Refine
Has Fulltext
- no (132)
Year of publication
Document Type
- Article (130)
- Monograph/Edited Volume (1)
- Doctoral Thesis (1)
Is part of the Bibliography
- yes (132)
Keywords
- NICS (8)
- Through-space NMR shieldings (TSNMRS) (8)
- NMR spectroscopy (7)
- Theoretical calculations (7)
- Anisotropy effect (6)
- Ring current effect (6)
- Aromaticity (5)
- DFT calculations (5)
- Conformational analysis (4)
- ICSS (4)
- NMR (4)
- TSNMRS (4)
- conformational analysis (4)
- GIAO (3)
- (Anti)aromaticity (2)
- Anisotropic effect (2)
- Cytotoxicity (2)
- Iso-chemical-shielding surfaces (ICSS) (2)
- Leguminosae (2)
- NBO analysis (2)
- NHCs (2)
- Plasmodium falciparum (2)
- Push-pull character (2)
- Steric effect (2)
- Taft equation (2)
- anisotropic effects (2)
- aromaticity (2)
- modified Mannich reaction (2)
- shieldings (TSNMRS) (2)
- (+)-Tephrodin (1)
- (1)H NMR (1)
- (13)C NMR (1)
- (TSNMRS) (1)
- 1 (1)
- 1,2,4-Dithiazole (1)
- 1,2-Dithiole (1)
- 1,2-diboretane-3-ylidene (1)
- 2'-bipyridine (1)
- 2,2-Disubstituted adamantane derivatives (1)
- 2-Dicyanoethene-1 (1)
- 2-Dithiooxalate (1)
- 2-Dithiosquarate (1)
- 2-Substituted adamantane derivatives (1)
- 2-dithiolate (1)
- 3,4-Dihydroisoquinoline (1)
- 3c,2e-bonding (1)
- 4 (1)
- 4'-Bis(tert-butyl)-2 (1)
- 4-Oxothiazolidine (1)
- 4-Substituted cyclohexanones (1)
- 4-methylene-cyclohexyl pivalate (1)
- 6 alpha-Hydroxy-alpha-toxicarol (1)
- 9-Arylfluorenes (1)
- ALTONA equation (1)
- Ab initio MO computations (1)
- Alkenyl cyclohexanone (1)
- Alkenyl cyclohexenone (1)
- Aminonaphthol (1)
- Aminonaphthols (1)
- Annelation effect (1)
- Anserine (1)
- Anti-aromaticity (1)
- Anti-inflammatory (1)
- Antimicrobial (1)
- B,N heterocycles (1)
- B3LYP/6-31+G(d,p) calculations (1)
- Benzazepine (1)
- Benzenoid structure (1)
- Benzenoid structures (1)
- Benzyne-allene or cumulene-like structure (1)
- Betaines (1)
- C-13 NMR (1)
- C-13 NMR spectroscopy (1)
- C-13 chemical shift (1)
- C-13 chemical shifts (1)
- CAACs (1)
- Carbene or zwitterions (1)
- Carbenes (1)
- Chelatoaromaticity (1)
- Conformation analysis (1)
- Conformational equilibria (1)
- Copper (1)
- Copper Metal Complexes (1)
- Coumaronochromone (1)
- Coumestan (1)
- Cyanine/merocyanine-like structures (1)
- Cyclazines (1)
- Cyclobutylcarbene (1)
- Cyclohexyl esters (1)
- Dative vs. coordinative NHC -> BR3 bond (1)
- Dehydro[n]annulenes (1)
- Dual Scale Factors (1)
- Dual scale factors (1)
- Dynamic NMR (1)
- Dynamic NMR spectroscopy (1)
- EPR (1)
- F-C coupling constants (1)
- GIAO calculations (1)
- Glycol podands (1)
- H-1 NMR (1)
- H-1 NMR spectroscopy (1)
- Hammett-Brown plots (1)
- Hemiporphyrazines (1)
- IR and Raman spectra (1)
- Iso-chemical shielding surfaces (ICSS) (1)
- Isoflavone (1)
- Lannea rivae (1)
- Lannea schweinfurthii (1)
- Matrix IR spectrum (1)
- Mesomeric equilibrium of carbene/zwitterion (1)
- Mesomerism (1)
- Millettia dura (1)
- Millettia lasiantha (1)
- Millettia micans (1)
- Modified Mannich reaction (1)
- Multiple NHC(CAAC)-Boron bonds (1)
- NBO and STERIC analyses (1)
- Naphthoxazinoquinazolines (1)
- Naphthoxazinoquinazolinones (1)
- Nickel (1)
- Peripheral ring current (1)
- Polar effect (1)
- Polar substituent constant (1)
- Porphyrins (1)
- Pterocarpan (1)
- Push-pull allenes (1)
- Quantum Chemical Calculations (1)
- Quantum chemical calculations (1)
- Quasi-aromaticity (1)
- Quinonoid structure (1)
- Quotient method (1)
- RA-intramolecular hydrogen bond (1)
- Rearrangement to trithiaazapentalene (1)
- SQM FF (1)
- SQM-FF (1)
- Salicylic acid (1)
- Simulation of H-1 NMR spectra (1)
- Spatial NICS (1)
- Stereochemistry (1)
- Steric substituent constant (1)
- Substituent chemical shifts (1)
- Substituent effects (1)
- Tautomerism (1)
- Tephrosia purpurea (1)
- Tephrosia subtriflora (1)
- Tephrosia villosa (1)
- Tetraoxo[8]circulenes (1)
- Thienopyridine (1)
- Through -space NMR (1)
- Through-space NMR (1)
- Trithiapentalene (1)
- Trough-space NMR shieldings (TSNMRS) (1)
- X-ray structure (1)
- Y-aromaticity (1)
