Synthese und chemische Eigenschaften von Pentafluorbenzolselenonsäure und Derivatisierung der Trifluormethanselenonsäure

Synthesis and Chemical Properties of Pentafluorobenzeneselenonic Acid and Derivatives of Trifluoromethaneselenonic AcidOxidation of C6F5SeO2H with KMnO4 in aqueous solution gives C6F5SeO3K(1a), which is converted into C6F5SeO3H·2H2O by 70% HClO4. Dehydration at 80°C in vacuo leads to C6F5SeO3H (1), which is converted into its anhydride 1h by further dehydration at 200°C in vacuo. The acid is neutralized with MOH (M = Li, Na, NH4, 1/2 Ba) to form the corresponding salts C6F5SeO3M (1b–e). By metatheses with MNO3 1a is converted to C6F5SeO3M′ [M′ = Cs, Ag (1f, g)]. With RI or (CH3)3SiCl, respectively, C6F5SeO3Ag (1f) forms C6F5SeO3R [R = CH3, C2H5, n‐C3H7, (CH3)3Si (2a–d)]. At – 40°C, reaction between C6F5SeO3C2H5 (2b) and (CH3)2NH leads to C6F5SeO2‐N(CH3)2 (2e), which decomposes above – 20°C. If (CH3)2NH is used in excess, 4‐(CH3)2NC6F4SeO2N(CH3)2 (2f) is formed. It hydrolyses to 4‐[(CH3)2NH2][4‐(CH3)2NC6F4SeO3] (2g). Chlorination of C6F5SeO2H with SO2Cl2 yields C6F5Se(O)Cl. Esterification of CF3SeO3H is accomplished by treating CF3SeO3Ag with C2H5I. The ester 3a reacts with (CH3)2NH at – 40°C to form CF3SeO2N(CH3)2 (3b), which like the pentafluorobenzene compound is also unstable above – 20°C.