Computational Study on the Fate of Oxidative Directing Groups in Ru(II), Rh(III), and Pd(II) Catalyzed C-H Functionalization.

Activation of C-H bonds assisted by a directing group is indispensable in organic synthesis. Among them, utilizing oxidative directing groups that can serve as an internal oxidant to drive the M/M catalytic cycle has recently become a promising strategy. A survey of published reactions involving -alkoxyamides or -acyloxyamides reveals that not all N-O bonds act as an internal oxidant. We have therefore systematically investigated the effect of the oxidative groups on a model reaction catalyzed by Ru(II), Rh(III), and Pd(II) complexes. DFT calculations show that -methoxy and -acyloxy groups oxidize Ru(II) to Ru(IV) and Rh(III) to Rh(V), but cannot oxidize a cyclo-Pd(II) intermediate to Pd(IV). The stability of the metal imido intermediate (M = Ru, Rh, and Pd) controls whether the oxidation occurs or not. -Acyloxy groups show a more pronounced selectivity than -methoxy to oxidize Ru(II) and Rh(III) species, while no distinctive effect is observed for Pd(II).