ISSN:
0018-019X
Schlagwort(e):
Chemistry
;
Organic Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
1H-NMR. Spectroscopic Determination of Enantiomeric Purities of Allenic Esters Using Optically Active Europium Shift ReagentsThe racemic allenic methyl esters 3--7 and the racemic allenic diesters 8--10 (cf. Scheme 2) in 1,1,2-trichloro-1,2,2-trifluoroethane (TCFE) and CCl4 in the presence of optically active tris[3-(heptafluorobutyryl)-(+)-camphorato]europium(III) (Eu(hfc)3) have induced unlike 1H-NMR. shift differences (ΔΔδ) for the protons of the methoxycarbonyl groups of their enantiomers. In some allenic esters the shift reagent causes additional separation of resonance signals; thus, further substituents on the allenic framework may be differentiated in the racemic mixture. This finding provides a widely applicable method for the determination of absolute enantiomeric purities of allenic esters and their corresponding acids. Accordingly we found for optically pure (+)-(S)-2-methyl-2,3-pentadienoic acid ((+)-(S)-13; cf. Fig. 2) a calculated [α]58920 value of + 73.3 ± 1.8°. Finally, the substituent effects on ΔΔδ-values (cf. Table 1--3) are discussed.
Zusätzliches Material:
2 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/hlca.19790620413
