Basicity of Phenyl-Substituted 1,3-Oxazoles

Phenyl substituents in positions 2, 4, and 5 of the oxazole ring exert different effects on the electronic structure of the heteroring, which are reflected in the basicity constants of isomeric phenyl-substituted oxazoles and in changes of the spectral patterns on protonation. The calculated (AM1) gas-phase proton affinities and energies of ionization of isomeric methyl-, phenyl-, and methylphenyloxazoles were correlated with the experimental pKBH ⁺ values. In acid medium specific solvation of phenyloxazoles is possible with participation of the heterocyclic fragment.     

A General and Efficient Route for the Preparation of Phenyl-Substituted Vinyl Fluorides

α-Fluorobenzyl phosphonate (EtO)₂P(O)CFHPh ( 2 ) prepared from diethyl α-hydroxyphosphonate (EtO)₂P(O)CH(OH)Ph ( 1 ) and diethylaminosulfur trifluoride (DAST), reacts with bases such as butyllithium, tert-butyllithium, lithium bis(trimethylsilyl)amide, or lithium diisopropylamide at −78° in THF to give the phosphonate carbanion [(EtO)₂P(O)CFPh]⁻Li⁺ ( 3 ) which was detected by acylation with propionyl chloride or by addition of MeOD to the reaction mixture to give (EtO)₂P(O)CF(COEt)Ph ( 4 ) and (EtO)₂P(O)CFDPh ( 5 ), respectively. Addition of aldehydes or ketones to a THF solution of carbanion 3 led to moderate-to-good yields of phenyl-substituted vinyl fluorides RR′C=CFPh 6 . The stereoselectivity of the products PhCH=CFPh ( 6a ) and Ph(Me)C=CFPh ( 6i ) formed in the reaction was examined. The presence of hexamethylphosphoric triamide or N,N′-dimethylpropyleneurea as cosolvent in the preparation of 6a and 6i increased the (Z)-stereoselectivity. However, the presence of LiCl in THF did not alter the (E)/(Z)-ratio of the product.     

Preparation and Structures of Dication Salts of Phenyl-Substituted TTF Vinylogues

Some TTF vinylogues 1 containing phenyl groups at the vinyl positions were synthesized. The redox properties were investigated by cyclic voltammograms, showing that they are strong electron donors and the Coulomb repulsion is decreased in the dication states. Some of the donors afforded their dication salts as single crystals by electrochemical oxidation or the reaction with CuCl₂. X-ray structure analysis has revealed that the dication molecules have structures with planar TTF vinylogue units and twisted phenyl groups. The crystal structures are unusual to avoid the steric interactions of the phenyl groups.     

苯基取代聚苯撑乙烯的合成及其电致发光性能

聚苯撑乙烯(PPV)类聚合物是优异的发光材料, 有望作为全色显示中三基色的材料之一得到应用. 我们采用2-溴-1,4-亚二甲苯二乙酯为原料, 合成了商品名为Supper Yellow PPV (SY PPV)的苯基取代PPV. 中间体、单体和聚合物的结构都通过核磁共振、元素分析进行了表征. SY PPV的吸收峰在434 nm, 吸收边在510 nm, 带隙2.44 eV. 光致发光峰值和电致发光峰值分别在516和552 nm. SY PPV的器件性能为: 启动电压为2.4 V, 最大亮度大于49000 cd·m^-2, 最大流明效率为21 cd·A^-1, 显著优于采用老方法合成SY PPV的最大流明效率(16-18 cd·A^-1).     

Extraction of Cobalt(II) from Sulfate Medium with Substituted Salicylideneanilines

Russian Journal of Physical Chemistry A - The liquid-liquid extraction of cobalt(II) from sulfate media (Na2SO4) with substituted salicylideneanilines (SAN) is investigated. The stoichiometry of...     

Methyl-and ethyl carbonates derived from vanillin and vanillal in the synthesis of nitrogen-containing compounds

Reactions of 4-hydroxy-3-methoxybenzaldehyde and 3-ethoxy-4-hydroxybenzaldehyde with methyl and ethyl chloroformates in the presence of pyridine gave the corresponding methyl and ethyl carbonates which were brought into condensation with biphenyl-4-amine, naphthalen-1-and-2-amines, and 3-and 4-aminobenzoic acids to obtain the corresponding Schiff bases. Alkyl 4-(9,9-dimethyl-11-oxo-7,8,9,10,11,12-hexahydrobenzo[a]acridin-12-yl)-2-alkoxyphenyl carbonates were selectively synthesized by cascade heterocyclization of naphthalen-2-amine, 5,5-dimethylcyclohexane-1,3-dione, and 4-formyl-2-methoxy(or ethoxy)phenyl methyl(or ethyl) carbonates. Ammonium salts were obtained from the benzoacridine derivatives and Schiff bases derived from aminobenzoic acids.     

