Scoping the triphasic/PTC conditions for the Juliá–Colonna epoxidation reaction

Geller, Thomas; Krüger, Christa M.; Militzer, Hans‐Christian

doi:10.1016/j.tetlet.2004.04.189

Cited by 36 publications

(14 citation statements)

References 9 publications

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“…24 Efforts in phase transfer catalysis have previously been undertaken with regards to the Julia−Colonna epoxidation, specifically in the use of additives to increase the concentration of peroxide in the organic layer. 25 Building on this approach, the authors synthesized poly(Leu) peptides with an imidazolium-containing initiator to form peptide 2.3a (Figure 2a). When comparing this catalyst to the poly(Leu) peptide synthesized with n-butylamine as an initiator (2.3b) in the epoxidation of 2.1, imidazolium-containing 2.3a provided epoxide 2.2 in substantially higher yield and enantioselectivity (Figure 2b).…”

Section: Oxidationmentioning

confidence: 99%

Asymmetric Catalysis Mediated by Synthetic Peptides, Version 2.0: Expansion of Scope and Mechanisms

et al. 2020

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Low molecular weight synthetic peptides have been demonstrated to be effective catalysts for an increasingly wide array of asymmetric transformations. In many cases, these peptide-based catalysts have enabled novel multifunctional substrate activation modes and unprecedented selectivity manifolds. These features, along with their ease of preparation, modular and tunable structures, and often biomimetic attributes make peptides well-suited as chiral catalysts, and of broad interest. Many examples of peptide-catalyzed asymmetric reactions have appeared in the literature since the last survey of this broad field in Chemical Reviews (Chem. Rev. 2007, 107, 5759-5812). The overarching goal of this new review is to provide a comprehensive account of the numerous advances in the field. As a corollary to this goal, we survey the many different types of catalytic reactions, ranging from acylation to C-C bond formation, in which peptides been successfully employed. In so doing, we devote significant discussion to the structural and mechanistic aspects of these reactions that are perhaps specific to peptide-based catalysts and their interactions with substrates and/or reagents.

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Section: Oxidationmentioning

confidence: 99%

Asymmetric Catalysis Mediated by Synthetic Peptides, Version 2.0: Expansion of Scope and Mechanisms

et al. 2020

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“…Moreover, when PPL was synthesized by polymerization at higher temperatures, it proved to be more active than the ''normal'' PLL (which was used at 0.01 mol% in the presence of TBAB), and afforded the epoxide of trans-chalcone in 60% yield and 80% ee. These new triphasic/PTC conditions were successfully scaled up to the 100 g substrate level, which permitted differently substituted enones to be epoxidized under triphasic/PTC conditions with a high yield, a good to high ee-value, and short reaction times [70].…”

Section: Polyamino Acidsmentioning

confidence: 99%

Asymmetric Epoxidations of α,β‐Unsaturated Carbonyl Compounds

Lattanzi

2010

Catalytic Asymmetric Conjugate Reactions

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The asymmetric epoxidation of alkenes is a fundamental process in organic synthesis, and unquestionably the most exploited approach to synthesize epoxides [1]. Alternative useful strategies to access these molecules concern the enantioselective alkylidenation of carbonyl compounds by ylides [2] and the Darzens condensation [3]. Enantioenriched epoxides are important targets of biological and pharmaceutical interest. Moreover, their high synthetic potential as intermediates is exemplified by the stereoselective ring opening with nucleophiles, which affords a variety of compounds with two contiguous chiral centers, the absolute configuration of which can be controlled [4].During the past few decades, metal-based electrophilic asymmetric methodologies of epoxidation have been successfully developed and found widespread application in multistep synthesis; these include: the Sharpless' epoxidation of allylic alcohols mediated by the Ti/tartrate system [5]; and the Jacobsen's and Katsuki's epoxidation of unfunctionalized alkenes by using Mn-and Ti-/Salen complexes [6]. More recently, chiral Ru-Pt and Fe-Pt complexes have proved to be effective in the enantioselective epoxidation of disubstituted aromatic and challenging terminal unfunctionalized alkenes [7]. Impressive results have been achieved by the groups of Yang [8] and Shi [9] for the electrophilic organocatalyzed asymmetric epoxidation of a great variety of olefins such as trisubstituted, disubstituted trans-alkenes, terminal alkenes, dienes, and enynes (to cite the most relevant examples), and by the in situ generation of dioxiranes derived from chiral ketones. Within the context of asymmetric epoxidation catalyzed by organic promoters, notable achievements have also been attained by using chiral oxaziridines [10], oxaziridinium salts [11], amines [12], and peptide-based peracids [13].The epoxidation of α,β-unsaturated carbonyl compounds leads to the formation of another valuable class of functionalized epoxides [14], the carbonyl and epoxide groups of which can be selectively manipulated to provide enantioenriched products such as allylic epoxy alcohols, α-or β-hydroxy ketones, and α,β-epoxy esters [15]. The general approach for the epoxidation of electron-poor Catalytic Asymmetric Conjugate Reactions. Edited by Armando Córdova

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“…Researchers at Bayer AG addressed these critical issues and developed successful solutions enabling commercial application of Julia-Colonna-type epoxidation [35][36][37][38][39][40]. Starting with optimization of catalyst preparation, a straightforward synthesis based on inexpensive reagents and requiring a shorter reaction time was developed for the poly-Leu-catalyst [35].…”

Section: Enantioselectivity Conversion and Catalytic Loadingmentioning

confidence: 99%

“…Starting with optimization of catalyst preparation, a straightforward synthesis based on inexpensive reagents and requiring a shorter reaction time was developed for the poly-Leu-catalyst [35]. Furthermore, the catalyst prepared by the ''Bayer route'' is much more active and does not require preactivation [35][36][37][38][39][40]. Furthermore, the catalyst prepared by the ''Bayer route'' is much more active and does not require preactivation [35][36][37][38][39][40].…”

Section: Enantioselectivity Conversion and Catalytic Loadingmentioning

confidence: 99%

“…It was found that the reaction was strongly enhanced when performed in the presence of a phasetransfer catalyst as achiral additive [35][36][37][38][39][40]. It was found that the reaction was strongly enhanced when performed in the presence of a phasetransfer catalyst as achiral additive [35][36][37][38][39][40].…”

Section: Enantioselectivity Conversion and Catalytic Loadingmentioning

confidence: 99%

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