Mechanistic Insight into the Rh(III)-Catalyzed C—H Activation of 2-Acetyl-1-Arythydrazines in Water

Abstract

A mechanistic study of the Cp*Rh III -catalyzed C—H functionalization of 2-acetyl-1-arythydrazines with diazo compounds in water was carried out by using density functional theory calculations. The results reveal that the acetyl-bonded N—H deprotonation is prior to the phenyl C—H activation. The mechanisms from protonation by acetic acid disagree with the proposal by the Wang group. Different from the Rh(III)-catalyzed C—H activation reported by experimental literature, the rate-determining step of the whole catalytic cycle with an overall barrier of 31.7 kcal mol –1 ( IV → TS12-P′ ) is the protonation process of hydroxy O rather than the C—H bond cleavage step. The present theoretical study rationalizes the experimental observation at the molecular level.