Reduction of Aldehydes and Ketones by Sodium Dithionite

Abstract

Conditions have been developed for the effective reduction of aldehydes and ketones by sodium dithionite, Na2S2O4. Complete reduction of simple aldehydes and ketones can be achieved with excess Na2S2O4 in H2O/dioxane mixtures at reflux temperature. Some aliphatic ketones, for example, pentanone and 4-heptanone, are reduced only sluggishly under these conditions. Good conversions can be achieved, however, by adding dimethylformamide to the reaction mixture, again held at reflux. The reductions of 17 compounds are described and the scope of the reaction is discussed. α-Hydroxy sulfinates are suggested as probable intermediates in these reductions.