Switchable catalysis

Literature Seminar
Yuya Morita (M2)2013/7/1

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Contents
1. Introduction
2. Photoswitchable Catalysts
3. Metal-Cation-Switchable catalysts
4. Supramolecular Approaches
4-1. Layered Systems
4-2. Rotaxanes
5. Summary and Perspective2

1. Introduction

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for the development of a “smart” catalysts

4Switchable Catalysts
In the living cell, uncountable reactions occur in parallel. To ensure that all theseprocesses proceed without interfering with one another, these operations must becontrolled, their function must be switchable, and the switching must be reversible.

5Switchable Catalysts

62. Photoswitchable Catalysts
Light is perhaps the most advantageous stimulus as it is a noninvasive stimulus that canbe conveniently manipulated by modern optics, potentially enabling the setup of highly
parallel processes.

Photocontrolled thermal catalysis (b and c) is clearly an appealing yet challenging
concept that offers great potential for the realization of smart catalysts.
S. Hecht, et al. Angew. Chem. Int. Ed. 2010, 49, 5054

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The design of photoswitchable catalysts
・in order to realize a reversible process, photochromic moieties have to be incorporated
into the catalyst system
・two different light stimuli reversibly shuttle the catalytic system between an active ONstate and an inactive OFF state.

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2-1. Inhibitor
A. Ueno, et al. J. Chem. Soc. Chem. Commun. 1980, 837

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2-2. Activator
S. Inoue, et al. J. Am. Chem. Soc. 1999, 121, 2325

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2-3. Template
J. Rebek, Jr., et al. Angew. Chem. Int. Ed. 1995, 34, 446112-3. Template
R. Cacciapaglia, et al. J. Am. Chem. Soc. 2003, 125, 2224

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2-3. Template
R. Cacciapaglia, et al. J. Am. Chem. Soc. 2003, 125, 2224

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2-3. Template
R. Cacciapaglia, et al. J. Am. Chem. Soc. 2003, 125, 2224

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2-3. Template
B. L. Feringa, et al. Science 2011, 331, 142915

2-3. Template

B. L. Feringa, et al. Science 2011, 331, 1429

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2-3. Template
B. L. Feringa, et al. Science 2011, 331, 142917

2-3. Template
B. L. Feringa, et al. Science 2011, 331, 142918

2-4. Shielding19

2-4. Shielding
S. Hecht, et al. Angew. Chem. Int. Ed. 2008, 47, 5968

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2-4. Shielding
S. Hecht, et al. Angew. Chem. Int. Ed. 2008, 47, 5968

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2-5. Electronic effects
T. Kawashima, et al. Org. Lett. 2005, 7, 3909

N. R. Branda, et al. Angew. Chem. Int. Ed. 2008, 47, 5034

Neither Kawashima’s nor Branda’s system have been used as photoswitchable Lewis acids
to control any chemical transformation…

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2-5. Electronic effects
C. W. Bielawski, et al. J. Am. Chem. Soc. 2012, 134, 12693

The activity of the NHC organocatalyst was remotely tuned via exposure to UV and visible
light. This is rare example of a photoswitchable catalyst that operates via the remotephotomodulation of its electronic structure.

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3. Metal-Cation-Switchable Catalysts
M. Shibasaki, et al. J. Am. Chem. Soc. 2009, 131, 3779

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3. Metal-Cation-Switchable Catalysts
M. Schmittel, et al. Angew. Chem. Int. Ed. 2012, 51, 3832

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4. Supramolecular approaches
Supramolecular approaches display a distinct three-dimensional architecture throughnoncovalent interactions, while a reasonable degree of conformational freedom remains
to allow modification of its three-dimensional shape in response to specific signals.

