Can Hetero‐Polysubstituted Cyclodextrins be Considered as Inherently Chiral Concave Molecules?

Guieu, Samuel; Zaborova, Elena; Blériot, Yves; Poli, Giovanni; Jutand, Anny; Madec, David; Prestat, Guillaume; Sollogoub, Matthieu

doi:10.1002/anie.200907156

Cited by 43 publications

(25 citation statements)

References 52 publications

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“…When the ligand system positions the metal in close proximity to the cavity, the latter can play the role of host for an exogenous ligand and can constitute a second coordination sphere. 7 Interesting catalytic behaviors have been observed with the use of metal-capped CDs, such as enantioselectivities, [8][9][10][11] regioselectivities, 8 and extremely high turnover numbers. 12 Notably, in all these examples, the CD rather…”

Section: Introductionmentioning

confidence: 99%

Artificial Chiral Metallo-pockets Including a Single Metal Serving as Structural Probe and Catalytic Center

Zhang

Tugny

Suárez

et al. 2017

Chem

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A series of capped metallo-cyclodextrins were synthesized, affording a variety of artificial chiral metallo-pockets through modulation of the space around the metal. Carbene ligands were used as caps for placing a silver, gold, or copper center at a well-defined location inside the cyclodextrin cavity. Multiple weak interactions involving the d 10 metal center and intra-cavity hydrogen atoms, including anagostic interactions, were observed in solution. Thus, the metal was used as a probe for assessing intra-cavity metal-H distances for building 3D models, revealing the very different shapes of capped a-, band nd g-cyclodextrins and the helical shape of the chiral pocket of some modified cyclodextrins. This series of N-heterocyclic-carbene-based cyclodextrins were compared in gold-catalyzed cycloisomerization reactions, for which the 3D models were used to rationalize the observed regio-and stereoselectivities.

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Section: Introductionmentioning

confidence: 99%

Artificial Chiral Metallo-pockets Including a Single Metal Serving as Structural Probe and Catalytic Center

Zhang

Tugny

Suárez

et al. 2017

Chem

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“…In the framework of our studies on cyclodextrin (CD)based metal catalysts, [12] we developed N-heterocyclic carbene (NHC)-capped CD complexes,c alled (ICyD)M,w here the metal is literally wrapped by the CD scaffold. [13] The position of an appended metal inside this cavity forces external ligands to be influenced by its shape to interact with the metal center.…”

Section: Encapsulated Metal Complexes Show Distinctive Behaviorsmentioning

confidence: 99%

Cyclodextrin Cavity‐Induced Mechanistic Switch in Copper‐Catalyzed Hydroboration

et al. 2017

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Encapsulated metal complexes show distinctive behaviors resulting from the confinement of the metal.[1] The cavity plays the role of second coordination sphere, which impacts reactivity and selectivity. [2][3][4][5][6][7] Alterations in regioselectivity were observed with encapsulated metal catalysts in hydratation or hydroformylation reactions. [8][9][10][11] An unusual coordination mode of the complex imposed by the confinement, or a controlled approach of the substrate imposed by sterics have been raised to explain the changes. Hence, regioselectivity is influenced by confinement of the reactive center but the reaction mechanism itself was not invoked. We present here a system in which not only the regioselectivity can be switched by only changing the size of a cavity but also the actual mechanism of the reaction. We also demonstrate another benefit of encapsulation in the discovery of new mechanisms.In the framework of our studies on cyclodextrin (CD)-based metal catalysts, [12] we developed N-heterocyclic carbene (NHC)-capped CD complexes, called (ICyD)M, where the metal is literally wrapped by the CD scaffold.[13] The position of an appended metal inside this cavity forces external ligands to be influenced by its shape to interact with the metal center. Thus, these particular structures were found to induce shapedependent enantio-and regioselectivities in gold-catalyzed cycloisomerisation reactions. [14] Structural analyses of (-ICyD)M and (-ICyD)M complexes, derived from  and -CD, respectively, revealed significant differences in shape, in particular in the close surroundings of the metal. For instance, -and -ICyD-based complexes both present a groove leading to the metal, but for (-ICyD)M, a pit situated next to the metallic center is observed whereas the metal is tightly wrapped in (-ICyD)M (Figure 1). [14] This suggests that a lateral approach to the metal may be conceivable for (-ICyD)M complexes but precluded for

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“…6,15,18,metacyclophane-2,11-dione 3 was prepared by the reaction of 2,6-bis(bromomethyl)-4-tert-butylanisole TosMIC adduct 1 with 1,1-bis(5-tertbutyl-2-methoxyphenyl)methane 2 according to a reported procedure. Proton nuclear magnetic resonance ( 1 H NMR) and 13 C NMR spectra were recorded on a Nippon Denshi JEOL FT-300 NMR spectrometer and Varian-400MR-vnmrs400 spectrometer.…”

Section: Generalmentioning

confidence: 99%

Synthesis and conformational studies of chiral macrocyclic [1.1.1]metacyclophanes containing benzofuran rings

et al. 2015

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Macrocyclic [1.1.1]metacyclophanes (MCPs) containing benzene and benzofuran rings linked by methylene bridges and which can be viewed as calixarene analogues, have been synthesized by demethylation of [3.3.1]MCP-diones with trimethylsilyl iodide (TMSI) in MeCN. The [3.3.1]MCP-diones are synthesized by using (p-tolylsulfonyl)methyl isocyanide (TosMIC) as the cyclization reagent in N,N-dimethylformamide (DMF) with an excess of sodium hydride. (1)H NMR spectroscopy revealed that the remaining hydroxyl group on the phenyl ring is involved in intramolecular hydrogen bonding with the oxygen of one of the benzofuran rings. O-Methylation at the lower rim of monohydroxy[1.1.1]MCP in the presence of K2CO3 in acetone afforded a novel and inherently chiral calixarene analogue, namely the macrocyclic [1.1.1]MCP, possessing C1 symmetry. The inherent chirality of the two conformers was characterized by (1)H NMR spectroscopy by addition of an excess of Pirkle's chiral shift reagent, which caused a splitting of the corresponding methylene protons to AB patterns. Single crystal X-ray analysis revealed the adoptation of a hemisphere-shaped cone isomer. DFT calculations were carried out to investigate the energy-minimized structures and the hydrogen bonds of the synthesized MCPs.

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Can Hetero‐Polysubstituted Cyclodextrins be Considered as Inherently Chiral Concave Molecules?

Cited by 43 publications

References 52 publications

Artificial Chiral Metallo-pockets Including a Single Metal Serving as Structural Probe and Catalytic Center

Artificial Chiral Metallo-pockets Including a Single Metal Serving as Structural Probe and Catalytic Center

Cyclodextrin Cavity‐Induced Mechanistic Switch in Copper‐Catalyzed Hydroboration

Synthesis and conformational studies of chiral macrocyclic [1.1.1]metacyclophanes containing benzofuran rings

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