Trifluoromethoxylation Reactions of (Hetero) arenes,Olefinic Systems and Aliphatic Saturated Substrates

Direct fluoroalkoxylation reactions of (hetero)arenes, carbon-carbon multiple bonds, and substitution reactions at Csp³ carbon centers by CF₃O, CHF₂O, and (CF₃)₂CFO groups are discussed. Emphasis on thermal radical, electron transfer, photocatalytic, electrochemical and redox-neutral radical methods are placed to accomplish fluoroalkoxylation reactions. All these methods employ either radical fluoroalkoxylating reagents or some nucleophilic trifluoromethoxylating sources of CF₃O. A summary of all these methods is provided in Table 2.     

Direct, easy, and scalable preparation of (diacetoxyiodo)arenes from arenes using potassium peroxodisulfate as the oxidant

The reaction of arenes with potassium peroxodisulfate, elemental iodine, and acetic acid in the presence of concd sulfuric acid, efficiently generates the corresponding (diacetoxyiodo)arenes in good yields, providing an easy, safe, and effective method for preparing (diacetoxyiodo)arenes from arenes and iodine.     

具有C2对称的氮磷-氧磷配体双噁唑啉磷乙烷的合成及在不对称催化加氢中的应用

利用易得的光学纯N-甲基氨基醇与1,2-双(二氯磷)乙烷缩合合成了一类新的具有C₂对称轴的氮磷-氧磷配体(R,R)-双噁唑啉磷乙烷(BOAPE) 1～4. 该类配体不仅具有C₂对称结构和刚性五元环, 还具有富电子特性, 利用500 MHz进行了¹H NMR, ³¹P NMR, ¹³C NMR表征. 与这些配体配位形成的Rh配合物用于N-苯甲酰基脱氢丙氨酸衍生物和α-功能化酮不对称加氢, 分别可以得到99%和98%的ee. 这类配体比它们相对应的非C₂对称的氮磷-氧磷化合物(AMPP)配体具有更高的对映选择性. 在这四个新的配体中配体(R,R)-Ph-BOAPE (2)的催化性能最优. 催化剂[Rh(COD)(R,R)-Ph-BOAPE]BF₄的半反应周期t_1/2和周转频率(TOF)在N-苯甲酰基肉桂酸甲酯的不对称加氢反应中分别为12 min和6.5 min^－1.     

Thermal Stability of Some Polynuclear Coordination Compounds in the Systems Ln(III)—Co(II)—Oxalate

This paper reports an investigation of the thermal stabilities of the class of coordination compounds containing lanthanide ions Ln(III) (Ln=La, Sm, Eu, Dy, Er), Co(II) ions and oxalate anions C₂O ₄ ^2– . The thermal decomposition steps were identified, and in some cases the values of the non-isothermal kinetic parameters were determined.This revised version was published online in November 2005 with corrections to the Cover Date.     

Modular Functionalization of Arenes in a Triply Selective Sequence: Rapid C(sp2) and C(sp3) Coupling of C−Br,C−OTf,and C−Cl Bonds Enabled by a Single Palladium(I) Dimer

Full control over multiple competing coupling sites would enable straightforward access to densely functionalized compound libraries. Historically, the site selection in Pd⁰‐catalyzed functionalizations of poly(pseudo)halogenated arenes has been unpredictable, being dependent on the employed catalyst, the reaction conditions, and the substrate itself. Building on our previous report of C?Br‐selective functionalization in the presence of C?OTf and C?Cl bonds, we herein complete the sequence and demonstrate the first general arylations and alkylations of C?OTf bonds (in <10 min), followed by functionalization of the C?Cl site (in <25 min), at room temperature using the same air‐ and moisture‐stable Pd^I dimer. This allowed the realization of the first general and triply selective sequential C?C coupling (in 2D and 3D space) of C?Br followed by C?OTf and then C?Cl bonds.     

