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 wi th 2KHSO(5). KHSO4. K2SO4 to yield cis- and trans-3,6-bis(1,1,3,3-tetrameth yl-4-oxo-4-phenylbutyl)1,2,4,5-tetrathianes. The formation mechanism of the tetrathianes is discussed. X-Ray crystallography disclosed that the cis- a nd tuans-isomers take twist and chair conformations, respectively, in the s olid state. Variable-temperature H-1 NMR spectroscopy in solution showed th at 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 a t 50 degrees C to give the corresponding di-2-thianyl disulfide.