1949 年 69 巻 3 号 p. 140-143
Condensation of 4-methoxyquinaldine methiodide and piperonal, if performed in EtOH with triethylamine as a catalyst, gives 4-ethoxyquinaldine methiodide when the amount of the amine is kept under 1/8mol. but 4-ethoxypiperonylidene-quinaldine methiodide as well is obtained if the amount is around 1/2mol. If piperidine is used as a catalyst, the methoxyl radical at C4 changes to ethoxyl, resulting in 4-ethoxypiperonylidene-quinaldine methiodide. Absence of piperonal results in a condensation to isocyanine to 1, 1′, 2′-trimethyl-4-ethoxy-2, 4′-monomethine-quinocyanine iodide possessing λ (max) of 5390Å.
From these results, it was assumed that the methoxyl radical in 4-methoxyquinaldine methiodide, under the presense of amine as a catalyst, was substituted by the solvent alcohol. Therefore, the same reactions were experimented with n-butyl and n-propyl alcohol by which compounds substituted with these alcohols were obtained. At the same time, it was found that these reactions were reversible. From these facts, the author assumed ionic reactions, the direction of which being decided by the slight move in the equilibrium.