Oxidation with chromium(VI) complexes: Difference between revisions

Revision as of 15:13, 17 November 2024

Revision as of 15:17, 17 November 2024

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==Scope and limitations==

Buffering agents may be used to prevent acid-labile protecting groups from being removed during chromium(VI)-amine oxidations. However, buffers will also slow down oxidative cyclizations, leading to selective oxidation of alcohols over any other sort of oxidative transformation. Citronellol, for instance, which cyclizes to pugellols in the presence of PCC, does not undergo cyclization when buffers are used.<ref>Fieser, L. F.; Fieser, M. ''Reagents for Organic Synthesis''; Wiley-Interscience, New York, 1979, '''7''', 309.</ref><ref name=whatup>Babler,{{cite J.journal|title=A H.;Facile Coghlan,Method M.for J.the ''Synth.Bishomologation Commun.''of '''1976''',Ketones ''6''to α,β-Unsaturated Aldehydes: Application to the Synthesis of the Cyclohexanoid Components of the Boll Weevil Sex 469.</ref>Attractant

|author=James H. Babler, Michael J. Coghlan|page= 469-474|year= 2007|doi=10.1080/00397917608082626|journal=Synthetic Communications}}</ref>

<span style="float:right;padding-right:50px;padding-top:30px;">'''''(6)'''''</span>{{center|[[File:ChroScope1.png]]}}

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Oxidative cyclization can be used to prepare substituted tetrahydrofurans. Cyclization of dienols leads to the formation of two tetrahydrofuran rings in a ''syn'' fashion.<ref name=OR/>

<span style="float:right;padding-right:50px;padding-top:30px;">'''''(7)'''''</span>{{center|[[File:ChroScope2.png]]}}

Enones can be synthesized from tertiary allylic alcohols through the action of a variety of chromium(VI)-amine reagents, in a reaction known as the [[Babler oxidation]]. The reaction is driven by the formation of a more substituted double bond. (''E'')-Enones form in greater amounts than (''Z'') isomers because of chromium-mediated geometric isomerization.<ref name=whatup /><ref name=OR/>

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