Abstract A series of 5-(alkyl) thianthrenium triflates (3a–d, g–i) with alkyl (R) groups Me (a), Et (b), isoPr (c), 2-Bu (d), cyclopentyl (g), cyclohexyl (h) and cycloheptyl (i) were prepared by alkylation of thianthrene (Th) with alkyl formate and trifluoromethanesulfonic (triflic) acid. Benzylation (3f) was achieved with benzyl bromide and silver triflate. 5-(Neopentyl) thianthrenium perchlorate (3e) was prepared by reaction of thianthrene cation radical ...