by successive reaction with PCl5 and Lawesson reagent in pyridine. This new thioketone 4b was transformed into 1-chlorocyclobutanesulfanyl chloride 5 and chloro 1-chlorocyclobutyl disulfide 9 by treatment with PCl5 and SCl2, respectively, in chlorinated solvents (Schemes 1 and 2). These products reacted with S- and P-nucleophiles by substitution of Cl− at the S-atom; e.g., the reaction with 4b yielded