Cavity-Directed, Highly Stereoselective [2+2] Photodimerization of Olefins within Self-Assembled Coordination Cages

Yoshizawa, Michito; Takeyama, Yoshihisa; Kusukawa, Takahiro; Fujita, Makoto

doi:10.1002/1521-3773(20020415)41:8<1347::aid-anie1347>3.0.co;2-x

Cited by 334 publications

(183 citation statements)

References 49 publications

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“…Accordingly, p-ethyl toluene can be combined with a number of coencapsulation partners, of which the benzene is at near optimum at filling 53% of the space (16). This matching of host space and guest size drives much encapsulation and is especially good for arranging bimolecular reactions inside (17,18). It lies at the heart of the studies reported here.…”

supporting

confidence: 66%

Adaptations of guest and host in expanded self-assembled capsules

Ajami

Rebek

2007

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

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Reversible encapsulation complexes create spaces where two or more molecules can be temporarily isolated. When the mobility of encapsulated molecules is restricted, different arrangements in space are possible, and new forms of isomerism (''social isomerism'') are created: the orientation of one encapsulated molecule influences that of the other in the confined space. Expansion of a capsule's length is possible through addition of small-molecule spacer elements. The expanded capsules have dimensions that permit the observation of social isomerism of two identical guests, and they adopt arrangements that properly fill the host's space. The host also can adapt to longer guests by incorporating additional spacers, much as protein modules are added to a viral capsid in response to larger genomes. Arachidonic and related fatty acid derivatives act in this way to induce the assembly of further extended capsules having sufficient length to accommodate them.encapsulation ͉ self-assembly ͉ social isomers E ncapsulation complexes are synthetic, self-assembled hosts that more or less completely surround their guest molecules. They are dynamic and form reversibly in solution with lifetimes ranging from milliseconds to days. The capsules isolate molecules from the bulk solution, and they reveal behaviors that cannot be seen otherwise. They have become a tool of modern physical organic chemistry (1). For example, cylindrical host 1.1 (Fig. 1) self-assembles only in the presence of suitable guests to give encapsulation complexes (2-4). Combinations of different guests (5) inside this capsule have allowed its use as a reaction chamber (6), a chiral receptor (7), and a space where singlemolecule solvation can be observed (8). Elsewhere, reversible encapsulation complexes have been used to stabilize reactive intermediates (9, 10) and even transition states (11, 12) as well as to alter the course of reactions in the limited quarters (13). New forms of stereochemistry also have emerged from coencapsulation studies (14). For example, with benzene and p-ethyl toluene, two complexes coexist (Fig. 1). The two molecules are too large to slip past each other, and the p-ethyl toluene is too long to tumble freely while inside the capsule. Either of these motions could interconvert the complexes, but they are slow on the NMR time scale and separate spectra are seen for the two isomers. These ''social isomers'' are different arrangements in space that arise from the interactions of at least two encapsulated molecules. They also are constitutional isomers, but mechanical barriers hold these arrays in place rather than covalent bond ''connectedness.'' Accordingly, the term supramolecular diastereomers better describes the relationships. This stereoisomerism is related to the carceroisomerism (15) observed in covalently bound capsules with one guest.The self-assembly of the benzene/p-ethyl toluene pair owes its stability to the optimal filling of the capsule's space. Two benzene molecules can assemble the capsule as guests in that solvent and f...

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supporting

confidence: 66%

Adaptations of guest and host in expanded self-assembled capsules

Ajami

Rebek

2007

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

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“…103 Upon irradiation of acenaphthylene 33 in the presence of 30 in water, the syn-dimer 34 was formed exclusively in a yield of >98% (Figure 6a).…”

Section: Noncovalent Systemsmentioning

confidence: 99%

Self‐Assembled Nanoreactors

et al. 2005

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“…They are of great interest as nanoreactors 4,5 , in which fleeting intermediates are stabilized [6][7][8][9] , reactions accelerated 10,11 and regio-and stereochemistry altered [12][13][14] , as well as for solar energy conversion 15 , nanodevice fabrication 16 , drug delivery 17 , storage and separation technology 18 . The discovery of self-assembly processes involving hydrogen bonding or metal coordination, in which multiple building blocks spontaneously assemble to form spherically and cylindrically shaped molecular capsules held together by hydrogen bonding or metal-ligand interactions, has tremendously increased the diversity of capsules with respect to shape and size [19][20][21][22][23] .…”

Section: Introductionmentioning

confidence: 99%

A simple one-pot multicomponent synthesis of an octahedral nanocontainer molecule

Liu

Warmuth

2007

Nat Protoc

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A nearly quantitative 18-component synthesis of a nanocontainer, which is built up from six bowl-shaped cavitands that are connected together with 12 -CH¼N-CH 2 CH 2 -N¼CH-linkers, and its subsequent reduction are described. This nanocontainer has an estimated cavity volume of 1,700 Å 3 , large enough to encapsulate several smaller guest molecules or a small-sized biomacromolecule. Potential uses of this nanocontainer and of water-soluble derivatives are in drug delivery, wastewater detoxification, separation technology and as molecular reactor for controlled oligomerizations. Typically, the four-step synthesis of the cavitand building block and the subsequent multicomponent synthesis of the nanocontainer, including its purification, can be accomplished in about 4 weeks.

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Cavity-Directed, Highly Stereoselective [2+2] Photodimerization of Olefins within Self-Assembled Coordination Cages

Cited by 334 publications

References 49 publications

Adaptations of guest and host in expanded self-assembled capsules

Adaptations of guest and host in expanded self-assembled capsules

Self‐Assembled Nanoreactors

A simple one-pot multicomponent synthesis of an octahedral nanocontainer molecule

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