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NMR of Enaminones Part 3— 1 H, 13 C and 17 O NMR Spectroscopic Studies of Acyclic and Cyclic N ‐Aryl Enaminones: Substituent Effects and Intramolecular Hydrogen Bonding
Author(s) -
Zhuo JinCong
Publication year - 1997
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(199705)35:5<311::aid-omr94>3.0.co;2-m
Subject(s) - chemistry , substituent , intramolecular force , moiety , aryl , carbon 13 nmr , chemical shift , hydrogen bond , stereochemistry , medicinal chemistry , computational chemistry , molecule , organic chemistry , alkyl
17 O, 13 C and 1 H NMR spectra for para ‐ and meta ‐substituted 4‐arylaminopent‐3‐en‐2‐ones (acyclic enaminones, 1 and 2) and 3‐arylaminocyclohex‐2‐en‐1‐ones (cyclic enaminones, 3 and 4) are reported. The 17 O, 13 C and 1 H shift values of these enaminones correlate well with σ m 0 and σ p ‐ constants in the correlations for meta and para derivatives, and with p K a values of the corresponding anilines. Dual substituent parameters analyses were also performed. Correlations of 17 O and 13 C chemical shifts of the carbonyl groups with those of the corresponding N ‐acylanilines indicate that the enaminone moiety as a whole has electronic properties similar to those of the RCONH group. The 17 O shift values of the carbonyl O atoms of enaminones correlate well with their 1 H and 13 C data. Shieldings of 33–45 ppm for O atoms are observed for 1 and 2 compared with 3 and 4, respectively. This is attributed to intramolecular hydrogen bonding. © 1997 by John Wiley & Sons, Ltd.