Synthesis and conformational analysis of new naphth[1,2-e][1,3]oxazino[3,4-c]quinazoline derivatives

A new highly functionalized aminonaphthol derivative, 1-(amino(2-aminophenyl)methyl)-2-naphthol (4), was synthesized by the reaction of 2-naphthol, 2-nitrobenzaldehyde and tert-butyl carbamate or benzyl carbamate, followed by reduction and/or removal of the protecting group. The aminonaphthol derivative thus obtained was converted in ring-closure reactions with formaldehyde, benzaldehyde and/or phosgene to the corresponding naphth[1,2-e][1,3]oxazino[3,4-c]quinazoline derivatives. The conformational analysis of some derivatives by NMR spectroscopy and accompanying molecular modelling are also reported.     

NMR Crystallography Enhanced by Quantum Chemical Calculations and Liquid State NMR Spectroscopy for the Investigation of Se-NHC Adducts**

N-heterocyclic carbene ligands (NHC) are widely utilized in catalysis and material science. They are characterized by their steric and electronic properties. Steric properties are usually quantified on the basis of their static structure, which can be determined by X-ray diffraction. The electronic properties are estimated in the liquid state; for example, via the ⁷⁷Se liquid state NMR of Se-NHC adducts. We demonstrate that ⁷⁷Se NMR crystallography can contribute to the characterization of the structural and electronic properties of NHC in solid and liquid states. Selected Se-NHC adducts are investigated via ⁷⁷Se solid state NMR and X-ray crystallography, supported by quantum chemical calculations. This investigation reveals a correlation between the molecular structure of adducts and NMR parameters, including not only isotropic chemical shifts but also the other chemical shift tensor components. Afterwards, the liquid state ⁷⁷Se NMR data is presented and interpreted in terms of the quantum chemistry modelling. The discrepancy between the structural and electronic properties, and in particular the π-accepting abilities of adducts in the solid and liquid states is discussed. Finally, the ¹³C isotropic chemical shift from the liquid state NMR and the ¹³C tensor components are also discussed, and compared with their ⁷⁷Se counterparts. ⁷⁷Se NMR crystallography can deliver valuable information about NHC ligands, and together with liquid state ⁷⁷Se NMR can provide an in-depth outlook on the properties of NHC ligands.     

Assignment of the relative configuration of spiro[4.5]decanes by 13C, 15N and 17O NMR

The relative configuration of 11 1,4-diazaspiro[4.5]decanes (1a-1j and 1m), 15 1,4-oxazaspiro[4.5]decanes (2a-2o) and 10 1,4-dioxaspiro[4.5]decanes (3a-3n) substituted at the 2-, 6-, 7- or 8-position by a methyl group or using the tert-butyl group as a model for the ananchomeric structure is reported. The relative stereochemistry was analyzed by 1H, 13C, 15N and 17O NMR and all isomers present were characterized spectroscopically. Compounds with a methyl group in the six-membered ring show a chair conformation preference with the methyl group in the equatorial position. Compounds with one or two nitrogens exhibit a tautomeric equilibrium between the imine-diazolidine forms, as demonstrated by IR and 13C NMR.     

Synthesis, 13C NMR spectrum and crystal structure of 10-Phenylpyrido[3,2-b][1,4]benzothiazine 5-Oxide

The compound 10-phenylpyrido[3,2-b][1,4]benzothiazine 5-oxide, 1 , has been obtained in nearly quantitative yield oxidation of 10-phenylpyrido[3,2-b][1,4]benzothiazine with oxygen in dioxane solution. The ¹³C nmr chemical shift assignments of 1 are reported. Its structure has been determined by X-ray single crystal methods. The crystals of 1 are monoclinic, space group P2₁/n. There are four molecules in a unit-cell of dimensions a = 12.347(3), b = 12.947(3), c = 8.987(1)Å, β = 106.73(1)° and V = 1375.8(5) ų. The central ring is in a boat conformation and the sulfoxide oxygen atom occupies the axial position. The folding angle between the planes of the pyrido and the benzo planes is 161.55(9)°.     

