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Palladium‐Catalyzed Cross‐Dehydrogenative Coupling of o ‐Xylene: Evidence of a New Rate‐Limiting Step in the Search for Industrially Relevant Conditions
Author(s) -
ÁlvarezCasao Yolanda,
van Slagmaat Christian A. M. R.,
Verzijl Gerard K. M.,
Lefort Laurent,
Alsters Paul L.,
FernándezIbáñez M. Ángeles
Publication year - 2018
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201701973
Subject(s) - catalysis , chemistry , palladium , dissociation (chemistry) , dimer , kinetic isotope effect , carboxylate , rate determining step , limiting , deuterium , monomer , photochemistry , inorganic chemistry , polymer chemistry , combinatorial chemistry , organic chemistry , polymer , mechanical engineering , physics , quantum mechanics , engineering
An efficient cross‐dehydrogenative coupling of o ‐xylene under neat conditions, which brings important industrial benefits towards the synthesis of a monomer used in polyimide resins, is reported. The catalyst based on the combination of Pd/N ligand/carboxylate=1:1:2 does not require a Cu cocatalyst and proceeds at 11 bar of O 2 pressure. Evaluation of the deuterium kinetic isotope effect (KIE) provides evidence for three different rate‐determining steps, which depend on the reaction conditions (medium, temperature). Under the reported neat conditions, the dissociation of a carboxylate‐bridged dimer to generate a more reactive monometallic Pd species is proposed to be the rate‐limiting step.