Cobalt‐Catalyzed ortho‐Methylation of Ferrocenes Bearing ortho‐Directing Groups by Catalytic Directed C–H Bond Activation

Transition‐metal‐catalyzed C–H functionalization is an emerging powerful alternative to ortho‐lithiation protocols. For ferrocene systems almost exclusively noble‐metal catalysts have so far been used. Herein we present the first examples of cobalt‐catalyzed ortho‐methylations by C–H activation at ferrocenes bearing various ortho‐directing groups (ODGs). The cobalt‐catalyzed ortho‐methylation results in the formation of racemic 1,2‐disubstituted ferrocenes in 21–89 % yield. In some cases symmetric 2,5‐dimethylated ferrocenes prevailed or even were the only isolated products.