The First Anionic Thia‐Fries Rearrangement at the Cobaltocenium Cation

While the chemistry of ferrocene is rich and widely explored, this not case for isoelectronic cobaltocenium cation. Here we report first syntheses triflate substituted cations based on respective (cyclopentadienone)(cylopentadienyl)cobalt(I) complexes, which have been reported by Vollhardt et al. ca. forty years ago. Reaction with triflic anhydride affords cations, upon treatment lithium diisopropylamide undergo anionic thia-Fries rearrangements complexes. To our knowledge, is, in addition, a deprotonation complex base. Alternatively, desilylation silyl derivatives cesium fluoride caused anion formation leading to rearrangement products higher yields. The 2-(trifluoromethylsulfonyl)(cyclopentadienone) complexes obtained were fully characterized including crystal structure analysis. As ferrocene, mesylates or tosylates do rearrangement.