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1.
A series of 2,2‐dimethyl‐5‐(5′‐R‐hetarylidene)‐1,3‐dioxane‐4,6‐diones has been synthesized for examing a structure–activity relationship. Furyl and thienyl derivatives of Meldrum's acid possess neurotropic activity comprising both depriming and activating components. Comparison of acute toxicity of carbon, silicon and germanium analogues in the furan series of the compounds has demonstrated that the germanium derivative is 11.5 times less toxic than the carbon analogue and four times less toxic than the silicon derivative. 2,2‐Dimethyl‐5‐(5′‐triethylsilyl‐2′‐thenylidene)‐1,3‐dioxane‐4,6‐dione has moderate toxicity with the highest neurotropic and cytotoxic activity Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
2.
G. L. Morgans S. M. Scalzullo M. A. Fernandes J. P. Michael W. A. L. van Otterlo 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(5):o309-o311
The title compound, C20H19NO5S2, crystallizes as an almost 2:1 mixture of two molecular orientations (described as Orient‐A and Orient‐B). The consequences of these two orientations is the formation of three types of N—H...O hydrogen‐bonded dimers in which the (Orient‐A + Orient‐A) dimers are likely to be the most stable, while the mixed (Orient‐A + Orient‐B) dimers are more frequent. Extra interactions in the form of C—H...O and C—H...π interactions act to further stabilize these dimers and probably allow the less energetically favourable (Orient‐A + Orient‐B) and (Orient‐B + Orient‐B) hydrogen‐bonded dimers to exist by preventing their conversion to (Orient‐A + Orient‐A)‐only hydrogen‐bonded dimers during the crystal‐growth process. 相似文献
3.
Addition of chlorotrimethylsilane (Me3SiCl) to the mixture of a carbamoyl‐substituted Meldrum's acid, i.e., a 5‐[(arylamino)hydroxymethylene]‐2,2‐dimethyl‐1,3‐dioxane‐4,6‐dione of type 1 and a secondary amine as nucleophile strongly accelerated the rate of their reaction. The reason for this phenomenon observed, during our previous research, remained, however, unclear. To elucidate the mechanism of this reaction, we assumed and verified three possible pathways for the action of Me3SiCl (cf. Scheme 2): The acceleration of the reaction is caused i) by formation of a O‐trimethylsilylated Meldrum's acid of type 2 , ii) by the silylated amine 3 , or iii) by the presence of HCl liberated from Me3SiCl. The performed experiments revealed that the faster course of reaction is caused by the formation of N‐trimethylsilylated amines of type 3 . 相似文献
4.
Vratislav Langer Pavel Mach
ubomír Smr
ok Viktor Milata 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(4):o183-o185
The title compound, C12H12FNO3, a potential precursor for fluoroquinoline synthesis, is essentially planar, with the most outlying atoms displaced from the best‐plane fit through all non‐H atoms by 0.163 (2) and 0.118 (2) Å. Molecules are arranged in layers oriented parallel to the (011) plane. The arrangement of the molecules in the structure is controlled mainly by electrostatic interactions, as the dipole moment of the molecule is 5.2 D. In addition, the molecules are linked by a weak C—H...O hydrogen bond which gives rise to chains with the base vector [1,1,1]. Electron transfer within the molecule is analysed using natural bond orbital (NBO) analysis. Deviations from the ideal molecular geometry are explained by the concept of non‐equivalent hybrid orbitals. 相似文献
5.
John Nicolson Low Justo Cobo Manuel Nogueras Adolfo Snchez Braulio Insuasty Harlen Torres 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(1):o39-o41
2,2‐Dimethyl‐5‐[3‐(4‐methylphenyl)‐2‐propenylidene]‐1,3‐dioxane‐4,6‐dione, C16H16O4, crystallizes in the triclinic space group , with two molecules in the asymmetric unit. These molecules and a centrosymmetrically related pair, linked together by weak C—H?O hydrogen bonds, form a tetramer. 5‐[3‐(4‐Chlorophenyl)‐2‐propenylidene]‐2,2‐dimethyl‐1,3‐dioxane‐4,6‐dione, C15H13ClO4, also crystallizes in the triclinic space group , with one molecule in the asymmetric unit. Centrosymmetrically related molecules are linked together by weak C—H?O hydrogen bonds to form dimers which are further linked by yet another pair of centrosymmetrically related C—H?O hydrogen bonds to form a tube which runs parallel to the a axis. 相似文献
6.
