Permethylated NHC‐Capped α‐ and β‐Cyclodextrins (ICyD<sup>Me</sup>) Regioselective and Enantioselective Gold‐Catalysis in Pure Water

Zhu, Xiaolei; Xu, Guangcan; Chamoreau, Lise‐Marie; Zhang, Yongmin; Mouriès‐Mansuy, Virginie; Fensterbank, Louis; Bistri‐Aslanoff, Olivia; Roland, Sylvain; Sollogoub, Matthieu

doi:10.1002/chem.202001990

Cited by 36 publications

(19 citation statements)

References 111 publications

(142 reference statements)

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“…A prerequisite for a detailed study of the electronic effects involving the coinage metal encapsulated in the cyclodextrin cavity of an ICyD ligand is to get a crystal structure. We have shown that the replacement of benzyl groups with methyls on ICyD ligands could lead to the crystallization of (α‐ICyD Me )AgCl [39] . We also previously synthesized (α‐ICyD Me )CuCl, (α‐ICyD Me )AgCl, and (α‐ICyD Me )AuCl and characterized them by NMR.…”

Section: Resultsmentioning

confidence: 99%

Mapping C−H⋅⋅⋅M Interactions in Confined Spaces: (α‐ICyD^Me)Au, Ag, Cu Complexes Reveal “Contra‐electrostatic H Bonds” Masquerading as Anagostic Interactions**

Gomes

Zhu

et al. 2021

Chemistry A European J

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What happens when a C−H bond is forced to interact with unpaired pairs of electrons at a positively charged metal? Such interactions can be considered as "contraelectrostatic" H-bonds, which combine the familiar orbital interaction pattern characteristic for the covalent contribution to the conventional H-bonding with an unusual contra-electrostatic component. While electrostatics is strongly stabilizing component in the conventional C−H×××X bonds where X is an electronegative main group element, it is destabilizing in the C−H×××M contacts when M is Au(I), Ag(I), or Cu(I) of NHC−M−Cl systems. Such remarkable C−H×××M interaction became experimentally accessible within (a-ICyD Me )MCl, NHC−Metal complexes embedded into cyclodextrins. Computational analysis of the model systems suggests that the overall interaction energies are relatively insensitive to moderate variations in the directionality of interaction between a C−H bond and the metal center, indicating stereoelectronic promiscuity of fully filled set of d-orbitals. A combination of experimental and computational data demonstrates that metal encapsulation inside the cyclodextrin cavity forces the C−H bond to point toward the metal, and reveals a still attractive "contra-electrostatic" Hbonding interaction.

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Section: Resultsmentioning

confidence: 99%

Mapping C−H⋅⋅⋅M Interactions in Confined Spaces: (α‐ICyD^Me)Au, Ag, Cu Complexes Reveal “Contra‐electrostatic H Bonds” Masquerading as Anagostic Interactions**

Gomes

Zhu

et al. 2021

Chemistry A European J

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“…Thus, using [Tol‐BINAP(AuCl) 2 ] as precatalyst we only achived good results with one substrate with a phenyl‐substituted alkyne [17] . Since then, other groups achieved moderate enantioselectivities with chiral gold(I) catalysts, [18, 19] the exception being the recent elegant work of Sollogoub, Fensterbank, and Mouriès‐Mansuy using NHC‐capped β‐cyclodextrin gold(I) catalysts, which led to up to 94–98 % ee in the hydroxy‐ and methoxycyclization of 1,6‐enynes [14d,e] . However, being based on cyclodextrins, these catalysts only provide one of the two possible enantiomeric forms of the final cyclized products.…”

Section: Methodsmentioning

confidence: 99%

Enantioselective Alkoxycyclization of 1,6‐Enynes with Gold(I)‐Cavitands: Total Synthesis of Mafaicheenamine C

et al. 2021

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Chiral gold(I)‐cavitand complexes have been developed for the enantioselective alkoxycyclization of 1,6‐enynes. This enantioselective cyclization has been applied for the first total synthesis of carbazole alkaloid (+)‐mafaicheenamine C and its enantiomer, establishing its configuration as R. The cavity effect was also evaluated in the cycloisomerization of dienynes. A combination of experiments and theoretical studies demonstrates that the cavity of the gold(I) complexes forces the enynes to adopt constrained conformations, which results in the high observed regio‐ and stereoselectivities.

