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

Abstract: Bromination of the ethano-dimer of α-tocopherol ( 6 ) afforded pyrano-spirodimer of α-tocopherol ( 7 ) quantitatively, while the methano-dimer of α-tocopherol ( 10 ) produced a mixture of products, including the furano-spirodimer 11 , pyrano-spirodimer 7 , and 5-bromo-γ-tocopherol ( 12 ), 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. [Copyright &y& Elsevier]