| 摘要 |
PURPOSE: Provided is a process for the catalytic isomerization of Z-3-methylpent-2-en-4-yn-1-ol to E-3-methylpent-2-en-4-yn-1-ol, wherein the Z-pentol is a useful intermediate for the manufacture of vitamin A, and the stereoisomer produced and isolated in the smaller proportion, and E-pentol is also a useful intermediate, in this case for the manufacture of astaxanthin, zeaxanthin and further carotenoids. CONSTITUTION: The process for catalytically isomerizing Z-3-methylpent-2-en-4-yn-1-ol to E-3-methylpent-2-en-4-yn-1-ol in a mixture of both these stereoisomers, is characterized in that as the isomerization catalyst there are employed bromine radicals and the isomerization is conducted in a two-phase system of an aqueous phase and the stereoisomeric mixture phase, wherein the stereoisomeric mixture optionally is present in an essentially water-immiscible organic solvent, with intermixing of the reaction mixture and at temperatures from about -10 deg.C to about 100 deg.C.
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