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1.
J Org Chem ; 86(19): 13491-13502, 2021 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-34514788

RESUMO

In this study we found that 2,6-dimethanolpyridine displays good complementarity toward di(ethylene glycol) for the complexation of Na+ ions, allowing us to use this recognition system for the efficient synthesis of hetero[2]catenanes; indeed, it allowed us to attach multiple copies of [2]catenanes to branched systems presenting multiple isophthalaldehyde units. When we attempted to form a catenane from a preformed macrocycle featuring only a single di(ethylene glycol) unit, reacting it with a di(ethylene glycol) derivative presenting two amino termini, isophthalaldehyde, and templating Na+ ions [i.e., with the aim of using di(ethylene glycol)·Na+·di(ethylene glycol) recognition to template the formation of the interlocked imino macrocycle], the yields of the hetero[2]catenane and homo[2]catenane, comprising two imino macrocyclic units, were both poor (14% and 7%, respectively). In contrast, when one or two 2,6-dimethanolpyridine units were present in the preformed macrocycles, their reactions with the same diamine, dialdehyde, and Na+ ions provided the hetero[2]catenanes with high selectivity and efficiency (44% and 64% yields, respectively), with minimal formation of the competing homo[2]catenane. The high complementary of the 2,6-dimethanolpyridine·Na+·di(ethylene glycol) ligand pair allowed us to synthesize [2]catenane dimers and trimers directly from corresponding isophthalaldehyde-presenting cores, with yields, after subsequent reduction and methylation, of 42% and 31%, respectively.

2.
Org Lett ; 23(15): 5787-5792, 2021 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-34240877

RESUMO

We report a new slippage system based on p-tert-butylbenzyl-terminated imidazolium ions and di(ethylene glycol)-containing macrocycles and their use as linking units for the construction of a prototypical molecular "Lock & Lock" box from a resorcinarene-based cavitand "bowl" and a porphyrin "cover". The multivalent structure with four slippage linkers provided the molecular box with high stability, yet the system dissociated into its two components upon application of suitable external stimuli.

3.
Chem Commun (Camb) ; 56(35): 4773-4776, 2020 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-32232269

RESUMO

In this study imidazolium and imidazolinium centers in precursor [2]rotaxanes were deprotonated to obtain interlocked molecules featuring stabilized N-heterocyclic carbene centers. The encircling macrocyclic components enhanced the persistence of the otherwise unstable imidazolidin-2-ylidenes in solution at 253 K for more than a week in the absence of air.

4.
Angew Chem Int Ed Engl ; 59(28): 11278-11282, 2020 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-32249512

RESUMO

We have prepared NHC-CuI complexes with a rotaxane structure and used them as sterically sensitive catalysts for one-pot sequential copper-catalyzed azide/alkyne cycloadditions in solutions containing all of the coupling partners premixed in unprotected form. Most notably, a photolabile and sterically encumbered complex first catalyzed the coupling of a less bulky azide/alkyne pair; after removing the protective macrocyclic component from the rotaxane structure, through irradiation with light, the exposed dumbbell-shaped NHC-CuI complex catalyzed the second click reaction of a bulkier azide/alkyne pair. Using this approach, we obtained predominantly, from a single sealed pot, a bis-triazole product (84 %) from a mixture of two sterically distinct azides and a diyne.

5.
Org Lett ; 21(14): 5708-5712, 2019 07 19.
Artigo em Inglês | MEDLINE | ID: mdl-31283244

RESUMO

The absolute configurations of the two enantiomers of a topologically chiral [2]catenane were determined unambiguously based on HPLC resolution and X-ray crystal analysis. Although structurally dissimilar to simple amino acids, the optical rotations of these separated [2]catenanes share the Clough-Lutz-Jirgensons behavior of amino acids: the optical rotation flips direction in the presence of acid and base, the first example of such behavior for a mechanically interlocked topologically chiral catenane.

