Some pyridine derivatives as “route-specific markers” in 4-methoxyamphetamine (PMA) prepared by the Leuckart method

The two previously unknown isomeric aryl-methylpyridines were prepared and analysed. Both 2,6-dimethyl-3,5-(4′-methoxyphenyl)pyridine and 2,4-dimethyl-3,5-di-(4′-methoxyphenyl)pyridine have been identified as a new by-product in the crude 4-methoxyamphetamine (PMA) obtained via the Leuckart method. The synthesis of 2,6-dimethyl-3,5-diphenylpyridine, which is connected to amphetamine chemistry, is also reported. It was also found that different reagents (formamide, formamide/HCOOH, ammonium formate) used in the course of the Leuckart synthesis of PMA significantly affected the impurity content. The presented results point out on the “high-boiling pyridines” as compounds especially useful in the comparative analysis, since their profile seems to be independent on the purification procedure and may be conveyed from the crude reaction mixture even into a carefully purified final product.