Photoreduction of pyridine N-oxide, which has a key structure of antitumor agents for hypoxic solid tumors, by 1-benzyl-1, 4-dihydronicotinamide in deaerated aprotic media resulted in generation of hydroxyl radical, leading to the oxidation of salicylic acid to 2, 3-and 2, 5-dihydroxybenzoic acids, and catechol.