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 1 H and 13 C 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 1 H and 13 C 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 1 H and 13 C NMR spectroscopy.

Addition of the Phenoxathiin Cation Radical to Alkenes and Nonconjugated Dienes. Formation of (E)- and (Z)-(10-Phenoxathiiniumyl)alkenes and (E)- and (Z)-(10-Phenoxathiiniumyl)dienes on Basic Alumina

“…The larger value of J defines trans protons. A similar pattern of coupling constants was found for the alkene protons in the Th + −dienes corresponding to 13 and 14 . , …”

“…Additions to Dienes. The thianthrene cation radical was shown recently to add to one or both of the double bonds of a nonconjugated diene, depending on whether an excess of diene or Th •+ was used. , The additions gave complex mixtures of mono-, di(mono)-, bis-, and di(bis)adducts with structures analogous to those of 2 and 3 . In the present work, addition of PO •+ to four dienes was achieved and was less complex than the Th •+ additions.…”

“…Numerous reactions of the thianthrene cation radical (Th •+ ) have been reported since it was first characterized with ESR spectroscopy. − Most of those reactions were with nucleophiles and with electron transfer agents. − With alkynes 8,9 and alkenes, however, additions of Th •+ to the unsaturated bonds occur, among which the detailed characteristics of additions to alkenes and cycloalkenes have been established only in more recent years. − Two types of adducts are formed, namely, a monoadduct ( 2 ) having a cyclic structure, and a bisadduct ( 3 ). They are formed in a way that retains the configuration of the alkene, that is, from a stereospecifically formed cyclic cation radical ( 1 ), as shown in Scheme .…”