Highly enantiodifferentiating photoisomerization of cyclooctene by congested and/or triplex-forming chiral sensitizers

Inoue, Yoshihisa; Yamasaki, Noritsugu; Yokoyama, Taizo; Tai, Akira

doi:10.1021/jo00057a009

Cited by 62 publications

(58 citation statements)

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“…Equation 1 indicates that the logarithm of k S /k R is proportional to reciprocal temperature, and that the activation parameters (∆∆H ‡ S-R and ∆∆S ‡ S-R ) can be calculated from the slope and intercept of the ln(k S /k R )-versus-1/T plot. Hence, the enantiodifferentiating photoisomerization of 1Z sensitized by a variety of chiral sensitizers was performed at several temperatures to give 1E in varying ee's, and the ln(k S /k R ) value was plotted against the reciprocal temperature to give an excellent straight line for each sensitizer [6][7][8][9]. Typical absolute ∆∆H ‡ S-R and T∆∆S ‡ S-R values obtained for non-ortho sensitizers are <0.1 and <0.2 kcal•mol -1 , respectively, while those for ortho sensitizers are as high as 0.5-1.1 and 0.5-3.5 kcal•mol -1 , respectively.…”

Section: Temperature Switchingmentioning

confidence: 99%

“…Indeed, a great deal of effort has been devoted to the enantio-and diastereodifferentiating photochemical reactions, which afford good to excellent enantomeric excesses (ee's) and diastereomeric excesses (de's), using diverse chiral sensitizers and auxiliaries, respectively [2][3][4]. A more intriguing phenomenon, as revealed by the mechanistic investigation of asymmetric photosensitizations is the inversion of product chirality; induced by the alteration of environmental factors such as temperature [6][7][8][9][10][11][12][13], pressure [14], solvent [15], and substrate concentration [16]. The chirality switching behavior is not only of mechanistic interest but also of particular practical importance, since such a switching enables us to control the chirality and optical yield of the photoproduct simply by maneuvering these entropy-related external factors, affording both enantiomers without using the antipodal chiral sources.…”

Section: Introductionmentioning

confidence: 99%

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Vital role of entropy in photochirogenesis

Inoue¹,

Sugahara

Wada

2001

Pure and Applied Chemistry

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The effects of temperature, pressure, solvent, and substrate concentration upon several enantio-and diastereodifferentiating photochemical reactions have been investigated and discussed in detail. These entropy-related external factors, which manipulate the weak electronic and steric interactions in the excited state, dynamically control the stereochemical outcome of asymmetric photochemical reactions, and even switch the product chirality. A global view on the "entropy chemistry" and its potential applications are also discussed.

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Section: Temperature Switchingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Vital role of entropy in photochirogenesis

Inoue¹,

Sugahara

Wada

2001

Pure and Applied Chemistry

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“…In the previous studies, we systematically investigated the enantiodifferentiating photoisomerization of 1Z using a wide variety of chiral sensitizers to reveal a significant correlation between the sensitizer structure and the ee of 1E produced. In general, aromatic sensitizers multiply substituted by bulky chiral auxiliaries with the stereogenic center located closer to the chromophore are more advantageous in inducing high enantioselectivity, presumably as a result of the congested arrangement of chiral auxiliaries around the sensitizing aromatic moiety . External factors, such as temperature, solvent, and pressure, also affect the enantioselectivity …”

Section: Resultsmentioning

confidence: 99%

Supramolecular Photochirogenesis with Novel Cyclic Tetrasaccharide: Enantiodifferentiating Photoisomerization of (Z)‐Cyclooctene with Cyclic Nigerosylnigerose‐Based Sensitizers

et al. 2012

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Isophthalic and terephthalic acid monoesters of cyclic nigerosyl-(1→6)-nigerose (CNN), a cyclic tetrasaccharide composed of four d-glucopyranosyl residues connected by alternating α-1,3- and α-1,6-linkages, were synthesized as novel chiral supramolecular sensitizers for enantiodifferentiating photoisomerization of (Z)-cyclooctene (1Z) to planar chiral (E)-isomer (1E). Despite the saucer-shaped shallow cavity of CNN that does not immediately guarantee strong ground-state interactions with 1Z, the sensitizer-appended CNNs afforded optically active 1E in such enantiomeric excesses that are much improved than those obtained with an α-cyclodextrin analog and comparable with those obtained with a β-cyclodextrin analog. Interestingly, the enantiomeric excess values obtained were a critical function of temperature and solvent to show an inversion of the product chirality by changing the environmental variants. Nevertheless, all of the differential activation parameters calculated from the temperature-dependent enantiomeric excesses gave an excellent compensatory enthalpy-entropy relationship, indicating an operation of a single enantiodifferentiating mechanism in the present chiral photosensitization with modified CNNs.

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“…This method has been used in photochemical Diels-Alder (Scheme 21) [89] in isomerization reactions [90][91][92][93][94][95][96], and in some other photochemical reactions [97][98].…”

Section: Chiral Photosensitizersmentioning

confidence: 99%

Concepts of Stereoselective Photochemistry and a Case Study: the Paterno-Buchi Reaction

D’Auria¹,

Racioppi

2009

COC

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The main methods reported in literature to obtain stereoselective photochemical reaction is reviewed. The most important approached attempted to obtain stereoselective photochemical reaction are:1.) the use of diastereoselective photochemical reactions, 2.) the use of molecules with prevented mobility (this approach can be obtained 1. introducing chiral auxiliary, 2. introducing chiral molecules in the reaction mixture able to give complexes with a reduced mobility, 3. performing the reaction in organized media such as zeolites or cyclodextrins, 4. performing the reaction on single crystal, 5. performing the reaction on single crystals of molecules able to give crystal in chiral space group, and, 6. finally performing the reaction in solid phase on inclusion complexes of the substrate with chiral molecules); 3.) using chiral solvents and chiral light, and 4.) using chiral photosensitizers.The case of the diastereoselective Paternò-Büchi reaction on furan derivatives is also discussed.

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Highly enantiodifferentiating photoisomerization of cyclooctene by congested and/or triplex-forming chiral sensitizers

Cited by 62 publications

References 0 publications

Vital role of entropy in photochirogenesis

Vital role of entropy in photochirogenesis

Supramolecular Photochirogenesis with Novel Cyclic Tetrasaccharide: Enantiodifferentiating Photoisomerization of (Z)‐Cyclooctene with Cyclic Nigerosylnigerose‐Based Sensitizers

Concepts of Stereoselective Photochemistry and a Case Study: the Paterno-Buchi Reaction

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