A Kinetically Stable Macrocycle Self-Assembled in Water

Zhang, Yang; Zheng, Xujun; Cao, Ning; Yang, Chuluo; Li, Hao

doi:10.1021/acs.orglett.8b00693

Cited by 28 publications

(26 citation statements)

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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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confidence: 99%

“…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.…”

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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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Dynamic Covalent Self‐Assembly Based on Oxime Condensation

Shen

Cao

et al. 2018

Angewandte Chemie

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“…In 2018, Li and co‐workers employed this novel dynamic approach for synthesizing a cage and a macrocycle . The cage 6 6+ ⋅6 Cl − was self‐assembled in high yields by the [3+2] condensation of carbonohydrazide 5 with the trialdehyde 1 3+ ⋅3 Cl − in water (Figure ).…”

Section: Self‐assembly Based On Acylhydrazone Formation In Watermentioning

confidence: 99%

Self‐Assembly in Water with N‐Substituted Imines

Jiao

Zhang

et al. 2020

Angew Chem Int Ed

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Imine synthesis has enjoyed along history as the dynamic covalent reaction of choice for the construction of purely covalent molecular architectures.Ino rganic solvents,t he formation of imine bonds is reversible but leads to thermodynamically stable products.I nt he presence of water,however,imine bonds are labile,afact whichlimits their utility as mediators of self-assembly in aqueous and biological media. In this Review,wediscuss water-compatible dynamic covalent bonds based on N-substituted imine derivatives,n amely hydrazones and oximes,f or the self-assembly of metal-free organic architectures with well-defined structures.The reasons why hydrazones and oximes are more robust in water than their parent imines are explained. Recent progress in the self-assembly,characterization, and design principles of avariety of complex molecules including macrocycles,c ages,catenanes,a nd knots in aqueous media is highlighted. Emerging applications for these molecules,including guest recognition and separations, are also discussed. From the Contents 1. Introduction 18351 2. Mechanism for the Formation of Imines and N-Substituted Derivatives 18353 3. N-Substituted Imines in the Syntheses of Dynamic Combinatorial Libraries and Polymeric Products as well as Bioconjugation 18354 4. Self-Assembly Based on the Formation of Imines in Water 18355

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“…The partially negatively‐charged carbon atom is therefore less electrophilic, protecting the C=N bond from nucleophilic attack by water molecules or other nucleophiles. A variety of macrocycles, cages, catenanes as well as knots were obtained in water based on hydrazone condensation in pure water. The dynamic nature of hydrazone, however, jeopardizes the inherent stabilities of the self‐assembled products.…”

Section: Figurementioning

confidence: 99%