Dibenzo-l,2,5,6-tetrathiocine

X-Ray crystallography has confirmed the existence of 1,2,5,6-tetrathiocine 3 as the twisted conformer 4 (see Section 14.09.2) <1996AGE2357>. The fluoro-substituted dibenzo-l,2,5,6-tetrathiocine 6 (X = F) adopts the chair conformation 8 in the crystalline state, while the chloro compound 6 (X = Cl) was found in the twist boat conformation 7 in solid state (see Section 14.09.2) <1998CJC1093>. The calculated difference in the energies of the two conformers 7 and 8 for the fluoro-substituted derivative 6 is very small (<5 kj mol-1), and its slow conformational isomerization in solution was... 

Treatment of dibenzo-l,2,5,6-tetrathiocine 1,1,5,5-tetroxide (22) with t-butylthiolate gave 2-(r-butyldithio)benzenesulfinic acid, which was trapped with methyl iodide or benzenesulfenyl chloride in 90% and 70% yields, respectively (Scheme 2) <83JOC2943>. Reaction of (22) with sodium sulfite gave a quantitative yield of Bunte salt (23) (Scheme 2) <83JOC2943>. 

Literature on the stability of individual cyclic disulfides covers (i) compounds that polymerize on standing like 3,3-dimethyl-1 -dithiolane [124,125], 3-hydroxy-l,2-dithiolane [126] and JV-phenyl-4-oxo-5-aza-l,2-dithia-cyclohexane [127,128] ii) compounds which polymerizes on heating such as dibenzo-l,2,5,6-tetrathiocin [129] and iii) compoimds that polymerize in neat form when a catalyst is added, such as ds-l,2-dithiacyclohex-4-ene [130] and l-oxa-4,5-dithiacycloheptane [13, 119, 130]. Detailed study of the stability of cyclic disul les towards polymerization revealed that 1,2-dithianes are the only class of simjde cyclic disulfides that is thermodynamically stable with respect to its polyn rization in the melt or as concentrated solutions [131]. 

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