Selection approaches to catalytic systems

Brady, Paul A.; Sanders, Jeremy K. M.

doi:10.1039/cs9972600327

Cited by 135 publications

(51 citation statements)

References 39 publications

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“…Recently, dynamic covalent chemistry (37)(38)(39)(40), exemplified by reversible imine formation (41,42), metal-ligand exchange (43), and olefin metathesis (44,45), has been demonstrated to be an effective tool for the preparation of various exotic mechanically interlocked molecular compounds. It has been found that, in the presence of an appropriate template, one of the possible compounds in the dynamic library, after mixing the different components, can be amplified to give the thermodynamically most stable product.…”

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Efficient production of [ n ]rotaxanes by using template-directed clipping reactions

Leung

Stoddart

2007

Proc. Natl. Acad. Sci. U.S.A.

116

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In this article, we report on the efficient synthesis of well defined, homogeneous [n]rotaxanes (n up to 11) by a template-directed thermodynamic clipping approach. By employing dynamic covalent chemistry in the form of reversible imine bond formation, [ dynamic covalent chemistry ͉ molecular recognition ͉ polyrotaxanes ͉ self-assembly ͉ template-directed synthesis M echanically interlocked and knotted compounds, such as rotaxanes (1-5), catenanes (6-10), suitanes (11, 12), trefoil knots (13-17), , and Solomon knots (21), represent challenging synthetic goals that have nevertheless been realized. These molecular compounds are usually synthesized by a template-directed approach (22) that depends on molecular recognition and self-assembly processes. Recently, their potential applications as molecular switches for nanoelectronics (23, 24) and molecular actuators for constructing artificial muscles (25), for fabricating smart surface materials (26), and for controlling the nanoscale release of molecules trapped in mesoporous silica (27)(28)(29) were demonstrated. Polyrotaxanes and well defined, homogeneous oligorotaxanes, in which the recognition sites on a dumbbell (an axle terminated by bulky stoppers) are encircled by large rings or macrocycles (wheels) by dint of molecular recognition, have become (30-36) one of the most intensively investigated subjects in mechanical chemistry. A general synthetic method for making rotaxanes, namely, the ''threading-followed-by-stoppering'' approach (Fig. 1, method A), involves (30-32) several macrocycles. First, the macrocycles are threaded onto oligomeric or polymeric axles carrying recognition sites at prescribed intervals along the axles to form pseudorotaxanes, then both ends of the axles are stoppered with bulky groups. Although this approach is relatively simple, it does not provide complete control over the number of threaded macrocycles, that is, the rings or beads are often not threaded onto all of the available recognition sites on the axles. Alternatively, a template-directed ''clipping'' approach (Fig. 1, method B), in which the macrocycles are formed from acyclic precursors in the presence of templating recognition sites on the dumbbells, has provided (33-36) a versatile means for the construction of some lower-order rotaxanes. Nonetheless, the efficient synthesis of well defined, homogeneous, higher-order polyrotaxanes continues to be a challenge to synthetic chemists.Recently, dynamic covalent chemistry (37-40), exemplified by reversible imine formation (41, 42), metal-ligand exchange (43), and olefin metathesis (44, 45), has been demonstrated to be an effective tool for the preparation of various exotic mechanically interlocked molecular compounds. It has been found that, in the presence of an appropriate template, one of the possible compounds in the dynamic library, after mixing the different components, can be amplified to give the thermodynamically most stable product. We have reported (see refs. 46-49) an example of such a template-directed synthesis of ...

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Efficient production of [ n ]rotaxanes by using template-directed clipping reactions

Leung

Stoddart

2007

Proc. Natl. Acad. Sci. U.S.A.

116

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“…As an alternative, several selection-based approaches to the discovery of new catalytic systems are being developed. [1] Selection can be based on activity such as in the in vitro evolutionary screening and selection of ribozymes, [2] while another approach involves selection of receptors on the basis of the affinity for the transition state of a given reaction. In practice, screening is based on the affinity for a stable transition-state analogue (TSA).…”

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Selection and Amplification of a Catalyst from a Dynamic Combinatorial Library

2003

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“…Current approaches sharing this idea include molecular biology, organic and inorganic synthesis, and polymer and solid-state chemistry; these have been reviewed elsewhere [1,10]. We have been exploring a synthetic chemistry approach using dynamic combinatorial libraries (DCLs).…”

Section: The Selection Approachmentioning

confidence: 99%

Adventures in molecular recognition. The ins and outs of templating

Sanders

2000

Pure and Applied Chemistry

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Two different approaches are described for the creation of supramolecular systems potentially capable of recognition and catalysis. Using the design approach, we have been able to accelerate and influence two different Diels-Alder reactions within the cavities of porphyrin dimers and trimers; this is templating from the outside inwards. The selection approach is a synthetic chemical attempt to capture some of the key evolutionary features of biological systems: dynamic combinatorial chemistry is used to create equilibrating mixtures of potential receptors, and then a template is used to select and amplify the desired system. Five potential reactions for such dynamic chemistry are discussed: base-catalyzed transesterification, hydrazone exchange, disulfide exchange, alkene metathesis, and Pd-catalyzed allyl exchange, and preliminary templating results (inside outwards) are presented.

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Selection approaches to catalytic systems

Cited by 135 publications

References 39 publications

Efficient production of [ n ]rotaxanes by using template-directed clipping reactions

Efficient production of [ n ]rotaxanes by using template-directed clipping reactions

Selection and Amplification of a Catalyst from a Dynamic Combinatorial Library

Adventures in molecular recognition. The ins and outs of templating

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