Formation, Structure, and Thionation of 1,2,4,5-Tetrathianes [cis- and trans-3,6-Bis(1,1,3,3-tetramethyl-4-oxo-4-phenylbutyl)-1,2,4,5-tetrathianes]

2,2,4,4-Tetramethyl-1-phenyl-6,7-dithiabicyclo[3.1.1]heptane was treated with 2KHSO5·KHSO4·K2SO4 to yield cis- and trans-3,6-bis(1,1,3,3-tetramethyl-4-oxo-4-phenylbutyl)-1,2,4,5-tetrathianes. The formation mechanism of the tetrathianes is discussed. X-Ray crystallography disclosed that the cis- and trans-isomers take twist and chair conformations, respectively, in the solid state. Variable-temperature 1H NMR spectroscopy in solution showed that the cis-isomer takes a twist conformation exclusively in the temperature range, whereas the trans-isomer exists as an equilibrium mixture of chair and twist conformers. The cis-tetrathiane reacted with Lawesson's reagent at 50 °C to give the corresponding di-2-thianyl disulfide.