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

We have reported previously that an iron(III) complex supported by an anionic pentadentate monoamido ligand, dpaqH (dpaqH=2-[bis(pyridin-2-ylmethyl)]amino- N-quinolin-8-yl-acetamido), promotes selective CH hydroxylation with H2O2 with high regioselectivity. Herein, we report on the preparation of FeIII-dpaq derivatives that have a series of substituent groups at the 5-position of a quinoline moiety in the parent ligand dpaqH (dpaqR, R: OMe, H, Cl, and NO2), and examine them with respect to their catalytic activity in CH hydroxylation with H2O2. 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. [ABSTRACT FROM AUTHOR]