Oxidation with chromium(VI) complexes: Difference between revisions

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Enones can be synthesized from tertiary allylic alcohols through the action of a variety of chromium(VI)-amine reagents. The reaction is driven by the formation of a more substituted double bond. (E) enones form in greater amounts than (Z) isomers due to chromium-mediated geometric isomerization<ref>Majetich, G.; Condon, S.; Hull, K.; Ahmad, S. ''Tetrahedron Lett.'', '''1989''', ''30'', 1033.</ref>.

<span style="float:right;padding-right:50px;padding-top:10px;">'''''(7)'''''</span><center>[[File:ChroScope3.png]]</center>

Suitably substituted olefinic alcohols undergo oxidative cyclization to give tetrahydrofurans. Further oxidation of these compounds to give tetrahydropyranyl carbonyl compounds maythen occuroccurs<ref>Schlecht, M. F.; Kim, H.-J. ''Tetrahedron Lett.'', '''1986''', ''27'', 4889.</ref>.

<span style="float:right;padding-right:50px;padding-top:30px;">'''''(8)'''''</span><center>[[File:ChroScope4.png]]</center>

In addition to the limitations described above, chromium(VI) reagents are often unsuccessful in the oxidation of substrates containing heteroatoms (particularly nitrogen). Coordination of the heteroatoms to chromium (with displacements of the amine ligand originally attached to the metal) leads to deactivation and eventual decomposition of the oxidizing agent.