6.
Acc Chem Res ; 51(6): 1324-1337, 2018 06 19.
Artigo em Inglês | MEDLINE | ID: mdl-29745639

RESUMO

In 1987, Pedersen, Cram, and Lehn were awarded the Nobel Prize in Chemistry to honor their achievements in, among other things, the selective recognition of alkali metal ions by synthetic hosts. Almost three decades later, the 2016 Nobel Prize went to Stoddart, Sauvage, and Feringa for the development of artificial molecular machines, in which interlocked molecules play a significant role. Surprisingly, although many rotaxane- and catenane-based molecular machines have been constructed using various templating approaches, alkali metal ions, which are good templates for crown ether synthesis, have only rarely been applied as templates for the assembly of these interlocked molecules. This paucity of examples is probably due to the less well defined coordination numbers and geometries in the complexation of alkali metal ions to common oxygen-containing ligands, resulting in much weaker metal-ligand interactions and less predictable structures for their complexes compared with those formed between transition metal ions and common pyridine-containing ligands. Nevertheless, the ease of removing alkali metal ions from interlocked compounds and their much lower toxicity compared with that of transition metal ions are attractive features that have inspired their use as templates in the synthesis of interlocked molecules. About a decade ago, we began investigating the feasibility of using alkali metal ions to template the formation of catenanes and rotaxanes, with the hope of developing facile, broadly applicable, green, and efficient methods for their construction. We noticed that the interactions between oxygen-containing ligands and alkali metal ions can be strengthened by minimizing the effects of competing interactions from solvent molecules and counteranions. Thus, to increase the solubility of the metal ion salts in less polar solvents (e.g., CH2Cl2, CHCl3) and minimize ion pairing, we chose tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (TFPB), a weakly coordinating anion, as the counteranion for the alkali metal ions applied as templates. Our strategy has been based on the association of simple and general recognition units: (i) the orthogonal arrangement of two oligo(ethylene glycol) chains around an alkali metal ion and (ii) the encircling of a single urea/amide unit by an oligo(ethylene glycol)-containing macrocycle in the presence of a templating alkali metal ion. The former recognition system has allowed the facile construction of many interesting interlocked structures, including cyclic [2]catenane trimers and tetramers; the latter has provided several rotaxanes, including some incorporating monomers of practically important (macro)molecules (e.g., peptides, polymers) and some that behave as switches with unique functions (e.g., catalysis, gelation). The components in these recognition systems possess high flexibility in terms of their structures and the choice of suitable alkali metal ion templates. This Account tells the story of the concept behind this alkali metal ion-templating approach as well as its elaboration, scope, and recent advances. We hope to convince the reader that alkali metal ions are powerful templates for assembling interlocked structures and compounds and also to demonstrate the range of possibilities that they provide for future endeavors.

7.
Org Lett ; 20(8): 2416-2419, 2018 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-29611414

RESUMO

Simple cyclophanes containing four distant amino N atoms or ether O atoms behave as hosts for the threading of guest diarylguanidinium ions. The recognition system exhibits high synthetic flexibility, allowing unique O-free [2]rotaxanes to be synthesized efficiently (yields of up to 80%) through both "threading-followed-by-stoppering" and "clipping" approaches.

8.
J Org Chem ; 83(10): 5619-5628, 2018 05 18.
Artigo em Inglês | MEDLINE | ID: mdl-29701970

RESUMO

Sodium ion-controlled switching from "folded" to "linear" states results in significant changes in the molecular shape of a [2]catenane, such that it mimics the operation of a gin trap, with a fluorescent alarm signal appearing when pyrene side arms were present on its two macrocyclic components.

9.
Chemistry ; 24(7): 1522-1527, 2018 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-29226433

RESUMO

[2]Rotaxanes displaying one-off photo-triggerable gelation properties have been synthesized through the "clipping" of photo-degradable macrocycles around the amide or urea functionalities of organo- and hydrogelators. Irradiation with UV-light cleaved the photo-labile macrocyclic components from the [2]rotaxanes, resulting in the free gelators being released into solution and, thereafter, forming gels. When the rate of gelation was sufficiently rapid, selective gelation of specific regions of the solution-and, indeed, photo-patterning of the solution-was possible.

10.
Chemistry ; 23(41): 9756-9760, 2017 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-28577323

RESUMO

We have prepared [2]rotaxanes, the behavior of which as switchable catalysts depends on their pirouetting motion, which can be controlled through the addition and removal of Na+ ions. At least three sequential on/off cycles of a Michael reaction can be performed in situ when using the NaTFPB/[2.2.2]cryptand reagent pair to switch "on" and "off" the catalytic ability of the [2]rotaxanes.

11.
Chemistry ; 22(48): 17468-17476, 2016 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-27778390

RESUMO

Size-complementary cyclotriveratrylene (CTV)-based hosts can incarcerate C76 , C78 , and C84 , thus allowing the selective isolation of these higher-order fullerenes from a commercially available mixture of fullerenes. The hemicarceplexes, formed after the encapsulation of the size-complementary fullerenes within the hosts, are isolated by column chromatography and released at elevated temperature, thereby leading to the isolation of C76 /C78 and C84 in good purities (up to 95 and 88 %, respectively).

12.
Org Biomol Chem ; 14(3): 1153-60, 2016 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-26646655

RESUMO

An investigation into the most suitable alkali metal ions for templating the assembly of [2]catenanes from di-, tri-, and tetra(ethylene glycol)-containing guest diamines and isophthalaldehyde has indicated that Na(+), K(+), and Rb(+) ions are optimal for preparing [2]catenanes containing at least one di(ethylene glycol) unit, two tri(ethylene glycol) units, and at least one tetra(ethylene glycol) unit [in the absence of a di(ethylene glycol) unit], respectively.

13.
Angew Chem Int Ed Engl ; 54(40): 11745-9, 2015 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-26308558

RESUMO

Dimeric, trimeric, and tetrameric cyclic [2]catenanes have been prepared directly through one-pot sodium-ion-templated dynamic imine formation from a diamine and a tetraaldehyde. NaBH4 mediated reduction of the labile imino bonds of these cyclic [2]catenane oligomers, followed by methylation of the resulting secondary amino groups enabled the isolation and characterization of oligomeric cyclic [2]catenanes as stable, covalently linked compounds.

