Method of making carotenoids

Abstract

A widely applicable process for the manufacture of carotenoids by a Wittig reaction comprises carrying out the Wittig reaction in a polar reaction medium in a manner such that neither the reactants nor the thus-manufactured carotenoid are significantly dissolved in the reaction medium. An especially suitable reaction medium is a polar, toxicologically harmless solvent which remains monophasic on the addition of water in an amount up to about 30 vol. % and which permits the triarylphosphine oxide which is formed to dissolve well. Lower alcohols and acetone, as sole solvents or as mixtures with one another and/or with water, are especially suitable as the polar reaction medium. This process permits the use of much more concentrated reaction mixtures, simplifies the regeneration of the solvent and generally the reaction procedure, and avoids toxicologically objectionable solvents such as halogenated hydrocarbons.

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