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Mechanistic Investigations of a Stable, Highly Active, Extremely Sterically Shielded Molecular Gold Catalyst
Author(s) -
Weber Simone G.,
Zahner David,
Rominger Frank,
Straub Bernd F.
Publication year - 2013
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.201200944
Subject(s) - steric effects , chemistry , catalysis , carbene , cationic polymerization , alkyne , photochemistry , methanol , ligand (biochemistry) , kinetic isotope effect , combinatorial chemistry , medicinal chemistry , organic chemistry , biochemistry , physics , receptor , deuterium , quantum mechanics
An N‐heterocyclic carbene gold complex IPr**AuNTf 2 has been synthesized, spectroscopically investigated, structurally characterized, and used as a highly active and stable catalyst in the Hashmi phenol synthesis (IPr**=1,3‐di‐ p ‐tolylimidazol‐2‐ylidene with four di‐ tert ‐butylbenzhydryl ortho substituents, Tf=trifluoromethansulfonyl). A side reaction comprises an irreversible arene oxide ring opening with subsequent 1,2 methyl shift. The advantage of the steric demand of the ancillary ligand was explained by higher equilibrium concentrations of the cationic gold species, the circumvention of inactive dinuclear intermediates, and the inhibition of catalyst decomposition pathways. The methanol addition–hydration of alkynes featured a turnover‐limiting proton transfer step of an alkenylgold catalyst resting state, indicated by a large primary kinetic isotope effect and an alkyne competition experiment.