Chemistry of the phenoxathiins and isosterically related heterocycles. XVI. The synthesis and molecular structure of 3-azaphenoxathiin: Evidence in support of factors responsible for control of the dihedral angle

The synthesis of the 3-azaphenoxathiin ring system and its molecular structure are reported. Based on ¹³C-nmr chemical shift additivities associated with the insertion of an annular nitrogen atom and the observed ¹³C-nmr shift of Cα, the title compound was predicted to have a dihedral angle θ = 160.2°. The observed dihedral angle from the crystal structure was found to be θ = 167.07° which is in reasonably good agreement with the predicted value. It is proposed that the position of the annular nitrogen atom is solely in-control of the observed dihedral angle.     

Chemistry of the phenoxathiins and isosterically related heterocycles. XXXI. Synthesis of the 1,3-diazaphenoxathiin ring system and the relationship of the 13C-NMR chemical shift of the C-10a resonances to the molecular dihedral angle determined by X-Ray diffraction: A further investigation

Synthesis of the 1,3-diazaphenoxathiin ring system and the confirmation of its structure by ¹³C-nmr spectroscopy and X-ray crystallography are reported. Implications of the ¹³C-nmr chemical shift of the C-10a resonance and its relationship to the molecular dihedral angle are presented. The molecule crystallizes in the Pbca space group and was found to have a dihedral angle of 165.5(9)°, the structure refining to a final R-factor of T = 0.0427.     

Chemistry of the phenoxathiins and isosterically related heterocycles. XI . The synthesis and 13C-NMR spectroscopy of 2-azaphenoxathiin

The synthesis of the 2-azaphenoxathiin ring system via the intermediary 2-azaphenoxathiin 2-oxide is described. Complete assignment of the ¹³C-nmr spectrum is reported, based on the observed heteronuclear ¹H-¹³C spin-couplings of the system and calculated chemical shifts as assignment criteria. The possible relation of the chemical shift of Cα to the dehidral angle of the system is also discussed.     

Chemistry of the phenoxathiins and isosterically related heterocycles. X. Correlation of the dihedral angles of phenoxathiin analogs with the 13NMR chemical shifts of the sulfur bearing la carbon

The observation of a linear relationship between the ¹³C-nmr chemical shifts of the C-la carbon and the dihedral angle in a series of phenoxathiin analogs is reported. Presently available data, although limited, is presumed to be indicative of a more general behavior which has not been previously recognized or utilized. Extension of this observation to include other sulfur containing tricyclic systems may be expected to provide a useful means for the preliminary estimation of dihedral angles from solution ¹³C-nmr measurements after suitable parameterization.     

Chemistry of the phenoxathiins and isosterically related heterocycles. XXIII . 1-azathianthrene: First reported synthesis of a monoazathianthrene and the investigation of the 13C-NMR spectrum using two-dimensional NMR techniques

The reaction of the dianion of 3-mercaptopyridin-2(1H)-thione with 2-chloronitrobenzene in N,N-dimethylformamide leads to the formation of 1-azathianthrene, the first reported mono-aza analog of the thianthrene ring system. A partial assignment of the ¹³C-nmr spectrum of the title compound is reported, the assignment based on chemical shift arguments, spin-lattice (T₁) relaxation times and ¹H-¹³C spin coupling constants. Amplitude modulated two-dimensional Fourier transform (AM2DFT) techniques were employed for the acquisition of the heteronuclear spin-coupling constants.     

Chemistry of the phenoxathiins and isosterically related heterocycles. XVIII. The synthesis, 1H- and 13C-NMR Spectroscopy of benzo[b]-1,4,9-triazaphenoxathiin

The first synthesis of a triazaphenoxathiin system, benzo[b]-1,4,9-triazaphenoxathiin, is reported. Attempts directed toward the total assignment of the ¹³C-nmr spectrum of the title compound failed to produce an unequivocal assignment. The carbons of the benzo-portion of the molecule could not be unequivocally assigned at 25.2 MHz but were subgrouped into permutable pairs of resonances on the basis of relaxation times, a result of the antisotropic reorientation of the molecule. Further attempts to complete the ¹³C-nmr assignment at 100 MHz by selective on-resonance decouplings in the 400 MHz ¹H-nmr spectrum were also unsuccessful because of similarities in the chemical shifts of the benzo-protons. Complete ¹H-nmr chemical shifts and homo-nuclear spin-coupling constants were obtained using the PANIC program.     

