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Computational Study of the Cu‐Free Allylic Alkylation Mechanism with Grignard Reagents: Role of the NHC Ligand
Author(s) -
Poblador Bahamonde Amalia I.,
Halbert Stéphanie
Publication year - 2017
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201701010
Subject(s) - chemistry , nucleophile , solvation , allylic rearrangement , ligand (biochemistry) , sn2 reaction , tsuji–trost reaction , alkylation , bifunctional , medicinal chemistry , stereochemistry , combinatorial chemistry , solvent , organic chemistry , catalysis , biochemistry , receptor
The mechanism of Cu‐free allylic alkylation reactions catalyzed by an NHC ligand with Grignard reagents has been explored by using the hybrid B3PW91 DFT method. The nature of the bonding of the active Mg species, which was validated by reference to the 13 C NMR chemical shift, was found to be highly ionic. In particular, a strong nucleophilic Mg–R (R = CH 3 ) bond was explained by the activation of the NHC Lewis base ligand on Mg. The effect of ethereal solvent was examined by using explicit dimethyl ether solvent and a density‐based solvation model. An adequate representation of solvation is required to properly reproduce the formation of the supposed active species. The mechanism of the allylic alkylation emphasizes the bifunctional role of the Mg center that activates both the nucleophile and nucleofuge promoting an S N 2‐type mechanism. The NHC ligand bonded to Mg is crucial and activates the Mg–R bond favoring C–C bond formation.