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 thermal decomposition of 5-morpholino-1,2,3,4-thiatriazole (7), which leads to the extrusion of an active form of sulfur, in the presence of different thioketones is described. The interception of the S-atom by the C=S bond leads to in situ formation of an elusive thiocarbonyl S-sulfide of type 5. This intermediate is a prone 1,3-dipole, which undergoes effectively [2+3] cycloadditions with thioketones to yield 1,2,4-trithiolane derivatives in a regioselective manner. Unexpectedly, 3,3-dichloro-2,2,4,4-tetramethyl-3-thioxocyclobutanone (1c) does not lead to the expected symmetrical 1,2,4-trithiolane. This result can be explained by the reduced stability of the corresponding thiosulfine 5c. Three-component reactions, which were carried out in the presence of equimolar amounts of two different thioketones, result in the formation of 'mixed' 1,2,4-trithiolanes of type 8.
The reactions of 3-phenyl-1-azabicyclo[1.1.0]butane with a-chlorosulfenyl chlorides and sulfinyl chlorides lead to the corresponding sulfenamides and sulfinamides, respectively, which possess an azetidine ring. It is proposed that a two-step mechanism occurs involving an intermediate carbenium ion, which is formed by the addition of the electrophile at the N-atom and cleavage of the N(1)ÀC(3) bond. The structures of 9b and 10b are established by X-ray crystallography.
The reaction of 4-(phenylimino)butan-2-ol with ammonium polysulfide in refluxing EtOH yields 3-hydroxy-N-phenylbutanethioamide as the only isolated product. The structure has been established by single-crystal X-ray diffraction. Treatment of N-benzylidenamines with ammonium polysulfide has proven a general method for the preparation of thiobenzamides.
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