bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multivariate investigation of 1H and 13C NMR shifts of 2‐ and 3‐substituted furans, thiophenes, selenophenes and tellurophenes
Authors: Ebert Cynthia , Gianferrara Teresa , Linda Paolo , Masotti Paola 
Published: May 2005

AbstractThe effect of substituents on 13C and 1H NMR chemical shifts in 2‐ and 3‐substituted furans, thiophenes, seleno‐phenes and tellurophenes was studied by means of principal components analysis (PCA) and partial least squares (PLS) analysis. The analysis of the data by PCA showed that for both series the substituents are grouped into four different classes depending on the heteroatom present in the ring, and that the substituent‐heteroatom interaction has the same nature for all the rings. PLS analysis of the data sets allowed the prediction of the chemical shift values of a different ring having the same substituents.
Fluorine NMR spectra of some 9α‐fluorosteroids
Authors: Smith Leland L. , Ezell Edward L. 
Published: May 2005

AbstractFluorine NMR spectra of 23 9α‐fluorocorticosteroid analogs established that the 9α‐fluorine is subject to deshielding effects by remote structural features (A‐ring olefinic unsaturation, A‐ring 1α‐ and 2β‐hydroxy and acetoxy features and D‐ring 16α‐methyl substitution) and to minor shielding effects by vicinal 11β‐alcohol dehydrogenation and acetylation, and by B‐ring olefinic unsaturation. Substitutions in the 6α‐, 6β‐, 16α‐ and 16β‐positions and D‐ring homoannulation do not alter the 19F chemical shift significantly. Coupling constants of the 9α‐fluorine to vicinal 8β‐ and 11α‐hydrogens are not altered appreciably by structural changes, except for introduction of a Δ6‐double bond or 11β‐alcohol dehydrogenation, indicating that the conformations of the tetracyclic ring system and particularly the B/C‐ring junction were very similar for these 9α‐fluorosteroids.
13C nuclear magnetic resonance studies on 1,3‐diphenylprop‐2‐enones
Authors: Parmar V. S. , Sharma Sunil , Rathore J. S. , Garg Meenu , Gupta Sandhya , Malhotra Sunita , Sharma V. K. , Singh Suddham , Boll P. M. 
Published: May 2005

AbstractThe 13C NMR spectra of 48 differently substituted chalcones (1,3‐diphenylprop‐2 enones) have been recorded and the results are discussed. The data will be useful in the identification of new/natural chalcones.
Spectroscopic analysis of (1‐α,2‐α′: η4‐quinodimethane)tris(trimethylphosphine)ruthenium(0)
Authors: Simpson Nigel J. , Mackie Raymond K. , Cole‐Hamilton David J. 
Published: May 2005

AbstractThe 1H, 13C and 31P NMR spectra of [Ru(CH2C6H4CH2)(PMe3)3], which contains a coordinated o‐xylidene moiety, have been analysed. Parameters such as the geminal coupling in the methylene groups, P,H couplings and the chemical shifts of the quaternary ring carbon atoms all point to a metal‐o‐xylidene binding that is intermediate between σ2,π and π2. Spectral assignment is assisted by P‐H correlation spectroscopy using the COLOC sequence. The best parameter for identifying the bonding mode is the chemical shift for the quaternary aromatic carbon atoms.
Structural analysis and complete assignment of the 1H and 13C NMR spectra of thiele's ester
Authors: Minter David E. , Marchand Alan P. , Lu Shao‐po 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of ‘Thiele's ester,’ i.e. dimethyl 3α 4α, 7α, 7α‐tetrahydro‐4,7‐methano‐1H‐indene‐2,6‐dicarboxylate, have been assigned completely by using a combination of one‐ and two‐dimensional NMR techniques. The results thereby obtained afford the first unambiguous assignment of the structure of Thiele's ester that has been made solely on the basis of NMR spectral analysis. The structure obtained is fully consistent with that of Thiele's ester established previously by chemical methods.
Study of the hydrolysis of combined Al3+ and Ga3+ aqueous solutions: Formation of an extremely stable GaO4Al12(OH)24(H2O) polyoxycation
Authors: Bradley Susan M. , Kydd Ronald A. , Yamdagni Raghav 
Published: May 2005

