Use of a confined space (zeolite) in enantio- and diastereo-selective photoreactions

Shailaja, J.; Sivaguru, Jayaraman; Uppili, Sundararajan; Joy, Abraham; Ramamurthy, V.

doi:10.1016/s1387-1811(01)00348-1

Cited by 19 publications

(9 citation statements)

References 17 publications

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“…A remarkable enhanced diastereoselection for the ene pathway was also reported by our group [73] in the photooxygenation of the monoterpene (R)-(-)-α-phellandrene (54). The oxygenated products for the reaction of 54 with 1 O 2 in solution [74] are the two diastereoisomeric endoperoxides 54a and 54b (major products), while five isomeric ene adducts (54c-g) are formed in various amounts ( Table 9).…”

Section: Diastereoselectivity-induced By a Remote Chiral Substituentsupporting

confidence: 67%

“…By suitably mixing chiral compounds such as (-)-ephedrine, (-)-pseudoephedrine or (-)-norephedrine, a "chiral zeolite" can be produced. Ramamurthy and co-workers have successfully used this approach to perform a variety of enantioselective photochemical reactions with Na-Y, obtaining remarkable enantioselectivities in certain cases [54]. The attempts to achieve an enantioselective photooxygenation within a chirally-modified zeolite Na-Y are very limited.…”

Section: Intrazeolite Asymmetric Phootoxyge-nation Of Alkenesmentioning

confidence: 99%

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Oxyfunctionalization of Alkenes by Dye-Sensitized Intrazeolite Photooxygenation

Stratakis

2005

COS

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Section: Diastereoselectivity-induced By a Remote Chiral Substituentsupporting

confidence: 67%

Section: Intrazeolite Asymmetric Phootoxyge-nation Of Alkenesmentioning

confidence: 99%

Oxyfunctionalization of Alkenes by Dye-Sensitized Intrazeolite Photooxygenation

Stratakis

2005

COS

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“…For zeolite-entrapped complexes, the steric and electrostatic constraint imposed on the complexes within the channels or cages of zeolites can alter the photochemical and photophysical properties of the guest complexes and diminish the photodegradation and undesirable electron transfer reactions. Rhenium complexes such as ReX(CO) 3 (bpy) (X ¼ Cl, Br and bpy ¼ 2,2¢-bipyridine) and Re(CO) 2 (bpy) [P(OEt) 3 ] 2 have been used as photocatalysts for CO 2 reduction to CO in a solvent mixture of triethanolamine(TEOA) and dimethylformamide(DMF) [15,16] so that their potential utility for photochemical activation of CO 2 has been steadily paid to attention to a purpose of construction of artificial photosynthetic systems [15][16][17]. Most studies on photochemical reduction of CO 2 using Re(I) complexes have focused on the homogeneous solution systems.…”

Section: Photocatalytic Activation Of Co 2 On Rhenium Complex Encapsumentioning

confidence: 99%

“…The unique and fascinating properties of molecular sieves involving transition metal ions within the molecular sieve frameworks or cavities have opened new possibilities for many applications, not only in catalysis [10][11][12][13] but also for various photochemical processes [14][15][16][17][18]. The transition metal ions in metallosilicate catalysts are considered to be highly dispersed at the atomic level and well defined, existing in a specific structure of the molecular sieve framework.…”

Section: Introductionmentioning

confidence: 99%

Photoreduction of Carbondioxide on Surface Functionalized Nanoporous Catalysts

et al. 2005

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Nanoporous photocatalysts have been designed to exhibit unique photocatalytic activities through framework substitution of titanium species or surface immobilization of rhenium complex onto mesoporous silica. This article summarizes recent work on the synthesis, characterization and photocatalytic activities of the designed porous photocatalysts performed by the present authors. Various spectroscopic investigations revealed that the photo-excited states of these catalysts play a vital role in the photocatalytic reactions and their photocatalytic reactivities are strongly dependent on structures of active sites, which are confined and immobilized in the restricted framework structure of the mesoporous silica. Highly dispersed titanium oxide species incorporated in the framework of mesoporous silica exhibited high and unique photocatalytic reactivity for the reduction of CO 2 with H 2 O to produce CH 4 and CH 3 OH under UV irradiation, its reactivity being much higher than bulk TiO 2 . The cationic rhenium(I) complex was encapsulated into a mesoporous AlMCM-41 material by ion-exchange method, yielding a visible light photocatalyst to be active for photocatalytic reduction of CO 2 .

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“…The results presented in Scheme 5, Scheme 6 and Scheme 7 show that electrocyclization can proceed in a stereoselective fashion within zeolites [62,63,64,65]. Maximum ee in the case of 6 and 7 (Scheme 5) was obtained with bifunctional chiral agents, suggesting that multipoint interaction is essential for chiral induction to occur within zeolites.…”

Section: Chiral Inductor As a Passive Co-guest: Chiral Induction Omentioning

confidence: 96%

Achiral Zeolites as Reaction Media for Chiral Photochemistry

Ramamurthy

2019

Molecules

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Obtaining enantiomerically-enriched photoproducts from achiral reactants has been a long-sought goal. The various methods developed to achieve chiral induction in photoproducts during the last fifty years still suffer from a lack of predictability, generality, and simplicity. With the current emphasis on green chemistry, obtaining enantiomerically enriched products via photochemistry is a likely viable alternative for the future. Of the various approaches developed during the last three decades, the one pioneered in the author’s laboratory involved the use of commercially-available and inexpensive achiral zeolites as the media. This approach does not use any solvent for the reaction. Examples from these studies are highlighted in this article. Since no chiral zeolites were available, when the work was initiated in the author’s laboratory, commercially-available zeolites X and Y were modified with chiral inductors so that the reaction space becomes chiral. The results obtained established the value of chirally-modified, commercial zeolites as media for achieving chiral induction in photochemical reactions. A recent report of the synthesis of a chiral zeolite is likely to stimulate zeolite-based chiral photochemistry in synthesizing enantiomerically-pure organic molecules. The availability of chiral zeolites in future is likely to energize research in this area. Our earlier observations on this topic, we believe, would be valuable for progress of the field. Keeping this in mind, I have summarized the work carried out in our laboratory on chiral photochemistry on chirally-modified zeolites. This review does not include examples where high chiral induction has been obtained via a strategy that examines molecules appended with chiral auxiliary within achiral and chirally-modified zeolites. The latter approach yields products with diastereomeric excess >80%.

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Use of a confined space (zeolite) in enantio- and diastereo-selective photoreactions

Cited by 19 publications

References 17 publications

Oxyfunctionalization of Alkenes by Dye-Sensitized Intrazeolite Photooxygenation

Oxyfunctionalization of Alkenes by Dye-Sensitized Intrazeolite Photooxygenation

Photoreduction of Carbondioxide on Surface Functionalized Nanoporous Catalysts

Achiral Zeolites as Reaction Media for Chiral Photochemistry

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