1952 年 72 巻 7 号 p. 865-868
By passing a mixture of quinaldine (I) and air over a catalyst of V2O5, MoO3 and WO3, heated to 450-480°, quinaldoin (III), C20H14O2N2, was isolated from the product as brown microprisms, m. p. 233° (decomp.), with a very small amount of quinoline aldehyde (II). During its recrystallization from a mixture of dioxane and alcohol, (III) undergoes autoxidation to give quinaldil (IV), C20H12O2N2, as yellow, long needles, m. p. 269°. Oxidation of (III) with potassium permanganate or conc. nitric acid easily changes it to (IV), which returns to (III) on catalytic hydrogenation with PtO2. This relationship is the same as that seen with 6, 6′-dimethyl-α-pyridoin and 6, 6′-dimethyl-α-pyridil. Catalytic vapor-phase oxidation of (I) failed to yield quinoline or quinoline-2-carboxylic acid. Oxidation of (I) With SeO2 in dioxane or alcohol, chiefly gives (II) with a small amount of (III), or vice versa, according to the reaction conditions. The yield ratio of (II) and (III) was found to be independent of the freshness or age of SeO2.