Ring-chain isomerism of 1,3,3-trimethyl-2-formylmethylene-indoline (fischer aldehyde) oxime and associated reactions (original) (raw)
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Journal of Chemical Crystallography, 2010
Abstract Schiff base 4-[(2-hydroxy-3-methoxybenzylideneamino)-N-(5-methylisoxazol-3-yl)benzene-sulfonamide has been synthesized from the reaction of 4-amino-N-(5-methylisoxazol-3-yl)benzenesulfonamide(sulfamethoxazole) with 2-hydroxy-3-methoxybenzaldehyde. It has been characterized by elemental analysis, MS, IR, 1H NMR, 13C NMR, HETCOR and UV–Visible techniques. The structure of it also has been examined crystallographically. For the compound exist as dominant form of enol-imines in both the solid state and the solutions. It crystallizes in the monoclinic space group P21/c with a = 8.2694(7), b = 8.3453(5), c = 26.260(2) Å, β = 97.142(7) °, V = 1798.1(2) Å3, D x = 1.431 g cm−3, R 1 = 0.0529 and wR 2 = 0.1370 [I > 2σ(I)], respectively. Index Abstract The tautomerism in the Schiff base ligands plays an important role for distinguishing their photochromic and thermochromic characteristics. Both phenomena is associated with a proton transfer (enol-imine, O–H···N, keto-amine, O···H–N).
HETEROCYCLES, 1994
Whereas 1,3,10,10a-tetrahydro-5H-oxazolo[3,4-b]isoquinoline adopts an equilibrium in CDC13 solution at 295 K in which the trans-fused conformation predominates, 1,5,6,l0b-tetrahydro-3H-oxazolo[4,3-alisoquinoline adopts the 0-inside cis-fused conformation. This difference in conformational preference has been explained partly in terms of ring-fusion strain. Perhydro-oxazolo[3,4-alppidine adopts a conformational equilibriumZ in CDC13 solution at 298 K between 67% trans-fused conformer (1-t) and 33% 0-inside cis-fused conformer (1-c) whereas indolizidine shows3 an extreme preference for the trans-conformer (2-1). In addition to differences in non-bonded interactions between the two systems4 and the generalised anomeric effectS in 1, ring fusion strain (cf. trans-hydrindane6) may also be partially responsible for the difference in positions of conformational equilibria. Any ring fusion strain present in trans-indolizidine (24) is expected4,7 to increase in trans-perhydro-oxazolo[3,4-alpyridine (I-t) as a result of the sho~ter C-0 bonds (1.43A) in 1-t compared to the corresponding CC bonds (1.54A) in 24. The magnitude of such strain should be affected by changes in the conformation of the six-membered ring and accordingly 1,3,10,10a-tetrahydro-5H-oxazolo[3,4-b]isoquinoline (3) and 1,5,6.10b-tetrahydr0-3Hoxazolo[4.3-a]iso~uinoline (4) containing non-chair piperidine rings were chosen for study.
DFT, FT-IR, FT-Raman and NMR studies of 4-(substituted phenylazo)-3,5-diacetamido-1H-pyrazoles
Journal of Molecular Structure, 2011
We present a detailed analysis of the structural and vibrational spectra of some novel azo dyes. 2-(Substituted phenylazo)malononitriles were synthesized by the coupling reaction of the diazonium salts, which were prepared with the use of various aniline derivatives with malononitrile, and then 4-(substituted phenylazo)-3,5-diamino-1H-pyrazole azo dyes were obtained via the ring closure of the azo compounds with hydrazine monohydrate. The experimental and theoretical vibrational spectra of azo dyes were studied. The structural and spectroscopic analysis of the molecules were carried out by using Becke's three-parameters hybrid functional (B3LYP) and density functional harmonic calculations. The 1 H nuclear magnetic resonance (NMR) chemical shifts of the azo dye molecules were calculated using the gaugeinvariant-atomic orbital (GIAO) method. The calculated vibrational wavenumbers and chemical shifts were compared with the experimental data of the molecules.
The Journal of Physical Chemistry A, 2009
The electronic structures of a homologous series of indole and benzofuran derivatives, in which the nitrogen or oxygen atom is replaced by group 15 and group 16 heavier heteroatoms, have been investigated by means of various spectroscopic techniques coupled with density functional calculations. It was found that the excitation energies of the group 16 benzoheteroles systematically shift to the red in the order of benzofuran , benzothiophene , benzoselenophene (8), and benzotellurophene . In contrast, the electronic absorption spectra of the group 15 benzoheteroles, 1-phenyl derivatives of indole (1b), phosphindole (2b), arsindole (3b), stibindole (4b), and bismuindole (5b), did not exhibit this type of spectral shift. X-ray analysis and density functional theory (DFT) studies revealed that 2b-5b adopt a bent conformation both in the crystalline and in the solution phases. In contrast, planar structures were calculated for the group 16 heterocycles. Using the observed spectroscopic properties and time-dependent density functional theory (TDDFT) calculations, the electronic absorption spectra of the present heterocycles were assigned. A molecular orbital analysis was performed to rationalize the effect of replacement of the heteroatom on the electronic structures. The observed magnetic circular dichroism (MCD) sign patterns of these heterocycles are interpreted according to Michl's perimeter model.
1. INTRODUCTION The synthesis of halogen substituted isoxazoline derivatives has increase the attention as a source of new pharmacological agents. The isoxazoline derivatives have been reported to possess antifungal 1 , antimicrobial 2 , antitumor 3 , anti-inflammatory 4,5 , antidepressant 6,7 and analgesic 8 activity. The halogen group can alter the course of the reaction as well as the biological activities. In addition, isoxazoline derivatives have played a crucial role in the theoretical development of heterocyclic chemistry and are also used extensively in organic synthesis 9,10. For study of halogen substituted isoxazoline drug, mainly study the effect of halogen group over the drug activity is important. To study such effect the synthesis of isoxazoline is not necessary. Many theoretical methods are available like QSAR, ab-initio, semi-imperical, DFT, HF method etc, to predict such drug activity without synthesis. Amongst these, the DFT method has commonly used to determined molecular effect of halogen group on pharmacological activity 11. In this work we have studied the computational method for 8-(5-((4-fluoro phenyl)amino)-4-(4chlorobenzoyl)-4,5-dihydroisoxazole-3-yl)-7-hydroxy-4-methyl-2H-chromen-2-one (Ia) and 8-(5-((4chlorophenyl)amino)-4-(4-chlorobenzoyl)-4,5-dihydroisoxazole-3-yl)-7-hydroxy-4-methyl-2H-chromen-2-one (Ib) including electronic structure spectroscopic and thermo-dynamical properties. 2. COMPUTATIONAL DETAILS The ground state geometry optimizations were carried out at the DFT 12-16 using the modified hybrid functional of Perdew, Burke and Ernzerhof (PBE1PBE) 17,18 with the 6-311g basis set 19-23. Electronic absorption spectra were computed as vertical electronic excitations from the ground state using TD-DFT 24-26 with PBE1PBE/6-311g basis set. The optimized structural parameters were used for vibrational frequency calculation to characterize all the stationary points as minima. All the calculations performed with Gaussian-03 package 27. Molecular visualization and the vibrational frequency assignment were made by using Gauss View 3.07 program. The gauge-including atomic orbital (GIAO) approach 28 was used to ensure gauge invariance of the result. The calculated chemical shifts were transformed to the -scale as the difference between the isotropic part of magnetic shielding tensor and that of TMS.