Synthesis, Characterization, and Anodic Oxidation of Selected Norbornyl Dithioethers

Both 2-exo- and 2-endo-[(methylthio)methyl]-6-endo-(methylthio)bicyclo[2.2.1]heptane (1a and 2a, respectively) were prepared by standard methods. Treatment of episulfide 3 with sulfur dichloride followed by reduction and alkylation afforded 2-endo, 6-endo-bis(methylthio)-3-exo, 5-exo-dichlorobicyclo[2.2.1]heptane (2d). The structure of 2d was unequivocally established by X-ray crystallographic analysis. An interesting feature of the structure of 2d is the unusually short S⋯S nonbonded distance of 3.179 (1) Å. Electrochemical oxidation of 1a, 2a, and 2d was studied by using cyclic voltammetric and rotating-disk techniques. Anodic oxidation of 2a is almost 600 mV easier than that of its isomer 1a because of intramolecular interaction between the two sulfur atoms in 2a but not 1a on oxidation. The vertical ionization potentials for the nonbonding sulfur 3p lone-pair electrons were determined by photoelectron spectroscopy for 1a, 2a, and 2d.