Govindaiah Darshan Deepak Chopra Janardhanan Saravanan 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(12):o571-o574
The title isomers, viz. the N‐(3‐methylphenyl)‐, (I), and N‐(2‐methylphenyl)‐, (II), derivatives, both C26H28N2O4S, adopt an E configuration that places the thiophene and trimethoxyphenyl groups on opposite sides of the C=N double bond, providing a suitable orientation for formation of an intramolecular N—H...N hydrogen bond. However, while the molecule in (I) is close to being planar, the N‐methylphenyl group in (II) is twisted significantly from the plane of the remainder of the molecule. Both crystal structures are essentially layered and there are no intermolecular N—H...O hydrogen bonds. Compound (I) has a significantly higher calculated density than (II) (1.340 cf 1.305 Mg m−3), indicating that the molecular packing in the meta isomer is overall more efficient than that in the ortho isomer. 相似文献
7.
Vratislav Langer Eva Scholtzov Miroslav Ko 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(6):o340-o342
In the crystal structure of the title compound, C23H22BrN3, a strong conjugation of the pyrazoline chromophore with the aromatic rings at positions 1 and 3 is observed, as well as a significant shift in the synclinal→synperiplanar direction. The absolute structure was unequivocally determined. In the absence of clasical hydrogen‐bond donors, the structure is stabilized by weak C—H...π interactions. This paper also reports the electronic structure of the title compound using NBO (natural bond order) analysis. The contributions of lone pairs to the relevant bonds were revealed. 相似文献
8.
Youssef Arfaoui Salah Kouass Nesrine Salah Azaiez Ben Akacha Abderrahmen Guesmi 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(7):o353-o355
In the title compound, C11H21N2O5P, one of the two carbazate N atoms is involved in the C=N double bond and the H atom of the second N atom is engaged in an intramolecular hydrogen bond with an O atom from the dimethylphosphorin‐2‐yl group, which is in an uncommon cis position with respect to the carbamate group. The cohesion of the crystal structure is also reinforced by weak intermolecular hydrogen bonds. Density functional theory (DFT) calculations at the B3LYP/6‐311++g(2d,2p) level revealed the lowest energy structure to have a Z configuration at the C=N bond, which is consistent with the configuration found in the X‐ray crystal structure, as well as a less stable E counterpart which lies 2.0 kcal mol−1 higher in potential energy. Correlations between the experimental and computational studies are discussed. 相似文献
9.
Pierre Valat Vronique Wintgens Jean Kossanyi Lszl Biczk Attila Demeter Tibor Brces 《Helvetica chimica acta》2001,84(9):2813-2832
The fluorescence behavior of 2‐(3‐fluorophenyl)‐2,3‐dihydro‐1H‐benzo[f]isoindole‐1,3‐dione ( 1 ) was studied in solvents of different polarity and viscosity. Dual luminescence is observed and the short‐wavelength emission is found to increase considerably with the solvent polarity. The ratio of the fluorescence quantum yield of the two states emitting, the one (SW*) at short wavelength and the other (LW*) at long wavelength, shows a bell‐shaped dependence on the reciprocal of the temperature in diethyl ether, butyronitrile, and propane‐1,2,3‐triol triacetate (glycerol triacetate; GTA). This has been interpreted as the result of a reversible interconversion between the two states. The enthalpy difference between the SW* and LW* excited states, as deduced from the slope of the ln (Φ/Φ) vs. 1/T curves in the high temperature range, is found to be solvent polarity and solvent viscosity independent as the same value (−7.3 kJ/mol) is obtained in the three above‐mentioned solvents. The independence from polarity is the consequence of a similar difference in dipole moment between the ground‐state and the SW* and LW* excited states (4.5 and 4.9 D, respectively, derived from solvatochromy). The activation energy of the SW*→LW* step deduced from the low temperature measurements in the nonviscous solvents, increases with solvent polarity (11.6 and 17.5 kJ/mol for diethyl ether and butyronitrile, respectively); they are greater than the viscous‐flow activation energy of the solvents indicating that the resolvation of the excited dipole controls the kinetics. In the nonviscous solvents, the LW* state originates from the SW* state, while in the viscous GTA solution, both states are formed simultaneously within the 1‐ps laser pulse. 相似文献
10.
