Enantioselective Oxidation of Thioethers . An Improved Route To the Resolution of [1,1'-binaphthalene]-2,2'-dithiol

(+/-)-[1,1'-Binaphthalene]-2,2'-bis-methylthioether (+/-)-1 was oxidized with high enantioselectivity by using our asymmetric reagent [Ti(IV) : (+)-DET : TBBP = 1 : 4 : 2]. An appropriate substrate/oxidant ratio afforded such a product distribution that allowed us to obtain, after chromatographic separation and chemical transformations, optically pure [1,1'-binaphthalene]-2,2'-dithiol in ca. 80% yield based on the racemic starting material