A method of synthesizing for 3, 6-disubstituted 2, 9-dioxo-2, 3, 6, 9-tetrahydrothiazolo-[5, 4-f] quinoline-8-carboxylic acids via the thiazolium salts was studied and proved to be practical. The reactions of the thiazolium salt with various nucleophilic reagents afforded several new derivatives. Gould-Jacobs reaction of the benzothiazole-2-ones and benzothiazole-2-thione derivatives were also carried out.
