Nickel‐Catalyzed Alkoxy–Alkyl Interconversion with Alkylborane Reagents through C−O Bond Activation of Aryl and Enol Ethers

A nickel‐catalyzed alkylation of polycyclic aromatic methyl ethers as well as methyl enol ethers with B ‐alkyl 9‐BBN and trialkylborane reagents that involves the cleavage of stable C(sp 2 )−OMe bonds is described. The transformation has a wide substrate scope and good chemoselectivity profile while proceeding under mild reaction conditions; it provides a versatile way to form C(sp 2 )−C(sp 3 ) bonds that does not suffer from β‐hydride elimination. Furthermore, a selective and sequential alkylation process by cleavage of inert C−O bonds is presented to demonstrate the advantage of this method.