Solvent-free optical resolution of N-methylamphetamine by distillation after partial diastereoisomeric salt formation.

Solvent-free optical resolution of N-methylamphetamine was developed by distillation after partial diastereoisomeric salt formation. From the 18 chiral acids tested by this method, five provide by this method resolution: O,O'-dibenzoyltartaric acid, O,O'-di-p-toluoyltartaric acid, 6-methoxy-alpha-methyl-2-naphthaleneacetic acid (Naproxen), the cis-permetrinic acid, and the 2-phenoxypropionic acid. Among them the O,O'-dibenzoyltartaric acid in water-free form provided the more effective resolution. The efficiency of this resolution S = 0.74 is in the range of the industrial-scale resolutions and not worse than the efficiency achieved by optical resolution via fractional crystallization.