Catalytic Acyl Transfer by a Cyclic Porphyrin Trimer: Efficient Turnover without Product Inhibition

Mackay, Lindsey G.; Wylie, R. Stephen; Sanders, Jeremy K. M.

doi:10.1021/ja00086a061

Cited by 159 publications

(104 citation statements)

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“…19,32,59 Moreover, the resulting catalysts are not so versatile because they are often highly specific to only a limited number of reactions. 54,58,[63][64][65][66][67][68][69] It is for this reason that in the past decade a shift has been observed in the approach to construct these catalysts, from traditional covalent chemistry to multicomponent selfassembly of relatively small complementary building blocks. Self-assembled capsules are receptors with enclosed cavities that are formed through reversible, noncovalent interactions between two or more complementary subunits.…”

Section: Noncovalent Systemsmentioning

confidence: 99%

Self-Assembled Nanoreactors

et al. 2005

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Section: Noncovalent Systemsmentioning

confidence: 99%

Self-Assembled Nanoreactors

et al. 2005

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“…56 We hypothesized that the pyridylcarbinol and acetylimidazole substrates could be brought together within the cavity of 15a by cofacial Zn II metal centers and converted to the products in a catalytic fashion by virtue of their proximity (Figure 3). Furthermore, reactions involving 1-acetylimidazole and differentially substituted Xpyridylcarbinol (where X = 2, 3, or 4) can be used to evaluate the ability of 15a to act allosterically: only the combination of substrates with the right distance can span the cavity and react at an accelerated rate.…”

Section: Acyl Transfer Catalytic Experimentsmentioning

confidence: 99%

Supramolecular Allosteric Cofacial Porphyrin Complexes

et al. 2006

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Nature routinely uses cooperative interactions to regulate cellular activity. For years, chemists have designed synthetic systems that aim toward harnessing the reactivity common to natural biological systems. By learning how to control these interactions in situ, one begins to allow for the preparation of man-made biomimetic systems that can efficiently mimic the interactions found in Nature. To this end, we have designed a synthetic protocol for the preparation of flexible metal-directed supramolecular cofacial porphyrin complexes which are readily obtained in greater than 90% yield through the use of new hemilabile porphyrin ligands with bifunctional ether-phosphine or thioetherphosphine substituents at the 5 and 15 positions on the porphyrin ring. The resulting architectures contain two hemilabile ligand-metal domains (Rh I or Cu I sites) and two cofacially aligned porphyrins (Zn II sites), offering orthogonal functionalities and allowing these multimetallic complexes to exist in two states, "condensed" or "open". Combining the ether-phosphine ligand with the appropriate Rh I or Cu I transition-metal precursors results in "open" macrocyclic products. In contrast, reacting the thioether-phosphine ligand with Rh I or Cu I precursors yields condensed structures that can be converted into their "open" macrocyclic forms via introduction of additional ancillary ligands. The change in cavity size that occurs allows these structures to function as allosteric catalysts for the acyl transfer reaction between X-pyridylcarbinol (where X = 2, 3, or 4) and 1-acetylimidazole. For 3-and 4-pyridylcarbinol, the "open" macrocycle accelerates the acyl transfer reaction more than the condensed analogue and significantly more than the porphyrin monomer. In contrast, an allosteric effect was not observed for 2-pyridylcarbinol, which is expected to be a weaker binder and is unfavorably constrained inside the macrocyclic cavity.

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“…The development in supramolecular chemistry has evolved such that several synthetic systems are now available to also study the reactivity in confined nano-spaces, such as the well-defined cavities of metal-organic frameworks, and (supra)molecular capsules. It has been demonstrated by the pioneering work of Sanders and co-workers 15 , Rebek and co-workers [16][17][18][19] , Fujita and co-workers 20 and Raymond and co-workers 21 that organic reactions that occur in such restricted environments can result in unusual selectivities and rate enhancements. These all are elegant examples in which it has been demonstrated that the activity or selectivity of organic reactions can be controlled by nano-capsules.…”

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Capsule-controlled selectivity of a rhodium hydroformylation catalyst

et al. 2013

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Chemical processes proceed much faster and more selectively in the presence of appropriate catalysts, and as such the field of catalysis is of key importance for the chemical industry, especially in light of sustainable chemistry. Enzymes, the natural catalysts, are generally orders of magnitude more selective than synthetic catalysts and a major difference is that they take advantage of well-defined cavities around the active site to steer the selectivity of a reaction via the second coordination sphere. Here we demonstrate that such a strategy also applies for a rhodium catalyst; when used in the hydroformylation of internal alkenes, the selectivity of the product formed is steered solely by changing the cavity surrounding the metal complex. Detailed studies reveal that the origin of the capsule-controlled selectivity is the capsule reorganization energy, that is, the high energy required to accommodate the hydride migration transition state, which leads to the minor product.

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Catalytic Acyl Transfer by a Cyclic Porphyrin Trimer: Efficient Turnover without Product Inhibition

Cited by 159 publications

References 0 publications

Self-Assembled Nanoreactors

Self-Assembled Nanoreactors

Supramolecular Allosteric Cofacial Porphyrin Complexes

Capsule-controlled selectivity of a rhodium hydroformylation catalyst

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