Synthesis and reactions of a new cyclobutanethione derivative

Abstract

The 3,3-dichloro-2,2,4,4-tetramethylcyclobutanethione (4b) was prepared from the parent diketone 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 the di- and trisulfides 6b and 11, respectively. Surprisingly, only pentasulfide 12 was formed in the reaction of 9 with thiobenzophenone (Scheme 3). In contrast to 5 and 9, the corresponding chloro 1-chlorocyclobutyl trisulfide 13 could not be detected, but reacted immediately with the starting thioketone 4b to give the tetrasulfide 14 (Scheme 4). Oxidation of 4b with 3-chloroperbenzoic acid (mCPBA) yielded the corresponding thione oxides (= sulfine) 15, which underwent 1,3-dipolar cycloadditions with thioketones 3a and 4b (Scheme 5). Furthermore, 4b was shown to be a good dipolarophile in reactions with thiocarbonylium methanides (Scheme 6) and iminium ylides (= azomethine ylides; Scheme 7). In the case of phenyl azide, the reaction with 4b gave the symmetrical trithiolane 25 (Scheme 8).