Phosphine-Directed sp C-H, C-O, and C-N Borylation.

Benzylic C-H borylation reactions are limited, requiring new approaches to exploit their reactivity for efficient selective functionalization. The recent development of phosphine-directed C-H borylation of arenes has now been extended to benzylic substrates, providing high yield of the mono- and geminal bis-borylation products. Attempts to borylate the C-H bond α to a benzylic ether or amine resulted in C-O and C-N borylation, followed by C-H borylation to provide geminal bis-borylated products.