Solubility of H2S in ionic liquids [hmim][PF6], [hmim][BF4], and [hmim][Tf2N]

The solubility of hydrogen sulphide in three ionic liquids, viz. 1-hexyl-3-methylilmidazolium hexafluorophosphate ([hmim][PF₆]), 1-hexyl-3-methylimidazolium tetrafluoroborate ([hmim][BF₄]), and 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([hmim][Tf₂N]), at temperatures ranging from 303.15 K to 343.15 K and pressures up to 1.1 MPa were determined. The solubility values were correlated using the Krichevsky–Kasarnovsky equation and Henry’s constants were obtained at different temperatures. Partial molar thermodynamic functions of solvation such as standard Gibbs free energy, enthalpy, and entropy were calculated from the solubility results. Comparison of the values obtained show that the solubility of H₂S in these three ionic liquids was in the sequence: [hmim][BF₄] > [hmim][PF₆] ≈ [hmim][Tf₂N].     

The physicochemical properties of some imidazolium-based ionic liquids and their binary mixtures

The density, viscosity and conductivity of ionic liquids (ILs), 1-octyl-3-methylimidazolium tetrafluoroborate ([omim][BF4]), 1-octyl-3-methylimidazolium chloride ([omim][Cl]), 1-hexyl-3-methylimidazolium tetrafluoroborate ([hmim] BF4]), 1-hexyl- 3-methylimidazolium chloride ([hmim][Cl]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF6]), and the [omim][BF4] + [omim][Cl], [hmim][BF4] + [hmim][Cl], and [hmim][PF6] + [hmim][Cl] binary mixtures were studied at dif- ferent temperatures. It was demonstrated that the densities of both the neat ILs and their mixtures varied linearly with temper- ature. The density sensitivity of a binary mixture is between those of the two components. The excess molar volumes (VE) of [hmim][BF4] + [hmim][Cl] and [hmim][PF6] + [hmim][Cl] mixtures are positive in the whole composition range. For [omim][BF4] + [omim][Cl], the VE is also positive in the [omim][Cl]-rich region, but is negative in the [omim][BF4]-rich re- gion. The viscosity or conductivity of a mixture is in the intermediate of those of the two neat ILs. For all the neat ILs and the binary mixtures studied, the order of conductivity is opposite to that of the viscosity. The Vogel-Tammann-Fulcher (VTF) equations can be used to fit the viscosity and conductivity of all the neat ILs and the binary mixtures. The neat ILs and their mixtures obey the Fractional Walden Rule very well, and the values of the Walden slopes are all smaller than unit, indicating obvious ion associations in the neat ILs and the binary mixtures.     

Understanding the interactions between tris(pentafluoroethyl)-trifluorophosphate-based ionic liquid and small molecules from molecular dynamics simulation

Tris(pentafluoroethyl)trifluorophosphate ([FEP])-based ionic liquids have been widely applied in many fields. For better understanding the properties of [FEP]-based ionic liquids, the interactions between 1-hexyl-3-methylimidazolium ([hmim])[FEP] and small molecules were investigated by molecular dynamics simulations in this work. The small molecules are water, methanol and dimethyl ether. The united-atom (UA) force fields were proposed for methanol and dimethyl ether based on AMBER force field. The densities, enthalpies of vaporization, excess molar properties, and diffusion coefficients of the mixtures were calculated, as well as the microscopic structures characterized by radial distribution functions. Both of the results of the excess energies and microscopic properties show that the strongest interaction is between [hmim][FEP] and dimethyl ether, whereas the interaction between [hmim][FEP] and water is the weakest. Moreover, [hmim][FEP] is more hydrophobic than [hmim] hexafluorophosphate ([PF6]), and the three solutes are mainly distributed around [FEP] anion.     

One‐Pot Four‐Segment Ligation Using Seleno‐ and Thioesters: Synthesis of Superoxide Dismutase

The synthesis of a peptide selenoester was efficiently carried out by the 9‐fluorenylmethoxycarbonyl (Fmoc) method using N‐alkylcysteine, at the C‐terminus of the peptide, as the N‐to‐S acyl shift device. The selenoester selectively reacted with the terminal amino group of the peptide aryl thioester in the presence of N ,N ‐diisopropylethylamine and dipyridyldisulfide, thus leaving the aryl thioester intact. Combined with silver‐ion‐promoted and silver‐ion‐free thioester activation methods, a one‐pot four‐segment ligation was realized. The method was successfully used to assemble the entire sequence of superoxide dismutase (SOD), which is composed of 153 amino‐acid residues, in one pot. After the folding reaction, the fully active SOD was obtained.     

