Fluorosulfonylferrocene, (Trifluoromethylsulfonyl)ferrocene and New Ferrocenyl Sulfonates: Directed ortho Lithiation and New Anionic Thia-Fries Rearrangements at Ferrocene

Abstract

Ferrocenyl triflates are known to undergo anionic thia-Fries rearrangements at low temperature in high yields. In order to expand the scope of this reaction, ferrocenyl sulfonates and sulfonylferrocenes were prepared and their reactivity investigated. Treatment of ferrocenyl fluorosulfonate with lithium 2,2,6,6-tetramethylpiperidide gave rise to a new anionic thia-Fries rearrangement at ferrocene. The formation of a rare oxathiine was observed with ferrocenyl (pentafluorophenyl)sulfonate as a result of an ortho lithiation and a subsequent intramolecular nucleophilic aromatic substitution. In contrast to fluorinated ferrocenyl sulfonates, fluorosulfonylferrocene as well as (trifluoromethylsulfonyl)ferrocene underwent ortho lithiation under comparable reaction conditions.