| 摘要 |
Disclosed is a process for the coupling of a Grignard reagent RMgX with an allylic halide in the presence of a dipolar aprotic solvent wherein the improvement, for obtaining improved yield and selectivity, comprises adding a catalyst to said Grignard or allylic halide and then carrying out the coupling reaction by the addition of the Grignard reagent to the allylic halide, said reaction being characterized by the displacement at the gamma position (relative to the halide) of the allylic halide with R of the Grignard reagent, migration of the allylic double bond in the direction of the halogen atom and loss of halogen. The present invention also resides in the discovery of certain novel procedures for the synthesis of Vitamin E. Specific embodiments of this aspect of the invention reside in the syntheses of 6,7-dehydrophytol, 10,11-dihydrofarnesene, phytone, hexahydropseudoionone, and related compounds as precursors for Vitamin E.
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