[60]富勒烯衍生物的对称性、碳笼结构与13C NMR谱

本文全面综述了多种[60]富勒烯衍生物的结构,阐述了(13)~C NMR谱在[60]富勒烯衍生物结构表征中的应用,重点讨论了不同对称性[60]富勒烯衍生物的(13)~C NMR谱图特征.通过[60]富勒烯部分(13)~C共振线的化学位移、数目和相对强度,可以确定[60]富勒烯衍生物的对称结构和加成方式.对于C_s、C_(2v)和C_(3v)对称性的[60]富勒烯衍生物,镜面上的碳原子的相对化学位移很大程度上取决于他们距加成位置的距离.因此,(13)~C NMR谱在碳笼具体结构的确定中具有不可替代的作用.     

Preparation and Conformation of Organo‐Bridged Bis[tris(arylchalcogenolato)tin] Compounds – An Experimental and Quantum Chemical Study

Seven organo‐bridged bis[tris(arylchalcogenolato)tin] compounds with the general formulae (R′E)₃Sn–R–Sn(ER′)₃ (R = –(CH₂)₄–, 1,4‐bis(methyl)benzene, 4,4′‐bis(methyl)biphenyl; R′ = Ph, 1‐Np, 2‐Np; E = S, Se) were synthesized and characterized by means of X‐ray diffractometry as well as NMR spectroscopy. Three different conformations of the arylchalcogenolato groups ER′ with respect to the bridging group R were rationalized and explained by means of quantum chemical investigations.     

3-(D-葡萄糖-1-基)-6-芳基-7H-1，2，4-三唑并[3，4-b][1，3，4]噻二嗪类化合物的合成及波谱研究

ω-溴代芳香基乙酮与3-(D-葡萄糖-1-基)-4-氨基-5-巯基-1，2，4-三唑反应 合成了一系列新颖的3-(D-葡萄糖-1-基)-6-芳基-7H-1，2，4三唑并[3，4-b[1，3 ，4]噻二嗪．用元素分析，IR，NMR，MS对其结构进行了表征，研究了其NMR波谱特 征，并以^1H-^1H COSY，^13C-^1H COSY，COLOC二维NMR技术对其^1H NMR，^13C NMR的谱峰进行了全归属     

The Solid Solution Sr1−xBaxGa2: Substitutional Disorder and Chemical Bonding Visited by NMR Spectroscopy and Quantum Mechanical Calculations

Complete miscibility of the intermetallic phases (IPs) SrGa₂ and BaGa₂ forming the solid solution Sr_1?xBa_xGa₂ is shown by means of X‐ray diffraction, thermoanalytical and metallographic studies. Regarding the distances of Sr/Ba sites versus substitution degree, a model of isolated substitution centres (ISC) for up to 10 % cation substitution is explored to study the influence on the Ga bonding situation. A combined application of NMR spectroscopy and quantum mechanical (QM) calculations proves the electric field gradient (EFG) to be a sensitive measure of different bonding situations. The experimental resolution is boosted by orientation‐dependent NMR on magnetically aligned powder samples, revealing in first approximation two different Ga species in the ISC regimes. EFG calculations using superlattice structures within periodic boundary conditions are in fair agreement with the NMR spectroscopy data and are discussed in detail regarding their application on disordered IPs.     

Theoretical calculations on C30H12 bowl-shaped hydrocarbons: NMR shielding constants,stability, and aromaticity

Density Functional Theory (DFT) calculations at the B3LYP/6-31G* level have been performed on four bowl-shaped polyaromatic hydrocarbons of C₃₀H₁₂ molecular formula ( 1 – 4 ) showing C₃ ( 1 ), C_2v ( 2 and 4 ), and C_2h ( 3 ) symmetries. The geometrical and electronic properties of the compounds studied have been analyzed to explain their relative stability. NMR chemical shifts parameters for the atoms and Nucleus Independent Chemical Shifts (NICSs) for the rings were calculated using the GIAO method. The ¹³C and ¹H chemical shifts calculated are in very good agreement with the experimental data. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 1412–1421, 1999     

Synthesis and Crystal Structure of 2-Ethoxy-spiro[2H-1, 4,2-benzoxazaphosphorine-3（4H）, 1＇-Cycloheptane] 2-Oxide