trans‐4‐[4‐(Dimethylamino)phenyl­iminomethyl]‐N‐phenylpyridinium hexafluorophosphate

The crystal structure of the dipolar chromophoric title compound, C₂₀H₂₀N₃⁺·PF₆^?, is described. The phenyl­ene and pyridyl rings are almost coplanar [dihedral angle 7.5 (2)°], but the phenyl substituent forms a dihedral angle of 56.6 (1)° with the pyridyl ring. The compound crystallizes in the non‐centrosymmetric space group Cc and is a likely candidate for the display of quadratic non‐linear optical effects.     

Chemistry of the phenoxathiins and isosterically related heterocycles. XXX. The crystal and molecular structure of 2-AZA-phenoxathiin 2-oxide: Further evidence in support of the relationship between the 13C-NMR chemical shift of C-10a resonance and the molecular dihedral angle

The synthesis of 2-azaphenoxathiin 2-oxide ( 4 ) and the total assignment of the ¹³C-nmr spectrum is described. Facile assignment was obtained from the assigned spectrum of 2-azaphenoxathiin with additivities obtained from a comparison of 1-azaphenoxathiin and its N-oxide. The crystal structure has also been determined from three dimensional X-ray diffraction data. The compound crystallizes in the monoclinic space group P2₁/n with a = 17.50(2)Å, b = 7.147(3)Å, c = 16.044(7)Å, β = 110.60(5) and Z = 8. Intensity data were collected at - 135 ± 2°C on an automatic diffractometer using nickel-filtered CuKα radiation. The structure was solved by direct methods and was refined by least-squares techniques to give a final R-value of 0.045 for all 3831 independent reflections.     

Chemistry of the phenoxathiins and isosterically related heterocycles. XXXII . The synthesis of 2-azathianthrene and selected analogs

The synthesis of 2-azathianthrene ([1,4]benzodithiino[2,3-c]pyridine), the only remaining monoazathianthrene yet to be reported, is described. Attempts at the direct condensation of disubstituted pyridines with the dianion of 1,2-dimercaptobenzene were generally unsuccessful requiring that the alternative condensation of the dianion with disubstituted pyridine 1-oxides be employed. The title compound was characterized by physical means including ¹³C-nmr spectroscopy. One analog, 4-nitro-2-azathianthrene was also studied by X-ray crystallographic means; the molecule crystallized with two molecules in the asymmetric unit P2₁/n, a = 20.712(3), b = 7.8109(13), c = 13.720(2)Å, β = 107.880(11)°, Z = 8, the data refined to a final R = 0.051 for 3061 reflections. Dihedral angles between the planes of the phenyl rings were 135.00(13) and 132.52(13)° for the two independent molecules contained in the crystal. Close non? bonded S ?O intramolecular contacts were observed in both molecules between the sulfur and nitro-group oxygens. Both nitro groups are twisted out of the plane of the pyridine ring and are oriented at angles of 28.75 and 38.82° respectively.     

Ab initio and semiempirical computational studies on 1‐{(2E)‐2‐[(aminocarbonothioyl)hydrazono]‐2‐(3‐mesityl‐3‐methylcyclobutyl)ethyl}‐pyrrolidine‐2,5‐dione

The molecular geometry, vibrational frequencies, and gauge including atomic orbital (GIAO) ¹H‐ and ¹³C NMR chemical shift values of the title compound in the ground state have been calculated using the Hartree‐Fock (HF) and density functional theory (DFT) methods with 6‐31G(d) basis sets, and compared with the experimental data. The calculated results show that the optimized geometries can well reproduce the crystal structural parameters and the theoretical vibrational frequencies, and ¹H‐ and ¹³C NMR chemical shift values show good agreement with experimental data. To determine conformational flexibility, the molecular energy profile of the title compound was obtained by semiempirical (AM1) calculations with respect to the selected torsion angle, which was varied from ?180° to +180° in steps of 10°. The energetic behavior of the title compound in solvent media was examined using the B3LYP method with the 6‐31G(d) basis set by applying the Onsager and the polarizable continuum model (PCM). The results obtained with these methods reveal that the PCM method provided more stable structure than Qnsager's method. By using TD‐DFT method, electronic absorption spectra of the title compound have been predicted and a good agreement with the TD‐DFT method and the experimental one is determined. The predicted nonlinear optical properties of the title compound are much greater than ones of urea. In addition, the molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis, NBO analysis and thermodynamic properties of the title compound were investigated using theoretical calculations. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Chemistry of the phenoxathiins and isosterically related heterocycles. IX.N-oxidation on the 13C-nmr chemical shifts and coupling constants of the 1-azaphenoxathiin system

