Infrared spectra of nitrostyrene derivatives

The IR spectra of a series of 6 phenylnitroethenes (PNE) and 6 phenylnitropropenes (PNP) were assigned, based on a normal coordinates calculation performed on styrene and styrene-d₈. Some frequencies were sensitive to the electronic properties of the substituents, and others to the substitution on Cβ. AM1 minimum energy conformations and rotational barriers around the ClCα bond were calculated. According to these calculations, PNE are planar and PNP display an angle of 45° between the ethylenic and aromatic planes. AM1 underestimates the height of the electronic barriers, which is however modulated by the electron donor properties of the substituent on the ring. A correlation between the calculated electronic barrier and the CC ethylenic stretching frequency was observed.     

Tetraaminoethylenes as Strong Electron Donors

Depending on the nature of the electron acceptor and of the tetraaminoethylene (TAE), the electron pairs of the ethylenic double bond (A), of the nitrogen (B), or of the entire electronic system (C) of TAE react with the acceptor. Thus oxidizing agents convert TAE into the mono-and dications TAE⁺ and TAE²⁺ by path (A); acids add on to the ethylenic carbon (A) or the amine nitrogen (B) (the addition of acid is often followed by cleavage of the C?C or C? N bond); organic π-electron acceptors from deeply colored donor-acceptor complexes with TAE (C).     

1,3-Dipolar cycloaddition reactions of isothiazol-3(2H)-ones with nitrile oxides. An unexpected site selectivity of the carbonyl bond of 5-benzoyl-isothiazol-3(2H)-one

2,6-Dichlorobenzonitrile oxide ( 2a ) reacts with isothiazolones 1a and 1b at the ethylenic double bond to give 4 via transformation of the primary cycloadducts 3 . Mesitonitrile oxide ( 2b ) adds preferentially to the carbonyl double bond of 1b yielding the monoadduct 5 and the bisadduct 6 .     

Organic reactions in strong alkalis-I Fission of ethylenic acids (the varrentrapp reaction)

On treatment with molten potassium hydroxide, ethylenic acids are converted initially into a mixture of isomers, by reversible migration of the double bond in both directions along the chain, and finally into a saturated acid, with two fewer carbon atoms than the starting material, and acetic acid in high yield. A number of minor side-reactions also occur.

The mechanisms of these processes are discussed.     

A detailed evaluation of the dependence of 3J(H?H) on bond angle in alkenes and cycloalkenes

Newly determined and accurate data for the magnitudes of cis vinyl proton-proton spin-spin coupling constants in cis-dialkylethylenes and cycloalkenes have been obtained. With these new data and also values taken from the recent literature, it has proved possible to make a critical determination of the correlation between ³J(H? H) and C?C? H bond angles in ethylenic systems. It is suggested that it is possible to obtain accurate estimates of bond angles using NMR coupling constants, even though much more data will be required to fully substantiate this proposal. Whereas cis-³J(H? H) decreases rapidly with increasing C?C? H bond angles, evidence is presented that the opposite is the case for trans-³J(H? H). A brief theoretical discussion of these trends in coupling constants is given.     

Synthese de nouveaux acides sulfoniques et de sila-sultones ethyleniques

The sulfonation of 1-sila-3-clopentenes and corresponding silabicyclohexanes by CISO₃SiMe₃ leads to novel ethylenic silasultones which are hydrolyzed to their sulfonic acids. Depending upon the degree of substitution of the double bond or cyclopropane ring, a competition may occur between the usually observed C-Si bond cleavage and the until now more rarely observed CH cleavage. An interpretation of these results is proposed.     

Molecules organiques coordinees a un metal. : Nouveaux complexes olefiniques d'α-enones par le fer(0)

Heterodienetricarbonyliron complexes react with ligands ( L = PMe₂Ph, P(OMe)₃ or P(OPh)₃) to give the adducts (enone)Fe(CO)₃L with the ethylenic double bond coordinated only to the iron(0). Electron-releasing and low-steric effects of L make the reaction which is specific for enones easier compared to that for dienes. PMe₂Ph allows enone exchange and P(OPh)₃ promotes carbonyl elimination. Ligand influence is shown by infrared spectroscopy and by the shielding of ethylenic protons in NMR spectroscopy.     

