Magnesium → alpha-Tocopherol

Participants

Reaction Steps

6.26 g (20 millimoles) of (2RS)-2,5,7,8-tetramethyl-6-hydroxy-2-(2-bromoethyl)-chroman were dissolved in 20 ml of absolute THF. 16.2 ml of a 1.5-molar solution of vinyl-magnesium chloride in THF were added to the above solution at -20° C. and the mixture was stirred for 1 hour at the same temperature. Thereafter, a solution of (2RS,6RS)-1-chloro-2,6,10-trimethylundecyl-magnesium chloride, which had been prepared by reacting a solution of 0.86 g (35.8 millimoles) of magnesium in 10 ml of absolute THF with a solution of 8.16 g (34 millimoles) of (2RS,6RS)-1-chloro-2,6,10-trimethyl-undecane in 10 ml of THF and stirring the mixture for 2 hours at +70° C. was added dropwise to the above solution at -20° C., followed by dropwise addition of 1.4 ml of an 0.5-molar solution of di-lithium tetrachlorocuprate in absolute THF. The reaction mixture was then stirred for 3 hours at -20° C. and 15 hours at room temperature. After it had been worked up by the method of Example 1c, 3.3 g of α-tocopherol were isolated by distillation at 210° C./0.2 mbar. This corresponds to a yield of 38% of theory.

Provenance & Evidence