Acyloin condensation

[1][2][3] The reaction is most successful when R is aliphatic and saturated, and typically performed with a silyl chloride reactant to trap the product as a disilyl enediol ether.

Independent of dilution, acyloin condensation of a diester favours intramolecular cyclisation (for all but the smallest rings) over intermolecular polymerisation.

This effect is believed to originate in weak adsorption of the ester terminals at nearby sites on the sodium metal.

Concentration is much less important a factor for obtaining high yields for the acyloin condensation, as the reaction occurs on the surface of the sodium metal.

[8] Although, the need for sodium metal limits the functional group tolerance of the reaction, compared to more modern cyclization reactions (e.g. Yamaguchi esterification, ring-closing olefin metathesis), the acyloin condensation continues to be used in the synthesis of complex natural products for the preparation of challenging ring systems.