Ultrafast excited-state dynamics of tetraphenylethylene studied by semiclassical simulation

Detailed simulation study is reported for the excited-state dynamics of photoisomerization of cis-tetraphenylethylene (TPE) following excitation by a femtosecond laser pulse. The technique for this investigation is semiclassical dynamics simulation, which is described briefly in the paper. Upon photoexcitation by a femtosecond laser pulse, the stretching motion of the ethylenic bond of TPE is initially excited, leading to a significant lengthening of ethylenic bond in 300 fs. Twisting motion about the ethylenic bond is activated by the energy released from the relaxation of the stretching mode. The 90 degrees twisting about the ethylenic bond from an approximately planar geometry to nearly a perpendicular conformation in the electronically excited state is completed in 600 fs. The torsional dynamics of phenyl rings which is temporally lagging behind occurs at about 5 ps. Finally, the twisted TPE reverts to the initial conformation along the twisting coordinate through nonadiabatic transitions. The simulation results provide a basis for understanding several spectroscopic observations at molecular levels, including ultrafast dynamic Stokes shift, multicomponent fluorescence, viscosity dependence of the fluorescence lifetime, and radiationless decay from electronically excited state to the ground state along the isomerization coordinate.     

Preparation and crystal structure of dioxotetrachloro-(N,N′-ethylenebis(salicylideneiminato)bis(triphenylphosphine)-dirhenium(V) dichloromethane solvate

The complex ReOCl₃(PPh₃)₂ reacts with bis(trimethylsilyl)-N,N′-ethylenebis(salicylideneiminato) to give a complex in which the “salen” ligand bridges two rhenium atoms, viz. dioxotetrachloro(N,N′-ethylenebis(salicylideneiminato)bis(triphenylphosphine)dirhenium(V). Its crystal and molecular structure have been determined by a single crystal X-ray diffraction analysis. The crystals are monoclinic space group P2₁/c with four molecules in a cell of dimensions a 18.609(4), b 16.286(4), c 18.600(4)Å and β 105.00(2)°. Least squares refinement of 5867 observed reflections measured on a diffractometer reached R = 0.045. The “salen” ligand bridges two rhenium atoms which present a distorted octahedral coordination. The two halves of the molecule are approximately related by a non-crystallographic two fold axis perpendicular to the CC bond of the ethylenic group.     

Aldéhydes phénylchlorogermaniés,alcools éthyléniques α-germaniés et α-germacycloalcanols

Phenylhydrogermanes and phenylchlorohydrogermanes, as a rule, add to the carbon-carbon double bond of conjugated or non-conjugated ethylenic aldehydes upon radicalar catalysis or just heating. However, steric hindrance about the ethylenic double bond could direct the radicalar addition to the carbonyl group with formation of an alkenoxygermane. These reactions are inhibited by “galvinoxyl” and do not take place in nitromethane.However, under these conditions, and in the cases of Ph₂ClGeH and PhCl₂GeH, the slightly positive character of the proton bonded to germanium (increased in polar solvents like CH₃NO₂) favours the 1,2-dipolar addition of hydrogermane to the carbonyl group leading to ethylenic chlorogermylalcohol.The main properties of these phenylchlorogermylaldehydes and alcohols are described.Reduction of these last-named compounds leads to ethylenic phenylhydrogermyl alcohols, which lead to new α-germacycloalkanols by intramolecular addition

, under radicalar initiation. The addition of diphenylgermane to ethylenic aldehydes leads to oxagermacycloalkanes by radicalar cycloaddition.     