Christina A. Capacci-Daniel Jeffery A. Bertke Shoaleh Dehghan Rupa Hiremath-Darji Jennifer A. Swift 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(9):692-696
Hydrogen bonding between urea functionalities is a common structural motif employed in crystal‐engineering studies. Crystallization of 1,3‐bis(3‐fluorophenyl)urea, C13H10F2N2O, from many solvents yielded concomitant mixtures of at least two polymorphs. In the monoclinic form, one‐dimensional chains of hydrogen‐bonded urea molecules align in an antiparallel orientation, as is typical of many diphenylureas. In the orthorhombic form, one‐dimensional chains of hydrogen‐bonded urea molecules have a parallel orientation rarely observed in symmetrically substituted diphenylureas. 相似文献
11.
Vratislav Langer Dalma Gyepesov Jozef Lusto Juraj Kronek Eva Scholtzov Miroslav Ko 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(7):o416-o418
In the crystal structure of the title compound, C11H13NO2, there are strong intermolecular O—H⋯N hydrogen bonds which, together with weak intramolecular C—H⋯O hydrogen bonds, lead to the formation of infinite chains of molecules, held together by weak intermolecular C—H⋯O hydrogen bonds. A theoretical investigation of the hydrogen bonding, based on density functional theory (DFT) employing periodic boundary conditions, is in agreement with the experimental data. The cluster approach shows that the influence of the crystal field and of hydrogen‐bond formation are responsible for the deformation of the 2‐oxazoline ring, which is not planar and adopts a 4T3 (C3TC2) conformation. 相似文献
12.
Roser Cervellera Xavier Ramis Josep Maria Salla Angels Serra Ana Mantecn 《Journal of polymer science. Part A, Polymer chemistry》2006,44(15):4546-4558
Ytterbium and lanthanum triflates were used as initiators to cure a mixture of diglycidylether of bisphenol A (DGEBA) and 5,5‐dimethyl‐1,3‐dioxane‐2‐one (DMTMC). The evolution of the curing was studied by differential scanning calorimetry (DSC) and Fourier transform infrared in the attenuated‐total‐reflection mode (FTIR/ATR). FTIR/ATR was used to monitor the competitive reactive processes and to quantify the evolution of the groups involved in the curing process. We observed the formation of a five‐membered cyclic carbonate, which remains unreacted at the chain ends because of an equilibrium process between the spiroortho carbonates that had formed as intermediate species and also the loss of CO2, which was quantified by thermogravimetry. The kinetics were studied by DSC and analyzed by isoconversional procedures. Thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA) experiments were used to evaluate the properties of the thermosets obtained. The phenomenological changes that take place during curing were studied and represented in a time‐temperature‐transformation (TTT) diagram. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4546–4558, 2006 相似文献
13.
Tuncay Karakurt Muharrem Dinçer Alaaddin Çukurovali 《International journal of quantum chemistry》2012,112(2):394-413
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 相似文献
14.
A. Subbiah Pandi D. Velmurugan S. Shanmuga Sundara Raj Hoong‐Kun Fun P. R. Seshadri D. Thirumalai 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(7):821-824
10‐(4‐Fluorophenyl)‐3,3,6,6,9‐pentamethyl‐3,4,6,7,9,10‐hexahydroacridine‐1,8(2H,5H)‐dione, C24H28FNO2, (I), crystallizes with two crystallographically independent molecules (which differ slightly in conformation), while 10‐(4‐fluorophenyl)‐9‐propyl‐3,3,6,6‐tetramethyl‐3,4,6,7,9,10‐hexahydroacridine‐1,8(2H,5H)‐dione, C26H32FNO2, (II), crystallizes with one molecule per asymmetric unit. In both structures, the central ring in the acridine moiety is in a sofa conformation, while the outer rings adopt intermediate half‐chair/sofa conformations. The central pyridine ring is orthogonal to the substituted phenyl ring. In both structures, the packing of the crystal is stabilized by C—H?O intermolecular hydrogen bonds. 相似文献
15.
