Method for the production of amp;bgr;-ionone from pseudoionone

摘要

A process is described for the manufacture of &bgr;-ionone by the sulphuric acid-catalyzed cyclization of pseudoionone in a two-phase solvent system comprising concentrated sulphuric acid and a second solvent essentially immiscible with water, which process comprises using carbon dioxide liquefied under pressure as the second solvent. This process is carried out, inter alia, under a pressure of about 50 bar to about 150 bar and at temperatures from about -15° C. to about +15. degree. C. prior to the subsequent stopping (quenching) of the cyclization reaction. The process in accordance with the invention is preferably carried out continuously and is an important intermediate stage in the synthesis of vitamin A.