Symmetrical carotenoids prodn. - by reacting ylid cpds. with peroxy acids or their salts or esters

In the prepn. of symmetrical carotenoids from the half-molecules via an ylid in the presence of a base in a solvent at -20 to +60 degrees C, the reaction is carried out in the presence of a peroxy acid or ester or its salt and a base. The carotenoids obtd. can be used as feed additives and as dyes for foods and cosmetics. The process can be applied e.g., to the final liquors from vitamin A synthesis in order to make them technically utilisable. The reaction can be carried out in the presence of water, and the carotenoids are obtd. in very pure, crystalline form. In an example, axerophthylphosphonium hydrogen sulphate was prepd. from vitamin A acetate, dissolved in water, and treated with peracetic acid. NaHCO3 soln. was added and the mixt. stirred for 18 hrs. at room temp. to give beta-carotene in 55% yield.