Preparation and reactivity of tris(trifluoromethylselanyl)carbenium |(CF3Se)3C+l and trifluromethylsulfanylacetic acid derivates [CF3S3-nCXn(O)R]

Article abstract of DOI:10.1002/cber.19961291112

Reaction pathways for the synthesis of the (CF₃E)₃C moieties (E = Se, S) are described. [(CF₃Se)₃C⁺HAsF₆^-] was found to be a suitable synthon for the preparation of (CF₃Se)₃C derivatives. It can be prepared either from (CF₃Se)₄C or (CF₃Se)₃CF and AsF₅ in liquid SO₂. Direct access to (CF₃Se)₃CF was realized by the reaction of FCBr₃ with Hg(SeCF₃)₂. Treatment of [(CF₃Se)₃C⁺][AsF₆^-] with potassium halides provided (CF₃Se)₃CX (X = F, Cl, Br). A different course took the reaction with KI, as CF₃SeSeCF₃ and (CF₃Se)₂C=C(SeCF₃)₂ were formed as main products. Minor amounts of (CF₃Se)₃CC(SeCF₃)₃ were formed which could be isolated and unambiguously characterized. Only two routes led to a threefold CF₃S-substituted acetic acid ester (CF₃S)₃CC(O)OR [R= CH₃, (CH₃)₃C]: Metatheses between (CF₃S)₂CBrC(O)OCH₃ and Hg(SCF₃)₂ and metalation of (CF₃S)₂CHC(O)OR [R = CH₃, (CH₃)₃C] with NaH followed by reaction with CF₃SCL. Other precursors such as (CF₃S)₂CXC(O)OR′ [X = H, Br; R′ = Me₃Si, (n-C₄H₉)₃Sn] and (CF₃S)₂CBrC(O)Y (Y = Cl, Br) were synthesized but could not be converted to the corresponding (CF₃S)₃C derivatives. Attempts to hydrolyze (CF₃S)₃CC(O)OR to (CF₃S)₃CC(O)OH failed. VCH Verlagsgesellschaft mbH, 1996.