Hansley-Prelog acyloin condensation

What is Hansley-Prelog acyloin condensation?

The first report of this reaction can be traced back to 1935 when Hansley observed it during the preparation of open-chain α-ketols. Later, in the 1940s-1950s, Prelog expanded on this observation. Hansley-Prelog acyloin condensation involves using colloidal sodium to react with esters of saturated or unsaturated dicarboxylic acids in high dilution to produce cyclic acyloins containing more than 20 carbon atoms (8 or more carbon atoms).

Hansley-Prelog acyloin condensation - general reaction scheme
Hansley-Prelog acyloin condensation

These acyloins can be transformed into cyclic ketones with the same carbon number by reducing zinc and hydrochloric acid HCl in acetic acid. The reaction is generally carried out above the melting point of sodium while maintaining the colloidal dispersion of sodium and adding esters of dicarboxylic acid in very diluted concentrations. Toluene and xylene are equally effective solvents for this reaction.

For dicarboxylic acid esters with fewer carbon atoms, t-butyl or sec-butyl esters are preferred as they yield higher yields than methyl esters per unit volume of solvents.

Hansley-Prelog acyloin condensation can be widely used for producing cyclic ketones with moderate to large ring sizes.


  • Hansley, V. L., J. Am. Chem. Soc., 1935, 57, 2303
  • Prelog, V.; Frenkiel, L.; Kobelt, M. and Barman, P., Helv. Chim. Acta, 1947, 30, 1741
  • Sheehan, J. C.; O’Neill, R. C. and White, M. A., J. Am. Chem. Soc., 1950, 72, 3376
  • Prelog, V.; Schenker, K and Günthard, H. H., Helv. Chim. Acta, 1952, 35, 1598
  • Prelog, V. and Schenker, K., Helv. Chim. Acta, 1952, 35, 2044
  • Prelog, V.; Schenker, K. and Küng, W., Helv. Chim. Acta, 1953, 36, 471