4-Substituted quinoline N-oxides were reduced by sodium borohydride and the reaction mechanism was discussed. It was revealed, for example, that 4-nitroquinoline N-oxide underwent competitive nucleophilic reactions to produced denitrated quinoline N-oxide, deoxygenated 4-nitroquinoline and 4-hydroxylaminoquinoline N-oxide which is a reduction product of nitro group, respectively.
