Synthesis of Ethyl 2-Thioxo (and 2-Methylene) thiazoline-4-acetates

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Reaction of ethyl 4-chloro (and 4-bromo) acetoacetate (1 and 2) with ammonium benzyldithiocarbamate gave ethyl 3-benzyl-4-hydroxy-2-thioxothiazolidine-4-acetate (3a), which was treated with 10% hydrochloric acid to afford ethyl 3-benzyl-2-thioxo-4-thiazoline-4-acetate (4a). Reaction of 1 (and 2) with N-substituted dithiocarbamates prepared from carbon disulfide and amines, followed by treatment with 10% hydrochloric acid gave the corresponding 4-thiazolines 4a-e. Reaction of 1 (and 2) with thioacetanilide derivatives prepared from phenyl isothiocyanate and active methylene compounds such as ethyl cyanoacetate, malononitrile, ethyl malonate, and cyanoacetamide in the presence of sodium ethoxide gave 2-substituted 4-hydroxythiazolidines 9a-c and thiophene derivative 10. Treatment of 9a-c with acid gave 4-thiazolines 8a-c, which were also prepared from compound 4e, ethyl iodide, and active methylene compounds.