Structures and Stability of Complexes of E(C6F5)3 (E = B,Al, Ga,In) with Acetonitrile

Complexes formed by interaction of E(C₆F₅)₃ (E = B, Al, Ga, In) with excess of acetonitrile (AN) were structurally characterized. Quantum chemical computations indicate that for Al(C₆F₅)₃ and In(C₆F₅)₃ the formation of a complex of 1:2 composition is more advantageous than for B(C₆F₅)₃ and Ga(C₆F₅)₃, in line with experimental observations. Formation of the solvate [Al(C₆F₅)₃ · 2AN] · AN is in agreement with predicted thermodynamic instability of [Al(C₆F₅)₃ · 3AN]. Tensimetry study of B(C₆F₅)₃ · CH₃CN reveals its stability in the solid state up to 197 °C. With the temperature increase, the complex undergoes irreversible thermal decomposition with pentafluorobenzene formation.     

Molecular dynamics in bulk and surface species of cyanophenyl alkyl benzoates with 2, 3 and 7 carbon atoms in the alkyl chain: comparison in the whole homologous series

ABSTRACT

Molecular mobility of cyanophenyl alkylbenzoates (CPnBs) (n = 2, 3, 7 – number of carbon atoms in the alkyl chain) in the bulk and in composites with aerosil A380 is investigated by broadband dielectric spectroscopy, while thermal analysis and infrared spectroscopy were applied to characterise the molecular species. The work completes preliminary results obtained for the members with n = 4 … 6. An interaction by hydrogen bonding, between aerosil surface – OH groups and – CN or ester groups of the CPnB molecules takes place. It slows down the relaxation process as observed for related composites in comparison to the pure materials. The existence of two types of bonding might be the reason that Vogel temperature for the relaxation process in the surface layer does not show the odd-even effect. Temperature dependence of the relaxation rates for composites shows a crossover behaviour from a high to a low temperature regime. Moreover, the temperature dependence of the dielectric strength is unusual. As the loading degree is similar, comparison of the dielectric, spectroscopic and thermal data obtained here and with the results obtained for the composites with n = 4 … 6 can be directly done. Increasing the number of the members of the homologous series confirms and hardens the preliminary conclusions.     

Quantum chemical study of alternating N/B and N/C π bonds in (un)charged even‐membered 4n and 4n+2 cyclic systems and their related open systems

With semi‐empirical MO and ab initio calculations at different levels, we investigated the π conjugation of alternating X? Y bonds with X? Y for N/B and N/C combinations in an open and cyclic arrangement. Although the intrinsic symmetry is lost for the acyclic even‐membered compounds, the alternation is still reflected in its geometry and electron‐density transfer. For the cyclic π compounds, we focused our attention on borazine N₃B₃H₆ (D_3h symmetry), which is isoelectronic with benzene (D_6h symmetry). Specific attention is given to the electrophilic behavior of borazine with respect to CH and SiMe. The dynamics based on the results of FT‐ICR mass spectrometry was studied in more detail. In addition, the results of the cyclic systems with 4n and 4n+2 π electrons concerning their geometries are compared with the corresponding carbon compounds. Attention is also given to the dication of borazine, because of the corresponding triplet ground state of the benzene dication. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Sm（ClO4）3与N,N‘—二安替比林—1,6—己二酰胺（BAPHDCA）配合行为的相平衡

Ｓｍ（ＣｌＯ４）３与Ｎ，Ｎ┐二安替比林┐１，６┐己二酰胺（ＢＡＰＨＤＣＡ）配合行为的相平衡崔斌＊唐宗薰张逢星郭志箴（西北大学化学系西安７１００６９）关键词二安替比林－己二酰胺，高氯酸钐，相平衡，三元体系１９９７－０８－０６收稿，１９９８－０１－０５...     