- Ylide (1)
- Zinc (1)
- [4+2] cycloaddition (1)
- ab initio calculations (1)
- antiplasmodial (1)
- benzenoid structures (1)
- carbene electron deficiency (1)
- carbenes (1)
- ciprofloxacin (1)
- computational chemistry (1)
- cyclic imines (1)
- cycloaddition (1)
- cytotoxicity (1)
- density functional calculations (1)
- dynamic NMR spectroscopy (1)
- electrospray ionization mass spectrometry and modeling (1)
- exo-methylene conformational effect at cyclohexane (1)
- nucleus-independent chemical shift (1)
- nucleus-independent chemical shifts (NICS) (1)
- ortho-quinone methide (o-QMs) (1)
- para-Nitro-pyridine N-oxides (1)
- pi interactions (1)
- pi-Electron delocalization (1)
- prenylated flavanonol (1)
- quantum chemical calculations (1)
- quinoid structures (1)
- silver(1) complexes (1)
- spectroscopy (1)
- stability (1)
- subtriflavanonol (1)
- sulfur heterocycles (1)
- through space NMR shieldings (1)
- zwitterions (1)
Institute
- Institut für Chemie (132) (remove)
1H, 13C, and 15N NMR study of the solution structure of metabridged bis(benzo-15-crown-5-ether)s
(1995)
The complex formation of the following diazaperylene ligands (L) 1,12-diazaperylene 1, 1,1-bisisoquinoline 2, 2,11-disubstituted 1,12-diazaperylenes (alkyl=methyl, ethyl, isopropyl, 3, 5, 7), 3,3-disubstituted 1,1-bisisoquinoline (alkyl=methyl, ethyl, isopropyl, 4, 6, 8 and with R=phenyl, 11 and with pyridine 12), and the 5,8-dimethoxy-substituted diazaperylene 9, 6,6-dimethoxy-substituted bisisoquinoline 10 with AgBF4 was investigated. Collision-induced dissociation measurements were used to evaluate the relative stabilities of the ligands themselves and for the [1:1](+) complexes as well as for the homoleptic and heteroleptic silver [1:2](+) complexes in the gas phase. This method is very useful in rapid screening of the stabilities of new complexes in the gas phase. The influence of the spatial arrangement of the ligands and the type of substituents employed for the complexation were examined. The effect of the preorganization of the diazaperylene on the threshold activation voltages and thus of the relative binding energies of the different complexes are discussed. Density functional theory calculations were used to calculate the optimized structures of the silver complexes and compared with the stabilities of the complexes in the gas phase for the first time.
To synthesize functionalized Mannich bases that can serve two different types of ortho-quinone methide (o-QM) intermediates, 2-naphthol and 6-hydroxyquinoline were reacted with salicylic aldehyde in the presence of morpholine. The Mannich bases that can form o-QM and aza-o-QM were also synthesized by mixing 2-naphthol, 2-nitrobenzaldehyde, and morpholine followed by reduction of the nitro group. The highly functionalized aminonaphthol derivatives were then tested in [4+2] cycloaddition with different cyclic imines. The reaction proved to be both regio- and diastereoselective. In all cases, only one reaction product was obtained. Detailed structural analyses of the new polyheterocycles as well as conformational studies including DFT modelling were performed. The relative stability of o-QMs/aza-o-QM were also calculated, and the regioselectivity of the reactions could be explained only when the cycloaddition started from aminodiol 4. It was summarized that starting from diaminonaphthol 25, the regioselectivity of the reaction is driven by the higher nucleophilicity of the amino group compared with the hydroxy group. 12H-benzo[a]xanthen-12-one (11), formed via o-QM formation, was isolated as a side product. The proton NMR spectrum of 11 proved to be very unique from NMR point of view. The reason for the extreme low-field position of proton H-1 could be accounted for by theoretical calculation of structure and spatial magnetic properties of the compound in combination of ring current effects of the aromatic moieties and steric compression within the heavily hindered H(1)-C(1)-C(12b)-C(12a)-C(12)=O structural fragment.
