The structure of a typical acyloin.

In organic chemistry, acyloins or α-hydroxy ketones[1] are a class of organic compounds of the general form R−C(=O)−CR'(OH)−R", composed of a hydroxy group (−OH) adjacent to a ketone group (>C=O). The name acyloin is derived from the fact that they are formally derived from reductive coupling of carboxylic acyl groups (R−C(=O)−).[1] They are one of the two main classes of hydroxy ketones, distinguished by the position of the hydroxy group relative to the ketone; in this form, the hydroxy is on the alpha carbon, explaining the secondary name of α-hydroxy ketone.

Synthesis

Classic organic reactions exist for the synthesis of acyloins.

Enolate oxidation by sulfonyloxaziridines

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

Voigt amination

See also

References

  1. ^ a b IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "acyloins". doi:10.1351/goldbook.A00126
  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 (12): 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. PMID 16048308. Archived from the original (PDF) on 4 September 2006.
  5. ^ von Meyer, E.; Voigt, Karl (1886). "Ueber die Einwirkung von primären aromatischen Aminen auf Benzoïn" [On the effect of primary aromatic amines on benzoin]. J. Prakt. Chem. (in German). 34 (1): 1–27. doi:10.1002/prac.18860340101.
  6. ^ Lawrence, Stephen A. (2004). Amines: Synthesis, Properties and Applications. Cambridge University Press. ISBN 978-0-521-78284-5.
  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]. Archiv der Pharmazie (in German). 305 (3): 159–171. doi:10.1002/ardp.19723050302. PMID 5048240. S2CID 84990819.
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