Effets de substituants et conformation de stilbenes

Simultaneous study of para nitrostilbenes by X-ray diffraction and ¹³C nuclear magnetic resonance shows a quantitative relationship between the effect of a para nitro substituent on the chemical shift of ethylenic carbon not adjacent to the substituted phenyl ring and the dihedral angle between this phenyl ring and the central double bond. The alternative introduction of substituents in each phenyl ring discloses at the position of carbon β a certain π-polarization which extends to the double bond and to an unsaturated group carried by carbon α.     

Nitrile oxides cycloadditions to cinnamaldehyde. Facile dehydrogenation of 4-formyl-4,5-dihydroisoxazoles

Nitrile oxides (1) react with cinnamaldehyde (2) at the ethylenic double bond to give 4-formyl-4,5-dihydro-isoxazoles (3) as the predominant regioisomers (¹H nmr). These primary cycloadducts easily dehydrogenate to the corresponding isoxazoles (4). In the presence of an excess of nitrile oxide (1), either the aldehydes (3) and (4) undergo further cycloaddition at the C?O bond yielding the bis-cycloadducts (5) and (6), respectively.     

噻吩多烯基噻吩酮系列化合物的气相紫外光电子能谱研究

本文提供了噻吩多烯基噻吩酮系列化合物的气相HeI光电子能谱(UPS), 并进行了每个研究分子的MNDO量子化学计算。 表明乙烯基基团的数目与其分子的HOMO实验电离能(L~p)呈线性递降关系。MNDO计算结果不但很好地指认了每个研究分子UPS谱的归属, 而且从分子轨道特性上提供了该类化合物分子为三岔共轭体系的理论基础。     

Fluoration anodique dans le chlorure de methylene (polymethyl- et vinylbenzenes)

The anodic oxidation of polymethyl and of ethylenic derivatives of benzene in CH₂Cl₂/Et₄NF, 3HF or Et₃N, 3HF has been studied. The fluoro compounds are obtained in good yields. With the ethylenic compounds cis-addition products predominate.     

New perspectives in the chemistry of 1-azidohydrazones

Thermal decomposition of 1-azidohydrazones [I] results in tricyclic products [III], probably arising from nitrene intermediates through an intramolecular cycloaddition to the ethylenic bond.     

Theoretical insights into the relative bonding of normal and abnormal N‐heterocyclic carbenes in [PdCl2(NHCR)2] and [PdCl2(NHCR)(aNHCR)] (R = H,Ph, Mes)

Quantum chemical insights into normal Pd‐C2(NHC^R) and abnormal Pd‐C5(aNHC^R) bonding, dominated by dispersion interactions in N‐hetereocyclic carbene complexes [PdCl₂(NHC^R)₂] ( I , R = H; II , R = Ph; III , R = Mes (2,4,6‐trimethyl)phenyl)) and [PdCl₂(NHC^R)(aNHC^R] ( IV , R = H; V , R = Ph; VI , R = Mes) have been investigated at DFT and DFT‐D3(BJ) level of theory with particular emphasis on the effects of the noncovalent interactions on the structures and the nature of Pd‐C2(NHC^R) and Pd‐C5(aNHC^R) bonds. The optimized geometries are good agreement with the experimental values. The Pd‐C bonds are essentially single bond. Hirshfeld charge distributions indicate that the abnormal aNHC^R carbene ligand is relatively better electron donor than the normal NHC^R carbene ligand. The C2 atom has larger %s contribution along Pd‐C2 bond than the C5 atom along Pd‐C5 bond. As a consequence the Pd‐C2(NHC^R) bonds are relative stronger than the Pd‐C5(aNHC^R) bonds. Thus, the results of natural hybrid orbital analysis support the key point of the present study. Calculations predict that for bulky substituent (R = Ph, Mes) at carbene, the Pd‐C2(NHC^R) bond is stronger than Pd‐C5(aNHC^R) bond due to large dispersion energy in [PdCl₂(NHC^R)₂] than in [PdCl₂(NHC^R)(aNHC^R)]. However, in case of non‐bulky substituent with small and almost equal contribution of dispersion energy, the Pd‐C2(NHC^R) bond is relative weaker than Pd‐C5(aNHC^R) bond. The bond dissociation energies are dependent on the R substituent, the DFT functional and the inclusion of dispersion interactions. Major point of this study is that the abnormal aNHCs are not always strongly bonded with metal center than the normal NHCs. Effects of dispersion interaction of substituent at nitrogen atoms of carbene ligand are found to play a crucial role on estimation of relative bonding strengths of the normal and abnormal aNHCs with metal center. © 2016 Wiley Periodicals, Inc.     

