Oxidation of the model compounds of tocopherols with bis (salicylidene) ethylenediiminocobalt (1) was examined. Oxidation of 6-hydroxy-2, 2, 5, 7, 8-pentamethylchroman (2) in methanol gave 12.8% of trimer (3), 8.3% of spirodienonedimer (4), 3.7% of 1-(6-hydroxy-2, 2, 7, 8-tetramethylchroman-5-yl)-2-[5, 6-dimethyl-2-(3-hydroxyisoamyl)-p-benzoquinon-3-yl] ethane (5), and 20.3% of 2-(3-hydroxyisoamyl)-3, 5, 6-trimethyl-p-benzoquinone (6), while that of 6-hydroxy-2, 2, 5, 8-tetramethylchroman (9) gave 21.2% of 6-hydroxy-2, 2, 5, 8-tetramethyl-7-(2, 2, 5, 8-tetramethyl-6-chromanyloxy) chroman (10) and 8.9% of 3, 6-dimethyl-2-(3-hydroxyisoamyl)-p-benzoquinone (11). The reaction of 6-hydroxy-2, 2, 7, 8-tetramethylchroman (12) in methanol afforded 49.6% of 2, 2, 7, 8-tetramethyl-5, 6-chromandione (13), 5.3% of 8-methoxymethyl-2, 2, 7-trimethyl-5, 6-chromandione (14), and 6.2% of 1, 2-bis (2, 2, 7-trimethyl-5, 6-chromandion-8-yl) ethane (15). The structure of 13 and 14 was determined by deriving them to phenazine derivatives, 2, 3-dihydro-3, 3, 5, 6-tetramethyl-1H-pyrano [3, 2-a] phenazine (16) and 2, 3-dihydro-5-methoxymethyl-3, 3, 6-trimethyl-1H-pyrano [3, 2-a] phenazine (17), respectively. The reaction of 12 in benzene or dimethylformamide gave 6-hydroxy-2, 2, 7, 8-tetramethyl-5-(2, 2, 7, 8-tetramethyl-6-chromanyloxy) chroman (18) (28.6% from benzene, 13.8% from dimethylformamide), 6-hydroxy-5-(6-hydroxy-2, 2, 7, 8-tetramethylchroman-5-yl)-2, 2, 7, 8-tetramethylchroman (19) (15.2 and 3.5%), 13 (24.3 and 40.9%), and 15 (1.9 and 10.0%). Oxidation of 6-hydroxy-2, 2, 8-trimethylchroman (21) gave 4.8% of 6-hydroxy-2, 2, 8-trimethyl-5-(2, 2, 8-trimethyl-6-chromanyloxy) chroman (22), 4.8% of 6-hydroxy-5-(6-hydroxy-2, 2, 8-trimethylchroman-5-yl)-2, 2, 8-trimethylchroman (23), 2.7% of trimer (24), and 19.7% of 2, 2, 8-trimethyl-5, 6-chromandione (25). The structure of 25 was determined by deriving it to the phenazine derivative, 2, 3-dihydro-3, 3, 5-trimethyl-1H-pyrano [3, 2-a] phenazine (26). The reaction of 2, 2-dimethyl-6-hydroxychroman (27) afforded 3.5% of 5-(2, 2-dimethyl-6-chromanyloxy)-6-hydroxychroman (28), 2.1% of 2, 2-dimethyl-5-(2, 2-dimethyl-6-chromanyloxy)-6, 7-chromandione (29), and 1.3% of 2, 2-dimethyl-6-hydroxy-5-(6-hydroxy-2, 2-dimethylchroman-5-yl) chroman (30). Thus, oxidation with 1 resulted in the simultaneous progress of introduction of oxygen and carbon-oxygen or carbon-carbon coupling.
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