Trishomobullvalyl cation

Preparation of Carbocations, Onium Ions, and Their Salts. SbFs is a preferred medium for the preparation of carbocations and onium ions. In fact, the first observation of stable carbocations was achieved in this medium. - By dissolving /-butyl fluoride in an excess of SbFs, the /-butyl cation was obtained (eq 26). Subsequently, many alkyl cations have been obtained in SbFs (either neat or diluted with SO2, SO2CIF, or SO2F2). The 2-norbomyl cation, one of the most controversial ions in the history of physical organic chemistry, was prepared from exo-2-fluoronorbomane in SbFs/S02 (or SO2CIF) solution (eq 27). Bridgehead cations such as 1-adamantyl, 1-trishomobarrelyl, and 1-trishomobullvalyl cations have also been similarly prepared with the use of SbFs. ... 

Optical resolution of 1-trishomobarrelenecarboxylic acid (206) with (+)-a-phenylethylamine was carried out by Spielmann and de Meijere (171), who converted the resulting (+)-acid (206) into the chloride (207) of C3 symmetry, [a]D +159°. A dramatic change of optical rotation was observed when the chloride (+)-207 was dissolved in SbF3/CH2Cl3 solution to be converted into trishomobarrelyl cation (208), [a]D -1516°. Similar inversion of rotation occurred when (+)-l-trishomobullvalyl chloride (210), [a]p +273°, prepared from acid (+)-209, was converted into the cation 211 [a]D -2473°. 

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