Oxidation of Natural Targets by Dioxiranes. 3.1 Stereoselective Synthesis of (all-R)-Vitamin D3 Triepoxide and of Its 25-Hydroxy Derivative

Curci, Ruggero; Detomaso, Antonia; Prencipe, Teresa; Carpenter, Gene B.

doi:10.1021/ja00097a018

Cited by 36 publications

(16 citation statements)

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“…In the case of 72 , a combination of the electron-withdrawing influence of the epoxides and the sterically hindered C17 and C20 positions, results in selective oxidation at C25. [92] In this example, there is a tertiary position which is both distal from EWGs and relatively unhindered and consequently this position is selectively oxidized with TFDO.…”

Section: Case Studiesmentioning

confidence: 99%

If CH Bonds Could Talk: Selective CH Bond Oxidation

2011

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C–H oxidation has a long history and an ongoing presence in research at the forefront of chemistry and interrelated fields. As such, numerous highly useful texts and reviews have been written on this subject. Logically, these are generally written from the perspective of the scope and limitations of the reagents employed. This minireview instead attempts to emphasize chemoselectivity imposed by the nature of the substrate. Consequently many landmark discoveries in the field of C–H oxidation are not discussed, but hopefully the perspective taken herein will allow for the more ready incorporation of C–H oxidation reactions into synthetic planning.

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Section: Case Studiesmentioning

confidence: 99%

If CH Bonds Could Talk: Selective CH Bond Oxidation

2011

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“…Asymmetric epoxidations of prochiral alkenes provide versatile intermediates for the synthesis of functionalized optically active organic substances. During the last decade, a number of new stereoselective epoxidation methods have been developed, including highly effective catalytic processes. − We wish to understand the source of chiral discrimination in these reactions, and to design even more effective catalysts, through a detailed mapping of the transition structures of these reactions.…”

Section: Introductionmentioning

confidence: 99%

Transition States of Epoxidations: Diradical Character, Spiro Geometries, Transition State Flexibility, and the Origins of Stereoselectivity

et al. 1997

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The transition structures for the epoxidations of ethylene by performic acid, dioxirane, oxaziridine, and peroxynitrous acid have been located with density functional theory methods using the Becke3LYP functional and 6-31G* basis set. All of the epoxidations have spiro transition states; those with performic acid and dioxirane are early and involve synchronous oxygen transfer, while those with oxaziridine and peroxynitrous acid are later with asynchronous oxygen transfer. The results from Becke3LYP/6-31G* theory are compared with MP2/6-31G* literature values. Substitution on ethylene by methoxy, methyl, vinyl, and cyano groups changes the transition state geometries toward asynchronous spiro structures. The activation energies are lowered by all substituents except the cyano group in reactions of performic acid and dioxirane. Experimental stereoselectivities are rationalized by using transition structure models based upon these transition structures.

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“…Bei 72 führt eine Kombination des elektronenziehenden Einflusses der Epoxide und der sterisch gehinderten C17-und C20-Positionen zur selektiven Oxidation an C25. [92] In diesem Beispiel gibt es eine tertiäre Position, die sowohl von den EWGs weit genug entfernt als auch verhältnismäßig ungehindert ist und infolgedessen mit TFDO selektiv oxidiert wird.…”

Section: -Zentrenunclassified

Wenn C‐H‐Bindungen sprechen könnten – selektive Oxidationen von C‐H‐Bindungen

2011

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Die C‐H‐Oxidation hat eine lange Geschichte und ist seit jeher Teil der Spitzenforschung in der Chemie und verwandten Gebieten. Folgerichtig wurde bereits eine große Zahl sehr nützlicher Originalbeiträge und Übersichten zu diesem Thema veröffentlicht. Logischerweise wurden diese Artikel im Allgemeinen mit Blick auf die Anwendungsmöglichkeiten und Grenzen der verwendeten Reagentien geschrieben. Ziel dieses Kurzaufsatzes ist es hingegen, stattdessen die durch die Eigenschaften der Substrate hervorgerufene Chemoselektivität herauszuarbeiten. Dies bringt es mit sich, dass viele bahnbrechende Entdeckungen auf dem Gebiet der C‐H‐Oxidationen nicht behandelt werden; die hier eingenommene Sichtweise wird aber hoffentlich eine schnellere Aufnahme von C‐H‐Oxidationsreaktionen in Syntheseplanungen ermöglichen.

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Oxidation of Natural Targets by Dioxiranes. 3.1 Stereoselective Synthesis of (all-R)-Vitamin D3 Triepoxide and of Its 25-Hydroxy Derivative

Cited by 36 publications

References 0 publications

If CH Bonds Could Talk: Selective CH Bond Oxidation

If CH Bonds Could Talk: Selective CH Bond Oxidation

Transition States of Epoxidations: Diradical Character, Spiro Geometries, Transition State Flexibility, and the Origins of Stereoselectivity

Wenn C‐H‐Bindungen sprechen könnten – selektive Oxidationen von C‐H‐Bindungen

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