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“…[ 37 , 38 ] Thus, using NHC‐capped β‐cyclodextrin gold(I) catalyst 31 , the Sollogoub group achieved excellent enantioselectivities (up to 94–98 % ee ) in the hydroxy‐ and methoxycyclization of 1,6‐enynes 14 (Scheme 8 ). [ 37c , 37d ]…”

Section: Intramolecular Gold(i)‐catalyzed Transformationsmentioning

confidence: 99%

New‐Generation Ligand Design for the Gold‐Catalyzed Asymmetric Activation of Alkynes

et al. 2021

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Gold(I) catalysts are ideal for the activation of alkynes under very mild conditions. However, unlike allenes or alkenes, the triple bond of alkynes cannot be prochiral. In addition, the linear coordination displayed by gold(I) complexes places the chiral ligand far away from the substrate resulting in an inefficient transfer of chiral information. This poses a significant challenge for the achievement of high enantiocontrol in gold(I)‐catalyzed reactions of alkynes. Although considerable progress on enantioselective gold(I)‐catalyzed transformations has recently been achieved, the asymmetric activation of non‐prochiral alkyne‐containing small molecules still represents a great challenge. Herein we summarize recent advances in intra‐ and intermolecular enantioselective gold(I)‐catalyzed reactions involving alkynes, discussing new chiral ligand designs that lie at the basis of these developments. We also focus on the mode of action of these catalysts, their possible limitations towards a next‐generation of more efficient ligand designs. Finally, square planar chiral gold(III) complexes, which offer an alternative to chiral gold(I) complexes, are also discussed.

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Permethylated NHC‐Capped α‐ and β‐Cyclodextrins (ICyD^Me) Regioselective and Enantioselective Gold‐Catalysis in Pure Water

Cited by 36 publications

References 111 publications

Mapping C−H⋅⋅⋅M Interactions in Confined Spaces: (α‐ICyD^Me)Au, Ag, Cu Complexes Reveal “Contra‐electrostatic H Bonds” Masquerading as Anagostic Interactions**

Mapping C−H⋅⋅⋅M Interactions in Confined Spaces: (α‐ICyD^Me)Au, Ag, Cu Complexes Reveal “Contra‐electrostatic H Bonds” Masquerading as Anagostic Interactions**

Enantioselective Alkoxycyclization of 1,6‐Enynes with Gold(I)‐Cavitands: Total Synthesis of Mafaicheenamine C

New‐Generation Ligand Design for the Gold‐Catalyzed Asymmetric Activation of Alkynes

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Permethylated NHC‐Capped α‐ and β‐Cyclodextrins (ICyDMe) Regioselective and Enantioselective Gold‐Catalysis in Pure Water

Cited by 36 publications

References 111 publications

Mapping C−H⋅⋅⋅M Interactions in Confined Spaces: (α‐ICyDMe)Au, Ag, Cu Complexes Reveal “Contra‐electrostatic H Bonds” Masquerading as Anagostic Interactions**

Mapping C−H⋅⋅⋅M Interactions in Confined Spaces: (α‐ICyDMe)Au, Ag, Cu Complexes Reveal “Contra‐electrostatic H Bonds” Masquerading as Anagostic Interactions**

Enantioselective Alkoxycyclization of 1,6‐Enynes with Gold(I)‐Cavitands: Total Synthesis of Mafaicheenamine C

New‐Generation Ligand Design for the Gold‐Catalyzed Asymmetric Activation of Alkynes

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Product

Resources

About

Permethylated NHC‐Capped α‐ and β‐Cyclodextrins (ICyD^Me) Regioselective and Enantioselective Gold‐Catalysis in Pure Water

Mapping C−H⋅⋅⋅M Interactions in Confined Spaces: (α‐ICyD^Me)Au, Ag, Cu Complexes Reveal “Contra‐electrostatic H Bonds” Masquerading as Anagostic Interactions**

Mapping C−H⋅⋅⋅M Interactions in Confined Spaces: (α‐ICyD^Me)Au, Ag, Cu Complexes Reveal “Contra‐electrostatic H Bonds” Masquerading as Anagostic Interactions**