Electronic Tuning of Iron-Oxo-Mediated C-H Activation: Effect of Electron-Donating Ligand on Selectivity

摘要

We have reported previously that an iron(III) complex supported by an anionic pentadentate monoamido ligand, dpaq~H (dpaq~H=2-[bis(pyridin-2- ylmethyl)]amino-N-quinolin-8-yl-acetamido), promotes selective C-H hydroxylation with H_2O_2 with high regioselectivity. Herein, we report on the preparation of Fe~(III)-dpaq derivatives that have a series of substituent groups at the 5-position of a quinoline moiety in the parent ligand dpaq~H (dpaq~R, R: OMe, H, Cl, and NO_2), and examine them with respect to their catalytic activity in C-H hydroxylation with H_2O_2. As the substituent group becomes more electron-withdrawing, both the selectivity and the turnover number increase, but the selectivity of epoxidation shows the opposite trend.