Oxy- und Aminomethylenmeldrumsäuren

17O NMR of Enamino-Diesters: Intramolecular Hydrogen Bonding in 5-Alkylaminomethylene-2,2-dimethyl-1,3-dioxane-4,6-diones

“…These studies confirmed the presence of an intramolecular C=O ... HN bond in primary and secondary enamino-diesters. 17 O NMR is a particularly useful tool for the study of intramolecular hydrogen bonding in organic compounds [11,12]. Recently the 17 O NMR spectra of enaminones and enamino-diketones have been investigated [13].…”

“…17 O NMR is a particularly useful tool for the study of intramolecular hydrogen bonding in organic compounds [11,12]. Recently the 17 O NMR spectra of enaminones and enamino-diketones have been investigated [13]. The shielding of the carbonyl O-atom by intramolecular hydrogen-bonding (∆δ HB ), ranging from -14 to -47 ppm, was sensitive to the nature, number and position of the substituents.…”

“…The shielding of the carbonyl O-atom by intramolecular hydrogen-bonding (∆δ HB ), ranging from -14 to -47 ppm, was sensitive to the nature, number and position of the substituents. 17 …”

“…To evaluate the sensitivity of the C=O ... H-N type of intramolecular hydrogen bonding on the 17 O shift value of the hydrogen bonded carbonyl group, the 17 O NMR spectra of a series of 5-alkylaminomethylene-2,2-dimethyl-1,3-dioxane-4,6-diones (1a-1h) have been investigated.…”

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Abstract: Natural abundance 17 O NMR spectra of a series of 5-alkylaminomethylene-2,2-dimethyl-1,3-dioxane-4,6-diones, recorded in acetonitrile solution, are reported. The δ( 17 O) values correlate well with those of 4-alkylaminobut-3-en-2-ones and with the pK a values of amines.

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