Hydrogen bonds promote site-selective phenol functionalization enabled by Cl- anion

Most of studies for hydrogen bonds focus on the static model especially between two polar atoms. In contrast, introducing the third polar atom may emerge the competitive hydrogen bonds, which would represent a distinct perspective to perturb the catalytic chemical transformation. Herein, we report quantum mechanics calculations and quasi-classical direct dynamics simulations that demonstrate a triangle form of proton accepters enabled by Cl- anion can afford diverse hydrogen bonds, which control the reactivity and selectivity of Rh catalyzed phenol functionalization. A redox mechanism for carbene insertions with notable ligand effect was discovered and supported by both calculations and the experimental kinetic isotopic effect. The quaternary ammonium additive can stabilize key oxonium ylide intermediates with O-H…Cl hydrogen bonds that inhibit the common O-H insertion and promote the carbene C-H insertion product. The dynamic hydrogen bonds coupling with Rh complex dissociation may result in an intermediate shuttle of oxonium ylides, which unify the site-selective of the direct phenol functionalization.