Self-templated synthesis of an orthoformate <i>in</i>,<i>in</i>-cryptand and its bridgehead inversion by dynamic covalent exchange

Löw, Henrik; Mena‐Osteritz, Elena; Delius, Max von

doi:10.1039/c9cc05968g

Cited by 17 publications

(25 citation statements)

References 45 publications

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“…In stark contrast to previously reported orthoformate 1.1.1 ‐cryptands and trithioformate cages, the ring is sufficiently large to enable this isomerization and o ‐(H out ) 2 ‐2.2.2 is thermodynamically favored over o ‐(H in ) 2 ‐2.2.2 (2 : 1 molar ratio in CD 3 CN, Figure c, II ). In less polar solvent chloroform we observed an equimolar mixture of o ‐(H out ) 2 ‐2.2.2 and o ‐(H in ) 2 ‐2.2.2 (1 : 1 molar ratio in CDCl 3 , see Supporting Information), which can be rationalized by a less effective completion of the solvent with the intramolecular hydrogen bonds.…”

Section: Methodscontrasting

confidence: 69%

“…Further examples for in,out ‐isomerization are based on protonation/deprotonation of Brønsted basic bridgehead atoms or pyramidal inversion of one bridgehead atom . A case of bridgehead inversion by dynamic covalent chemistry (DCvC) was recently demonstrated by our own group in a study on small orthoformate in,in ‐ and out,out ‐cryptands (Scheme a) …”

Section: Methodsmentioning

confidence: 91%

“…Following up on our preliminary studies on orthoformate o ‐(H in ) 2 ‐1.1.1 and o ‐(H out ) 2 ‐1.1.1 cryptands and their bridgehead inversion by dynamic covalent exchange, we aimed at exploring the potential in,out ‐isomerism of larger orthoformate 2.2.2 ‐cryptands. To this end, trimethoxy orthoformate and triethylene glycol (TEG) as ligand for cation binding were subjected to previously optimized conditions for orthoester exchange .…”

Section: Methodsmentioning

confidence: 99%

“… a) Previous work on self‐templated cryptand o ‐(H in ) 2 ‐1.1.1 . b) Synthesis and adaptive response of larger orthoformate 2.2.2 ‐cryptands: out,out ‐, in,in ‐ and in,out ‐cryptands.…”

Section: Methodsmentioning

confidence: 99%

“…[6] A case of bridgehead inversion by dynamic covalent chemistry (DCvC) was recently demonstrated by our own group in a study on small orthoformate in,in-and out,outcryptands (Scheme 1a). [7] We have recently utilized the dynamic covalent reaction [8] between orthoesters and diols [9] for the template synthesis of monometallic cryptates. [10] Most recently, we reported inherently dynamic architectures based on the acidic NH 4 + template [11] and a "self-templated" orthoformate cryptand, which is stabilized by intramolecular hydrogen bonds (Scheme 1a).…”

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confidence: 99%

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Self‐Assembly, Adaptive Response, and in,out‐Stereoisomerism of Large Orthoformate Cryptands

et al. 2020

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We report on triethylene glycol-based orthoformate cryptands, which adapt their bridgehead configurations in response to metal templates and intramolecular hydrogen bonding in a complex manner. In contrast to smaller 1.1.1-orthoformate cryptands, the inversion from out,out-2.2.2 to in,in-2.2.2 occurs spontaneously by thermal homeomorphic isomerization, i. e., without bond breakage. The global thermodynamic minimum of the entire network, which includes an unprecedented third isomer (in,out-2.2.2), could only be reached under conditions that facilitate dynamic covalent exchange. Both inversion processes were studied in detail, including DFT calculations and MD simulations, which were particularly helpful for explaining differences between equilibrium compositions in solvents chloroform and acetonitrile. Unexpectedly, the system could be driven to the in,out-2.2.2 state by using a metal template with a size mismatch with respect to the out,out-2.2.2 cage.Certain macrocycles and macrobicycles (e. g. cryptands [1] ) are subject to a type of stereoisomerism that results from different orientations of a substituent or lone pair at bridgehead atoms. [2] Many large macrocycles can, for instance, invert between out,out-and in,in-isomers via homeomorphic isomerization. [2a,3] [a] H. This is an open access article under the terms of the Creative Commons Attribution Non-Commercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.Scheme 1. a) Previous work on self-templated cryptand o-(H in ) 2 -1.1.1. [7] b) Synthesis and adaptive response of larger orthoformate 2.2.2-cryptands: out,out-, in,in-and in,out-cryptands. ChemPlusChem Communications

