Cyanine dyes from naphtho [1,2-6]thiazolo[3,2-d][1,4]thiazine

Deeply colored cyanine dyes have been synthesized from the previously unknown 3-methyl-12H-naphtho[1,2-b]thiazolo[3,2-d][1,4]thiazinium salts. It is assumed that the deep color of the new cyanines is connected with the conversion of the nonaromatic 1,4-thiazine ring in the dye molecule into an aromatic thiazine ring with three double bonds in a six-membered ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1282–1284, September, 1973.