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NMR of enaminones. Part 8— 1 H, 13 C and 17 O NMR spectra of primary and secondary 1,2‐disubstituted enaminones: configuration, conformation and intramolecular hdydrogen bonding
Author(s) -
Zhuo JinCong
Publication year - 1998
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/(sici)1097-458x(199808)36:8<565::aid-omr338>3.0.co;2-h
Subject(s) - chemistry , intramolecular force , carbon 13 nmr , chemical shift , stereochemistry , hydrogen bond , nmr spectra database , spectral line , crystallography , molecule , organic chemistry , physics , astronomy
The 1 H, 13 C and 17 O NMR spectra for four series of C‐2‐substituted enaminones are reported: MeCO(Me)C=CHNHR ( 1 ), EtCO(Me)=CHNHR ( 2 ), PhCO(Me)C=CHNHR ( 3 ) and MeCO(Me)C=CHNHR ( 4 ). The 1 H, 13 C and 17 O NMR data for these enaminones show that 1 and 2 exist as mixtures of E ‐ and Z ‐forms, 3 exists mainly in the E ‐form and 4 is in the Z ‐form. The E ‐ and Z ‐forms exist in the E ‐ s ‐ E ‐ s ‐ E and Z ‐ s ‐ Z ‐ s ‐ E conformations, respectively. The 17 O shift values of the carbonyl groups in the four series of enaminones show that the influence of N substituents is essentially identical and is additive. The shielding of the carbonyl O atom by intramolecular hydrogen bonding (Δδ HB ), ca . ‐30 ppm, is dependent on the donor ability of the amino groups and the type of C‐1 and C‐2 substituents. Correlations of the 1 H, 13 C and 17 O NMR data between the E ‐ and Z ‐forms of enaminones are excellent. © 1998 John Wiley & Sons, Ltd.