Independent Synthesis of the Violet Dyes and of a By-product Formed in the Reaction of 1,2-Naphthoquinone-4-sulfonic Acid with Primary Aliphatic Amines

Article abstract of DOI:10.1002/ardp.19843170407

4-Dimethylamino-1,2-naphthoquinone (8) and 2-dimethylamino-1,4-naphthoquinone (10) are O-methylated by methyl fluorosulfonate to form the stable iminium salts 9 and 11.In analogous way the 2-alkylamino-1,4-naphthoquinones 13 were transformed into the iminium salts 14.These salts condense with 3-amino-4-hydroxynaphthalene-1-sulfonic acid (15) to give the violet 3-<(3-alkylamino-4-oxo-1-naphthyliden)amino>-4-hydroxynaphthalene-1-sulfonic acids 2.The iminium salt 14c reacts with benzylamine to yield the vinylogous amidinium salt 19, which is oxidised by silver oxide inpyridine to give the N-benzylidene-2-phenyl-5-naphth<2,1-d>oxazolamine 20.Reduction of 20 with LiAlH4 leads to the formation of N-benzyl-2-phenyl-5-naphth<2,1-d>oxazolamine (7).