CHARGE-TRANSFER INTERACTIONS AND REACTIONS OF ALPHA-TOCOPHERYL METHYL-ETHER WITH SOME ACCEPTORS

Charge transfer (CT) interactions of alpha-tocopheryl methyl ether (al pha TME) with chloranil (CHL), tetracyanoethylene (TCNE), 7, 7, 8, 8-t etracyanoquinodimethane (TCNQ) and 2, 3-dichloro-5, 6-dicyano-p-benzoq uinone (DDQ) have been investigated. In spite of being highly electron rich alpha TME forms weak CT complexes. The results are discussed in the light of steric and electronic features of alpha-tocopheryl system and have important bearings on the mechanism of antioxidant action of tocopherols. Thermal reaction of alpha TME with DDQ affords 3, 4-dehy dro-alpha-tocopheryl methyl ether (2) as major product (90%) along wit h 2, 3-dichloro-5, 6-dicyano-hydroquinol-alpha TME coupled product (3, 4%); 2 is also obtained as major product (54%) from thermal reaction of alpha TME with CHL along with 2, 3, 5, 6-tetrachlorohydroquinol-alp ha TME coupled product (4, 6.5%). The obtained modes of reactions and regioselectivities In case of alpha TME contrast with modes of reactio ns and regiospecificities reported for reactions of alpha-tocopherol w ith quinones. Irradiation of alpha TME-TCNE CT complex affords three a dducts; adducts (5, 20%) and (6, 8%) are derived by O-demethylation of alpha TME and addition of tricyanovinyl moiety at C-9 and C-5, respec tively, whereas 7 ( similar to 8%) is formed by loss of C-4-H of alpha TME and addition of a tricyanovinyl moiety at C-9. A rationalization of the obtained results is proffered.