π-cyclohexadienyliron complexes bearing exocyclic double bonds

Sodium amide and sodium bis(trimethylsilyl)amide abstract α protons from certain π-arene-π-cyclopentadienylixon(II) cations to produce neutral π-cyclohexadienyl complexes bearing exocyclic CC or CN bonds. Also reported are the first examples of π-arene-π-cyclopentadienyliron(II) cations of aromatic amines synthesized by direct reaction of the amine, ferrocene and AlCl₃.     

钯催化剂于外向环双键立体选择合成上之应用

此报告描述钯配合物催化分子内嵌入相邻不饱和配位体及伴随之交叉偶合反应应用于各种立体选择外向环双键上之合成。亦叙述一种通用之高度位置及立体选择性α-亚烷基-γ-内酯合成法。     

Phosphasilaferracyclopropane: an activator of small molecules having polarized single, double, and aromatic unsaturated bonds

Irradiation of Cp*(CO)2FeSiMe2PPh2 resulted in the formation of phosphasilaferracyclopropane 2, which readily reacted with small organic molecules with polarized bonds to yield 3-5.     

Conformations of proline analogues having double bonds in the ring

The intrinsic conformational preferences of proline analogues having double bonds between carbon atoms in their rings have been investigated using quantum mechanical calculations at the B3LYP/6-31+G(d,p) level. For this purpose, the potential energy surface of the N-acety-N'-methylamide derivatives of three dehydroprolines (proline analogues unsaturated at alpha,beta; beta,gamma; and gamma,delta) and pyrrole (proline analogue with unsaturations at both alpha,beta and gamma,delta) have been explored, and the results are compared with those obtained for the derivative of the nonmodified proline. We found that the double bonds affect the ring puckering and the geometric internal parameters, even though the backbone conformation was influenced the most. Results indicate that the formation of double bonds between carbon atoms in the pyrrolidine ring should be considered as an effective procedure to restrict the conformational flexibility of prolines. Interestingly, we also found that the N-acetyl-N'-methylamide derivative of pyrrole shows a high probability of having a cis peptide bond preceding the proline analogue.     

1,3-Digermacyclobutanes with exocyclic C=P and C=P=S double bonds

New 1,3-digermacyclobutanes, with two exocyclic C=PMes* bonds, and the corresponding first bis(methylenethioxo)phosphoranes with C=P(S)Mes* moieties have been synthesized.     

meso-Alkylidene (m-benzi)pentaphyrin: a modified pentaphyrin bearing exocyclic double bonds at meso-positions

meso-Alkylidene (m-benzi)pentaphyrin containing exocyclic C=C double bonds at two meso-positions is synthesized and fully characterized for the first time. The single crystal X-ray crystallographic analysis shows a concave conformation with two pyrrole rings inverted. The first protonation occurs exclusively at core nitrogen. The synthesized compound displays concentration dependent chromogenic responses for fluoride anion in organic solvent.     

Relationship between lengths of endo- and exocyclic phosphorus-nitrogen bonds in substituted triazaphosphorines

Institute of Organic Chemistry, Academy of Sciences of the Ukrainian SSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 28, No. 4, pp. 164–165, July–August, 1987.     

The transformation of aromatic molecules into the subspace of their double bonds

A model of new submolecules is presented. As an application some absorptions of aromatic radicals are interpreted in UV and visible spectra. Extension of the model to biological systems is prejudged.     

Stereoselective synthesis of insect sex pheromone analogs having a fluorine atom on their double bonds

Insect sex pheromone analogs having a fluorine atom on their double bonds, (9E,11E)-1-acetoxy-9-fluorotetradecadiene, (10E,12E)-13-fluorohexadecadien-1-ol, (9Z,11E)-1-acetoxy-9-fluorotetradecadiene, (10E,12Z)-13-fluorohexadecadien-1-ol were stereoselectively synthesized using cross-coupling reactions of alkenylboranes with (E)- or (Z)-2-fluoro-1-iodo-1-alkenes, stereoselectively prepared from 1-alkynes by our currently developed methods.     

Mean amplitudes of vibration of molecules and ions with interhalogen bonds and related species

Mean amplitudes of vibration of molecules and ions containing interhalogen bonds are reviewed and critically analyzed. The presented information comprises pure interhalogen compounds as well as oxohalides. Correlations between mean amplitude values and structural and bond properties are discussed. Comparisons with data of related - specially isoelectronic - species are also performed. Characteristic ranges for the mean amplitudes of vibration for halogen-halogen and halogen-oxygen bonds could be established. The presented and discussed results are also of central importance for the analysis and interpretation of electron diffraction studies.     

Atoms and bonds in molecules and chemical explanations

The concepts of atoms and bonds in molecules which appeared in chemistry during the nineteenth century are unavoidable to explain the structure and the reactivity of the matter at a chemical level of understanding. Although they can be criticized from a strict reductionist point of view, because neither atoms nor bonds are observable in the sense of quantum mechanics, the topological and statistical interpretative approaches of quantum chemistry (quantum theory of atoms in molecules, electron localization function and maximum probability domain) provide consistent definitions which accommodate chemistry and quantum mechanics.     

Photoinitiators with double and triple bonds

In continuation of our research on new chromophores for photoinitiators (PIs) we investigated a series of double and triple bond containing PIs based on benzophenone (BP), thioxanthone, benzil (BZ), benzildimethylketal (BDK), and hydroxyalkylphenone. UV‐Vis spectroscopy revealed an absorption shifted up to 50 nm to the visible range of the spectrum. With steady state photolysis experiments, the rates of decomposition (R_d) were determined. Compared to the commercially available reference PIs the R_d of the new PIs were nearly identical. By quenching reactions with 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO), α‐cleavage was identified for Type I initiators. Generally, all new compounds are suitable as PI especially for longer wavelengths. Nevertheless it has to be noted that the PI concentration has to be selected carefully to achieve optimum reactivity. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 289–301, 2008     

Atoms and bonds in molecules from radial densities

Radial densities are explored as an alternative method for partitioning the molecular density into atomic regions and bonding regions. The radial densities for atoms in molecules are similar to those of an isolated atom. The method may also provide an alternative to Bragg-Slater radii.     

Transient bonds and chemical reactivity of molecules

Electron delocalization between the reagent and reactant molecules is the principal driving force of chemical reactions. It brings about the formation of new bonds and the cleavage of old bonds. By taking the aromatic substitution reaction as an example, we have shown the orbitals participating in electron delocalization. The interacting orbitals obtained are localized around the reaction sites, showing the chemical bonds that should be generated and broken transiently along the reaction path. By projecting a reference orbital function that has been chosen to specify the bond being formed on to the MOs of the reactant molecules, the reactive orbitals that are very similar to the interacting orbital have been obtained. The local potential of the reaction site for electron donation estimated for substituted benzene molecules by using these projected orbitals shows a fair correlation with the experimental scale of the electron-donating and -withdrawing strength of substituent groups. The reactivity is shown to be governed by local electronegativity and local chemical hardness and also by the localizability of interaction on the reaction site. © 1996 John Wiley & Sons, Inc.