Abstract71Ga and 27Al NMR and clay mineral pillaring studies were used to investigate the hydrolysis of Al(H2O)–Ga(H2O) solutions, mixed in an Al:Ga mole ratio of 12:1, and confirmed the formation of the previously proposed GaO4Al12(OH)24(H2O) polyoxycation. This species has been found to be formed in marked preference to both AlO4Al12(OH)24(H2O) and the previously identified GaO4Ga12(OH)24(H2O) ions, and further to have a much higher thermal stability in solution than either of these. It is suggested that the reason for the increased stability of the ‘GaAl12’ species is that the substitution of a larger metal into the central tetrahedral position has resulted in the formation of a less distorted structure.
1H and 13C NMR analysis of D‐amygdalin: Oligosaccharide assignment and sequencing
Authors: Ribeiro Anthony A. 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of D‐amygdalin, a cyanogenetic disaccharide accumulated in food plants, were assigned using a combination of NMR techniques. Methods applied include standard 1H–1H COSY, proton zero quantum coherence (ZQCOSY), 1D NOE, broad‐band decoupled 1H–13C chemical shift correlation and long‐range 1H–13C chemical shift correlation. ZQCOSY was especially useful in assigning the closely spaced sugar resonances, and long‐range 1H‐13C chemical shift correlation allowed sequencing of the monosaccharide rings. Coupling constants useful in conformational analysis are derived from highly digitized 1H 1D spectra and 2D J‐resolved spectroscopy. The 1H and 13C chemical shifts and coupling constants indicate that the β‐D‐glucopyranose rings of D‐amygdalin adopt a 4C1 chair conformation.
Carbon‐13 NMR spin–lattice relaxation time study of the molecular motions of 5‐nitro‐2‐(2‐pyridinylthio)pyridine
Authors: Amato Maria E. , Grassi Antonio , Perly Bruno 
Published: May 2005

AbstractThe motional behaviour of 5‐nitro‐2‐(2‐pyridinylthio)pyridine (NPTP) was ananlysed by 13C NMR spin‐lattice relaxation times (T1). The analysis of the experimental T1 data was performed by using an analytical model to describe the overall and internal motions fo the molecule. The results showed that on exchange exists between the two ‘enantiomeric’ preferred conformations of the molecule, which therefore assumes an enhanced conformationally rigid character in the liquid phase. The motional parameters, derived by the fitting procedure of the relaxation times, showed that strong intermolecular interactions occur in the liquid phase for NPTP and that, in particular, the dipole moment of the mitropyridine ring contributes greatly in determinating the motional dynamics of NPTP.
Disentangling coupling and NOE pathways involving poorly resolved proton signals: HMQC‐TOCSY and HMQC‐NOESY
Authors: Crouch Ronald C. , McFadyen Robert B. , Daluge Susan M. , Martin Gary E. 
Published: May 2005

AbstractCOSY and NOESY frequently fail when key proton signals are poorly resolved because of the proximity of the correlating off‐diagonal responses to the diagonal. Proton‐coupled heteronuclear multiple quantum relayed coherence spectroscopy (HMQC–TOCSY) and heteronuclear multiple quantum proton nuclear Overhauser effect (HMQC–NOESY) experiments to circumvent these problems are described. NMR data for a model carbocyclic nucleoside analog are presented for which assignments of resonances and stereochemistry were impossible by ‘conventional’ 2D NMR methods. Resonance and unequivocal stereochemical assignments were made, however, using the HMQC–TOCSY and HMQC–NOESY experiments, respectively.
Multinuclear NMR study of 1,3,3‐trimethylbicyclo[2.2.1]heptan‐2‐one (fenchone) and its six monochlorinated derivatives
Authors: Kolehmainen E. , Laihia K. , Korvola J. , Kauppinen R. , Pitkänen M. , Mannila B. , Mannila E. 
Published: May 2005

