Basicity and Proton Transfer in Proton Sponges and Related Compounds: An Ab Initio Study

Theoretical calculations at the B3LYP/6-31G* level were carried out on a family of 1,8-diR-naphthalenes, which include the proton sponge (1,8-bisdimethylaminonaphthalene, R = NMe₂) and other substituents (R = NH₂, R = OH, R = CH₃, R = F). Their basicity was compared with that of the corresponding monosubstituted benzenes. The dianion of 1,8-dihydroxynaphthalene should be a compound of extraordinary high basicity. The barriers to proton transfer, geometry, and density at the bond critical point of the hydrogen bond have been calculated and compared with experimental data when available.     

Theoretical study on the mechanism and kinetics of addition of hydroxyl radicals to fluorobenzene

Geometries, frequencies, reaction barriers, and reaction rates were calculated for the addition of OH radical to fluorobenzene using Möller–Plesset second‐order perturbation (MP2) and G3 methods. Four stationary points were found along each reaction path: reactants, prereaction complex, transition state, and product. A potential for association of OH radical and fluorobenzene into prereaction complex was calculated, and the associated transition state was determined for the first time. G3 calculations give higher reaction barriers than MP2, but also a significantly deeper prereaction complex minimum. The rate constants, calculated with Rice–Ramsperger–Kassel–Marcus (RRKM) theory using G3 energies, are much faster and in much better agreement with the experiment than those calculated with MP2 method, as the deeper well favors the formation of prereaction complex and also increases the final relative populations of adducts. The discrepancies between the experimental and calculated rate constants are attributed to the errors in calculated frequencies as well as to the overestimated G3 reaction barriers and underestimated prereaction complex well depth. It was possible to rectify those errors and to reproduce the experimental reaction rates in the temperature range 230–310 K by treating the relative translation of OH radical and fluorobenzene as a two‐dimensional particle‐in‐the‐box approximation and by downshifting the prereaction complex well and reaction barriers by 0.7 kcal mol^?1. The isomeric distribution of fluorohydroxycyclohexadienyl radicals is calculated from the reaction rates to be 30.9% ortho, 22.6% meta, 38.4% para, and 8.3% ipso. These results are in agreement with experiment that also shows dominance of ortho and para channels. © 2012 Wiley Periodicals, Inc.     

Effective Synthesis of Polysubstituted Pyrroles from (E)-Dimethyl 2-(Bromomethyl)-3-(diethoxyphosphoryl) Fumarate

Methyl 1-alkyl-4-(diethoxyphosphoryl)-5-oxo-2,5-dihydro-1H-pyrroles-3-carboxylate 4 was synthesized from the reaction of dimethyl 2-(bromomethyl)-3-(diethoxyphosphoryl) fumarate 3- E and primary amines in good yields.     

Dual functional novel catalytic Cu1−xZrxFe2O4 (x=0, 0.5, 1) nanoparticles for synthesis of polysubstituted pyridines and sunlight‐driven degradation of methylene blue

The effect of varied zirconium content on the structural, morphological, magnetic, optical, thermal and catalytic properties of nanoparticles of the ferrite Cu_1 ? xZr_xFe₂O₄ (x = 0, 0.5, 1) was investigated. The mixed ferrite was synthesized by the auto‐combustion method using nitrates of respective metals and citric acid as a chelating agent. The as‐prepared nanoparticles showed dual benefits. They were employed as a heterogeneous catalyst for one‐pot synthesis of polysubstituted pyridine derivatives as well as for catalytic degradation of industrial waste dyes such as methylene blue (MB). The highlight of the research reported is the catalytic degradation of industrial waste (MB) with high efficiency in eluent of a wide range of pH (3–13). The proposed nanoparticles arguably offer certain great advantages that include: low cost, facile nature, anti‐leaching property, magnetic recoverability and recyclability. The characterization of the as‐synthesized nanoparticles was done using various techniques. The leaching study was carried out using inductively coupled plasma optical emission spectroscopy. The formation of organic products was confirmed using Fourier transform infrared and ¹H NMR spectroscopies and examination of degradation products of MB dye was carried out using mass spectrometry and UV–visible spectroscopy.     

