Silicon-guided rearrangement of 10-methyl-4,5-epoxydecalins. Methyl versus methylene migration

The Lewis acid-promoted rearrangement of two 10-methyl-4,5-epoxydecalins bearing a trimethylsilyl (TMS) group on C-1 or C-9 has been studied. Migration of the C-9 methylene group to C-5 is the major reaction pathway when the TMS and the oxirane groups are on the same ring while methyl migration results exclusively when they are on different rings.