Abstract1H, 13C and 17O NMR spectra of fenchone and six monochlorofenchones have been recorded. The second‐order 1H NMR spectra were analysed by an iterative computer program. The 1H and 13C chlorine‐induced substituent chemical shifts (SCS) were calculated. The vicinal coupling constants proved to be essential in the assignment of the chemical shifts of the geminal methyls. No clear correlation was observed between the chemical shifts of the carbonyl oxygen and the carbonyl carbon. All monochlorofenchones were previously unknown compounds and were synthesized for this work.
Carbon‐13 and proton spectra of tetracyclododecanes: Long‐range steric effects
Authors: Seidl P. R. , Leal K. Z. , Costa V. E. U. , Poli N. D. 
Published: May 2005

AbstractThe 1H and 13C spectra of endo‐endo‐tetracyclo[6.1.13,6.02,7]dodec‐4‐en‐10‐ol have been interpreted using shift reagents and HETCOR experiments. Carbon chemical shifts are compared with tetracyclic analogs and bicyclic model compounds. Evidence for upfield δ and ε effects of 3–5 ppm is presented.
39K NMR spectroscopy of potassium solutions in tetrahydrofuran containing 18‐crown‐6. Relaxation study
Authors: Sokól Maria , Grobelny Janusz , Jedliński Zbigniew J. 
Published: May 2005

AbstractBlue potassium solution in THF containing 18‐crown‐6 was investigated by means of 39K NMR spectroscopy. The presence of potassium anions and complexed potassium cations was demonstrated. Spin‐lattice and spin‐spin relaxation times were measured in the temperature range 176–295 K. An attempt was made to explain the relaxation behaviour in the system.
SELRESOLV—inverse and selective detection of long‐range C,H spin coupling constants
Authors: Ochs Matthias , Berger Stefan 
Published: May 2005

AbstractA pulse sequence (SELRESOLV) for the proton‐detected determination of long‐range C,H coupling constants is described. The 2D J(HH) resolved experiment with selective 13C excitation separates J(HH) from J(CH) couplings. Application is demonstrated using crotonaldehyde and β‐naphthol as examples.
13C NMR analysis of sultones and sulphonate–sulphate anhydrides
Authors: Castro V. , Boyer J. L. , Canselier J. P. , Terjeson R. J. , Mohtasham J. , Peyton D. H. , Gard G. L. 
Published: May 2005

AbstractThe 13C NMR spectra of 20 compounds belonging to several types of monocyclic sultones and related ‘carbyl sulphates,’ including a series of fluorinated β‐sultones (1,2‐oxathietane 2,2‐dioxides), are reported. Chemical shift increment systems with n‐alkanes as reference molecules are established for non‐fluorinated sultones: they show a much less pronounced deshielding effect on the carbon α to oxygen in β‐sultones than in the other series. Chemical shifts for the parent β‐sultone, predicted in two ways (linear or cyclic model compound), are found to be almost consistent with a purely additive scheme. In fluorinated β‐sultones the α‐substituent increments relative to perfluoroethanesultone are also derived.
Phosphorus‐31 and platinum‐195 NMR studies of carboxylato‐bridged dinuclear platinum(II) complexes
Authors: Kannan S. , Jain V. K. 
Published: May 2005

AbstractCarboxylato‐bridged dinuclear platinum(II) complexes of the type [Pt2X2(μ‐OOCR′)2(PR3)2] [X = Cl, I; R′ = CH3, CF3; PR3 = PEt3n, PPr3n, PBu3n, PMe2Ph, PMePh2, PPh3, P(p‐Tol)3] were prepared and investigated by 31P and 195Pt NMR spectroscopy. The NMR data indicate that there is considerable platinum‐platinum interaction in these complexes.
Structure of a norbornane‐fused pentacyclic isoxazoline
Authors: Sohár Pál , Kövesdi István , Frimpong‐Manso Samuel , Stájer Géza , Bernáth Gábor 
Published: May 2005

