Shape‐Controlled Synthesis and Self‐Sorting of Covalent Organic Cage Compounds

Klotzbach, Stefanie; Beuerle, Florian

doi:10.1002/anie.201502983

“…

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. [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. [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.

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confidence: 99%

Dynamic Covalent Self‐Assembly Based on Oxime Condensation

Shen

¹

,

Cao

²

,

Lu

³

et al. 2018

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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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“…Ein bahnbrechendes Beispiel stellte die Arbeitsgruppe von Mukherjee vor,die fürein Gemisch von zwei Tr isaldehyden und zwei Diaminen die ausschließliche Bildung von nur zwei der vier mçglichen [2+ +3]-Käfige beobachtete. [151,175] Der zweite Fall ist dabei das erste Beispiel fürd ie emergente Erzeugung von komplexen organischen Käfigverbindungen aus kompetitiven Bausteinen. Im Nachgang konnten sie dieses Konzept auf wasserstoffbrückeninduzierte Selektionsprozesse ausweiten [173] und präsentierten auch eine selektive Bildung eines spezifischen Käfigisomers aus unsymmetrischen Bausteinen.…”

Section: Selbstsortierung Von Mehr-komponenten-mischungenunclassified

Kovalente organische Netzwerke und Käfigverbindungen: Design und Anwendungen von polymeren und diskreten organischen Gerüsten

Beuerle

¹

,

Gole

²

2018

Self Cite

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Poröse organische Materialien sind eine aufstrebende Klasse funktionaler Nanostrukturen mit beispiellosen Eigenschaften. Die dynamisch‐kovalente Organisation kleiner organischer Bausteine unter thermodynamischer Kontrolle wird dabei für die verblüffend einfache Bildung komplexer Architekturen in Eintopfreaktionen genutzt. In diesem Aufsatz werden die grundlegenden Designprinzipien analysiert, die zur Bildung von entweder kovalenten organischen Netzwerken als kristalline poröse Polymere oder kovalenten organischen Käfigverbindungen als formgetreue molekulare Objekte führen. Konventionelle Synthesevorschriften und Analysemethoden werden neben ausgefeilteren Strategien, wie postsynthetische Modifizierungen oder Selbstsortierung, diskutiert. Gegebenenfalls werden die entsprechenden Eigenschaften und Besonderheiten von polymeren Netzwerken und diskreten organischen Käfigen verglichen. Darüber hinaus wird das Potenzial dieser Materialien für Anwendungen, von der Gasspeicherung über die Katalyse bis hin zur organischen Elektronik, erörtert.

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“…[3] An interesting achievement in this field has been the implementation of at hreefold Ugi four-component reaction (4CR)-based macrocyclization (Scheme 1A)for the assembly of N-substituted glycine-based cryptands,c ryptophanes,a nd cages with high chemical efficiencya nd atom economy. [1,2,5] This Communication presents as ynthetic advance in the field of macrocyclization strategies targeting molecular cages. [1,2,5] This Communication presents as ynthetic advance in the field of macrocyclization strategies targeting molecular cages.…”

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confidence: 99%

“…[1,2,5] This Communication presents as ynthetic advance in the field of macrocyclization strategies targeting molecular cages. [7] Such ab ridgehead construction concept is different from most macrocyclization approaches for purely organic cages, [1,2,5] since it engages at least three dissimilar bifunctional building blocks in one step for creating ah ybrid macromulticyclic cavity. [7] Such ab ridgehead construction concept is different from most macrocyclization approaches for purely organic cages, [1,2,5] since it engages at least three dissimilar bifunctional building blocks in one step for creating ah ybrid macromulticyclic cavity.…”

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confidence: 99%