Gold(I)-Catalysed Asymmetric Hydroamination of Alkenes: A Silver- and Solvent-Dependent Enantiodivergent Reaction
Résumé
In the present study, we report the first silver dependent enantiodivergent gold catalysed reaction. The asymmetric intramolecular hydroamination of alkenes catalysed by the combination of a single chiral binuclear gold(I) chloride complex and silver perchlorate can afford both enantiomers of the products by a simple solvent change from toluene to methanol. Such an enantiodivergent reaction is strictly independent of the nature of the catalyst anion or the reaction temperature and displays the same first-order kinetic rate law with respect to substrate concentration in both solvents. Beyond a simple solvent effect, the enantioinversion is controlled by gold-silver chloride adducts which occur only in methanol and allow a dual activation of the reagent. While one single gold atom activates the alkene moiety, the other gold atom forms an oxophilic gold-silver chloride adduct which interacts with the carbamate function. By comparison with toluene which affords (S)-enantiomer, this proximal and bimetallic activation allows an opposite stereodifferentiation of the two diastereomeric intermediates during the final protodeauration step and leads therefore to the (R)-enantiomer.
Domaines
Chimie inorganique
Origine : Fichiers produits par l'(les) auteur(s)
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