Synthesis and Structure Elucidation of 1-Aryl-substituted Tetrahydropyridone Derivatives

A series of 1-aryl-1,4,5,6-tetrahydro-4(1H)-pyridones having substituents in 2,3- and 2,3,5-positions was prepared from N-aryl-β-alanines and ethyl acetoacetate or 2,4-pentanedione. Twelve tentative biologically active compounds were identified by the combination of ¹H, ¹³C and ¹H/¹³C NMR spectroscopy. The extensive interest has been focused on the influence of substituents as well as on the number, attachment position, and the nature of the substituents. The unknown shielding of the heterocyclic ring on the aromatic carbon atoms was determined and the averaged chemical shift increments were successfully used for the assignment of the aromatic moiety of the studied compounds. The presence of two chiral elements in compounds 16, 17, 20–21 resulted in the mixture of diastereomers and double sets of the resonances in NMR spectra. __________ Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 874–881, June 2005.     

The carbon-13 nuclear magnetic resonance spectra of some α-spirocyclopropyl ketones and related cyclohex-2-en-1-ones and 2-ethylidenecyclohex-3-en-1-ones

The ¹³C NMR spectra of a series of β,γ-unsaturated α-spirocyclopropylcyclohexanones and saturated α-spirocyclopropylcycloalkanones have been analyzed and compared with the spectra of diethyl cyclopropanedicarboxylate and a corresponding spiro acylal. The chemical shifts of the cyclopropane methylene carbons are correlated with spiroactivation of the cyclopropane ring to nucleophilic attack. In the case of the saturated spiro ketones these chemical shifts can also be correlated with their photochemistry. In the SFORD spectra of the spiro ketones the signals of the cyclopropane methylene carbons appear as complex multiplets: this is attributed to second-order coupling resulting from strong coupling between the vicinal cyclopropane protons. The ¹³C NMR spectra of a series of related cyclohex-2-en-1-ones and 2-ethylidenecyclohex-3-en-1-ones have also been analyzed; the chemical shift assignments for the latter corroborate the configurational assignments made on the basis of ¹H NMR spectroscopy.     

Einfluss der Orientierung von Substituenten auf die chemische Verschiebung von 13C. II. 13C-NMR.-spektroskopische Untersuchung von substituierten Spiro [cyclopropan-1′,9-fluorenen]

Effect of the Orientation of Substituents on the Chemical Shift of ¹³ II. ¹³C-NMR. Study of Substituted Spiro [cyclopropane-1′, 9-fluorenes] The ¹³C-NMR. spectra of spiro[cyclopropane-1′, 9-fluorenes] substituted at the cyclopropane ring have been assigned, largely with the aid of selective proton decoupling. The effects of the substituents upon the chemical shifts of the aromatic carbons are orientation dependent. the effects of cis-substituents on γ-carbon atoms are large and negative (inducing high field shifts), those of trans-substituents smaller and dependent on the electron donor/acceptor properties of the substituents. The effects on δ-carbon atoms in close proximity of the substituents are large and positive; they are interpreted in terms of electric field effects.     

NMR studies on 1,2‐dihydro‐2‐(4‐aminophenyl)‐4‐[4‐(4‐aminophenoxy)‐4‐phenyl]‐(2H)phthalazin‐1‐one

An unsymmetrical heterocyclic diamine, 1,2‐dihydro‐2‐(4‐aminophenyl)‐4‐[4‐(4‐aminophenoxy)‐4‐phenyl]‐(2H)phthalazin‐1‐one, was synthesized. Its ¹H and ¹³C NMR spectra were completely assigned by utilizing the two‐dimensional heteronuclear ¹³C–¹H multiple‐bond coherence (HMBC) spectroscopy, and heteronuclear ¹³C–¹H one‐bond correlation spectroscopy, homonuclear shift correlation spectroscopy (H,H‐COSY) and rotating frame Overhauser enhancement spectroscopy (ROESY). The structure of the compound was shown to be the phthalazinone rather than the phthalazine ether from cross peaks and chemical shifts of the protons. Copyright © 2002 John Wiley & Sons, Ltd.     

