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.

Keywords:

• Thianthrene cation radical
• Adducts of dienes
• NMR

Acknowledgements

H. J. S. thanks the Welch Foundation for support (Grant D-0028). K. H. W. thanks the Welch Foundation for support (Grant C-0976) and for the purchase of the CCD, and the National Science Foundation for support (Grant CHE-9983352). We thank Mr. David Purkiss (TTU) for the 500 MHz NMR spectroscopy.