The synthesis of 1-azaphenoxathiin N-oxide is described. Total assignment of the ¹³C-nmr spectrum and the effects of the N-oxide moiety on the chemical shifts and ¹H-¹³C spin couplings constants are described and compared to the parent 1-azaphenoxathiin system. The potential for the use of N-oxidation induced changes in ¹³C-nmr chemical shifts and ¹H-¹³C coupling constants as an assignment criterion is also discussed.     

The structure of thianthrenium biscarbethoxymethylide and the corresponding sulfoxide

Thianthrene reacts with one equivalent of diethyl diazomalonate to form the monosulfonium ylide thianthrenium biscarbethoxymethylide. Single crystal X-ray and ¹³C-nmr establish the conformation as pseudoequatorial (e') in both the solid state and solution. The angle of fold between aryl rings is 135.7°, the nearlyplanar malonylide fragment bisecting this angle. The carbonyl oxygen of the endo carbethoxy group is anti to the nonbonding electron pair on sulfur. The methylide carbon resonates at 50 ppm. The aromatic solvent induced shift (ASIS) technique indicates that thianthrene S? oxide also is e'.     

Cis-trans isomerization and 13C-NMR chemical shift of polyphenylacetylene

Before and after cis-trans isomerization, the observed ¹³C-NMR chemical shifts of poly(phenylacetylene) (PPA) in the solid state were investigated on the basis of ¹³C-NMR chemical shift calculations within AM1 for the cis-transoidal and deflected trans-transoidal forms. Two ¹³C-resonance peaks in the observed CP/MAS ¹³C-spectrum were assigned theoretically by the ¹³C chemical shifts of the main and side chains. After thermal isomerization, the ¹³C peak of the main chain for PPA shifted upfield by 3.5 ppm, in contrast to the downfield shift of the ¹³C peak for polyacetylene. This upfield shift of trans-PPA largely was attributed to the increases of the excitation energy from the ground state to the lowest φ_π–π* state in the paramagnetic terms of ¹³C chemical shift on the main chain carbons with the increase in deflected angle τ of 0 to 80°. The ±80° deflected conformation of the trans-transoidal chain due to the cis-trans isomerization was confirmed. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1657–1664, 1999     

The 13C,H coupling constants in structural and conformational analysis. III.. Long-range carbon–hydroxyl proton couplings as evidence of hydrogen bonding in some acylphloroglucinols

Proton coupled ¹³C NMR spectra have been recorded for some acylphloroglucinol derivatives. Significant couplings over two, three and four bonds were observed between the hydroxyl proton and aromatic carbons for those compounds where the hydroxyl group is hydrogen bonded strongly enough to the carbonyl carbon of the acyl side chain. Typical values were ²J = 4.8 Hz, and ³J = 5.6 Hz or 6.7 Hz corresponding to dihedral angles of c. 0° and c. 180°, respectively; the dihedral angle is defined as the angle between the O—H bond and the plane of the aromatic ring. A stereospecific ⁴J(COH) value of 1.2 Hz for a ‘W’ arrangement of coupled atoms was also found. An interesting example of ‘virtual’ J(CH) coupling was observed in the proton coupled spectrum of 1-butyrylphloroglucinol 2-monomethyl ether in acetone-d₆ caused by the accidentally equal chemical shifts of the two ring protons.     