13C FT-NMR spectra of alkyl substituted furans. A study of the influence of steric interactions

The ¹³C FT-NMR spectra of thirteen furans, monodi- or trisubstituted with methyl and/or t-butyl groups, were studied in detail. Substituent effects of methyl and t-butyl groups on the chemical shifts of ring carbon atoms are additive in nonsterically hindered furans. Steric shifts for the ring carbon atoms are found in furans with bulky neighbouring substituents, but the hybridisation of the carbon atoms in these hindered furans is not changed. The chemical shifts of the substituents are calculated according to the Grant-Cheney formula. No simple relationship between steric shift and steric hindrance can be ascertained.     

1H, 13C,and 14N NMR study of 3-methylfurazans with nitrogen-containing substituents at position 4

3-Methylfurazans with nitrogen-containing substituents at position 4 were studied by ¹H, ¹³C, and ¹⁴N NMR spectroscopy. A correlation between the chemical shifts in ¹³C NMR spectra of these furazans and monosubstituted benzenes with the same substituents was found. The increments for a number of furazan-containing substituents were determined for the first time.     

NMR spectroscopic study of 3-nitrofurazans

3-Nitrofurazans with different substituents at position 4 were studied by ¹H, ¹³C, and ¹⁴N NMR spectroscopy. A correlation between chemical shifts (CS) in the ¹³C NMR spectra of furazans and benzene with similar substituents was revealed. Increments for a series of new substituents were determined. The ¹³C and ¹⁴N CS values presented can be used as a reliable set of reference data.     

13C and proton NMR spectra of 2(1H)pyrazinones

¹³C and proton NMR spectra data are given for eleven 2(1H)pyraziones. Assignments of chemical shifts were made by methods which included: deuterium exchange with certain protons of 3-alkyl substituents; change of chemical shifts of certain carbon atoms with change in pH; the use of long-range coupling constants for ¹³C to protons; and various correlations among assigned spectra.     

Carbon-13 NMR studies of 1-aryl-3-phenyl-2-thioxo-4-imidazolidinones. Conformational isomerism and substituent effects

Characteristic ^13C chemical shift ranges and substituent shifts of heterocyclic ring carbon atoms have been identified for a number of 1-aryl-3-phenyl-2-thioxo-4-imidazolidinones. ¹³CNMR spectra may be used to detect slow internal rotation about the aryl C? N-1 bond in compounds with diastereomeric rotational isomers; many corresponding carbon atoms in the rotamers have distinctly different chemical shifts. The δ-effects originating from aryl ortho substituents are both electronic and steric in origin.     

1H and 13C nmr study of conformational and electronic structure of 1-vinylpyrroles

The ¹H and ¹³C NMR spectra of some 2-alkyl- and 2,3-dialkyl-1-vinylpyrroles as well as model 1-unsubstituted pyrroles were studied. Alkyi substituents affect electronic structures of the compounds through steric inhibition of p,π-conjugation and π-induction. Correlations of the ¹³C chemical shifts of the pyrrole ring carbon atoms with the total charge density (CNDO/2) of these atoms are established.     

New fluorinated polymers bearing pendant phosphonic groups for fuel cell membranes: Part 1 synthesis and characterizations of the fluorinated polymeric backbone

Radical copolymerizations of chlorotrifluoroethylene (CTFE) with vinyl ethers such as 2-chloroethyl vinyl ether (CEVE) and ethyl vinyl ether (EVE) were performed at 75 °C in the presence of peroxide initiator. Three copolymers were obtained and characterized by means of both NMR and elemental analysis. Then, the chlorine atoms in the side chains were converted into iodine atoms by nucleophilic substitution, which was monitored by ¹H NMR spectroscopy. A series of five copolymers with different amounts of iodine atoms in the side chains were thus obtained. These copolymers exhibited molecular weight values of about 25,000 g mol⁻¹, and the thermal analysis of the copolymers showed a starting degradation from about 220 °C. The T_g values were in the range of 34-41 °C and showed a linear dependence versus the content of iodine atoms.     

Configurational assignment of the geometric isomers of α,β-disubstituted vinyl methyl ethers from 13C nmr shift data

¹³C chemical shifts of the C atoms in the geometric isomers of some α,β-disubstituted vinyl methyl ethers have been measured. Configurational assignment is readily accomplished from the relative ¹³C chemical shift values of the β-C atoms, the signal of the Z isomer (with the β substituent in a cis position with respect of the MeO group) lying 11–15 ppm downfield from that of the E isomer. The higher chemical shifts of the β-C of the Z form are ascribed to reduced conjugation in the vinyloxy system, due to the nonplanar gauche configuration of the MeO group about the O-C(sp²) bond. Structural effects on the other ¹³C shift values are also discussed.     

