesium species could be directly observed by electrospray ionization mass spectroscopic analysis. Kinetic experiments indicate that a heterogeneous cobalt catalyst performs the C–O bond activation.