AbstractThe steric structure of a pentacyclic adduct formed as a by‐product in a retro‐Diels‐Alder reaction was elucidated by 1H and 13C NMR spectroscopy, making use of double resonance and differential nuclear Overhauser effect measurements.
Identification of oplopanonyl acetate isolated from Chamaecyparis pisifera
Authors: De Bruyn André , De Pooter Herman L. , De Buyck Laurent , Jans Arnold W. H. , Buděšínský Miloš , Sedmera Petr 
Published: May 2005

AbstractOplopanonyl acetate was isolated from Chamaecyparis pisifera. Its structure and stereochemical features were established using NMR techniques.
NMR spectra of the porphyrins. Part 39. Paramagnetic shifts in cobalt(II) porphyrins
Authors: Abraham Raymond J. , Marsden Ian , Xiujing Lucy 
Published: May 2005

AbstractA model of the paramagnetism in cobalt(II) porphyrin complexes has been developed which successfully calculates paramagnetic shifts for protons not affected by the contact term. The model utilizes a single large dipole positioned on the cobalt(II) atom, and calculates the pseudo‐contact shift using the dipole approximation.With this model the angle of twist of the peripheral meso phenyl rings in tetraphenylporphyrin (TPP) derivatives was determined. In TPP and the meta‐ and para‐substituted derivatives studied the phenyl rings are at ca. 65° to the porphyrin plane, whereas in the ortho‐substituted derivatives the phenyl rings are essentially orthogonal. Similarly, the geometry for the β‐ethyl groups of octaethylporphyrin and etioporphyrin I was found to be 50° out of the plane of the porphyrin inclined to the meso proton, and that of the comparable propionate groups of coproporphyrin I to be 55°. Finally, the novel compound meso‐tetra(p‐phenoxyphenyl)porphyrin, an analogue of diphenyl ether, was prepared to determine the twist angles between the two phenyl rings. These were found to be 60° by correlating observed paramagnetic shifts with those calculated. This agrees well with MNDO studies, which gave a value of 59°.
Erroneous assignments of configuration around CC double bonds
Authors: Kamieńska‐Trela Krystyna 
Published: May 2005

AbstractNMR studies on trans‐1‐trimethylsilyl‐1,2‐dibromoethene and cis‐secondary sulphinyl enamines were recently reported. However, it is shown that the assignment of the configuration should be reversed in both instances, i.e. the configuration of 1‐trimethylsilyl‐1,2‐dibromoethene should be cis and that of secondary β‐sulphinyl enamines should be trans..
Diacyl acid dihydrazides
Authors: Al‐Talib Mahmoud , Tashtoush Hasan , Odeh Nedal 
Published: May 2005

AbstractN,N′‐Diacyl acid dihydrazides were prepaed by the reaction of acid dihydazides with two equivalents of acyl chlorides. The structures of these compounds were elucidated by 1H and 13C NMR spectroscopy.
High‐field multinuclear magnetic resonance relaxation studies of pivalic acid in liquid and solid phases
Authors: Aksnes Dagfinn W. , Kimtys Liudvikas L. 
Published: May 2005

AbstractProton, 13C, deuteron and 17O NMR line widths and spin‐lattice relaxation times (T1) were measured at a field strength of 9.4T over a wide temperature region in liquid and solid pivalic acid (PA). A striking feature of the NMR spectra is that the methyl proton signal is much wider than the carboxyl proton signal in solid I, whereas the opposite is true for the corresponding deuteron signals. Molecular self‐diffusion and overall molecular tumbling with activation energies of 59 and 31 kJ mol−1, respectively, are responsible for the considerable line narrowing observed for the methyl proton and deuteron resonances in solid I. The narrow carboxyl proton resonance and the low activation energy for the motional narrowing process (18 kJ mol−1) indicate that the acid hydrogen is moving through the lattice at a much faster rate than the rest of the molecule.An analysis of the T1 relaxation times of PA is reported. Rotational correlation times and activation parameters for the overall tumbling, and also the internal methyl and tert‐butyl reorientations (C3 and C3′ motions) taking place in the liquid and solid phases of PA, have been obtained for the first time. The results show that the slower motion is overall tumbling with an activation energy of 20–32 kJ mol−1, while the faster motions are internal C3′ and C3 reorientations with activation energies of 10–15 kJ mol−1. On freezing, the rate of overall tumbling is reduced by a factor of 47 from 1.6 × 1010 to 3.3 × 108 s−1, whereas the rates of C3′ and C3 rotations (1.1 × 1011 and 3.2 × 1010 s−1, respectively) are hardly affected.
Solid‐state NMR studies of the structure and reactivity of molecular sieve catalysts
Authors: Klinowski Jacek , Anderson Michael W. 
Published: May 2005

