Two‐Component Liquid Crystals as Chiral Reaction Media: Highly Enantioselective Photodimerization of an Anthracene Derivative Driven by the Ordered Microenvironment

Ishida, Yasuhiro; Kai, Yukiko; Kato, S.; Misawa, Aya; Amano, Sayaka; Matsuoka, Yuki; Saigo, Kazuhiko

doi:10.1002/ange.200803242

Cited by 18 publications

(8 citation statements)

References 52 publications

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“…In fact, we have recently reported that the salts of trisA C H T U N G T R E N N U N G (alkyloxy)benzoic acid derivatives with various amino alcohols have a general tendency to exhibit thermotropic LC phases. [12,13,16] In this work, (1R,2S)-norephedrine (guest amine; G RS ) was selected, because an abundant amount of data have been accumulated by our group on the structure and properties of the LC salts of G RS with amphiphilic carboxylic acids. In addition, easy access to its antipode ((1S,2R)-norephedrine, G SR ) and diastereoisomers ((1R,2R)-and (1S,2S)-pseudonorephedrine, G RR and G SS ) would allow us to investigate the chirality recognition ability of the resultant polymers.…”

Section: Resultsmentioning

confidence: 99%

Guest‐Responsive Covalent Frameworks by the Cross‐Linking of Liquid‐Crystalline Salts: Tuning of Lattice Flexibility by the Design of Polymerizable Units

Ishida

Sakata

Achalkumar

et al. 2011

Chemistry A European J

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Cross-linked polymers prepared by the in-situ polymerization of liquid-crystalline salts were found to work as solid-state hosts with a flexible framework. As a component of such hosts, four kinds of polymerizable amphiphilic carboxylic acids bearing alkyl chains with acryloyloxy (A), dienyl (D), and/or nonreactive (N) chain ends (monomeric carboxylic acids; M(AAA), M(ANA), M(DDD), and M(DND)) were used. The carboxylic acids were mixed with an equimolar amount of a template unit, (1R,2S)-norephedrine (guest amine; G(RS)), to form the corresponding salts. Every salt exhibited a rectangular columnar LC phase at room temperature, which was successfully polymerized by (60)Co γ-ray-induced polymerization without serious structural disordering to afford the salt of cross-linked carboxylic acid (polymeric carboxylic acid; P(AAA), P(ANA), P(DDD), and P(DND)) with G(RS) . Owing to the noncovalency of the interactions between the polymer framework P and the template G(RS), the cross-linked polymers could reversibly release and capture a meaningful amount of G(RS). In response to the desorption and adsorption of G(RS), the cross-linked polymers dramatically switched their nanoscale structural order. A systematic comparison of the polymers revealed that the choice of polymerizable groups has a significant influence on the properties of the resultant polymer frameworks as solid-state hosts. Among these polymers, P(DDD) was found to be an excellent solid-state host, in terms of guest-releasing/capturing ability, guest-recognition ability, durability to repetitive usage, and unique structural switching mode.

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Section: Resultsmentioning

confidence: 99%

Guest‐Responsive Covalent Frameworks by the Cross‐Linking of Liquid‐Crystalline Salts: Tuning of Lattice Flexibility by the Design of Polymerizable Units

Ishida

Sakata

Achalkumar

et al. 2011

Chemistry A European J

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“…(iii) Owing to the availability of various photoreactive carboxylic acids, as well as the noncovalency of interaction between the two components, such 2-amino alcohol units would offer a special environment to various substrates/reactions. As the first successful example of this approach, we recently reported that the photodimerization of 2-anthracenecarboxilic acids generated a satisfactory yield with unprecedented high enantioselectivity, by using a two component LC matrix as the reaction medium ( Figure 11 ) [ 19 , 20 ].…”

Section: Tailored Reaction Mediamentioning

confidence: 99%

“…Therefore, in situ reactions in LCs would lead to a new type of tailored micro-environment, which may realize highly efficient/selective molecular recognitions and chemical reactions. This review summarizes our recent effort to develop a new class of micro-environment based on the in situ reactions in LCs [ 16 , 17 , 18 , 19 , 20 ]. In relation to our studies, we also provide an overview of notable works related to LC-template reactions, from historically important reports to recent trends.…”

Section: Introductionmentioning

confidence: 99%

Organic Zeolite Analogues Based on Multi-Component Liquid Crystals: Recognition and Transformation of Molecules within Constrained Environments

