A Strategy to Synthesize Molecular Knots and Links Using the Hydrophobic Effect

Cougnon, Fabien B. L.; Caprice, Kenji; Pupier, Marion; Bauzá, Antonio

doi:10.1021/jacs.8b05220

Cited by 86 publications

(97 citation statements)

References 60 publications

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“…Both conformations are in slow exchange,a si ndicated by the presence of exchange cross-peaks between 1 and 2 in the 2D NOESY spectrum ( Figure S5). [7] In this conformation, the broader range of aromatic-proton chemical shifts (d % 4-11 ppm) and the notable shielding of the isophthalic proton (k; d < 4ppm) reflect ac ompact stacking of all aromatic units. The 1 HNMR features of 2 perfectly coincide with those recorded in pure D 2 O.…”

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confidence: 98%

“…[7] Its 1 HNMR characterization, performed in D 2 O, previously demonstrated that SL was made of four interlocked arms,each constituted of an isophthalic moiety linked with hydrazone bonds to two quinolinium units.W epursued further analyses with the aim to gain additional structural information. [7] Its 1 HNMR characterization, performed in D 2 O, previously demonstrated that SL was made of four interlocked arms,each constituted of an isophthalic moiety linked with hydrazone bonds to two quinolinium units.W epursued further analyses with the aim to gain additional structural information.…”

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confidence: 99%

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Synchronized On/Off Switching of Four Binding Sites for Water in a Molecular Solomon Link

2019

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Am olecular Solomon link adopts different conformations in acetonitrile (1)a nd in water (2). Contrary to expectations,t he main driving force of the transformation is not the change in medium polarity,but the cooperative binding of about four molecules of water,forming atiny droplet in the central cavity of 2.M echanistic studies reveal that the four binding sites can simultaneously switch between an inactive state (unable to bind water) and an active state (able to bind water) during the transformation. Spatial and temporal coordination of switching events is commonly observed in biological systems but has been rarely achieved in artificial systems.H ere,t he concerted activation of the four switchable sites is controlled by the topology of the whole molecule.

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confidence: 98%

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Synchronized On/Off Switching of Four Binding Sites for Water in a Molecular Solomon Link

2019

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“…As ac onsequence, avariety of complex molecules [9][10][11][12][13] are obtained in high yields, especially when these self-assembled molecules are sophisticatedly designed to represent the most thermodynamically favoured products.One of the major disadvantages of iminebased DCC is that, this dynamic bond is apt to undergo hydrolysis in aqueous solution. Avariety of macrocycles, [15,16] cages, [17] catenanes [18,19] as well as knots [20] were obtained in water based on hydrazone condensation in pure water. Thepartially negatively-charged carbon atom is therefore less electrophilic,p rotecting the C=Nb ond from nucleophilic attack by water molecules or other nucleophiles.…”

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confidence: 99%

“…Therefore,the self-assembled products containing imine can hardly realize their functions in water, the medium of life.H ydrazone (-C=NÀN-), [14] am ore robust counterpart of imine,w as thus employed to develop water-compatible DCC approaches.T he higher stability of hydrazone results from the delocalization of the lone electron pair in the adjacent nitrogen atom onto to the C = Nd ouble bond, resulting in acharge-separated resonance form, namely -C À ÀN=N + -. Avariety of macrocycles, [15,16] cages, [17] catenanes [18,19] as well as knots [20] were obtained in water based on hydrazone condensation in pure water. Avariety of macrocycles, [15,16] cages, [17] catenanes [18,19] as well as knots [20] were obtained in water based on hydrazone condensation in pure water.…”

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Dynamic Covalent Self‐Assembly Based on Oxime Condensation