Reduction of Phenyl-Substituted Pyridinium Methoiodides with Sodium Borohydride. Formation of Amine-Borane Complexes in Water

Reduction of phenyl-substituted pyridinium methoiodides with sodium borohydride in water afforded besides the desired tetrahydropyridines substantial amounts of amine-borane complexes. Reduction in methanol afforded tetrahydropyridines in high yield, with almost no amine-boranes formed.     

Studies on the Metal Amide Bond 21. Metal Complexes of Chiral Phenyl-Substituted Bis-Picolinamide Tetradentates

Abstract

Two new C-phenyl bis-picolinamide tetradentates, N', N,'-bis(2-pyridinecarboxamide)-1,2-diphenyIethane (bpstienH₂) and N,N'-bis(2-pyridinecarboxamide)phenylethane (bpstyenH₂) together with their deproto-nated complexes of bivalent Cu, Ni and Pd have been prepared and characterised. A crystallographic analysis of the two copper(II) complexes is reported, with the S-bpstyenH₂ ligand found to be susceptible to racemisation under the warm basic conditions used in the syntheses.

{[N,N'-Bis(2-pyridinecarboxamido)-S',S-1,2-diphenylethane]copper(II)}, C₂₆H₂₀N₄O₂Cu is mono-clinic, spacegroup P2₁ (No. 4), with a = 11.170(3), b = 10.853(4), c = 18.570(7) Å, β = 103.74(3)°, Z = 4, with two molecules in the asymmetric unit. The structure was refined to R = 0.039 for 2519 reflexions. Each molecule is five coordinate with the fifth position occupied by an amide oxygen atom of a neighbouring molecule. These Cu-O(amide) distances are 2.554(7) and 2.757(6) Å. The stereochemistry of molecule 1 closely resembles a square-based pyramid, whereas that for molecule 2 approximates a distorted trigonal bipyramid. In each case the central five-membered chelate ring has a γ conformation with the two phenyl substituents occupying the axial positions in a rare configuration.

{Aqua[N,N'-bis(2-pyridinecarboxamido)phenylethane]-copper(II)}-sesquihydrate, C₂₀H₂₁N₄O₄₅Cu, is monoclinic, space group P2₁/c (No. 14), with a= 12.122(4), b= 10.691(2), c= 15.952(4)Å, β = 110.76(2)°, Z = 4. The structure was refined to R = 0.046 for 1939 reflexions. The stereochemistry of the five-coordinate copper atom approximates a square pyramid with the copper atom displaced 0.26 Å towards the apical water molecule (Cu-O 2.251(5) Å). In the enantiomer containing S-bpstyen the central five-membered chelate ring has a Δ conformation with the phenyl substituent occupying an equatorial position.

In solution the palladium(II) and nickel(II) deprotonated metal complexes of the S,S- and S- ligand forms are shown by ¹H NMR analysis, in conjunction with their chiroptical properties, to each have a X gauche central chelate ring conformation with the phenyl substituent(s) occupying axial positions.     

Synthesis of New Sulfur Heteroaromatics Isoelectronic with Dibenzo[g,p]chrysene by Photocyclization of Thienyl- and Phenyl-Substituted Ethenes

A series of new sulfur heteroarenes, isoelectronic with dibenzo[g,p]chrysene, have been prepared by double photocyclization of the corresponding tetraaryl substituted ethenes. The first step proceeds efficiently in each case, and the corresponding intermediate sulfur heteroarenes, isoelectronic with phenanthrene, have been isolated. The second ring closure is only efficient when one of the participating aryl substituents is thienyl, which thus manifests a higher electron density on the carbon atom involved in the excited singlet state reaction. Most of the new compounds are of minimal solubility in common solvents and do not display improved electron donor properties otherwise commonly found among heteroaromatics.     

Methyl-and tert-butyl-substituted hydroquinones and semiquinone radicals: Bond strength estimates, enthalpy of formation, and the rate constants of their reactions with peroxy radicals

The strength of the O-H bonds (D) in hydroquinone (HQH) and its alkyl derivatives has been estimated by the intersecting parabolas method using rate constants known for the reactions of these compounds with the styrene peroxy radical. For unsubstituted HQH, D = 352.6 kJ/mol; for substituted HQH derivatives, D = 349.9 (Me), 346.9 (2,5-Me₂), 343.0 (Me₃), 347.6 (CMe₃), and 340.2 (2,5-(CMe₃)₂) kJ/mol. The enthalpies of formation of these HQH derivatives have been calculated. The O-H bond strengths in the semiquinone radicals (HQ^.) resulting from the above HQH derivatives have been calculated using a thermochemical equation to be $D_{HQ^. } $ = 236.7, 237.4, 239.8, 244.7, 240.1, and 247.5 kJ/mol, respectively. Rate constants have been determined for the reactions of the hydroquinones with tertiary and secondary peroxy radicals and HOO^. at 323 K. The rate constants of the reactions between HOO^. and benzoquinones and the relative reactivities of the HQ^. radicals in their reactions with ROO^. have been estimated.