NMR of enaminones. Part 8—1H, 13C and 17O NMR spectra of primary and secondary 1,2-disubstituted enaminones: configuration, conformation and intramolecular hdydrogen bonding

✍ Scribed by Jin-Cong Zhuo

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 269 KB
• Volume: 36
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/(sici)1097-458x(199808)36:8<565::aid-omr338>3.0.co;2-h

✦ Synopsis

The 1H, 13C and 17O NMR spectra for four series of C-2-substituted enaminones are reported : MeCO(Me)CxCHNHR (1), EtCO(Me)xCHNHR (2), PhCO(Me)CxCHNHR (3) and MeCO(Me)CxCHNHR (4). The 1H, 13C and 17O 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 17O shift values of the carbonyl groups in the four series of enaminones show that the inÑuence of N substituents is essentially identical and is additive. The shielding of the carbonyl O atom by intramolecular hydrogen bonding ca.

[30 ppm, is dependent on the donor ability of the amino groups and (*d HB ), the type of C-1 and C-2 substituents. Correlations of the 1H, 13C and 17O NMR data between the E-and Z-forms of enaminones are excellent.