Phenyl:acetone mfr. from ephedrine cpds. e.g. pseudo:ephedrine - by reaction with 50-70% sulphuric acid and steam distillation from the reaction mixture

摘要

In the prodn. of phenylacetone from ephedrines using sulphuric acid, the reaction is carried out in 50-70% H2SO4 at 140-155 deg.C in the presence of 0.02-0.5% zinc chloride as catalyst, and the phenylacetone is distilled from the reaction mixt. with the aid of steam. H2SO4 concn. is pref. 60%. The ratio of ephedrine to acid is pref. ca. 1:1 to 1:10, esp. 1:2 to 1:5 w/w. Pref. the ephedrine sulphate salt is added continuously or portionwise to the hot H2SO4 and phenylacetone is continuously removed from the reaction mixt. by steam distillation. Conversion of ephedrines (e.g. ephedrine, pseudoephedrine, norephedrine, norpseudoephedrine, bis(1-phenyl-2- methylaminopropyl) ether) obtd. as by-prods. into phenylacetone in good (better than 80%) yield with relatively high reaction rates. The process is suitable for continuous operation.