Base‐Catalyzed Stereoselective Vinylation of Ketones with Arylacetylenes: A New C(sp3)?C(sp2) Bond‐Forming Reaction

Alkylaryl‐ and alkylheteroarylketones, including those with condensed aromatic moieties, are readily vinylated with arylacetylenes (KOH/DMSO, 100 °C, 1 h) to give regio‐ and stereoselectively the (E)‐β‐γ‐ethylenic ketones ((E)‐3‐buten‐1‐ones) in 61–84 % yields and with approximately 100 % stereoselectivity. This vinylation represents a new C(sp³)? C(sp²) bond‐forming reaction of high synthetic potential.     

Structural features for fluorescing present in methoxycoumarin derivatives

Structural features of fluorescent methoxycoumarins were examined from the viewpoint of substituent effect and ring structure in connection with intramolecular charge-transfer (ICT). The fluorescence of methoxycoumarins depended primarily upon the ICT from a C6-electron-donating group to the substituents at the C3-position of the coumarin ring. Furthermore, the presence of a lactone ring itself, including a carbonyl group, cyclic ether oxygen and ethylenic bond as partial ring structures, was found to be essential for fluorescing in methoxycoumarins according to the fluorescent behaviors of chemically deformed model compounds.     

Etude théorique par la méthode DFT des structures non-classiques des systèmes X2H2F2 (X=Si, Ge, Sn)

The structure and the relative stability of isomers of molecules X₂H₂F₂ (X=Si, Ge, Sn) have been studied using the density functional theory (DFT). We have determined the optimised structures of the substituted isomers. The XX bond have been studied and compared to that of the parent molecules: X₂H₄. It appears that, for the planar and trans ethylenic systems, the double bond character of the XX decreases when the hydrogen atoms are substituted by fluorine atoms. The most stable structure is shown to be the one where the two fluorine atoms are fixed on the same atom. The bridged structures are also studied.     

Microwave spectra and the metal-hydrogen bond lengths for the C5H5Mo(CO)3H and C5H5W(CO)3H complexes

The measurements of rotational spectra and metal-hydrogen bond lengths for molybdenum and tungsten hydride complexes were recently completed in our laboratory. The W-H and Mo-H bond lengths were obtained from high resolution rotational spectra of C5H5Mo(CO)3H, C5H5W(CO)3H, C5H5Mo(CO)3D, and C5H5W(CO)3D. Data for five molybdenum and four tungsten isotopomers were obtained for both the normal and deuterium-substituted species. The asymmetric-top rotational parameters A, B, C, DeltaJ, and deltaJ were determined from the least-squares fits and these results indicate that the structures of these complexes are nearly rigid. The hydrogen bond lengths were determined for both complexes using Kraitchman analyses. The molybdenum-hydrogen bond length for the C5H5Mo(CO)3H complex is rMo-H=1.80(1) A. The tungsten-hydrogen bond length for the C5H5W(CO)3H complex is rW-H=1.79(4) A. Density functional theory (DFT) calculations of the structures were performed to obtain the optimized theoretical structures for C5H5Mo(CO)3H and C5H5W(CO)3H. Results obtained from the DFT calculations are in good agreement with the experimental parameters, and the Mo-H value is in good agreement with previously reported Mo-H bond lengths for similar complexes.