Through the reactions of 1-aminomethyl-2-naphthol and substituted 1-aminobenzyl-2-naphthols with 3,4-dihydroisoquinoline or 6,7-dimethoxy-3,4-dihydroisoquinoline under microwave conditions, naphth[1,2-e][1,3]oxazino[2,3-a]-isoquinoline derivatives were prepared in good yields. The latter reaction was extended by using 2-aminoarylmethyl-1-naphthols, leading to isomeric naphth-[2,1-e][1,3]oxazino[2,3-a] isoquinolines. Beside the detailed NMR spectroscopic and theoretical study of both stereochemistry and dynamic behaviour of these new conformational flexible heterocyclic ring systems an unexpected dynamic process between two diastereomers was observed in solution, studied by variable temperature H-1 NMR spectroscopy and the mechanism proved by theoretical DFT computations.
The disubstitution effects of X and Y in 1-(Y-phenyl)-3-(X-phenyl)-2,3-dihydro-1H-naphth[1,2-e][1,3]oxazines on the ring-chain tautomerism, the delocalization of the nitrogen lone pair (anomeric effect), and the C-13 NMR chemical shifts were analyzed by using multiple linear regression analysis. Study of the three-component equilibrium B reversible arrow A reversible arrow C revealed that the chain reversible arrow trans (A reversible arrow B) equilibrium constants are significantly influenced by the inductive effect (sigma(F)) of substituent Y on the 1-phenyl ring. In contrast, no significant substituent dependence on Y was observed for the chain reversible arrow cis (A reversible arrow C) equilibrium. There was an analogous dependence for the epimerization (C reversible arrow B) constants of 1-(Y-phenyl)-3- alkyl-2,3-dihydro-1H-naphth[1,2-e] [1,3]oxazines. With these model compounds, significant overlapping energies of the nitrogen lone pair was observed by NBO analysis in the trans forms B (to sigma*(C1-C1'), sigma*(C1-C10b), and sigma*(C3-O4)) and in the cis forms C (to sigma*(C1-H), sigma*(C1-C10b), and sigma*(C3-O4)). The effects of disubstitution revealed some characteristic differences between the cis and trans isomers. However, the results do not suggest that the anomeric effect predominates in the preponderance of the trans over the cis isomer. When the C-13 chemical shift changes induced Y by substituents X and Y (SCS) were subjected to multiple linear regression analysis, negative rho(F)(Y) and rho(F)(X) values were observed at C-1 and C-3 for both the cis and trans isomers. In contrast, the positive rho(R)(Y) values at C-1 and the negative rho(R)(X) values at C-3 observed indicated the contribution of resonance structures f (rho(R) > 0) and g (rho(R) < 0), respectively. The classical double bond-no-bond resonance structures proved useful in explaining the substituent sensitivities of the donation energies and the behavior of the SCS values
The stabilities of the trans (B) and cis (C) tautomeric ring forms that are experimentally observed in the ring- chain tautomeric interconversion of 1-alkyl-3-aryl-2,3-dihydro-1H-naphth[1,2-e][1,3]oxazines has been investigated. Stability differences are explained by the analysis of the natural bond orbital results for the lone pairs of electrons that are on the heteroatoms in the oxazine ring system and by regression analysis of the calculated 13C NMR chemical shift values.