Shen

Cao

et al. 2018

Angewandte Chemie

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Oxime,w hose dynamic nature was reported to be switchable between ON/OFF by tuning the acidity,isemployed in anovel type of dynamic covalent approach that is amenable to use in water for self-assembly of purely organic molecules with complex topology.I ns trongly acidic conditions,t he dynamic nature of oxime is turned ON,allowing occurrence of error-checking and therefore acatenane and amacrocycle selfassembled in high yields.Inneutral conditions,oxime ceases to be dynamic,w hich helps to trap the self-assembled products even when the driving forces of their formation are removed. We envision that this switchable behaviour might help,atleast partially,t or esolve ac ommonly encountered drawbacko f dynamic covalent chemistry,n amely that the intrinsic stability of the self-assembled products containing dynamic bonds,such as imine or hydrazone,are often jeopardized by their reversible nature.Imine (-C=N-) condensation [1] has been considered as one of the most promising reaction motifs in dynamic covalent chemistry (DCC). [2][3][4][5][6][7][8] Its reversible nature allows the systems to perform error-checking and self-correcting during searching for their thermodynamic minimum. As ac onsequence, avariety of complex molecules [9][10][11][12][13] are obtained in high yields, especially when these self-assembled molecules are sophisticatedly designed to represent the most thermodynamically favoured products.One of the major disadvantages of iminebased DCC is that, this dynamic bond is apt to undergo hydrolysis in aqueous solution. Therefore,the self-assembled products containing imine can hardly realize their functions in water, the medium of life.H ydrazone (-C=NÀN-), [14] am ore robust counterpart of imine,w as thus employed to develop water-compatible DCC approaches.T he higher stability of hydrazone results from the delocalization of the lone electron pair in the adjacent nitrogen atom onto to the C = Nd ouble bond, resulting in acharge-separated resonance form, namely -C À ÀN=N + -. Thepartially negatively-charged carbon atom is therefore less electrophilic,p rotecting the C=Nb ond from nucleophilic attack by water molecules or other nucleophiles. Avariety of macrocycles, [15,16] cages, [17] catenanes [18,19] as well as knots [20] were obtained in water based on hydrazone condensation in pure water. Thed ynamic nature of hydra-zone,however, jeopardizes the inherent stabilities of the selfassembled products.F or example,w eo bserved that the catenanes [18,19] containing hydrazone undergo decomposition via hydrazone exchange during counteranion exchange or solvent removal, even in the condition of low temperature and/or in the absence of acid catalyst. Oxime, [21] namely -C= N À O-, is reported [22] to be more robust than hydrazone both thermodynamically and kinetically.T here are af ew reasons that can explain the enhanced stability of oxime compared to its hydrazone counterparts.F irst, the NH 2 unit in either the alkoxyamino (-OÀNH 2 )o rh ydrazide (-NHÀNH 2 )p recursor could undergo protonation in water, which...

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“…Controlling of chemical reactions by non-covalent or weak interactions are gaining significant interests.T om ake newer or functional materials on demanda ppropriate interactions like halogenb onding, [30] charge-transfer, [31] hydrophobic effect, [32] cation-p, [33] anion-p, [34] etc. are generallyu sed routinely.…”

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confidence: 99%

Unsymmetrical Disulfides Synthesis via Sulfenium Ion

Parida

Choudhuri

Mal

2019

Chemistry An Asian Journal

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An umpolunga pproachf or the synthesis of unsymmetrical disulfides via sulfenium ion is reported.I ns itu generated electrophilic sulfeniumi on from electron-rich thiols reacted with second thiols to yield unsymmetrical disulfides. Using an iodine catalysta nd 4-dimethylaminopyridine (DMAP)/water as promoter,t he target syntheses were achieved in one pot under aerobic condition.Organicd isulfides are important functional moieties found in variousm arine natural products, [1] pharmaceuticals, [2] materials [3] and polymers. [4] Disulfides are also known for their odors especially in kitchen items, like in onions and garlics. [5] Pharmaceutically active disulfides are known to have anti-inflammatory, [6] antitumour, [7] antioxidants [8] and antiulcer [9] activities. Chemically,o rgano-disulfides are being used in catalyst, [10] in ligand designing, [11] towards producing fine chemicals andi n functional group protections. [12] In addition, the concept of constitutional dynamic chemistry (CDC) [13] and dynamic combinatorial chemistry (DCC) [14] is documented using the chemistry of disulfides. Due to the reversibility nature of the disulfide bond, formation of many products could be possible when more than one thiol building blocks present in equilibrium. [15] Therefore, it's always challengingt os ynthesize selectively any unsymmetrical disulfides from mixtureo ft hiols in one pot. [16] In Figure 1a,f ew examples of either pharmaceutically important or naturallyo ccurring molecules containing disulfides functionalities are shown. [16b] The known approaches for the synthesis of disulfides are mainly based on using molecular oxygen, [17] transition metals, [18] phosphine-free cationic rhodium(I) complex catalyst, [19] Cu I -phenanthroline catalyst, [20] base catalyzed, [21] non-transition metals, [22] oxidants, [23] sodium perborate, [24] metal organicf rame works (MOFs), [25] microwavea ssisted, [26] electrochemical methods, [27] etc. Recently Dethe and co-workersd eveloped synthesis of unsymmetrical disulfides using fac-Ir(ppy) 3 as photocatalyst and visible light from white LED (Figure 1b). [28] Similarly,u nsymmetrical disulfide synthesis is also reported using O 2 as the oxidant and cobalt(II)phthalocyanine-tetra-sodium sulfonate as the catalyst (Figure 1b). [29] Herein, we reporto ne pot synthesis of unsymmetrical organodisulfides ( Figure 1c)v ia umpolung approach in ethanol sol-

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A Strategy to Synthesize Molecular Knots and Links Using the Hydrophobic Effect

Cited by 86 publications

References 60 publications

Synchronized On/Off Switching of Four Binding Sites for Water in a Molecular Solomon Link

Synchronized On/Off Switching of Four Binding Sites for Water in a Molecular Solomon Link

Dynamic Covalent Self‐Assembly Based on Oxime Condensation

Unsymmetrical Disulfides Synthesis via Sulfenium Ion

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