AbstractInsights into the structure of molecular sieves are provided by solid‐state NMR in ways which are herein reviewed and extended. The uses of 29Si, 27Al and 1H NMR are briefly discussed. Attention is then paid to recent work which examines, using 1H and 13C NMR, the chemical status of guest organic molecules and questions of shape selectivity, giving novel information relevant to catalytic reactions.
2D NOESY studies on [Pd(η3‐C10H15){(R)( + )‐BINAP}]+ defining the relative spatial orientation of the phenyl and π‐allyl moieties
Authors: Rüegger Heinz , Kunz Roland W. , Ammann Christian J. , Pregosin Paul S. 
Published: May 2005

Abstract2D NOESY, COSY and 31P,1H correlation measurements have been carried out on the optically active β‐pineneallyl‐(R)(+)‐BINAP palladium complex, [Pd(η3‐C10H15){(R)(+)‐BINAP}](CF3SO3). The ortho protons of the four non‐equivalent phenyl rings have been assigned, as have the 15 protons of the β‐pineneallyl. The 2D NOE data show selective interactions of the phenyl ortho protons with different sections of the allyl ligand, thereby contributing to our knowledge of the three‐dimensional solution structure of this cationic complex.
Application of two‐dimensional shift correlated NMR techniques to the structure determination of an unusual marine alkaloid, isosaraine‐2
Authors: Cimino G. , Fontana A. , Madaio A. , Scognamiglio G. , Trivellone E. 
Published: May 2005

AbstractAn extensive application of two‐dimensional proton–proton and proton–carbon shift correlated spectroscopy allowed the structural elucidation of isosaraine‐2, a minor component of an unique family of alkaloids from the sponge Reniera sarai.
Increased resolution in proton detected heteronuclear NMR experiments by folding in the hetero‐dimension
Authors: Schmieder P. , Zimmer S. , Kessler H. 
Published: May 2005

AbstractLimited resolution in indirect detected frequency dimensions (evolution periods) in multi‐dimensional spectroscopy is a common problem, especially in the carbon dimension of heteronuclear experiments. Folding of signals in empty regions can overcome these problems. To record the spectra in a pure phase certain conditions have to be fulfilled to account for unavoidable deviations from zero time of the zero increment. A new slight variation of inverse heteronuclear correlation pulse sequences is proposed to allow pure phase spectra. Practical applications are given.
13C NMR study of N‐substituted 3‐azachalcones
Authors: Szajda Maria 
Published: May 2005

Abstract13C NMR data are reported for new N‐benzyl and N‐alkyl derivatives of 3‐azachalcone. The unambiguous assignment of signals is based on 13C/1H heteroshift correlated 2D NMR spectra.
Multinuclear magnetic resonance study of organometallic substituted enamines—stereochemical dependence of vicinal 119Sn–15N spin–spin couplings
Authors: Kupče Ēriks , Wrackmeyer Bernd , Lukevics Edmunds 
Published: May 2005

Abstract1H, 13C, 15N, 29Si and 119Sn NMR data (chemical shifts and coupling constants) are reported for the organometallic substituted enamines Me3Sn(Me3M)CC(NEt2)CH2OMe [M = Sn (1), Ge (2), Si (3)], of which 2 and 3 are obtained as a mixture of E and Z isomers, and (Me3Sn)2CC(NEt2)CCNEt2. Since there is no inverse linear relationship between δ13C(MC) and δ15N, NC(pp)π interactions must be regarded as being very weak. All vicinal coupling constants, 3J(119Sn13C), 3J(119Sn15N) and 3J(29Si15N), across the CC double bond show the expected stereochemical dependence, with | 3Jtrans | > | 3Jcis |. To our knowledge, long‐range couplings of this type, involving 15N, are reported for the first time. The magnitude of | 3J(119Sn15N)trans | exceeds the magnitude of | 1J(119Sn15N) | in most trimethyltin amides. A relationship between the magnitude of | 3J(119Sn15N) | and the orientation of the nitrogen lone electron pair is proposed.
Sites of protonation in cardiotonic polyazaindolizines by NMR spectroscopy
Authors: Barraclough Paul , Firmin David , Lindon John C. , Nobbs Malcolm S. , Sanderson Paul N. , Smith Steven , Gillam Janet M. 
Published: May 2005