An Ab Initio Study and NBO Analysis of the Stability and Conformational Properties of Hexakis(trimethylelementhyl)benzene (Element = C,Si, Ge,and Sn)

Ab initio molecular orbital and density functional theory were used to investigate energetic and structural properties of the various conformations of hexa-tertbutylbenzene (1), hexakis(trimethylsilyl)benzene (2), hexakis (trimethylgermyl)benzene (3), and hexakis(trimethylstannyl)benzene (4). HF/3-21G//HF/3-21G and B3LYP/3-21G//HF/3-21G results revealed that the Twist-Boat (TB) conformer of compound 1 is more stable than the 1-Chair (C), 1-Boat (B), and 1-Planar (P) conformers. B3LYP/3-21G//HF/3-21G results show that the 1- TB conformer is more stable than 1- C, 1- B, and 1- P conformers of about 1.13, 4.34, and 99.94 kcal mol^?1 , respectively. Contrary to the stability order of compound 1 conformers, the C conformer of compounds 2–4 is more stable than TB, B, and P conformations, as calculated by B3LYP/3-21G//HF/3-21G and HF/3-21G//HF/3-21G levels of theory. The energy gap between the C and P conformers in compounds 1–4 is decreased in the following order: ΔE(4: C, P) < ΔE (3: C, P) < ΔE(2: C, P) < ΔE (1: C, P). This fact can be explained in terms of the increase of C _aromatic -M (M═C, Si, Ge, and Sn) bond lengths and the decrease of steric (van der Waals) repulsions in the previously discussed compounds. For compounds 1–3, the calculations were also performed at the B3LYP/ 6-31G*//HF/3-21G level of theory. However, the comparison showed that the results at B3LYP/3-21G//HF/3-21G methods correlated well with those obtained at the B3LYP/6-31G*// HF/6-31G method. Further, NBO analysis revealed that in compounds 1–4, the resonance energy associated with the σ_M-C1 to σ*_C2-C3 delocalization is 5.20, 9.68, 11.15, and 12.27 kcal mol^?1, respectively. These resonance energy values could explain the easiness of the ring flipping processes of C, B, and TB conformers of compounds 4 to 1. Also, the NBO results showed that by an increase of the σ_M-C1 → σ *_C2-C3 resonance energies in compounds 1–4, the σ_M-C1 bonding orbital occupancies decrease. This fact could fairly explain the increase of the C_aryl-M bond length from compound 1 to 4. The NBO results are also in good agreement with the calculated energy barriers for the ring flipping of the chair conformations in compounds 1–4, as calculated by B3LYP and HF methods.     

Liquid crystalline polyethers based on conformational isomerism. XIX. Synthesis and characterization of flexible polyethers based on 1-(4-hydroxyphenyl)-2-(2-r-4-hydroxyphenyl) ethane with H,F, CH3, Br,Cl, and CF3 as R groups

The synthesis of 1-(4-hydroxyphenyl)-2-(2-fluoro-4-hydroxyphenyl)ethane ( FBPE ), 1-(4-hydroxyphenyl)-2-(2-chloro-4-hydroxyphenyl)ethane ( CIBPE ), 1-(4-hydroxyphenyl)-2-(2-bromo-4-hydroxyphenyl)ethane ( BrBPE ), and 1-(4-hydroxyphenyl)-2-(2-trifluoromethyl-4-hydroxyphenyl)ethane ( CF₃BPE ), of the corresponding polymers based on 1,5-dibromopentane ( RBPE-5) , 1,8-dibromooctane ( RBPE-8 ), and of the copolymers based on various ratios of 1,5-dibromopentane and 1,8-dibromooctane [ RBPE-5/8(A/B )] is described. The phase transition temperatures and thermodynamic parameters of RBPE-5 and RBPE-8 polymers were compared to those of the corresponding polyethers based on 1,2-bis(4-hydroxyphenyl)ethane ( BPE ) and 1-(4-hydroxyphenyl)-2-(2-methyl-4-hydroxyphenyl)ethane ( MBPE ) which were reported previously. Both isotropic-nematic transition temperatures and corresponding thermodynamic parameters (i.e., enthalpy and entropy changes) decrease in the following order of the substituent R: H > F > CH₃ > Cl > Br > CF₃. This order corresponds to the increase of the breadth of the RBPE molecules, and agrees with the similar trends observed in low molar mass liquid crystals.     

