| 摘要 |
1-Bromo-4-chloro-2-methylbutane, (S)-1-bromo-4-chloro- 2-methylbutane (V) and (R)-5-chloro-3-methylpentanoic acid (Va) and the use of (S)-3-methylvalerolactone, (S)-1-bromo-4-chloro- 2-methylbutane (V) or (R)-5-chloro-3-methylpentanoic acid (Va) as optically active intermediates for the synthesis of the side chain of (R,R,R)- alpha -tocopherol and a process for the preparation of (3R,7R)-1-chloro-3,7,11-trimethyldodecane of the formula Ia <IMAGE> in which n is 1, characterised in that A) (S)-3-methylvalerolactone of the formula IV <IMAGE> is cleaved using liquid hydrogen chloride at 100 to 170 DEG C in a pressurised vessel to give the novel (3R)-5-chloro-3-methylpentanoic acid of the formula Va <IMAGE> B) this acid is converted in a manner known per se into the novel dihalide of the formula IIa <IMAGE> in which X represents Br or I, by decarboxylation with bromine or iodine, and C) this dihalide is reacted in the presence of copper ions with an organomagnesium compound of the formula IIIa <IMAGE> in which Y represents Cl, Br or I and n represents 1, at temperatures below 0 DEG C in an ether solvent, preferably tetrahydrofuran.
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