Synthesis, Structure and Biological Activities of S-[α-（ 4-Methoxyphenylcarbonyl ）-2-（1,2,4-triazole-l-yl） ethyl-N, N-dime-thyldithiocarbamate

The title compound was prepared by reaction of N, N‐dimethyldithiocarbamate sodium with l‐bromo‐l‐(4‐methoxyphenylcarbonyl)‐2‐(1, 2, 4‐triazole‐l‐yl) ethane. Its crystal structure has been determined by X‐ray diffraction analysis. The crystal belongs to triclinic with space group Pī, a = 0.7339(2) nm, b = 1.1032(2) nm, c = 1.1203(2) nm, a = 90.27(3)°, β = 102.03(3)°, γ = 104.91(3)°, Z=2, V = 0.8556(3) nm³, D_c = 1.360 g/cm³, μ =0.325 mm^?1, F(000)=368, final R₁ =0.0475. The planes of 4‐methoxybenzyl group and triazole ring are nearly perpendicular to each other. The dihedral angle is 83.97°. There is an obvious π‐π stacking interaction between the molecules in the crystal lattice. The results of biological test show that the title compound has fungicidal and plant growth regulating activities.     

4‐[2‐(4‐Methoxyphenyl)ethenyl]‐N‐methylpyridinium tetraphenylborate

In the cation of the title compound, C₁₅H₁₆NO⁺·C₂₄H₂₀B^?, the pyridyl ring makes a dihedral angle of 14.03° with the phenyl ring. The anion has a slightly distorted tetrahedral geometry and forms honeycomb‐like sheets which extend along the b axis, forming channels containing the cations. A comparison of packing energies reveals a difference between the title compound and a similar material which has non‐linear optical properties.     

Crystal structure of 2,2-diphenylethyl 2,4,6-trimethylphenyl ketone: Kohler's ketone. Mechanism of stereospecific enolization reaction with grignard reagents

The title compound crystallizes in the monoclinic space group P2₁/n with a = 10.875(2), b = 6.039(5), c- 29.015(8)A, and β = 91.29(2). The observed density for Z = 4 la 1.14(1) Mgm^-3 (D_c - 1.155 Mgm^-3). The reliability factors for 1127 unique reflections are R - 0.066 and R_w = 0.064. The dihedral angle between the mesityl ring and the carbonyl to α- carbon plane is 114.4° in contrast to an angle of 89.9° reported earlier for a substituted t-butyl mesityl ketone. A mechanism is proposed for the formation of an E-magnesium enolate from the reaction of Kohler's ketone with Grignard reagents.     

4‐[2‐(4‐Cyano­phenyl)ethenyl]‐N‐methyl­pyridinium tetra­phenyl­borate

In the title compound, C₁₅H₁₃N₂⁺·C₂₄H₂₀B⁻, the pyridyl ring of the cation makes a dihedral angle of 1.6° with the benzene ring. Each is rotated in the same direction with respect to the central –C—CH=CH—C– linkage, by 3.8 and 5.3°, respectively. The anions have a slightly distorted tetra­hedral geometry. Mol­ecular packing analysis was carried out using the packing energy portioning scheme in the program OPEC. Around each anion in the crystal structure there are eight anions, which inter­act with the central anion through C—H⋯π inter­actions. The cations are hydrogen bonded in a head‐to‐tail fashion, forming chains along [10].     

1-Methylphenanthro[3,4-b]thiophene: Determination of the tertiary structure in solution and in the crystalline state by NMR spectroscopy and X-ray diffraction

1-Methylphenanthro[3,4-b]thiophene was prepared by the photocyclization of 1-(4′-methyl-2′-thienyl)-2-(2″-naphthyl)ethene. The ¹H and ¹³C-nmr spectra were assigned using two-dimensional ¹H/¹³C heteronuclear chemical shift correlation and relayed coherence transfer (RELAY) experiments. From nuclear Overhauser difference spectra, the H11-C1 methyl-H intramolecular distance was determined to be 2.10 Å. The molecule crystallized from chloroform in the monoclinic system, space group P2₁/c. A total of 3536 unique reflections were measured and the structure was solved by direct methods and refined to a final R = 0.049. The molecule is helical with both chiral forms observed in the crystal. The H11-C1 methyl-H distance in the crystal was 2.12(3)Å in excellent agreement with the distance measured in solution by NOE techniques.     

Synthesis and structural study of quinuclidine spiro derivatives

The synthesis of quinuclidine-3-spiro-5′-oxazolidine-2′,4′-dione, quinuclidine-3-spiro-5′-hydantoin, and some 3′-derivatives is described. Based on the data from ¹H and ¹³C-nmr spectra the structure of the above mentioned compounds is established. A relationship between second order effects in ¹³C-nmr spectra and H-C-C-H dihedral angles is deduced.