Studies on the Steric Inversion of Alkamines. III

On the Reciprocal Inversion between Optical Active Ephedrines and Pseudoephedrines

Abstract

Application of PCl₅ to l-ephedrine (I) and d-Ψ-ephedrine (II) results in Walden conversion and formation of (+)-Ψ-1-phenyl-1-chloro-2-methylaminopropane hydrochloride (III) and (-)-1-phenyl-1-chloro -2-methylaminopropane hydrochloride (IV), respectively. Reaction of (II) and SOCl₂ gives chiefly (III) which, when warmed with AgNO₃ solution, gives a mixture of (I) and (II). Heating (III) with NaOH solution gives (-)-N-methyl-1-phenyl-2-methylethyl eneimine (V). Addition of AcCl to ethereal solution of (V) gives (+)-Ψ-1-phenyl-1-chloro-2-acetylmethylaminopropane (VI) which, when saponified with alkali, gives N-acetyl-1-ephedrine (VII) but gives l-ephedrine when saponified with acids with intermediate formation of O-acetyl-l-ephedrine hydrochloride (VIII).
In the same manner, l-Ψ-ephedrine was treated to give optical antipodes which were finally led to d-ephedrine.