Mechanistic studies of the palladium-catalyzed S,O-ligand promoted C–H olefination of aromatic compounds
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Date
2023-03Author
Naksomboon, Kananat
Gómez Bengoa, Enrique
Mehara, Jaya
Roithová, Jana
Otten, Edwin
Fernández Ibáñez, María Ángeles
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Chemical Science 14(11) : 2943-2953 (2023)
Abstract
Pd-catalyzed C–H functionalization reactions of non-directed substrates have recently emerged as an
attractive alternative to the use of directing groups. Key to the success of these transformations has
been the discovery of new ligands capable of increasing both the reactivity of the inert C–H bond and
the selectivity of the process. Among them, a new type of S,O-ligand has been shown to be highly
efficient in promoting a variety of Pd-catalyzed C–H olefination reactions of non-directed arenes.
Despite the success of this type of S,O-ligand, its role in the C–H functionalization processes is
unknown. Herein, we describe a detailed mechanistic study focused on elucidating the role of the S,O-
ligand in the Pd-catalyzed C–H olefination of non-directed arenes. For this purpose, several mechanistic
tools, including isolation and characterization of reactive intermediates, NMR and kinetic studies, isotope
effects and DFT calculations have been employed. The data from these experiments suggest that the
C–H activation is the rate-determining step in both cases with and without the S,O-ligand. Furthermore,
the results indicate that the S,O-ligand triggers the formation of more reactive Pd cationic species,
which explains the observed acceleration of the reaction. Together, these studies shed light on the role
of the S,O-ligand in promoting Pd-catalyzed C–H functionalization reactions