Crystal Structure, Phase Transition, and Thermodynamic Properties of Bis-dodecylammonium Tetrachlorozincate (C12H25NH3)2ZnCl4(s)

The crystal structure and composition of (C₁₂H₂₅NH₃)₂ZnCl₄(s) were characterized by chemical and elemental analysis, X‐ray powder diffraction technique and X‐ray crystallography. The lattice energy of the title compound was calculated to be U_POT=888.82 kJ·mol^?1. Low temperature heat capacities of the title compound have been measured by a precision automated adiabatic calorimeter over the temperature range from 80 to 403 K. An obvious solid to solid phase transition occurred in the heat capacity curve, and the peak temperature, molar enthalpy and molar entropy of the phase transition of the compound were determined to be T_trs= (364.02±0.03) K, (_trsH_m= (77.567±0.341) kJ·mol^?1, and (_trsS_m= (213.77±1.17) J·K^?1·mol^?1, respectively. Experimental molar heat capacities before and after the phase transition were respectively fitted to two polynomial equations. The smoothed molar heat capacities and fundamental thermodynamic functions of the sample relative to the standard reference temperature 298.15 K were calculated and tabulated at an interval of 5 K.     

苯二甲酸及咪唑衍生物构筑的一维链状镍配位聚合物的合成、晶体结构、热稳定性和磁性

以醋酸镍、5-溴间苯二甲酸(H2BIPA)和1,4-二咪唑基二甲苯(1,4-bimb)为原料,在水热条件下合成了1个一维链状配位聚合物[Ni(BIPA)(1,4-bimb)(H2O)2](1),利用红外光谱、元素分析、热重、X-粉末衍射以及X-单晶衍射对其进行了表征。化合物1是正交晶系,Pnma空间群。该化合物具有一维链状结构,结构中存在由配位水分子和羧酸氧原子所产生链内氢键作用。详细研究了该化合物的热稳定性和磁性。     

铀-2-(3,5-二溴-2-吡啶偶氮)-5-二乙氨基苯酚-Triton X-100析相体系的研究及应用

本文研究了铀-2-(3,5-二溴-2-吡啶偶氨)-5-二乙氨基苯酚(3,5-diBr-PADAP)-Triton X-100析相光度体系,建立了矿石中微量铀的测定方法,在pH 7.5三乙醇胺-盐酸介质中,将胶束溶液在 95±1℃加热 1h.络合物即被Triton X-100相完全富集.络合物最大吸收峰位于565nm.摩尔吸光系数为1.02×10～5L·mol～(-1)·cm～(-1),铀含量在0～12μg/5mL服从比耳定律.采用TBP萃淋树脂分离干扰离子,测定矿石中微量铀,结果满意.     

Measurement of atomic L shell fluorescence (ω1, ω2, ω3) and Auger (a1, a2 and a3) yields for some elements in the atomic number range 59≤Z≤85

A comprehensive set of theoretical Coster–Kronig and fluorescence yields are presented for atomic numbers 18≤Z≤100. These quantities are based on ab initio relativistic calculations. Agreement with experimental values is fair for ω₁ and generally good for ω₂, ω₃ (Z≥54) [1]. Therefore, atomic L shell fluorescence (ω₁, ω₂, ω₃) and Auger yields (a₁, a₂ and a₃) for some elements in the atomic number range 59≤Z≤85 were determined. These selected measured semi-empirical values were also fitted by least squares to polynomials in the Z of the form ∑_na_nZⁿ and compared with theoretical and with earlier fitted values.     

聚甲基三氟丙基硅氧烷固相微萃取涂层的制备及其对海水中酚类化合物的分析

采用溶胶-凝胶技术制备了聚甲基三氟丙基硅氧烷(PTFPMS)涂层,并将其作为萃取