Highly Stereoselective Synthesis of 1,3‐Dienes through an Aryl to Vinyl 1,4‐Palladium Migration/Heck Sequence

An efficient aryl to vinyl 1,4‐palladium migration/Heck sequence was developed for the stereoselective synthesis of 1,3‐dienes. High stereoselectivity was observed not only for 1,3‐dienes bearing two similar aryl groups at terminal positions, but also for those with configurations shown to be unfavorable with previous methods.     

Solubility of CO2 in imidazolium-based tetrafluoroborate ionic liquids

The solubility of CO₂ in imidazolium ionic liquids (ILs), 1-butyl-3-methyl imidazolium tetrafluoroborate ([bmim][BF₄]), 1-hexyl-3-methyl imidazolium tetrafluoroborate ([hmim][BF₄]) and 1-octyl-3-methyl imidazolium tetrtafluoroborate ([omim][BF₄]) was determined at 305-25 K and pressures from 1 to 9 MPa. The influence of chain length of alkyl substituents on the imidazolium cation on the solubility of CO₂ was investigated. The differences in solubility with chain length are in the sequence [omim][BF₄] > [hmim][BF₄] > [bmim][BF₄]. The solubility data were correlated by the extended Henry's law, and enthalpy, Gibbs free energy and entropy changes were obtained.     

Solubility of tetrafluoromethane in the ionic liquid [hmim][Tf2N

Experimental results for the solubility of tetrafluoromethane (CF4, R14) in the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf2N]) are presented for temperatures between 293.3 and 413.3 K, at pressures (gas molalities) up to 9.6 MPa (0.22 mol kg-1). The experimental results were determined with a high-pressure view-cell technique operating on the synthetic method. The experimental data were used to determine Henry's constant of tetrafluoromethane in [hmim][Tf2N]. The results for the Henry's constant (at zero pressure) are correlated (on the molality scale) within the experimental uncertainty (i.e., about 1.1%) by ln(k(0)(H,CF4)/MPa) = 7.537 - 893.8/(T/K) - 0.003977(T/K). Henry's law was also extended to describe the gas solubility at higher pressures. Furthermore, a cubic equation of state was used to correlate the gas solubility over the entire range of experimentally investigated temperature and pressure. Both methods proved suited for a reliable correlation of the new experimental data.     

酸性离子液体催化的羟基化合物对N-对甲苯磺酰基氮杂环丙烷的开环反应

本文研究了羟基化合物对两种类型N-对甲苯磺酰基氮杂环丙烷的开环反应。在功能性离子液体[hmim]HSO4存在条件下,氮杂环丙烷与醇反应,以中等到高的产率和非常高的区域选择性得到对应的β-胺基醚。并且离子液体[hmim]HSO4可以循环使用。     

Traceless Rhodium‐Catalyzed Hydroacylation Using Alkyl Aldehydes: The Enantioselective Synthesis of β‐Aryl Ketones

A one‐pot three‐step sequence involving Rh‐catalyzed alkene hydroacylation, sulfide elimination and Rh‐catalyzed aryl boronic acid conjugate addition gave products of traceless chelation‐controlled hydroacylation employing alkyl aldehydes. The stereodefined β‐aryl ketones were obtained in good yields with excellent control of enantioselectivity. Good variation of all three reaction components is possible.     

Exploring the Reactivity of α‐Lithiated Aryl Benzyl Ethers: Inhibition of the [1,2]‐Wittig Rearrangement and the Mechanistic Proposal Revisited

By carefully controlling the reaction temperature, treatment of aryl benzyl ethers with tBuLi selectively leads to α‐lithiation, generating stable organolithiums that can be directly trapped with a variety of selected electrophiles, before they can undergo the expected [1,2]‐Wittig rearrangement. This rearrangement has been deeply studied, both experimentally and computationally, with aryl α‐lithiated benzyl ethers bearing different substituents at the aryl ring. The obtained results support the competence of a concerted anionic intramolecular addition/elimination sequence and a radical dissociation/recombination sequence for explaining the tendency of migration for aryl groups. The more favored rearrangements are found for substrates with electron‐poor aryl groups that favor the anionic pathway.     

