Studies on the Voges-Proskauer Reaction. IV. Structural Determination of Colored Substance obtained from 1, 1-Dimethylguanidine, 1, 1-Pentamethyleneguanidine and Morpholinoamidine (On the Structure of Pigment A)

Abstract

The Voges-Proskauer reaction using 1, 1-dialkylguanidines, diacetyl, and 1-naphthol, in the presence of alkali, gave A and B pigments, besides C and D pigments as by-products. Pigment A was isolated as crystals by column chromatography, and its structure was elucidated. The molecular formula of each of Pigment A were C₁₇H₁₇ON₃ for 1, 1-dimethylguanidine (DMG), C₂₀H₂₁ON₃ for 1, 1-pentamethyleneguanidine (PMG), and C₁₉H₁₉O₂N₃ for morpholinoamidine (MA). From NMR, IR, Mass and UV data, the structure of Pigment A was determined as 5-[2'-(1'-naphthonylidenmethyl)]-(2-dialkylamino-4-methyl)imidazole.