Catalytic enantiodifferentiating photoisomerization of cyclooctene () included and sensitized by regioisomeric 6--(-, -, and -methoxybenzoyl)-β-cyclodextrins (CDs) was performed under a variety of solvent conditions for higher enantioselectivities. The enantiomeric excess (ee) of chiral ()-isomer () produced was a critical function of all the internal and external factors examined, in particular, the sensitizer structure and the solvent conditions, to afford ()- in record-high ee's of up to 67% upon sensitization with the -substituted β-CD host in water and salt solutions but neither in 50% aqueous ethanol nor with the - and -substituted hosts. The mechanistic origin of the sudden ee enhancement achieved under the specific conditions is discussed on the basis of the circular dichroism spectral behaviors upon substrate inclusion and the compensatory enthalpy-entropy relationship of the activation parameters for the enantiodifferentiating photoisomerization.
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http://dx.doi.org/10.1021/acs.joc.1c01748 | DOI Listing |
J Org Chem
February 2022
Department of Applied Chemistry, Osaka University, 2-1 Yamada-oka, Suita 565-0871, Japan.
Catalytic enantiodifferentiating photoisomerization of cyclooctene () included and sensitized by regioisomeric 6--(-, -, and -methoxybenzoyl)-β-cyclodextrins (CDs) was performed under a variety of solvent conditions for higher enantioselectivities. The enantiomeric excess (ee) of chiral ()-isomer () produced was a critical function of all the internal and external factors examined, in particular, the sensitizer structure and the solvent conditions, to afford ()- in record-high ee's of up to 67% upon sensitization with the -substituted β-CD host in water and salt solutions but neither in 50% aqueous ethanol nor with the - and -substituted hosts. The mechanistic origin of the sudden ee enhancement achieved under the specific conditions is discussed on the basis of the circular dichroism spectral behaviors upon substrate inclusion and the compensatory enthalpy-entropy relationship of the activation parameters for the enantiodifferentiating photoisomerization.
View Article and Find Full Text PDFOrg Lett
February 2017
Comprehensive Analysis Center, ISIR, Osaka University, 8-1 Mihogaoka, Ibaraki Osaka 5670047, Japan.
A biphenyl photosensitizer axle was implanted into the cavities of native and capped γ-cyclodextrins through rotaxanation using a cucubit[6]uril-templated azide-alkyne 1,3-dipolar cycloaddition, resulting in the construction of highly defined chiral binding/sensitizing sites. The orientation and interaction of the axle and capping moieties at the ground and excited states were interrogated by NMR, UV-vis, circular dichroism, and fluorescence spectroscopic studies. In situ photoisomerization of (Z,Z)-1,3-cyclooctadiene sensitized in the cavity of these [4]rotaxanes afforded (Z,E)-1,3-cyclooctadiene in up to 15.
View Article and Find Full Text PDFChem Sci
February 2015
Research Institute for Electronic Science , Hokkaido University, N20, W10, Kita-Ku , Sapporo 001-0020 , Hokkaido , Japan . Email:
The ability to photoinduce enantiomeric excess from the chirality of circularly polarized light (CPL) is pertinent to the study of the origin of homochirality in biomolecules. Such CPL-induced reactions, including both chirality generation and formation of partial enantiomeric imbalance, from nonchiral starting compounds have been known, however, only for the conversion of diarylolefins into chiral helicenes. In this study we synthesized three different prochiral molecules, each featuring a pair of photoisomerizable phenylazo moieties arranged symmetrically upon the phenyl rings of an sp-hybridized carbon atom (), the phenyl rings of [2.
View Article and Find Full Text PDFOrg Biomol Chem
March 2015
College of Chemistry, State Key Laboratory of Biotherapy, West China Medical School and State Key Laboratory of Polymer Materials Engineering, Sichuan University, 29 Wangjiang Road, Chengdu 610064, China.
Cyclic nigerosylnigerose (CNN), a saucer-shaped cyclic tetrasaccharide with a shallow concave surface, was reacted with pyromellitic dianhydride in 1:2 and 1:4 ratios to give two CNN-based polymers of different degrees of crosslinking, both of which swelled upon soaking in water, acting as a ‘nanosponge’ (NS). These NSs evolved several phases from isotropic solution to flowing and rigid gels via suspension by gradually increasing the concentration in water. The CNN-NSs thus prepared effectively mediated the enantiodifferentiating photoisomerization of (Z)-cyclooctene (1Z) to chiral (E)-isomer (1E).
View Article and Find Full Text PDFChem Commun (Camb)
May 2013
College of Chemistry, Sichuan University, Chengdu 610064, PR China.
Pyromellitate-bridged cyclodextrin nanosponges (CDNSs) evolved from sol into gel state upon gradual increase of the concentration from 0.2 to 2000 mg mL(-1) in water. The enantiodifferentiating geometrical photoisomerizations of (Z)-cyclooctene and (Z,Z)-1,3-cyclooctadiene sensitized by CDNS at various concentrations were critically affected by the phase transition of CDNS to afford the corresponding (E)- and (E,Z)-isomers in the highest enantiomeric excesses in the gel state.
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