Acyloin

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The structure of a typical acyloin.

In chemistry acyloins are a class of organic compounds which all possess the secondary alpha-hydroxy ketone functional group. Thus, they all contain a hydroxyl group placed on the α-position of a carbonyl group. The named acyloin is derived from the fact that they are formally derived from reductive coupling of carboxylic acyl groups.[1]

Synthesis of acyloins[edit]

Classic organic reactions exist for the synthesis of acyloins.

Enolate oxidation by sulfonyloxaziridines[edit]

Enolates can be oxidized by sulfonyloxaziridines.[2][3] The enolate reacts by nucleophilic displacement at the electron deficient oxygen of the oxaziridine ring.

Enolate oxidation by sulfonyloxaziridine

This reaction type is extended to asymmetric synthesis by the use of chiral oxaziridines derived from camphor (camphorsulfonyl oxaziridine). Each isomer gives exclusive access to one of the two possible enantiomers. This modification is applied in the Holton taxol total synthesis.

two optical isomers of camphorsulfonyl oxaziridine

In the enolate oxidation of the cyclopentaenone below[4] 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.

Enolate oxidation example[4]

Reactions of acyloins[edit]

Voigt amination

References[edit]

  1. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "acyloins".
  2. ^ Davis, Franklin A.; Vishwakarma, Lal C.; Billmers, Joanne G.; Finn, John (1984). "Synthesis of α-hydroxycarbonyl compounds (acyloins): direct oxidation of enolates using 2-sulfonyloxaziridines". J. Org. Chem. 49 (17): 3241–3243. doi:10.1021/jo00191a048. 
  3. ^ Davis, F. A.; Haque, M. S.; Ulatowski, T. G.; Towson, J. C. (1986). "Asymmetric oxidation of ester and amide enolates using new (camphorylsulfonyl)oxaziridines". J. Org. Chem. 51: 2402. doi:10.1021/jo00362a053. 
  4. ^ a b Hughes, Chambers C.; Miller, Aubry K.; Trauner, Dirk (2005). "An Electrochemical Approach to the Guanacastepenes" (PDF). Org. Lett. 7 (16): 3425–3428. doi:10.1021/ol047387l. 
  5. ^ Meyer, E. von; Voigt, Karl (1886). "Ueber die Einwirkung von primären aromatischen Aminen auf Benzoïn" [On the effect of primary aromatic amines on benzoin]. J. Prakt. Chem. 34 (1): 1–27. doi:10.1002/prac.18860340101. 
  6. ^ Lawrence, Stephen A. (2004). Amines: Synthesis, Properties and Applications. Cambridge University Press. ISBN 0-521-78284-8. 
  7. ^ Roth, Lepke (1972). "Synthese von Indol- und Carbazol-Derivaten aus α-Hydroxyketonen und aromatischen Aminen" [Synthesis of indole and carbazole derivatives from α-hydroxyketones and aromatic amines]. Arch. Pharm. 305 (3): 159–171. doi:10.1002/ardp.19723050302.