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Section: Methodscontrasting

confidence: 69%

Section: Methodsmentioning

confidence: 91%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Self‐Assembly, Adaptive Response, and in,out‐Stereoisomerism of Large Orthoformate Cryptands

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Self‐Assembly of a Purely Covalent Cage with Homochirality by Imine Formation in Water

Chen

et al. 2021

Angewandte Chemie

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Self‐assembly of host molecules in aqueous media via metal–ligand coordination is well developed. However, the preparation of purely covalent counterparts in water has remained a formidable task. An anionic tetrahedron cage was successfully self‐assembled in a [4+4] manner by condensing a trisamine and a trisformyl in water. Even although each individual imine bond is rather labile and apt to hydrolyze in water, the tetrahedron is remarkably stable or inert due to multivalence. The tetrahedral cages, as well as its neutral counterparts dissolved in organic solvent, have homochirality, namely that their four propeller‐shaped trisformyl residues adopt the same rotational conformation. The cage is able to take advantage of hydrophobic effect to accommodate a variety of guest molecules in water. When a chiral guest was recognized, the formation of one enantiomer of the cage became more favored relative to the other. As a consequence, the cage could be produced in an enantioselective manner. The tetrahedron is able to maintain its chirality after removal of the chiral guest—probably on account of the cooperative occurrence of intramolecular forces that restrict the intramolecular flipping of phenyl units in the cage framework.

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Dynamisch kovalente Selbstassemblierung von Chlorid‐ und Ionenpaar‐templierten Kryptaten

et al. 2022

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Während supramolekulare Wirte mit der Fähigkeit zum Binden und Transportieren von Anionen und Ionenpaaren heutzutage weit verbreitet sind, sind selbstassemblierte Architekturen immer noch selten, obwohl sie einen inhärenten Mechanismus für die Freisetzung der Gastionen bieten. In dieser Arbeit beschreiben wir die dynamisch kovalente Selbstassemblierung von dreizähnigen, Harnstoff-basierten Kryptaten, die durch zwei Orthoester-Brückenköpfe verbunden sind. Diese Wirte zeigen Affinitäten für Anionen wie Cl À , Br À und I À in moderater Höhe, die typischerweise vorteilhaft für Anwendungen im Membrantransport sind. In bislang beispiellosen Experimenten konnten wir das Ionenpaar Cs•Cl dissoziieren, indem wir simultan zwei passende Orthoester-Wirte für das Cs + and das Cl À Ion selbstassemblierten.

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Self-templated synthesis of an orthoformate in,in-cryptand and its bridgehead inversion by dynamic covalent exchange

Abstract: We report the template-free dynamic covalent self-assembly of a small orthoformate cryptand, which appears to be driven by the formation of two sets of intramolecular, four-centre hydrogen bonds.

Cited by 17 publications

References 45 publications

Self‐Assembly, Adaptive Response, and in,out‐Stereoisomerism of Large Orthoformate Cryptands

Self‐Assembly, Adaptive Response, and in,out‐Stereoisomerism of Large Orthoformate Cryptands

Self‐Assembly of a Purely Covalent Cage with Homochirality by Imine Formation in Water

Dynamisch kovalente Selbstassemblierung von Chlorid‐ und Ionenpaar‐templierten Kryptaten

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