Ishida

2011

Materials

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In liquid crystals (LCs), molecules are confined in peculiar environments, where ordered alignment and certain mobility are realized at the same time. Considering these characteristics, the idea of “controlling molecular events within LC media” seems reasonable. As a suitable system for investigating this challenge, we have recently developed a new class of ionic LCs; the salts of amphiphilic carboxylic acids with 2-amino alcohols, or those of carboxylic acids with amphiphilic 2-amino alcohols, have a strong tendency to exhibit thermotropic LC phases. Because of the noncovalent nature of the interaction between molecules, one of the two components can easily be exchanged with, or transformed into, another molecule, without distorting the original LC architecture. In addition, both components are common organic molecules, and a variety of compounds are easily available. Taking advantage of these characteristics, we have succeeded in applying two-component LCs as chiral media for molecular recognition and reactions. This review presents an overview of our recent studies, together with notable reports related to this field.

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“…In a more positive light, however, one can consider this complexity to be a probe to explore and monitor the molecular phenomena involved in the stereochemical course of a process, especially in terms of molecular arrangement, fine‐tuned by noncovalent interactions that participate in supramolecular chirogenesis. Substrate preorientation prior to photoreaction, governed by means of the supramolecular interactions, has recently been exploited to achieve highly regio‐ and enantioselective photodimerization of 2Ac in solution,3 in the solid state4 by using the inherently chiral cavity of γ‐cyclodextrin derivatives, and in two‐component liquid crystalline medium as well 5. However, all are sensitive to the design or fine‐tuning of the appropriate host molecules.…”

Section: Introductionmentioning

confidence: 99%

Transcription of Chirality in the Organogel Systems Dictates the Enantiodifferentiating Photodimerization of Substituted Anthracene

Dawn

Shiraki

Haraguchi

et al. 2010

Chemistry A European J

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An organogelator (G) that contains 2-anthracenecarboxylic acid (2Ac) attached covalently to a gelator counterpart that consists of 3,4,5-tris(n-dodecan-1-yloxy)benzoic acid by means of a chiral amino alcohol linkage has been synthesized. G acts as an efficient gelator of organic solvents, including mixed solvents and chiral solvents. Photodimers isolated after the photoreaction of the gel samples display different degrees of stereoselectivity. In the gel state, the formation of head-to-head (h-h) photodimers is always favored over head-to-tail (h-t) photodimers. Enantiomeric excess (ee) values of the major h-h photodimers reached as high as -56% in the case of the gels with enantiomeric glycidyl methyl ethers. Here, the solvent chirality is outweighed by the intrinsic chirality of the gelator molecule. The packing of the chromophore in the gel state has been characterized by the absorption and the emission behaviors and their variations during the course of gel-to-sol phase transition. Whereas for the hexane gel, emission intensity increases with an increase in temperature, other systems show a decrease in emission intensity. Redshift of the lambda(max) in the gel spectra indicates the J-aggregate arrangement of the chromophores. Chiral transcription in the gel state has been investigated by CD spectroscopy, which shows a decrease in CD intensity during the gel-to-sol phase transition. The X-ray diffraction study clearly differentiates among the gels in terms of the order of molecular arrangements. The gel systems are categorized as strong, moderately strong, and weak, that originate from the cooperative or individual participations of intermolecular hydrogen-bonding and pi-pi interactions, fine-tuned by the solvent polarity and the gelation temperature. A simple model based on the experimental findings and the molecular preorientation as evidenced by the stereochemistry of the photodimers has been proposed.

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Two‐Component Liquid Crystals as Chiral Reaction Media: Highly Enantioselective Photodimerization of an Anthracene Derivative Driven by the Ordered Microenvironment

Cited by 18 publications

References 52 publications

Guest‐Responsive Covalent Frameworks by the Cross‐Linking of Liquid‐Crystalline Salts: Tuning of Lattice Flexibility by the Design of Polymerizable Units

Guest‐Responsive Covalent Frameworks by the Cross‐Linking of Liquid‐Crystalline Salts: Tuning of Lattice Flexibility by the Design of Polymerizable Units

Organic Zeolite Analogues Based on Multi-Component Liquid Crystals: Recognition and Transformation of Molecules within Constrained Environments

Transcription of Chirality in the Organogel Systems Dictates the Enantiodifferentiating Photodimerization of Substituted Anthracene

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