1966 年 86 巻 10 号 p. 918-922
As a new method for synthesis of carbocyanine dyes, ketal-type intermediate (IV) was synthesized and its reaction with various active methylene compounds was examined. Reaction of 3-ethyl-2-acylmethylenebenzothiazoline (or benzoselenazoline)(II) with triethyloxonium fluoroborate gave III which was reacted with sodium alkoxide to obtain the ketal (IV) of II. IV underwent very facile reaction with active methylene compounds and afforded the objective carbocyanine dyes. This has shown that IV is a very useful compound as an intermediate in the syntheses of carbocyanine dyes. Many kinds of cyanine and merocyanine dyes were synthesized by the reaction of IV with various reactive methyl and methylene compounds.