Synthesis and structures of helical polycyclic aromatic hydrocarbons bearing aryl substituents at the most sterically hindered positions

A three-step synthetic sequence starting from condensation between a benzannulated enediyne and an aryl tert-butyl ketone was established to provide easy access to angularly fused polycyclic aromatic hydrocarbons bearing one or two aryl substituents at the most sterically hindered positions to cause helical twists. The dynamic behaviors involving the helix inversion and the restricted rotation of the aryl substituents were investigated by temperature-dependent NMR studies. The X-ray structure of an indeno-fused 1-phenylpentahelicene derivative showed severe distortion of the [5]helicene system from planarity.     

Ring expansion/homologation--aldehyde condensation cascade using tert-trihalomethylcarbinols

Treatment of cyclic tert-trihalomethylcarbinols with CrCl(2) in THF/HMPA in the presence of aryl or aliphatic aldehydes initiates a cascade sequence of one carbon ring expansion-olefination affording conjugated exocyclic ketones. Acyclic tert-trihalomethylcarbinols undergo a comparable cascade of one carbon homologation-olefination.     

Direct Cross‐Couplings of Propargylic Diols

[Pd(PPh₃)₄] catalyzes a Suzuki–Miyaura‐like twofold cross‐coupling sequence between underivatized propargylic diols and either aryl or alkenyl boronic acids to furnish highly substituted 1,3‐dienes. Thus, 2,3‐diaryl‐1,3‐butadienes and their dialkenic congeners ([4]dendralenes) are delivered in a (pseudo)halogen‐free, single‐step synthesis which supersedes existing methods. Allenols are also readily formed. Treatment of these single‐ and twofold cross‐coupled products with acid leads to remarkably short syntheses of highly‐substituted benzofulvenes and aryl indenes, respectively.     

C−F Arylation of Polyfluorophenols by Means of Sigmatropic Dearomatization/Defluorination Sequence

Selective C−F arylation of polyfluorophenols with aryl sulfoxides has been accomplished by means of a sigmatropic dearomatization/defluorination sequence. This sequence consists of three processes: 1) interrupted Pummerer reaction to form S−O-tethered sulfonium salt; 2) C−C-forming [3,3] sigmatropic rearrangement with dearomatization; and 3) Zn-mediated defluorinative rearomatization. The present biaryl construction provides a facile access to polyfluorinated biaryls that is difficult to synthesize by other methods. The synthetic utility of the strategy is clearly demonstrated by the synthesis of a fluorinated analogue of Maxipost, a potassium channel modulator.     

Catalytic asymmetric synthesis of quaternary carbons bearing two aryl substituents. Enantioselective synthesis of 3-alkyl-3-aryl oxindoles by catalytic asymmetric intramolecular heck reactions

A practical sequence involving three consecutive palladium(0)-catalyzed reactions has been developed for synthesizing 3-alkyl-3-aryloxindoles in high enantiopurity. The Heck cyclization precursors 10 and 11a-k are generated in one step by chemoselective Stille cross-coupling of 2'-triflato-(Z)-2-stannyl-2-butenanilide 9 with aryl or heteroaryl iodides. The pivotal catalytic asymmetric Heck cyclization step of this sequence takes place in high yield and with high enantioselectivity (71-98% ee) with the Pd-BINAP catalyst derived from Pd(OAc)(2) to construct oxindoles containing a diaryl-substituted all-carbon quaternary carbon center. A wide variety of aryl and heteroaryl substituents, including ones of considerable steric bulk, can be introduced at C3 of oxindoles in this way (Table 4). The only limitations encountered to date are aryl substituents containing ortho nitro or basic amine functionalities and the bulky N-alkyl-7-oxindolyl group. Asymmetric Heck cyclization of butenalide 22 having an o-(N-acetyl-N-benzylamino)phenyl substituent at C2 provided a approximately 1:1 mixture of amide atropisomers 23 and 24 in high yield and high enantioselectivity. These atropisomers are formed directly upon Heck cyclization of 22 at 80 degrees C, as they interconvert thermally to only a small extent at this temperature.     

