Enantioselective Organo‐Photocatalysis Mediated by Atropisomeric Thiourea Derivatives

Vallavoju, Nandini; Selvakumar, Sermadurai; Jockusch, Steffen; Sibi, Mukund P.; Sivaguru, Jayaraman

doi:10.1002/anie.201310940

Cited by 163 publications

(85 citation statements)

References 32 publications

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“…6,7 To date, only a handful of systems have been able to deliver high ee’s in primary photoreactions at reasonably low concentrations of chiral catalyst (e.g., >80% ee at <10 mol%). 8 Arguably the most well-established of these are chiral hydrogen-bonding organic photosensitizers developed by Bach 9 and Sivaguru, 10 both of which feature photosensitizing chromophores functionalized with a hydrogen-bonding moiety that orients a polar, achiral organic substrate within the stereocontrolling environment of the chiral photosensitizer (Scheme 1). Notably, the photocatalytic moieties in both systems are organic chromophores.…”

Section: Introductionmentioning

confidence: 99%

Enantioselective Excited-State Photoreactions Controlled by a Chiral Hydrogen-Bonding Iridium Sensitizer

et al. 2017

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Stereochemical control of electronically excited states is a long-standing challenge in photochemical synthesis, and few catalytic systems that produce high enantioselectivities in triplet-state photoreactions are known. We report herein an exceptionally effective chiral photocatalyst that recruits prochiral quinolones using a series of hydrogen-bonding and π–π interactions. The organization of these substrates within the chiral environment of the transition metal photosensitizer leads to efficient Dexter energy transfer and effective stereoinduction. The relative insensitivity of these organometallic chromophores towards ligand modification enables the optimization of this catalyst structure for high enantiomeric excess (ee) at catalyst loadings as much as 100-fold lower than the optimal conditions reported for analogous chiral organic photosensitizers.

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Section: Introductionmentioning

confidence: 99%

Enantioselective Excited-State Photoreactions Controlled by a Chiral Hydrogen-Bonding Iridium Sensitizer

et al. 2017

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“…[23] This catalyst was proposed to operate in asimilar manner to that of oxazaborolidine catalysts in that abathochromatic absorption shift occurs upon substrate binding. It was proposed that the catalyst engages in adual hydrogen-bonding interaction with the substrate according to the model (46)i llustrated in Scheme 7.…”

Section: Methodsmentioning

confidence: 99%

“…[17] Thus,u pon exposure of the quinoline 17 to the catalyst 24 and visible-light irradiation, the cyclobutane 18 was formed in good yield and excellent enantioselectivity.Avariety of other quinoline substrates which bear different tether substituents and alkene substitution patterns were tolerated (products [19][20][21]23). Ac losely related pre-transition-state assembly (25)tothat illustrated in Scheme 2, is likely operative with 24.…”

Section: Energy Transfermentioning

confidence: 99%

Cyclobutane and Cyclobutene Synthesis: Catalytic Enantioselective [2+2] Cycloadditions

2015

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Cyclobutanes and cyclobutenes are important structural motifs found in numerous biologically significant molecules, and they are useful intermediates for chemical synthesis. Consequently, [2+2] cycloadditions to access cyclobutanes and cyclobutenes have been established to be particularly useful transformations. Within the last 10 years, an increase in the frequency of publications for catalytic enantioselective [2+2] cycloadditions has occurred. These reactions provide access to a wide array of enantiomerically enriched chemical diversity that was not previously attainable. Described in this review are the advances made in catalytic enantioselective [2+2] cycloadditions to access cyclobutanes and cyclobutenes.

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“…[64] The thiourea moiety hydrogen-bonds to the carbonyl group of 39, while the binaphthyl part functions as a built-in chiral photosensitizer. The binding affinities of 39 to 41 are modest, with the combination of 39a and 41a showing an association constant of 84 M -1 in methylcyclohexane.…”

Section: Catalytic Supramolecular Photochirogenesis With Chiral Templmentioning

confidence: 99%

Catalytic Supramolecular Photochirogenesis

Yan¹,

Wu²,

Yang³

et al. 2015

Supramolecular Catalysis

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Supramolecular photochirogenesis is a new strategy for circumventing the inherent difficulties encountered in conventional photochirogenesis, i.e. the interactions associated with geometrically less-defined, short-lived excited states, by confining a prochiral substrate(s) in a chiral supramolecular environment(s) prior to photoexcitation. This rather simple, but very successful, strategy has been applied to a variety of chiral photoreactions. However, a stoichiometric, or even excess amount of supramolecular host is often needed to ensure full complexation of the substrate, and achieve the optimum stereochemical outcome. This apparent drawback has recently been removed by introducing a sensitizing moiety to the supramolecular host, or by bathochromically shifting the absorption band of substrate through Lewis acid, or charge-transfer complexation. Recent progress in catalytic supramolecular photochirogenesis will be reviewed.

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Enantioselective Organo‐Photocatalysis Mediated by Atropisomeric Thiourea Derivatives

Cited by 163 publications

References 32 publications

Enantioselective Excited-State Photoreactions Controlled by a Chiral Hydrogen-Bonding Iridium Sensitizer

Enantioselective Excited-State Photoreactions Controlled by a Chiral Hydrogen-Bonding Iridium Sensitizer

Cyclobutane and Cyclobutene Synthesis: Catalytic Enantioselective [2+2] Cycloadditions

Catalytic Supramolecular Photochirogenesis

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