4-1. Layered Systems

4-2. Rotaxanes

264-1-1. Layered Systems - Introduction
C. A. Mirkin, et al. Angew. Chem. Int. Ed. 2011, 50, 114

Structures formed through these supramolecular approaches can exhibit catalytic activities reminiscentof enzymes in terms of catalytic acceleration by proximity effects in cages, discrimination between
different isomers of a substrate, and regulation in terms of catalytic activity and selectivity.
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4-1-1. Layered Systems - Introduction
C. A. Mirkin, et al. Acc. Chem. Res. 2008, 41, 1618

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4-1-2. Macrocycle Approach
C. A. Mirkin, et al. J. Am. Chem. Soc. 2003, 125, 10508

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4-1-2. Macrocycle Approach
C. A. Mirkin, et al. J. Am. Chem. Soc. 2003, 125, 10508
This work represented the first demonstration of an allosteric catalyst made possible
through supramolecular coordination chemistry.

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4-1-3. Molecular Tweezers
C. A. Mirkin, et al. Angew. Chem. Int. Ed. 2004, 43, 5503

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4-1-3. Molecular Tweezers
C. A. Mirkin, et al. Angew. Chem. Int. Ed. 2004, 43, 5503

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4-1-4. Triple-Layer Catalysts
C. A. Mirkin, et al. Science 2010, 330, 66

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4-1-4. Triple-Layer Catalysts
C. A. Mirkin, et al. Science 2010, 330, 66

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4-1-4. Triple-Layer Catalysts
C. A. Mirkin, et al. Science 2010, 330, 66

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4-1-4. Triple-Layer Catalysts
C. A. Mirkin, et al. Science 2010, 330, 66

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4-2-1. Syntheses of Rotaxanes

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4-2-2. Application to Molecular Machines38

4-2-3. Application to Catalysts

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4-2-4. Rotaxane-Based Switchable Organocatalyst
D. A. Leigh, et al. Angew. Chem. Int. Ed. 2012, 51, 516640

4-2-4. Rotaxane-Based Switchable Organocatalyst
D. A. Leigh, et al. Angew. Chem. Int. Ed. 2012, 51, 516641

4-2-4. Rotaxane-Based Switchable Organocatalyst
D. A. Leigh, et al. Angew. Chem. Int. Ed. 2012, 51, 516642

4-2-4. Rotaxane-Based Switchable Organocatalyst
D. A. Leigh, et al. Angew. Chem. Int. Ed. 2012, 51, 5166

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5. Summary and Perspective
・Impressive and significant advances through allosteric regulation have led to thedevelopment of a number of switchable catalysts with multiple catalytic functions
having adequate temporal and spatial resolution.

・ For the practical application of switchable catalysts, the low catalytic efficiency
and the narrow scope of applicable reactions are problematic so far.
・ The goal of switchable catalysis is not only the mere enabling of a given chemicaltransformation but also the complete control over its outcome by developing
suitable catalysts to dictate chemoselectivity, regioselectivity, and stereoselectivityof the reaction. Applying these features to polymerization processes would beparticularly beneficial in this context.

・ Furthermore these catalysts are not only advantageous for their utility in organicsynthesis, but can also be applied to a much broader field such as materials anddevices because these catalysts can produce multiple outputs from an intricate
molecular ensemble.
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Useful reviews
S. Hecht, et al. Angew. Chem. Int. Ed. 2010, 49, 5054
C. A. Mirkin, et al. Angew. Chem. Int. Ed. 2011, 50, 114
C. J. Hawker, et al. Angew. Chem. Int. Ed. 2013, 52, 199
N. Kumagai.; M. Shibasaki. Cat. Sci. Technol. 2013, 3, 41

Other examples of switchable catalysts (not shown in slide)N. R. Branda, et al. Angew. Chem. Int. Ed. 2005, 44, 2019 (photoswitchable lignad)
C. A. Mirkin, et al. J. Am. Chem. Soc. 2005, 127, 1644 (layered system)
C. A. Mirkin, et al. J. Am. Chem. Soc. 2007, 129, 14182 (layered system)
K. Nagasawa, et al. Angew. Chem. Int. Ed. 2010, 49, 9254 (solvent-control)
J. Rebek, Jr.,et al. Angew. Chem. Int. Ed. 2011, 50, 9400 (light-responsive cavitand)N. R. Branda, et al. Angew. Chem. Int. Ed. 2012, 51, 5431 (electronic effects)

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