Ein völlig radikaler Zugang zur Stereoselektivitätskontrolle: Kupplung von prochiralen Radikalen mit chiralen Nitroxylradikalen

Braslau, Rebecca; Burrill, Leland C.; Mahal, Lara K.; Wedeking, Todd

doi:10.1002/ange.19971090310

Cited by 9 publications

(1 citation statement)

References 25 publications

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“…Diastereomeric excess has been previously noted fors tereoisomeric alkoxyamines upon reversible homolysis andc oupling, [65,66] by which an achiral nitroxide radical couples to a chiral carbon-centered radical ( Figure 10 A). However,n one of the so-far-investigated diastereomeric acyclica lkoxyamines 8-10,d escribed by Marque and Ananchenko, [67] Moad and Rizzardo, [68] and Georges, [69] exhibited large diastereomericp references on thermal homolysis/radical coupling reactions.…”

Section: Discussionmentioning

confidence: 99%

Unique Stereoselective Homolytic C−O Bond Activation in Diketopiperazine‐Derived Alkoxyamines by Adjacent Amide Pyramidalization

Amatov

Jangra

Pohl

et al. 2018

Chemistry A European J

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Simple monocyclic diketopiperazine (DKP)-derived alkoxyamines exhibit unprecedented activation of a remote C-O bond for homolysis by amide distortion. The combination of strain-release-driven amide planarization and the persistent radical effect (PRE) enables a unique, irreversible, and quantitative trans→cis isomerization under much milder conditions than typically observed for such homolysis-limited reactions. This isomerization is shown to be general and independent of the steric and electronic nature of both the amino acid side chains and the substituents at the DKP nitrogen atoms. Homolysis rate constants are determined, and they significantly differ for both the labile trans diastereomers and the stable cis diastereomers. To reveal the factors influencing this unusual process, structural features of the kinetic trans diastereomers and thermodynamic cis diastereomers are investigated in the solid state and in solution. X-ray crystallographic analysis and computational studies indicate substantial distortion of the amide bond from planarity in the trans-alkoxyamines, and this is believed to be the cause for the facile and quantitative isomerization. Thus, these amino-acid-derived alkoxyamines are the first examples that exhibit a large thermodynamic preference for one diastereomer over the other upon thermal homolysis, and this allows controlled switching of configurations and configurational cycling.

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Section: Discussionmentioning

confidence: 99%

Unique Stereoselective Homolytic C−O Bond Activation in Diketopiperazine‐Derived Alkoxyamines by Adjacent Amide Pyramidalization

Amatov

Jangra

Pohl

et al. 2018

Chemistry A European J

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Readily Accessible Oxazolidine Nitroxyl Radicals: Bifunctional Cocatalysts for Simplified Copper Based Aerobic Oxidation

Gartshore

Lupton

2010

Adv Synth Catal

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Using a two-step procedure a range of bifunctional oxazolidine nitroxyl radicals have been prepared. The application of these co-catalysts to the copper-based aerobic oxidation of alcohols was then investigated. From these studies it was found that the parent tetramethyloxazolidine nitroxyl radical L1 was competent for oxidation in the presence of 2,2'-bipyridine, and the bifunctional pyridyl-containing nitroxyl radicals L2 and L3 could be used in the absence of additional coordinating ligands. Following optimization, the scope of this simplified transformation was explored, demonstrating that a range of primary and secondary benzylic alcohols are readily oxidized. In addition, the oxidation of allylic alcohols and hydroquinone can be achieved.

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Catalyst‐Controlled Highly Selective Coupling and Oxygenation of Olefins: A Direct Approach to Alcohols, Ketones, and Diketones

Sun

et al. 2013

Angewandte Chemie

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Ein völlig radikaler Zugang zur Stereoselektivitätskontrolle: Kupplung von prochiralen Radikalen mit chiralen Nitroxylradikalen

Cited by 9 publications

References 25 publications

Unique Stereoselective Homolytic C−O Bond Activation in Diketopiperazine‐Derived Alkoxyamines by Adjacent Amide Pyramidalization

Unique Stereoselective Homolytic C−O Bond Activation in Diketopiperazine‐Derived Alkoxyamines by Adjacent Amide Pyramidalization

Readily Accessible Oxazolidine Nitroxyl Radicals: Bifunctional Cocatalysts for Simplified Copper Based Aerobic Oxidation

Catalyst‐Controlled Highly Selective Coupling and Oxygenation of Olefins: A Direct Approach to Alcohols, Ketones, and Diketones

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