1 INTRODUCTION α-Aminophosphonates are an important class of compounds since they are considered as structural analogues of the corresponding α-amino acids. Their utilities as enzyme inhibitors, antibiotics, pharma- cological agents and many other applications are well documented[1~5]. Moreover, cyclic α-amino- phosphonates, one important kind of α-aminopho- sphonates, have attracted chemists’ interests for a long time[6~11]. In order to search for potent and selec- tive herbicides a…     

Theoretical and experimental 1H, 13C and 15N NMR studies of N‐alkylation of substituted tetrazolo[1,5‐a]pyridines

The ¹⁵N as well as ¹H and ¹³C chemical shifts of nine substituted tetrazolopyridines and their corresponding tetrazolopyridinium salts have been determined by using NMR spectroscopy at the natural abundance level of all nuclei in CD₃CN. In this paper, we report, for the first time, the N‐alkylation reaction of electron deficient tetrazolopyridines. The treatment of tetrazolopyridines 5–13 with one equivalent of trialkyloxonium tetrafluoroborate leads to a mixture of two isomers, i.e. N3‐ and N2‐alkyl tetrazolo[1,5‐a]pyridinium salts. It has been observed that the N3‐isomer is always the major isomer, except in the case of the CF₃ substituent, where the two isomers are obtained in the same amount. The quaternary tetrazolopyridinium nitrogen N3 is shielded by around 100 ppm (parts per million) with respect to the parent tetrazolopyridine. Experimental data are interpreted by means of density functional theory (DFT) calculations, including solvent‐induced effects, within the conductor‐like polarizable continuum model (CPCM). Good agreements between theoretical and experimental ¹H, ¹³C and ¹⁵N NMR were found. The combination of multinuclear magnetic resonance spectroscopy with gauge including atomic orbital (GIAO) DFT calculations is a powerful tool in the structural elucidation for both neutral and cationic heterocycles and in the determination of the orientation of N‐alkylation of tetrazolopyridines. Copyright © 2009 John Wiley & Sons, Ltd.     

Structure elucidation of [1,3]oxazolo[4,5‐e][2,1]benzisoxazole and naphtho[1,2‐d][1,3]‐ and phenanthro[9,10‐d]oxazoles using gradient selected gHMBC,gHMQC and gHMQC‐TOCSY NMR techniques

Structure elucidation of compounds in the benzisoxazole series ( 1 – 6 ) and naphtho[1,2‐d][1,3]‐ ( 7 – 10 ) and phenanthro[9,10‐d][1,3]oxazole ( 11 – 14 ) series was accomplished using extensive 2D NMR spectroscopic studies including ¹H–¹H COSY, long‐ range ¹H–¹H COSY, ¹H–¹³C COSY, gHMQC, gHMBC and gHMQC‐TOCSY experiments. The distinction between oxazole and isoxazole rings was made on the basis of the magnitude of heteronuclear one‐bond ¹J_{C2, H2} (or ¹J_{C3, H3}) coupling constants. Complete analysis of the ¹H NMR spectra of 11 – 14 was achieved by iterative calculations. Gradient selected gHMQC‐TOCSY spectra of phenanthro[9,10‐d][1,3]oxazoles 11 – 14 were obtained at different mixing times (12, 24, 36, 48 and 80 ms) to identify the spin system where the protons of phenanthrene ring at H‐5, H‐6 and at H‐9 and H‐7 and H‐8 were highly overlapping. Copyright © 2003 John Wiley & Sons, Ltd.     

Preparation and steric structures of saturated or partially saturated cyclopentane-and cyclohexane[b]pyrrolo[1,2-a][3,1]benzoxazine isomers [1]

The reactions of 2-ethoxycarbonylmethyleyclopentanone (1) with cis- (3a) and trans-2-hydroxymethylcyclohex-4-enyl-1-amine (3b) and of 2-ethoxycarbonylmethylcyclohexanone (2) with stereoisomeric 2-hydroxymethyl-1-cyclohexylamines (4a,b) yield the isomeric cyclopentane-(5a,b) and cyclohexane[b] pyrrolo[1,2-a][3,1]benzoxazinones (6a,b) with unsaturated (5) or saturated (6) ring A. The steric structures were elucidated by means ¹H, ¹³C NMR and X-ray measurements.     

