The definite polymers containing 1,4‐dihydronicotinamide structure were prepared by reduction with sodium dithionite‐potassium carbonate in the presence of benzyltriethylammonium chloride. The reduction of vicinal tricarbonyl compounds such as alloxan and ninhydrin by polymers having the 1,4‐dihydronicotinamide moiety was performed to isolate the polymers' trapped radical anion of alloxan or ninhydrin.