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

Abstract

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.