Reaction of 5a-bromo-α-tocopherol with nucleophiles

Article abstract of DOI:10.1002/prac.199633801123

The synthesis of different classes of 5a-substituted tocopherols is described. These compounds are potent antioxidants and highly interesting as vitamin E carriers. The reaction of the readily available 5a-bromo-α-tocopherol with alcohols and phenols is shown to produce 5a-alkoxy-α-tocopherols (3-5, 8, 9) and 5a-aryloxy-α-tocopherols (6, 7), respectively, with high yields. 5a-α-Tocopheryl esters (10, 11) are prepared by reaction with metal carboxylates. 5a-Bromo-α-tocopherol is used as well to introduce tocopheryl groups into tertiary amines by quaternization, that renders these compounds (13, 14) soluble in water and in common organic solvents. 5a-Bromo-α-tocopherol also reacts as an alkylating agent with sterically hindered phenols in a Friedel-Crafts reaction. Phenols not highly substituted are exclusively alkylated in the para position at room temperature or below, whereas at higher temperature the para- as well as the orthoalkylated product is observed.