Reduction of aldehydes and ketones by sodium dithionite using viologens as electron transfer catalyst

It was found that aromatic aldehydes and ketones could be reduced smoothly at room temperature by sodium dithionite using viologen derivatives as an electron transfer catalyst to obtain the corresponding alcohols in good yields. Viologens (methyl viologen and polymer) acted catalytically and active species in the reduction were quinoid forms which were obtained by two-electron reduction of viologens.