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

Bromination of the ethano-dimer of α-tocopherol () afforded pyrano-spirodimer of α-tocopherol () quantitatively, while the methano-dimer of α-tocopherol () produced a mixture of products, including the furano-spirodimer , pyrano-spirodimer , and 5-bromo-γ-tocopherol (), the latter two formed in an unusual dealkylative fragmentation step. The mechanisms were studied by a combination of trapping reactions as well as kinetic and computational studies.