REARRANGEMENT IN TRICYCLIC SERIES - SYNTHESIS AND REACTIVITY OF BIS-TRIMETHYLSILYL-BICYCLO[N,1,0]2-ALKENE ANTIOXIDES

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 when n = 6 and 2,2'-bis-trimethylsilylcyclohex-3-ene carboxaldehyde when n = 4.