The (3)J(P,H) and (4)J(P,H) spin-spin coupling constants of a selected test set of organophosphorus compounds, calculated by density functional theory (DFT) methods, were found to correlate well with the experimentally measured coupling constants. The contribution of the spin-dipole (SD) term to the coupling constants was found to be negligible, and the diamagnetic and paramagnetic spin-orbit (DSO and PSO) terms cancelled each other, as in the case of J(H,H). Calculation solely of the Fermi contact (FC) term was found to be sufficient to provide good estimates of the coupling constants. In the second part of the work, the conformational equilibria and coupling constants in 2-bis(2- chloroethyl)amino-trans-octahydro-2H-1,3,2-benzoxazaphosphinine 2-oxide and its 3-methyl derivative were studied. DFT methods failed in predicting the relative stabilities of the conformations but yielded good geometries and coupling constants. Optimization of the conformations at the Moller-Plesset second-order perturbation theory (MP2) level resulted in energy differences compatible with previous experimental observations. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Four new primary aminonaphthols (4, 5, 9 and 10) were synthesized from 1- or 2-naphthol and 1- or 2- naphthaldehyde via naphthoxazines in modified Mannich condensations. Simple ring-closure reactions of these aminonaphthols with paraformaldehyde, 4-nitrobenzaldehyde, phosgene or 4-chlorophenyl isothiocyanate led to new heterocyclic derivatives. In these transformations, either an sp2 or an sp3 carbon was inserted between the hydroxy and amino groups. The effects of substituents and the naphthyl ring on the conformation were investigated by means of NMR measurements, employing both dipolar and scalar couplings. The structures were confirmed by DFT quantum chemical calculations involving computed coupling constants, intramolecular distances between nuclei and the relative energies of the preferred conformers.
Phytochemical investigation of the CH2Cl2/MeOH (1:1) extract of the roots of Lannea rivae (Chiov) Sacleux (Anacardiaceae) led to the isolation of a new alkenyl cyclohexenone derivative: (4R,6S)-4,6-dihydroxy-6-((Z)-nonadec-14′-en-1-yl)cyclohex-2-en-1-one (1), and a new alkenyl cyclohexanol derivative: (2S*,4R*,5S*)-2,4,5-trihydroxy-2-((Z)-nonadec-14′-en-1-yl)cyclohexanone (2) along with four known compounds, namely epicatechin gallate, taraxerol, taraxerone and β-sitosterol; while the stem bark afforded two known compounds, daucosterol and lupeol. Similar investigation of the roots of Lannea schweinfurthii (Engl.) Engl. led to the isolation of four known compounds: 3-((E)-nonadec-16′-enyl)phenol, 1-((E)-heptadec-14′-enyl)cyclohex-4-ene-1,3-diol, catechin, and 1-((E)-pentadec-12′-enyl)cyclohex-4-ene-1,3-diol. The structures of the isolated compounds were determined by NMR spectroscopy and mass spectrometry. The absolute configuration of compound 1 was established by quantum chemical ECD calculations. In an antibacterial activity assay using the microbroth kinetic method, compound 1 showed moderate activity against Escherichia coli while compound 2 exhibited moderate activity against Staphylococcus aureus. Compound 1 also showed moderate activity against E. coli using the disc diffusion method. The roots extract of L. rivae was notably cytotoxic against both the DU-145 prostate cancer cell line and the Vero mammalian cell line (CC50 = 5.24 and 5.20 μg/mL, respectively). Compound 1 was also strongly cytotoxic against the DU-145 cell line (CC50 = 0.55 μg/mL) but showed no observable cytotoxicity (CC50 > 100 μg/mL) against the Vero cell line. The roots extract of L. rivae and L. schweinfurthii, epicatechin gallate as well as compound 1 exhibited inhibition of carageenan-induced inflammation.
7a-O-methyldeguelol, a modified rotenoid with an open ring-C, from the roots of Derris trifoloata
(2005)
From the acetone extract of the roots of Derris trifoliata an isollavonoid derivative, named 7a-O- methyldeguelol, a modified rotenoid with an open ring-C, representing a new sub-class of isollavonoids (the sub-class is here named as rotenoloid), was isolated and characterised. In addition, the known rotenoids, rotenone, deguelin and alpha-toxicarol, were identified. The structures were determined on the basis of spectroscopic evidence. Rotenone and deguelin were identified as the larvicidal principles of the acetone extract of the roots of Derris trifoliata. (c) 2005 Elsevier Ltd. All rights reserved
As a part of searching for fully aromatic chelate compounds, copper complexes of malondialdehyde as well as its sulfur and selenium derivatives were investigated using the DFT quantum chemical methods. Chelate complexes of both Cu(I) and Cu(II) ions wereconsidered. Aromaticity of the metal complexes studied were analyzed using NICS(0), NICS(1), PDI, I-ring, MCI, ICMCI and I-B aromaticity indices, and by TSNMRS visualizations of the spatial magnetic properties. It seems that partial aromaticityof studied chelates increases when oxygen atoms in malondialdehyde are replaced by sulfur and selenium.