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Mechanistic Aspects of Submol % Copper‐Catalyzed CN Cross‐Coupling
Author(s) -
Larsson PerFredrik,
Wallentin CarlJohan,
Norrby PerOla
Publication year - 2014
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.201301088
Subject(s) - chemistry , deprotonation , catalysis , nucleophile , electron transfer , reagent , copper , metathesis , pyrrole , ligand (biochemistry) , computational chemistry , photochemistry , organic chemistry , ion , biochemistry , polymer , receptor , polymerization
Carbonnitrogen bond formation can be catalyzed by copper in very low concentrations (≈100 ppm), with mechanistic features that are distinct from those in the high‐concentration regime. The reaction was studied by initial rate kinetics, competitive Hammett studies, and DFT calculations. The deprotonation of the model nucleophile, pyrrole, is limited by mass transfer with the heterogeneous base. The positive reaction order in dimethylethylenediamine was explained by this reagent working not only as a ligand to Cu, but also as a facilitator for mass transfer. The selectivity‐determining step in the competitive Hammett study is oxidative addition. Alternative mechanisms for this step, such as single‐electron transfer, atom transfer, or σ‐bond metathesis, can be excluded based on the observed Hammett behavior and DFT calculations.