A new procedure for the Juliá–Colonna stereoselective epoxidation reaction under non-aqueous conditions: the development of a catalyst comprising polyamino acid on silica (PaaSiCat)

Geller, Thomas; Roberts, Stanley M.

doi:10.1039/a903219c

Cited by 74 publications

(31 citation statements)

References 10 publications

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“…Fast zwei Jahrzehnte später wurde ein verbessertes Verfahren verçffentlicht, das einen unlçslichen Katalysator in einem nichtwässrigen Lçsungsmittel -in Kombination mit einem Harnstoff-Wasserstoffperoxid-Komplex (UHP) als Oxidationsmittel und DBU als Base -umfasste. [16] 2.2. [14] Probleme durch nichtkatalysierte Epoxidierungen als Hintergrundreaktionen wurden durch Verwendung von Natriumpercarbonat sowohl als Base als auch als Oxidationsmittel umgangen (Bedingungen C).…”

Section: Epoxidierung Von Elektronenarmen Ab-ungesättigten Ketonenunclassified

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Organokatalytische asymmetrische Epoxidierungen – Reaktionen, Mechanismen und Anwendungen

Davis¹,

Stiller²,

Naicker³

et al. 2014

Angewandte Chemie

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Chirale Epoxide sind vielseitige Bausteine in der Synthese komplexer organischer Gerüste. Durch die hohe Spannung ihres dreigliedrigen Rings können Epoxide eine Reihe von nucleophilen Ringöffnungsreaktionen eingehen. Nach der Entwicklung der Sharpless‐Epoxidierung folgten zahlreiche wichtige Fortschritte, und das rasch aufstrebende Feld der asymmetrischen Organokatalyse stellt nun Katalysatoren für die Epoxidierung eines breiten Spektrums an ungesättigten Carbonylverbindungen bereit. In diesem Kurzaufsatz sind jüngste Entwicklungen auf dem Gebiet organokatalytischer asymmetrischer Epoxidierungen zusammengefasst. Die vorgeschlagenen Reaktionsmechanismen werden beschrieben, und Anwendungen werden beschrieben.

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Section: Epoxidierung Von Elektronenarmen Ab-ungesättigten Ketonenunclassified

“…[15] Die Adsorption des Polypeptids an Siliciumdioxid lieferte schließlich einen leicht wiederverwendbaren Katalysator, der eine hohe Aktivität und eine verbesserte Stereoselektivität aufwies (Bedingungen D). [16]…”

Section: Epoxidierung Von Elektronenarmen Ab-ungesättigten Ketonenunclassified

Organokatalytische asymmetrische Epoxidierungen – Reaktionen, Mechanismen und Anwendungen

Davis¹,

Stiller²,

Naicker³

et al. 2014

Angewandte Chemie

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“…This very simple methodology furnished a robust catalyst, which was employed in several epoxidation reactions with a high level of enantioselectivity and without loss of activity and enantioselectivity after several cycles [12] . Such an immobilization strategy is certainly one of the simplest approaches for obtaining a recyclable material since the procedure is based on mixing unmodifi ed amorphous silica gel and pLL followed by fi ltration.…”

Section: Noncovalently Linked: Silicamentioning

confidence: 99%

Recyclable Organocatalysts in Asymmetric Reactions

Gruttadauria

Giacalone

Noto

2011

Catalytic Methods in Asymmetric Synthesis

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“…As a result of these modifications, in both cases a significant reduction in reaction time was observed, the catalyst loading could be reduced to 5 mol%, and the epoxidation of enolizable enones proved equally feasible as those enones with alkyl groups at the β-position. Under such two-phase conditions, the recovery of PLL was enhanced by adsorbing the catalyst onto silica for flash chromatography [62]. Those epoxidations which used the silica-adsorbed poly-l-leucine (PLL) produced better rates of conversion and higher ee-values, while the catalyst loading could be reduced to 2.5 mol% and the catalyst completely recycled.…”

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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A new procedure for the Juliá–Colonna stereoselective epoxidation reaction under non-aqueous conditions: the development of a catalyst comprising polyamino acid on silica (PaaSiCat)

Cited by 74 publications

References 10 publications

Organokatalytische asymmetrische Epoxidierungen – Reaktionen, Mechanismen und Anwendungen

Organokatalytische asymmetrische Epoxidierungen – Reaktionen, Mechanismen und Anwendungen

Recyclable Organocatalysts in Asymmetric Reactions

Asymmetric Epoxidations of α,β‐Unsaturated Carbonyl Compounds

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