AbstractThe pKa, values of six sulmazole analogues were measured spectrophotometrically. The major protonation sites for most of these bridgehead nitrogen heterocycles were determined by 1H and 13C NMR methods. The aryl‐substituted imidazo[1,2‐a]pyrimidine (4), 8‐methoxyimidazo[1,2‐a]pyrazine (6), imidazo[1,2‐b]pyridazine (9) and imidazo[1,2‐b][1,2,4]triazine (11) undergo protonation at the imidazo nitrogen. The imidazo[1,2‐a]pyrazine (5) protonates mainly at N‐7. In some cases differences in basicity properties between these aryl analogues and the bridgehead heterocycles have been observed.
Application of deuteriated isotopomers in the analysis of 13C CP/MAS NMR spectra of some azo dyes
Authors: Straka Jaroslav , Schneider Bohdan , Lyčka Antonín , Jirman Josef 
Published: May 2005

Abstract13C CP/MAS NMR spectra (50.3 MHz) of 4‐[N,N‐bis(2‐hydroxyethyl)amino]azobenzene (1), (N,N‐dimethylamino)azobenzene (2), 4‐methoxyazobenzene (3), 2‐hydroxy‐5‐tert‐butylazobenzene (4) and 4‐hydroxyazobenzene (5) were recorded. The isotopomers of 1, 4 and 5 with pentadeuteriated unsubstituted aromatic rings were also studied. Dipolar dephased spectra of the deuteriated isotopomers were used for chemical shift interpretation in the solid state. The changes in cross‐polarization dynamics caused by deuteration were investigated for 1. The spectra of 1, 2, 3, and 5 were also measured at elevated temperature. It was found that in 1, 2 and 5, rotation of the aromatic rings is induced at elevated temperature.
Conformational analysis of 5,6,7‐trisubstituted flavones: 13C NMR and molecular mechanics study
Authors: Biekofsky Rodolfo R. , Buschi Carlos A. , Pomilio Alicia B. 
Published: May 2005

Abstract13C NMR spectra of six flavones from Gomphrena martiana were analysed and compared with those of two related flavones isolated from Popowia cauliflora. This series of compounds has a similar substitution pattern on ring A, all compounds having oxygenated substituents on C‐5, C‐6 and C‐7. Consistent trends in relating conformation to substituent chemical shift effects (SCS) were found by analysing the 13C NMR data for these compounds. Chemical shifts for ring A carbons were calculated using the principle of additivity of substituents and by taking into account the conformation of the substituents. A reasonable agreement between the calculated shifts and the experimental values was found. A molecular mechanics study of these compounds was undertaken in order to obtain a set of consistent molecular structures to search for correlations between molecular structure and measured 13C chemical shifts. Good agreement was found between the predicted molecular mechanics conformations and the 13C NMR spectral data.
New β‐dihydroagarofuran sesquiterpenoids from Celastrus paniculatus
Authors: Sang Hong , Wang Hanqing , Tu Yongqiang , Chen Yaozu 
Published: May 2005

AbstractTwo new β‐dihydroagarofuran sesquiterpene polyesters were isolated from Celastrus paniculatus. The structures were deduced using various 2D NMR techniques (HH COSY, CH COSY, COLOC, NOESY), NOE difference spectra and mass spectra. The positions of the ester moieties were located by 2D heteronuclear correlated spectra via long‐range coupling, or combined with NOE experiments. Their stereochemical structures were studied and the complete assignments of the 1H and 13C chemical shifts were made.