Acyloin
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[[Image:Acyloin.PNG|thumb|right|{size}|The structure of a typical acyloin.]]'''Acyloins''' are a class of [[organic compound]]s in [[organic chemistry]] sharing a common [[functional group]] consisting of a [[hydroxyl]] group placed on the α-position of a [[carbonyl]] group.
== Synthesis of acyloins ==<!-- This section is linked from [[Organic reaction]] -->
Classic organic reactions exist for the synthesis of acyloins.
* The [[acyloin condensation]] is a reductive coupling of esters
* The [[benzoin condensation]] is condensation reaction between aldehydes catalyzed by a cyanide ion
* Oxidation of [[carbonyl]]s is possible with molecular oxygen but not selective
* Better alternative is oxidation of corresponding silyl enol ethers with mCPBA in the [[Rubottom oxidation]]
* '''MoOPH oxidation''' of [[carbonyl]]s is a system with [[molybdenum]] [[peroxide]], [[pyridine]] and [[hexamethylphosphoramide]].
=== Enolate oxidation by sulfonyloxaziridines ===
[[Enolate]]s can be oxidized by sulfonyloxaziridines <ref>''Synthesis of .alpha.-hydroxycarbonyl compounds (acyloins): direct oxidation of enolates using 2 sulfonyloxaziridines'' Franklin A. Davis, Lal C. Vishwakarma, Joanne G. Billmers, John Finn [[J. Org. Chem.]]; '''1984'''; 49(17); 3241-3243. [http://pubs.acs.org/cgi-bin/abstract.cgi/joceah/1984/49/i17/f_jo00191a048.pdf Abstract]</ref> <ref>''Asymmetric Oxidation of Ester and Amide Enolates Using New (Camphorylsulfony1)oxaziridines'' Davis, F. A.; Haque, M. S.; Ulatowski, T. G.; Towson, J. C. [[J. Org. Chem.]] '''1986''', 51, 2402. [http://pubs.acs.org/cgi-bin/abstract.cgi/joceah/1986/51/i12/f_jo00362a053.pdf Abstract]</ref>. The enolate reacts by [[nucleophilic displacement]] at the electron deficient oxygen of the [[oxaziridine]] ring.
:[[Image:Enolate oxidation sulfonyloxazirines.png|600px|Enolate oxidation by sulfonyloxaziridine]]
This reaction type is extended to [[asymmetric synthesis]] by the use of [[optical isomer|chiral]] oxaziridines derived from [[camphor]] (camphorsulfonyl oxaziridine). Each isomer gives exclusive access to one of the two possible [[enantiomer]]s. This modification is applied in the [[Holton Taxol total synthesis]].
:[[Image:Camphorsulfonyl oxaziridine.png|250px|two optical isomers of camphorsulfonyl oxaziridine]]
In the enolate oxidation of the cyclopentaenone below <ref>''An Electrochemical Approach to the Guanacastepenes'' Chambers C. Hughes, Aubry K. Miller, and Dirk Trauner ORGANIC LETTERS '''2005''' Vol. 7, No. 16 3425-3428 [http://www.cchem.berkeley.edu/trngrp/traunerweb/Publications/electrochemical.pdf Article]</ref> with either camphor enantiomer the [[trans isomer]] is obtained because access for the hydroxyl group in the cis position is limited. The use of the standard oxaziridine did not result in an acyloin.
:[[Image:Acyloin example Hughes.png|500px|enolate oxidation example ref. Hughes 2005]]
== Reactions of acyloins ==<!-- This section is linked from [[Organic reaction]] -->
* [[organic reduction|Reduction]] of acyloins give [[diol]]s.
* [[Organic oxidation|Oxidation]] of acyloins give [[dione (chemistry)|dione]]s.
* Some acyloins rearrange with positions swapped under the influence of base in the [[Lobry-de Bruyn-van Ekenstein transformation]]
* A similar reaction is the so-called '''Voight amination''' <ref>{{cite journal
| author = E. von Meyer, Karl Voigt
| journal = [[Journal für Praktische Chemie]]
| title = Ueber die Einwirkung von primären aromatischen Aminen auf Benzoïn
| doi = 10.1002/prac.18860340101
| volume = 34
| year = 1886
| pages =1–27}}</ref> where an acyloin reacts with a primary [[amine]] and [[phosphorus pentoxide]] to an alpha-keto amine <ref>''Amines: Synthesis, Properties and Applications'' Stephen A. Lawrence 2004 Cambridge University Press ISBN 0521782848 </ref>:
:[[Image:VoightAmination.svg|400px|Voight amination]]
* Indole synthesis<ref>Roth, Lepke (1971): [http://www3.interscience.wiley.com/cgi-bin/abstract/113365854/ABSTRACT Archiv der Pharmazie, 159]</ref>, compare [[Bischler-Möhlau indole synthesis|Bischler-Möhlau]]
== References ==
<div class="references-small"><references /></div>
[[Category:functional groups]]
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