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Haloaldehyde polymers, 34. 1 H and 13 C NMR spectra of chloral oligomers prepared by lithium tert ‐butoxide initiation and the assignment of the meso/racemo addition products of the dimers

1989; Wiley; Volume: 190; Issue: 9 Linguagem: Inglês

10.1002/macp.1989.021900922

0025-116X

Koichi Hatada, Koichi Ute, Tamaki Nakano, František Vašš, Otto Vogl,

Analytical Methods in Pharmaceuticals

Abstract 1 H and 13 C NMR spectra of the mixture of chloral oligomers prepared by initiation with lithium tert ‐butoxide were examined in detail. 1 H and 13 C NMR signals due to meso and racemo diastereomers of the dimer fraction were unequivocally assigned through the 13 C‐ 1 H COSY spectrum and the 13 C NMR spectra with low‐power selective 1 H‐decoupling. The two‐dimensional NOESY spectrum showed correlation peaks between the signals due to the methine (acetal) protons of the neighbouring chloral monomeric units of the most abundant isomers in the trimer and tetramer fractions. The 1 H NOE enhancements and 3 J CH coupling constants were measured for the dimers; the results confirmed the meso/racemo assignments based on earlier conformational analysis.