14.
Org Lett ; 17(9): 2158-61, 2015 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-25905465

RESUMO

Di-, tri-, and tetra(ethylene glycol) units in both dumbbell-shaped and macrocyclic molecules can be used as primary recognition units for the clipping of macrocycles in the presence of templating Na(+) ions to form corresponding [2]rotaxanes and [2]catenanes. One such tri(ethylene glycol)-containing [2]catenane behaves as a Na(+) ion-controllable molecular switch.


Assuntos
Catenanos/síntese química , Compostos Macrocíclicos/química , Sódio/química , Catenanos/química , Etilenoglicol/química , Íons , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Rotaxanos/síntese química , Rotaxanos/química
15.
Molecules ; 20(2): 1775-87, 2015 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-25621422

RESUMO

The Na+ ion-assisted recognition of urea derivatives by BPX26C6 has allowed the construction of a redox-controllable [2]rotaxane-type molecular switch based on two originally very weakly interacting host/guest systems. Using NOBF4 to oxidize the triarylamine terminus into a corresponding radical cation attracted the macrocyclic component toward its adjacent carbamate station; subsequent addition of Zn powder moved the macrocyclic component back to its urea station.


Assuntos
Carbanilidas/química , Éteres de Coroa/química , Espectroscopia de Ressonância de Spin Eletrônica , Conformação Molecular , Oxirredução , Rotaxanos/síntese química , Sódio/química , Zinco/química
16.
Chem Commun (Camb) ; 50(79): 11709-12, 2014 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-25142618

RESUMO

A cyclotriveratrylene-based molecular cage forms hemicarceplexes that significantly increase the solubility of commercially available Sc3N@C80 in CDCl3. When incarcerated within the molecular cage, the two structural isomers of this metallofullerene, Sc3N@D5h-C80 and Sc3N@Ih-C80, displayed characteristic signals in both (1)H and (13)C NMR spectra, allowing direct identification of each isomer without the need to enrich the sample with (13)C atoms.


Assuntos
Fulerenos/química , Escândio/química , Isomerismo , Espectroscopia de Ressonância Magnética , Compostos Policíclicos/química
17.
J Org Chem ; 79(8): 3581-6, 2014 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-24665822

RESUMO

A highly stable C60-incarcerated hemicarceplex, which retains its molecular integrity after heating at 523 K in air for at least 3 h, significantly increases the solubility of C60 in nonpolar solvents and increases the reduction potentials of the entrapped fullerene. Modification with [(η(5)-C5Me5)Ru(II)](+) dramatically increases the solubility of this hemicarceplex in polar, protic solvents (e.g., MeOH).


Assuntos
Fulerenos/química , Compostos Macrocíclicos/química , Solventes/química , Tamanho da Partícula , Rutênio/química , Solubilidade
18.
Org Biomol Chem ; 12(18): 2907-17, 2014 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-24676312

RESUMO

Five analogues of the macrocycle BPX26C6 are also capable of recognizing single urea and/or amide functionalities in the presence of templating Na(+) ions. We have unambiguously confirmed the formation of such [2]pseudorotaxane complexes in solution through syntheses of the corresponding [2]rotaxanes.


Assuntos
Amidas/química , Compostos Macrocíclicos/química , Sódio/química , Ureia/química , Íons , Compostos Macrocíclicos/síntese química , Espectroscopia de Prótons por Ressonância Magnética , Rotaxanos/síntese química , Rotaxanos/química
19.
Chemistry ; 20(16): 4563-7, 2014 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-24633811

RESUMO

A single urea or amide functionality in a dumbbell-shaped guest can be "clipped" by a macrocycle generated from a diamine and a dialdehyde through the templating effect of a Na(+) ion (see scheme). The resulting imine-containing rotaxanes can then be reduced to allow isolation of stable amine-based rotaxanes.


Assuntos
Amidas/química , Rotaxanos/síntese química , Sódio/química , Ureia/química , Cristalografia por Raios X , Íons/química , Compostos Macrocíclicos/química , Conformação Molecular , Rotaxanos/química
20.
Org Lett ; 16(4): 1068-71, 2014 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-24499390

RESUMO

Threading of di-, tri-, and tetra(ethylene glycol) through the macrocycle BPX26C6 in the presence of templating Na(+) ions was proven by the synthesis of the corresponding [2]rotaxanes under solvent-free conditions. Among them, a [2]rotaxane featuring both tetra(ethylene glycol) and carbamate stations behaves as a molecular switch that can be controlled reversibly through the application of the KTFPB/[2.2.2]cryptand reagent pair.


Assuntos
Éteres de Coroa/química , Etilenoglicol/química , Rotaxanos/síntese química , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Rotaxanos/química
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