Abstract
Heating of dipotassium salt of 3, 6-dicarboxy-1, 4-dimethyl-2, 5-piperazinedione (4) with sulfur monochloride in dioxane gave 1, 4-dimethyl-3, 6-epidithio-2, 5-piperazinedione (11) in 33% yield with simultaneous decarboxylation. When the reaction mixture from 4 and S2Cl2 was reduced with NaBH4 and ethylated with ethyl iodide, cis 3, 6-bis (ethylthio) derivative (17) was obtained in 50% yield besides a trace amount of trans isomer (18) and the monoethylthio derivative (19). Reactions of other metal salts (16a, 16b, and 16c) with S2Cl2 did not improve the yield of 11. On the other hand the reaction of 4 with ethanesulfenyl chloride in dioxane did not yield 17, but gave 18, 19, and hydroxylated compounds (20, 21, and 22) in low yields. Similar results were obtained in the reaction of 4 with benzenesulfenyl chloride. The mechanism of the decarboxylative C-S bond formation was also discussed.
