Transposition en série tricyclique — synthèse et réactivité de bis-triméthylsilyl-bicyclo[n,1,0]2-alcène antioxydes

Abstract

The bis-trimethylsilyl-bicyclo[n,1,0]2-alkene antioxides (n = 4 and 6) have been synthesized from their 1,3-diene precursors by a three-step process (dichlorocyclopropanation, silylation, and epoxidation). Their rearrangement in the presence of solid and liquid Lewis acids was studied, and compared with the previously described reactivity of 2-carene oxide. With these silylated epoxides, the breaking of the C3—O bond is favoured while C2—O bond breaking had previously been observed with 2-carene oxide. All the resulting products were the three-membered ring-opened ones, but the opening mechanism differs according to the value of n, leading mainly to 7,8-bis-trimethylsilyl-9-hydroxy-bicyclo[4,3,0]non-6-ene when n = 6 and 2,2′-bis-trimethylsilyl-cyclohex-3-ene carboxaldehyde when n = 4.