Chiral NMR discrimination of amines: analysis of secondary, tertiary, and prochiral amines using (18-crown-6)-2,3,11,12-tetracarboxylic acid was written by Lovely, Ann E.;Wenzel, Thomas J.. And the article was included in Chirality in 2008.Safety of Ethyl 1-methylpipecolinate This article mentions the following:
Enantiomeric discrimination is observed in the 1H and 13C NMR spectra of secondary and tertiary amines in the presence of (-)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (1). Nonequivalence of the resonances of prochiral nuclei in primary and secondary amines is also observed when they associated with 1. The amines are added in their neutral form and are protonated by the carboxylic acid groups of 1 to produce the corresponding ammonium and carboxylate ions. Secondary amines associate with 1 through two hydrogen bonds and an ion pair interaction. Tertiary amines can only form one hydrogen bond to accompany the ion pairing. Chiral discrimination in the 1H and 13C NMR spectra of a series of aryl-containing secondary amines is of sufficient magnitude to determine enantiomeric purities. The discrimination in the spectra of tertiary amines with 1 is smaller, but 13C NMR spectra provided enough distinction for the determination of enantiomeric purity. In the experiment, the researchers used many compounds, for example, Ethyl 1-methylpipecolinate (cas: 30727-18-5Safety of Ethyl 1-methylpipecolinate).
Ethyl 1-methylpipecolinate (cas: 30727-18-5) belongs to piperidine derivatives. Piperidine is a saturated organic heteromonocyclic parent, an azacycloalkane, a secondary amine and a member of piperidines. Piperidine derivatives bearing a masked aldehyde function in the 蔚-position are easily transformed into quinolizidine compounds through intramolecular reductive amination.Safety of Ethyl 1-methylpipecolinate
Referemce:
Piperidine – Wikipedia,
Piperidine | C5H11N – PubChem