Carbon-13 magnetic resonance studies of cyclic compounds. 2. Carbon-13 chemical shift parameters for equatorial and axial substituents in cyclohexane: The substituents methyl,ethyl, isopropyl,methoxy and phthalimido

Carbon-13 chemical shift parameters for equatorial and axial substituents in cyclohexane are reported for methyl, ethyl, isopropyl, methoxy and phthalimido substituents. The usefulness of the alkyl parameters is demonstrated by the agreement between calculated and observed ¹³C shifts for trans-1,4-dialkylcyclohexanes (alkyl = Me, Et, i-Pr) and for both conformations of cis-1,4-dialkylcyclohexanes (alkyl = Me, Et, i-Pr).     

Synthesis and characterisation of water soluble ferrocenes: Molecular tuning of redox potentials

A range of novel water-soluble alkylated ferrocene sulfonate compounds are reported. Mono- and di-sulfonation on a series of alkyl ferrocenes produced 1,1′-dimethyl ferrocene sulfonate, 1,1′-dimethyl ferrocene disulfonate, 1,1′-diethyl ferrocene sulfonate, 1,1′-diethyl ferrocene disulfonate, t-butyl ferrocene sulfonate, t-butyl ferrocene disulfonate, ethyl ferrocene sulfonate, ethyl ferrocene disulfonate, n-butyl ferrocene sulfonate and n-butyl ferrocene disulfonate. All compounds were characterized by NMR spectroscopy, UV/Vis spectroscopy and electrochemical analysis. ¹H and ¹³C NMR studies have revealed the formation of several isomers with sulfonation occurring on positions α and β to the alkyl substituent or on the unsubstituted cyclopentadienyl ring. Variation of the alkyl group allowed the isomeric pattern to be tuned such that the final products followed either electronic or steric control. Cyclic voltammetry of the resulting products showed that the redox potential of the iron centre can be easily manipulated by changing the substituents on the cyclopentadienyl rings. This result has significant implications in the future development of homogenous redox mediators for sensing applications.     

PH-abhängigkeit der 13C-chemischen verschiebungen sechsgliedriger stickstoff-heteroaromaten

The ¹³C chemical shifts of the 6-membered nitrogen heteroaromatic compounds pyridine, pyrazine, pyrimidine, pyridazine, quinoline and isoquinoline have been measured as functions of P_H in aqueous solutions. On protonation of the nitrogen, the ¹³C signals of the C atoms in α position usually suffer an upfield shift; the signals of the more removed C atoms are mostly shifted to lower field. The P_H shifts can reach amounts in the order of 10 ppm. The P_H dependences of chemical shifts of the six heterocyclic compounds investigated follow classical titration curves, whose turning-points yield the P_K values of the bases in good agreement with other methods of measurement.     

Zur Kenntnis des Chinoiden Zustandes—XX: 13CMR-Untersuchungen an Cyclohexadienonen

The ¹³C-NMR-chemical shifts of 19 para- and 5 ortho-cyclohexadienones are determined by ¹³C-Fourier-transformation spectroscopy and assigned. The effect of substituents on the chemical shift of the ring carbon atoms is discussed. The mutual dependence of the shifts of the olefinic ring carbons and the allylic carbon atom in the para-quinolid ring system is shown by computing regression lines. A frequently observed correlation between ¹³C-NMR and ¹H-NMR is examined in the case of cyclohexadienones.     

A 1H and 13C NMR study of methoxyretinoids. Spectral assignment and determination of configuration

A number of modified retinals and retinoic esters carrying one or two methoxy groups or one methoxy and one methyl group on the polyene chain were investigated by ¹H and ¹³C NMR spectroscopy. Spectral assignments were made from homo- and selective ¹³C{¹H} hetero-decoupling experiments and from chemical shift comparisons. The configurations of the polyene double bonds were derived from vicinal H,H coupling constants, from ¹H and ¹³C chemical shifts and by measuring nuclear Overhauser enhancements. It is found that all double bonds with no additional substituents occur in the trans (E) and all methoxy-substituted double bonds in the cis (also E) configuration. Double bonds carrying methyl groups give rise to both cis (Z) and trans (E) isomers.