Metal-free ortho C-H borylation of 2-phenoxypyridines under mild conditions.

An efficient metal-free ortho C-H borylation has been developed via sequential borylation of substituted 2-phenoxypyridines with BBr3 following esterification with pinacol. The corresponding aryl boronates were obtained in good yields. The synthesized aryl boronates can be easily transformed into various useful products. Therefore, the present method makes functionalizations of aryl C-H bonds easy.