Three-component tandem reactions of (2-arylsulfanyl-3-aryl-2-oxiranyl)(aryl)methanones and o-phenylenediamine: formation of quinoxalines

A series of new quinoxalines has been obtained from a one pot, three-component reaction of (2-arylsulfanyl-3-aryl-2-oxiranyl)(aryl)methanones with o-phenylenediamine in the presence of a catalytic amount of acetic acid. This reaction presumably involves a tandem oxirane aminolysis-cyclisation-elimination-air oxidation-condensation sequence.     

Synthesis of tricyclic heterocycles via a tandem aryl alkylation/heck coupling sequence

A norbornene-mediated palladium-catalyzed sequence is described in which two alkyl-aryl bonds and one alkenyl-aryl bond are formed in one pot with use of microwave irradiation. A variety of symmetrical and unsymmetrical oxygen-, nitrogen-, silicon-, and sulfur-containing tricyclic heterocycles were synthesized from a Heck acceptor and an aryl iodide containing two tethered alkyl halides. This approach was further applied to the synthesis of a tricyclic mescaline analogue.     

Dissolution capacity and rheology of cellulose in ionic liquids composed of imidazolium cation and phosphate anions

Cellulose is one of the most abundant natural polymer sources, but the applications of cellulose are limited due to difficulty in dissolving cellulose in water and common chemical solvents. In the past decades, ionic liquids have been studied to dissolve cellulose efficiently, sustainably, and in an eco‐friendly manner. In this study, a series of imidazolium‐based ionic liquids were synthesized to explore as solvents for cellulose, including 1,3‐dimethylimidazolium dimethylphosphate ([mmim]dmp), 1‐ethyl‐3‐methylimidazolium dimethylphosphate ([emim]dmp), 1‐butyl‐3‐methylimidazolium dimethylphosphate ([bmim]dmp), 1‐hexyl‐3‐methylimidazolium dimethylphosphate ([hmim]dmp), 1‐ethyl‐3‐methylimidazolium diethylphosphate ([emim]dep), 1,3‐diethylimidazolium diethylphosphate ([eeim]dep), and 1‐butyl‐3‐ethylimidazolium diethylphosphate ([beim]dep). Rheology experiments were conducted to study the flow behavior of cellulose in these ionic liquids and cosolvents. We found that the dissolution capacity of cellulose increases with decreasing viscosity of the solvent and that the rheological properties depend most strongly on the concentration of cellulose dissolved. Systems composed of cellulose in [mmim]dmp, [emim]dmp, and [emim]dep behave as viscoelastic gels, while formulations of cellulose in [bmim]dmp, [hmim]dmp, [eeim]dep, and [beim]dep show viscoelastic liquid behavior. These results will impact development of new solvents for processing of cellulose‐based polymeric materials.     

钯催化卤代芳烃的胺化反应的研究进展

钯催化卤代芳烃的胺化是合成芳胺化合物的重要方法,综述了近年来钯催化卤代芳烃与胺等不同含氮化合物的胺化反应研究进展,重点讨论了钯催化剂配体的结构、反应物比例、溶剂及温度等因素对反应的影响.     

Thermodynamic modeling of the phase behavior of binary systems of ionic liquids and carbon dioxide with the group contribution equation of state

The group contribution equation of state (GC-EOS) was applied to predict the phase behavior of binary systems of ionic liquids of the homologous families 1-alkyl-3-methylimidazolium hexafluorophosphate and tetrafluoroborate with CO2. Pure group parameters for the new ionic liquid functional groups [-mim][PF6] and [-mim][BF4] and interaction parameters between these groups and the paraffin (CH3, CH2) and CO2 groups were estimated. The GC-EOS extended with the new parameters was applied to predict high-pressure phase equilibria in binary mixtures of the ionic liquids [emim][PF6], [bmim][PF6], [hmim][PF6], [bmim][BF4], [hmim][BF4], and [omim][BF4] with CO2. The agreement between experimental and predicted bubble point data for the ionic liquids was excellent for pressures up to 20 MPa, and even for pressures up to about 100 MPa, the agreement was good. The results show the capability of the GC-EOS to describe phase equilibria of systems consisting of ionic liquids.