Synthesis and Reactions of a New Cyclobutanethione Derivative

The 3,3‐dichloro‐2,2,4,4‐tetramethylcyclobutanethione ( 4b ) was prepared from the parent diketone by successive reaction with PCl 5 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 PCl 5 and SCl 2 , 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 ( m CPBA) 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 ).