Palladium-polymer nanoreactors for the aqueous asymmetric synthesis of therapeutic flavonoids

Lestini, Elena; Blackman, Lewis D.; Zammit, Charlotte M.; Chen, T.; Williams, Rebecca J.; Inam, Maria; Couturaud, Benoit; O’Reilly, Rachel K.

doi:10.1039/c7py02050c

Cited by 23 publications

(22 citation statements)

References 34 publications

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“…A RAFT polymerisa- tion reaction, in this case, led to a polymeric backbone with terminal catalytic centres [58] (Scheme 20). The results obtained were consistent with those reported by O'Reilly using a polymeric backbone with catalytic centres inside the chain [56].…”

Section: Catalytic Systems Based On Pyridineoxazolines Ligandssupporting

confidence: 91%

“…In 2018, the very first heterogeneous catalytic system for the addition of arylboronic acids to cyclic enones was introduced by O'Reilly and co-workers [56]. The micellar nanoreactor was tested for the preparation of flavanones.…”

Section: Catalytic Systems Based On Pyridineoxazolines Ligandsmentioning

confidence: 99%

“…Later in 2020, Zhou et al used an analogous heterogeneous system as O'Reilly (cf. Table 28) [56,58]. A RAFT polymerisa- tion reaction, in this case, led to a polymeric backbone with terminal catalytic centres [58] (Scheme 20).…”

Section: Catalytic Systems Based On Pyridineoxazolines Ligandsmentioning

confidence: 99%

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Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

Bartáček¹,

Svoboda²,

Kocúrik³

et al. 2021

Beilstein J. Org. Chem.

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The transition metal (palladium)-catalysed asymmetric 1,4-addition of arylboronic acids to conjugated enones belong to the most important and emerging strategies for the construction of C–C bonds in an asymmetric fashion. This review covers known catalytic systems used for this transformation. For clarity, we are using the type of ligand as a sorting criterion. Finally, we attempted to create a flowchart facilitating the selection of a suitable ligand for a given combination of enone and arylboronic acid.

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Section: Catalytic Systems Based On Pyridineoxazolines Ligandssupporting

confidence: 91%

Section: Catalytic Systems Based On Pyridineoxazolines Ligandsmentioning

confidence: 99%

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Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

Bartáček¹,

Svoboda²,

Kocúrik³

et al. 2021

Beilstein J. Org. Chem.

View full text Add to dashboard Cite

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“…The generation of the catalyst involves the formation of polymeric core‐shell micelles which coordinates palladium with a chiral pyridinooxazoline ligand (Scheme 36). [92] These amphiphiles cat act as nanoreactors to promote asymmetric conjugate addition of aryl boronic acids to chromones in aqueous media. The employment of the catalytic species allowed to increase catalyst activity, achieving yields up to 98% and enantio‐selectivities up to 84% ee with low metal loadings and without any additive.…”

Section: Chiral Micellesmentioning

confidence: 99%

Nanoconfinement Effects of Micellar Media in Asymmetric Catalysis

et al. 2022

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Replacement of organic solvents, in particular chlorinated, aromatic, and polar aprotic ones, is an emerging issue that can find a solution in the development of catalytic reactions in water. Nature performs a multitude of chemical transformations in water under mild conditions mediated by enzymes. In particular the nanoconfinement effects of the enzymes ensure high activity and impressive stereoselectivities. Micellar catalysis is nowadays a real alternative approach to catalysis in traditional organic media, enabling good activity under mild conditions, with the advantage of possible catalyst and micellar medium recycling. Micellar media emerged also as good nano‐environments for stereoselective reactions, with many examples of chemical transformations mediated by metal and organo‐catalysts for which improvements of stereoselectivity were observed with respect to the same reaction under homogeneous conditions in traditional organic solvents. More specifically, both the catalytically active site and the micelles provided by the surfactant can contribute to the asymmetric induction, partially resembling what known in terms of stereoselectivity imparted by the active site of enzymes and metallo‐enzymes.

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“…10 Micelles can provide the solubility and protective environment for the lipophilic reactants, shielding them from the surrounding aqueous environment. 11 , 12 In recent years, significant progress in conducting organic transformation and specifically organometallic reactions in water has been reported by Lipshutz, 12 − 17 Meijer, 3 , 18 , 19 Unciti-Broceta, 5 , 20 − 24 Zimmerman, 25 − 27 O’Reilly, 28 , 29 and others. 30 − 34 The ability to perform organometallic reactions in aqueous media can contribute significantly to increasing the sustainability of organic synthesis by reducing the usage of organic solvents.…”

Section: Introductionmentioning

confidence: 99%

Tuning the Reactivity of Micellar Nanoreactors by Precise Adjustments of the Amphiphile and Substrate Hydrophobicity

et al. 2021

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Polymeric assemblies, such as micelles, are gaining increasing attention due to their ability to serve as nanoreactors for the execution of organic reactions in aqueous media. The ability to conduct organic transformations, which have been traditionally limited to organic media, in water is essential for the further development of important fields ranging from green catalysis to bioorthogonal chemistry. Considering the recent progress that has been made to expand the range of organometallic reactions conducted using nanoreactors, we aimed to gain a deeper understanding of the roles of the hydrophobicity of both the core of micellar nanoreactors and the substrates on the reaction rates in water. Toward this goal, we designed a set of five metal-loaded micelles composed of polyethylene glycol–dendron amphiphiles and studied their ability to serve as nanoreactors for a palladium-mediated depropargylation reaction of four substrates with different log P values. Using dendrons as the hydrophobic block, we could precisely tune the lipophilicity of the nanoreactors, which allowed us to reveal linear correlations between the rate constants and the hydrophobicity of the amphiphiles (estimated by the dendron’s cLog P ). While exponential dependence was obtained for the lipophilicity of the substrates, a similar degree of rate acceleration was observed due to the increase in the hydrophobicity of the amphiphiles regardless of the effect of the substrate’s log P . Our results demonstrate that while increasing the hydrophobicity of the substrates may be used to accelerate reaction rates, tuning the hydrophobicity of the micellar nanoreactors can serve as a vital tool for further optimization of the reactivity and selectivity of nanoreactors.

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Palladium-polymer nanoreactors for the aqueous asymmetric synthesis of therapeutic flavonoids

Abstract: Polymeric core–shell micelles incorporating a chiral palladium pyridinooxazoline catalyst are presented as nanoreactors for the aqueous asymmetric synthesis of flavanones, a class of flavonoids, with therapeutic properties.

Cited by 23 publications

References 34 publications

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

Nanoconfinement Effects of Micellar Media in Asymmetric Catalysis

Tuning the Reactivity of Micellar Nanoreactors by Precise Adjustments of the Amphiphile and Substrate Hydrophobicity

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