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Mechanistic Study of Pd/NHC‐Catalyzed Sonogashira Reaction: Discovery of NHC‐Ethynyl Coupling Process
Author(s) -
Eremin Dmitry B.,
Boiko Daniil A.,
Kostyukovich Alexander Yu.,
Burykina Julia V.,
Denisova Ekaterina A.,
Anania Mariarosa,
Martens Jonathan,
Berden Giel,
Oomens Jos,
Roithová Jana,
Ananikov Valentine P.
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202003533
Subject(s) - sonogashira coupling , dissociation (chemistry) , catalysis , infrared multiphoton dissociation , chemistry , alkyne , photochemistry , fragmentation (computing) , combinatorial chemistry , palladium , computational chemistry , organic chemistry , computer science , operating system
The product of a revealed transformation—NHC‐ethynyl coupling—was observed as a catalyst transformation pathway in the Sonogashira cross‐coupling, catalyzed by Pd/NHC complexes. The 2‐ethynylated azolium salt was isolated in individual form and fully characterized, including X‐ray analysis. A number of possible intermediates of this transformation with common formulae (NHC) n Pd(C 2 Ph) ( n= 1,2) were observed and subjected to collision‐induced dissociation (CID) and infrared multiphoton dissociation (IRMPD) experiments to elucidate their structure. Measured bond dissociation energies (BDEs) and IRMPD spectra were in an excellent agreement with quantum calculations for coupling product π‐complexes with Pd 0 . Molecular dynamics simulations confirmed the observed multiple CID fragmentation pathways. An unconventional methodology to study catalyst evolution suggests the reported transformation to be considered in the development of new catalytic systems for alkyne functionalization reactions.