Trapping of Ag+ into a Perfect Six-Coordinated Environment: Structural Analysis,Quantum Chemical Calculations and Electrochemistry

Self-assembly of (Bu₄N)₄[β-Mo₈O₂₆], AgNO₃, and 2-bis[(2,6-diisopropylphenyl)-imino]acenaphthene (dpp-bian) in DMF solution resulted in the (Bu₄N)₂[β-{Ag(dpp-bian)}₂Mo₈O₂₆] (1) complex. The complex was characterized by single crystal X-ray diffraction (SCXRD), X-ray powder diffraction (XRPD), diffuse reflectance (DR), infrared spectroscopy (IR), and elemental analysis. Comprehensive SCXRD studies of the crystal structure show the presence of Ag⁺ in an uncommon coordination environment without a clear preference for Ag-N over Ag-O bonding. Quantum chemical calculations were performed to qualify the nature of the Ag-N/Ag-O interactions and to assign the electronic transitions observed in the UV–Vis absorption spectra. The electrochemical behavior of the complex combines POM and redox ligand signatures. Complex 1 demonstrates catalytic activity in the electrochemical reduction of CO₂.     

C6‐substituted purine derivatives: an experimental and theoretical 1H, 13C and 15N NMR study

We measured the ¹H, ¹³ C and ¹⁵ N chemical shifts for a series of purine derivatives bearing a norbornane substituent in position 9 and various substituents in position 6. The experimental data were complemented with density functional theory (DFT) calculations. The comparison of the calculated and experimental chemical shifts provided us with information about the tautomer and conformational equilibria of the studied compounds. Copyright © 2012 John Wiley & Sons, Ltd.     

Charged Si9 Clusters in Neat Solids and the Detection of [H2Si9]2− in Solution: A Combined NMR,Raman, Mass Spectrometric,and Quantum Chemical Investigation

Polyanionic silicon clusters are provided by the Zintl phases K₄Si₄, comprising [Si₄]⁴⁻ units, and K₁₂Si₁₇, consisting of [Si₄]⁴⁻ and [Si₉]⁴⁻ clusters. A combination of solid‐state MAS‐NMR, solution NMR, and Raman spectroscopy, electrospray ionization mass spectrometry, and quantum‐chemical investigations was used to investigate four‐ and nine‐atomic silicon Zintl clusters in neat solids and solution. The results were compared to ²⁹Si isotope‐enriched samples. ²⁹Si‐MAS NMR and Raman shifts of the phase‐pure solids K₄Si₄ and K₁₂Si₁₇ were interpreted by quantum‐chemical calculations. Extraction of [Si₉]⁴⁻ clusters from K₁₂Si₁₇ with liquid ammonia/222crypt and their transfer to pyridine yields in a red solid containing Si₉ clusters. This compound was characterized by elemental and EDX analyses and ²⁹Si‐MAS NMR and Raman spectroscopy. Charged Si₉ clusters were detected by ²⁹Si NMR in solution. ²⁹Si and ¹H NMR spectra reveal the presence of the [H₂Si₉]²⁻ cluster anion in solution.     

NMR parameters of the tetrahedrane [Fe2(CO)6(μ-SNH)], studied by experiment and DFT

The intramolecular dynamic behavior of the tetrahedrane-type cluster [Fe₂(CO)₆(μ-SNH)] 1 was studied by ¹³C NMR spectroscopy. The ⁵⁷Fe chemical shift of 1 and the coupling constants ¹ J(⁵⁷Fe,¹³C) were measured. These NMR parameters, and also ¹ J(⁵⁷Fe,¹⁵N), were found to be in good agreement with data calculated by using density functional theory (DFT) methods (B3LYP), based on the geometry calculated at the 6-311+G(d,p) level of theory. The isolobal replacement of the Fe(CO)₃ with BH fragments leads to the tetrahedranes [Fe(CO)₃(BH)(μ-SNH)] 2 and [(HB)₂(μ-SNH)] 3. Both were identified by calculations as minima on the respective potential energy surface (PES). However, the tetrahedrane-type structure of 3 is much higher in energy when compared with the planar cyclic isomers 3a and 3b.