2,2,4,4-Tetramethyl-3-thioxocyclobutanone (8b) easily reacts with gaseous chlorine to yield the stable alpha-chloro sulfenyl chloride 10. The same product was obtained when 8b was treated either with phosphorus pentachloride (PCl(5)) or sulfuryl chloride (SO(2)Cl(2)) in CCl(4) solution. Sulfur dichloride (SCl(2)) reacts with 8b to give the alpha-chloro thiosulfenyl chloride 12 along with an almost equimolar amount of the trisulfide 13b. The less reactive disulfur dichloride (S(2)Cl(2)) was shown to react slowly with 8b and the symmetrical tetrasulfide 15 was found as the exclusive product. The pure thiosulfenyl chloride 12 added to adamantanethione (8c) yielded the unsymmetrical trisulfide 13c. When 12 was treated with thioacetic acid, the acetylated trisulfide 17 was formed in high yield. "Unzipping" reactions with the acetylated disulfide 16 and trisulfide 17 with morpholine in THF at -40 degrees C led to the formation of mixtures of two sulfur-rich heterocycles identified as the pentathiepane 6b and the hexathiepane 7b. A mixture of analogous products was obtained when alpha-chloro sulfenyl chloride 10 was treated with sodium sulfide in anhydrous THF at -40 degrees C. The formation of 6b and 7b is believed to occur via the intermediate dithiirane 1b and/or the isomeric thiosulfine 2b. In the case of 17 the reaction starts probably with the formation of a nonisolable tetrathiane 18b as presented in Scheme 5.

No 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 diand 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). and 2). These products reacted with S-and P-nucleophiles by substitution of Cl -at the sulfanyl group; e.g. the reaction with 4b yielded the di-and trisulfane derivatives 6b and 11, respectively. Surprisingly, only pentasulfane 12 was formed in the reaction of 9 with thiobenzophenone (Scheme 3). In contrast to 5 and 9, the corresponding α-chloro trisulfanylchloride 13 could not be detected, but reacted immediately with the starting thioketone 4b togive the tetrasulfane 14 (Scheme 4). Oxidation of 4b with mCPBA yielded the corresponding sulfine 15, which underwent 1,3-dipolar cycloadditions with thioketones 3a and 4b (Scheme 5). Furthermore, 4b has been shown to be a good dipolarophile in reactions with thiocarbonyl methanides and azomethine ylides (Schemes 6 and 7). In the case of phenyl azide, the reaction with 4b gave the symmetrical trithiolane 25 (Scheme 8).

The four oligosulfanes, bis(1-chloro-2,2,4,4-tetramethyl-3-oxocyclobutan-1-yl)disulfane, C(16)H(24)Cl(2)O(2)S(2), (III), 1,3-bis(1-chloro-2,2,4,4-tetramethyl-3-oxocyclobutan-1-yl)trisulfane, C(16)H(24)Cl(2)O(2)S(3), (V), 1,4-bis(1-chloro-2,2,4,4-tetramethyl-3-oxocyclobutan-1-yl)tetrasulfane, C(16)H(24)Cl(2)O(2)S(4), (VII), and 1,6-bis(1-chloro-2,2,4,4-tetramethyl-3-oxocyclobutan-1-yl)hexasulfane, C(16)H(24)Cl(2)O(2)S(6), (VIII), all have similar geometric parameters, with the C-C bond lengths involving the chloro-substituted cyclobutanyl C atom being elongated to about 1.59 A. There are two molecules in the asymmetric units of the tri- and tetrasulfanes, and the molecules in the latter compound have local C(2) symmetry. The molecule of the hexasulfane has crystallographic C(2) symmetry. Most of the cyclobutanyl rings are not perfectly planar and have slight but varying degrees of distortion towards a flattened tetrahedron. The polysulfane chain in each structure has a helical conformation, with each additional S atom in the chain adding approximately one quarter of a turn to the helix.