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. 2010 Aug 1;1(2):10.1039/C0SC00255K.
doi: 10.1039/C0SC00255K.

Alkylgold complexes by the intramolecular aminoauration of unactivated alkenes

Rebecca L Lalonde  1 , William E Brenzovich Jr  1 , Diego Benitez  2 , Ekaterina Tkatchouk  2 , Kotaro Kelley  1 , William A Goddard 3rd  2 , F Dean Toste  1
Affiliations

Alkylgold complexes by the intramolecular aminoauration of unactivated alkenes

Rebecca L Lalonde et al. Chem Sci. .

Abstract

Alkylgold(I) complexes were formed from the gold(I)-promoted intramolecular addition of various amine nucleophiles to alkenes. These experiments provide the first direct experimental evidence for the elementary step of gold-promoted nucleophilic addition to an alkene. Deuterium-labeling studies and X-ray crystal structures provide support for a mechanism involving anti-addition of the nucleophile to a gold-activated alkene, which is verified by DFT analysis of the mechanism. Ligand studies indicate that the rate of aminoauration can be drastically increased by use of electron-poor arylphosphines, which are also shown to be favored in ligand exchange experiments. Attempts at protodeauration lead only to recovery of the starting olefins, though the gold can be removed under reducing conditions to provide the purported hydroamination products.

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Figures

Fig. 1
Fig. 1
ORTEP of alkylgold 2. Thermal ellipsoids shown at 50% probability. Hydrogens (except H19A, H19B, and H20) and DME solvent molecule omitted for clarity.
Fig. 2
Fig. 2
ORTEP of alkylgold 20. Thermal ellipsoids shown at 50% probability. Hydrogens omitted for clarity.
Fig. 3
Fig. 3
Hammett plot for the ligand exchange reaction of Ar3PAuCl with 2 for the isosteric ligand set (4-XC6H4)3P. Reactions were run at 0.1Min CDCl3 at room temperature for 12 h.
Fig. 4
Fig. 4
Time course of the aminoauration reaction with various arylphosphine ligands.
Fig. 5
Fig. 5
Comparison of aminoauration between p-substituted triphenylphosphine Au(I) species. (a) Enthalpic comparison and (b) representative structures for the (p-CF3Ph)3PAu(I) aminoauration reaction.
Scheme 1
Scheme 1
Proposed syn- and anti-mechanisms for the gold(I)-catalyzed hydroamination of alkenes.
Scheme 2
Scheme 2
Aminoauration of acidic protected amines (L = PPh3).
Scheme 3
Scheme 3
DFT computed potential enthalpies (ΔH) at 298 K for key hydroamination intermediates and transition structures (L = PH3) (a) in basic media, and (b) in acidic media.
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References

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