Vratislav Langer Eva Scholtzov Viktor Milata Tom Sol
an 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(9):o552-o554
Molecules of the title compound, C12H13NO3, are not planar and are stabilized by electrostatic interactions, as the dipole moment of the molecule is 3.76 D. They are also stabilized by intramolecular hydrogen bonds of N...O and C...O types, and by a complicated network of weak intermolecular hydrogen bonds of the C...O type. This paper also reports the theoretical investigation of the hydrogen bonding and electronic structure of the title compound using natural bond orbital (NBO) analysis. 相似文献
16.
17.
Maddalena Corsini Piero Zanello Renzo Cini Gabriella Tamasi 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(6):m219-m223
The title compound, [Cu(C10H9N2O)2] or [CuII(CYMB)2], (I), was obtained in an attempt to reduce trans‐bis(2‐{[3,5‐bis(trifluoromethyl)phenyl]iminomethyl}phenolato)copper(II), [Cu(TIMB)2], (II), with bis(pentamethylcyclopentadienyl)cobalt(II) [decamethylcobaltocene, Cp*2Co, (III)]. The molecular structure of (I) has the CuII centre located on an inversion centre of the C2/c space group. A density functional theory (DFT) analysis at the B3LYP/Lanl2dz(CuF);6‐31G**(CHNO) level performed in order to optimize the structures of the free ligands CYMB− and TIMB−, and the metal complexes [CuI/II(CYMB)2]−/0 and [CuI/II(TIMB)2]−/0, reproduced well the X‐ray diffraction structure and allowed us to infer the insertion of the cyanomethide anion on the 3,5‐bis(trifluoromethyl)phenyl system from an evaluation of the Mulliken atomic charges and the electronic energies. 相似文献
18.
Huey‐San Melanie Siah Carl Henrik Görbitz Lise‐Lotte Gundersen 《Journal of heterocyclic chemistry》2011,48(6):1375-1378
8‐Bromoadenine was benzylated in the presence of base to give a mixture of two regioisomers. One was easily recognized as 9‐benzyl‐8‐bromoadenine, but the other structure could not be determined with absolute certainty by NMR. Therefore, X‐ray crystallography was used to prove that the benzyl group was attached to N‐3. Furthermore, it is shown that the 3‐benzyl adenine derivative exists as the amine tautomer both in the crystalline state as well as in solution (DMSO‐d6), with restricted rotation around the N6? C6 bond. J. Heterocyclic Chem., (2011). 相似文献
19.
Nabanita Kundu Debdas Mandal Muktimoy Chaudhury Edward R. T. Tiekink 《应用有机金属化学》2005,19(12):1268-1270
The photoluminescence characteristics of the [Cd(bipy)3][PF6]2 complex are reported. A moderately large quantum yield (φ) of 1.07 × 10?2 is exhibited in acetonitrile solution at 298 K. Crystallography shows the dication to have a distorted octahedral geometry and the crystal structure to be stabilized by C? H···π and C? H···F interactions. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
20.
Graldine Calvet Nicolas Blanchard Cyrille Kouklovsky Rgis Guillot 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(6):o365-o368
The crystal structures of 2,2‐dimethyl‐5‐nitroso‐1,3‐dioxan‐5‐yl benzoate, C13H15NO5, (I), 2,2‐dimethyl‐5‐nitroso‐1,3‐dioxan‐5‐yl 4‐chlorobenzoate, C13H14ClNO5, (II), and 5‐nitroso‐1,3‐dioxan‐5‐yl 4‐chlorobenzoate, C11H11NO5, (III), have been determined in order to gain insight into the conformational preference of α‐benzoyloxynitroso. Unfavourable 1,3‐diaxial interactions force (I) and (II) to crystallize in the 2,5 twist‐boat conformation, whereas compound (III), lacking this destabilizing interaction, crystallizes in the chair conformation. 相似文献