Mechanism of Pd-catalyzed C(sp3)–H activation of aliphatic amines: an insight from DFT calculations

Abstract

A theoretical understanding of the Pd-catalyzed C(sp³)–H activation of aliphatic amines has been examined using the B3LYP density functional theory. The concerted metalation–deprotonation (CMD) mechanism is identified in the rate-determining steps of all possible reaction pathways. The rate- and regio-determining step of the catalytic cycle is deprotonation of the C_methyl–H bond through a six-membered cyclopalladation transition state. According to the relative activation barriers, the C_methyl–H activation is kinetically and thermodynamically more favorable than the C_ethyl–H activation. More important, the only acetoxylation product is located, ignoring the diethyl-substituted or the dimethyl-substituted in the morpholine and not producing the lactone amines molecules, which is in good agreement with the experimental observations.