Addition of thianthrene cation radical to non-conjugated dienes - Part II: Addition to two double bonds

Reaction of thianthrene cation radical tetrafluoroborate with 1,5-hexadiene, 1,7-octadiene, 1,8-nonadiene and 1,9-decadiene in the molar ratio 4:1 caused addition to occur to one and both of each diene's double bonds. A mixture of four adducts was thus obtained, namely a bisadduct (12a-d), a monoadduct (13a-d), a di(bis)adduct (14a-d) and a di(mono)adduct (15a-d). The di(mono)adducts (15b-d) were isolated and characterized with ¹H and ¹³C NMR spectroscopy. Under the same condition of excess of cation radical, addition occurred to only one double bond of 1,4-cyclohexadiene and 1,5-cyclooctadiene. Addition to both double bonds was not observed. The bisadduct (16) of 1,4-cyclohexadiene was characterized with ¹H and ¹³C NMR spectroscopy and X-ray crystallography. On activated alumina, 15b-d underwent fast opening of dicationic rings to form mixtures of (E, E)- (17b-d) and (E, Z)-di(5-thianthreniumyl)diene (18b-d) in which the (E, E)-isomer was dominant and was characterized with ¹H and ¹³C NMR spectroscopy.