多取代二乙烯基酮参与的[5C+1X]环合反应研究进展

六元环化合物是最常见的环状化合物之一,在许多天然产物和具有生物活性的化合物中存在六元环系,因此其合成方法学的研究一直受到化学工作者的重视.在众多合成方法中,[5+1]环合策略作为一种新颖的方法的研究已越来越多,应用得到进一步拓展.结合二乙烯基酮结构特点,就其参与的[5C+1X]成环反应最新进展做一综述.     

DFT study on the electron affinities of the chlorinated benzenes

The molecular structures and electron affinities of the C₆HCl₅ and C₆Cl₆ molecules have been determined using seven pure Density Functional Theory (DFT) or hybrid Hartree–Fock/DFT methods. The EAs of ten kinds of monochlorobenzene, dichlorobenzene, trichlorobenzene and tetrachlorobenzene are also predicted. The basis set used in this work is of double-ζ plus polarization quality with additional diffuse s- and p-type functions, denoted DZP++. These methods have been carefully calibrated (Chem. Rev. 2002, 102, 231). The geometries are fully optimized with each DFT method independently. The equilibrium configuration of hexachlorobenzene is found to be planar with D_6h symmetry. The pentachlorobenzene is planar with C_2υ symmetry. Three different types of the neutral-anion energy separations reported in this work are the adiabatic Electron Affinity (EA_ad), the vertical Electron Affinity (EA_vert), and the Vertical Detachment Energy (VDE). The most reliable adiabatic electron affinities of the chlorinated benzenes obtained at the BHLYP level of theory are −0.18 eV (C₆H₅Cl), 0.07 eV (1,2-C₆H₄Cl₂), 0.07 eV (1,3-C₆H₄Cl₂), 0.04 eV (1,4-C₆H₄Cl₂), 0.29 eV (1,2,3-C₆H₃Cl₃), 0.31 eV (1,2, 4-C₆H₃Cl₃), 0.31 eV (1,3,5-C₆H₃Cl₃), 0.51 eV (1,2,3,4-C₆H₂Cl₄), 0.48 eV (1,2,4,5-C₆H₂Cl₄), 0.50 eV (1,2,3,5-C₆H₂Cl₄), 0.74 eV (C₆HCl₅) and 0.79 eV (C₆Cl₆), respectively.     

Zr-promoted ‘pair’-selective and regioselective synthesis of penta-substituted benzene derivatives

Tetra-substituted zirconacyclopentadiene derivatives, obtainable via in situ generation of zirconacyclopropenes and their cyclic carbozirconation with alkynes, can be treated with alkynyllithiums to induce 1,2-migration accompanied by aromatization and protonolysis, leading to the formation of penta-substituted benzene derivatives, in which all five substituted may be different.     

Bi(OTf)3-catalyzed allylation of quinones with allyltrimethylsilane

p-Quinones react smoothly with allyltrimethylsilane in the presence of 2 mol% of Bi(OTf)₃ under mild reaction conditions to afford the corresponding allyl substituted benzene derivatives, p-allylquinols and allyl substituted 1,4-naphthoquinones in excellent yields with high regioselectivity. This method is very useful for the direct introduction of an allyl functionality onto a quinone moiety.     

Direct synthesis of 3-fluoroalkyl-2,6-diethoxycarbonyl phenols

Cyclocondensation of α-fluoroalkyl ketones or α-fluoroalkyl aldehyde (1) and diethyl 1,3-acetonedicarboxylate (2) affords 3-fluoroalkyl-2,6-diethoxycarbonyl-5-alkyl-phenols (3) in good yields. This provides a novel method for the preparation of meta-fluoroalkyl polysubstituted phenols.