Boron-mediated One-pot Access to Salicylaldehydes via ortho-C–H hydroxylation of benzaldehydes

A novel protocol has been devised for the ortho-C–H hydroxylation of benzaldehydes. Directed by a transient imine group, the borylation of benzaldehydes, sequentially followed by the hydroxylation, furnishes diverse salicylaldehydes in a one-pot manner. The metal-free condition is compatible with various benzaldehyde derivatives, including those with electron-withdrawn halogen groups. The transformation is also highly regioselective, cost-effective and practical. The resultant salicylaldehydes could be readily applied in the downstream synthesis to produce bioactive molecules such as coumarin and benzofuran.