Bromination of α-tocopherol methano-dimer and ethano-dimer

Bromination of ethano-dimer 6 afforded the pyrano-spirodimer 7 quantitatively, while methano-dimer 10 gave a product mixture, including furano-spirodimer 11, pyrano-spirodimer 7, and 5-bromo-γ-tocopherol (12), the latter being formed in an unusual dealkylation step.