An indium-TMSCl promoted reaction of diphenyl diselenide and diorganyl disulfides with aldehydes: novel routes to selenoacetals, thioacetals and alkyl phenyl selenides

The reactions of diphenyl diselenide and dialkyl disulfides with aldehydes in the presence of In-TMSCl have been investigated. Aliphatic aldehydes provide the corresponding selenoacetals and aromatic aldehydes lead predominantly to benzyl phenyl selenides on reaction with diphenyl diselenide. However, the reaction of dimethyl disulfide and diphenyl disulfide with both aromatic and aliphatic aldehydes produce dithioacetals. This provides a novel route to the synthesis of selenoacetals, thioacetals and selenides from aldehydes.     

离子色谱法同时分析离子液体中三氟乙酸根、四氟硼酸根和三氟甲烷磺酸根

建立了离子色谱-直接电导检测法同时测定离子液体中三氟乙酸根、四氟硼酸根和三氟甲烷磺酸根的方法。色谱分离采用Shim-packIC-A3阴离子交换色谱柱和邻苯二甲酸氢钾淋洗液。最佳色谱条件为:以邻苯二甲酸氢钾(1.2mmol/L)为淋洗液,柱温30℃,流速1.0mL/min。在此条件下,所测阴离子的检出限为0.06～3.07mg/L,保留时间和峰面积的相对标准偏差(n=5)分别不大于0.18%和1.62%。用来测定离子液体中三氟乙酸根、四氟硼酸根和三氟甲烷磺酸根,加标回收率为98.2%～101.8%,能够满足离子液体中的三氟乙酸根、四氟硼酸根和三氟甲烷磺酸根定量分析要求。     

Equations of states for an ionic liquid under high pressure: A molecular dynamics simulation study

The high-pressure dependence of density given by empirical equation of states (EoS) for the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate (or triflate), [C₄C₁im][TfO], is compared with results obtained by molecular dynamics (MD) simulations. Two EoS proposed for [C₄C₁im][TfO] in the pressure range of tens of MPa, which give very different densities when extrapolated to pressures beyond the original experiments, are compared with a group contribution model (GCM). The MD simulations provide support that one of the empirical EoS and the GCM is valid in the pressure range of hundreds of MPa. As an alternative to these EoS that are based on modified Tait equations, it is shown that a perturbed hard-sphere EoS based on the Carnahan–Starling–van der Waals equation also fits the densities calculated by MD simulations of [C₄C₁im][TfO] up to ∼1.0 GPa.     

Efficient Trimethylsilylation of Alcohols and Phenols with HMDS in the Presence of a Catalytic Amount of 1,3‐Dibromo‐5,5‐Dimethylhydantoin (DBDMH) as a Safe and Cheap Industrial Chemical

1,3‐Dibromo‐5,5‐dimethylhydantoin (DBDMH) is found to be an effective catalyst for trimethylsilylation various alcohols and phenols with hexamethyldisilazane (HMDS) in dichloromethane at room temperature.     

The dehydration process in the dl‐phenylglycinium trifluoromethanesulfonate monohydrate crystal revealed by XRD,vibrational and DSC studies

Thermal analysis, X‐ray diffraction and temperature‐dependent IR spectroscopy were used to study the dehydration process of crystalline dl ‐phenylglycinium trifluoromethanesulfonate monohydrate (PGTFH), C₈H₁₀NO₂⁺·CF₃SO₃^?·H₂O. PGTFH dehydrates in one step centred at 353 K and crystallizes in the monoclinic space group C2/c, whereas the anhydrous compound (PGTF) crystallizes in the triclinic space group P. The dehydration process in PGTFH is preceded by a weakening of both the noncovalent aromatic–aromatic interactions and the packing contacts. This process is accompanied by the breakage of medium‐strength O—H…O hydrogen bonds between ions inside layers and a reorganization of the ions within the layers. This reorganization results in the formation of two different ion pairs (dl ‐phenylglycinium trifluoromethanesulfonate) and the formation of a new hydrogen‐bond network. The dehydration process does not destroy the nature of the crystal structure. Both crystals, i.e. hydrated and anhydrous, have a layered structure, although the layers of each crystal are arranged somewhat differently.     

Synthesis of fluorinated allylic amines: Reaction of 2-(trimethylsilyl)ethyl sulfones and sulfoxides with fluorinated imines

A new synthesis of fluorinated allylamines through the reaction of 2-(trimethylsilyl)ethyl sulfones and sulfoxides (as vinyl anion equivalents) with imines and imino esters has been described. The process includes a TBAF-mediated fragmentation of 2-(trimethylsilyl)ethyl sulfones to afford the desired allylic amines. When the reaction is performed with the corresponding sulfoxides, the fragmentation takes place under the addition conditions, affording the final products in a single step.     

Formation of reactive o-quinone methides from the reaction of trimethylsilyl(methyl)-substituted 1,4-benzoquinones with nucleophiles

o-Quinone methides are formed from the reaction of nucleophiles with trimethylsilyl(methyl)-1,4-benzoquinones. These reactive intermediates are trapped by excess nucleophile to form substituted quinones following oxidation. In addition, varying amounts of a symmetrical dimer and a xanthen derivative were observed. The influence of different nucleophiles and ring substituents on the rate of reaction have been studied, and are consistent with rate-limiting formation of a vinylogous enolate initiated by attack of the nucleophile on the silyl group.     

Ytterbium triflate as an efficient catalyst for one-pot synthesis of substituted imidazoles through three-component condensation of benzil, aldehydes and ammonium acetate

Yb(OTf)₃ has been found to be an extremely efficient catalyst for the preparation of imidazoles derivatives via three-component coupling reactions of benzil, aldehydes and ammonium acetate under mild conditions. The process presented here is operationally simple, environmentally benign and has excellent yield. Furthermore, the catalyst can be recovered conveniently and reused for at least three reaction cycles without any loss of activity.     

Cadmium Malonate Complexation in Aqueous Sodium Trifluoromethanesulfonate Media to 75°C; Including Dissociation Quotients of Malonic Acid

The molal formation quotients for cadmium–malonate complexes were measured potentiometrically from 5 to 75°C, at ionic strengths of 0.1, 0.3, 0.6 and 1.0 molal in aqueous sodium trifluoromethanesulfonate (NaTr) media. In addition, the stepwise dissociation quotients for malonic acid were measured in the same medium from 5 to 100°C, at ionic strengths of 0.1, 0.3, 0.6, and 1.0 molal by the same method. The dissociation quotients for malonic acid were modeled as a function of temperature and ionic strength with empirical equations formulated such that the equilibrium constants at infinite dilution were consistent, within the error estimates, with the malonic acid dissociation constants obtained in NaCl media. The equilibrium constants calculated for the dissociation of malonic acid at 25°C and infinite dilution are log K _1a=-2.86 ± 0.01 and log K _2a=-5.71 ± 0.01. A single Cd–malonate species, CdCH₂C₂O₄, was identified from the complexation study and the formation quotients for this species were also modeled as a function of temperature and ionic strength. Thermodynamic parameters obtained by differentiating the equation with respect to temperature for the formation of CdCH₂C₂O₄ at 25°C and infinite dilution are: K = 3.45 ± 0.09, S° = 7 ± 6 kJ-mol^-1, S° = 91 ± 22 J-K^--mol^-1, and C _p ^o =400±300 J­K^-1­mol^-1.     

Copper-catalyzed synthesis of 5-substituted 1H-tetrazoles via the [3+2] cycloaddition of nitriles and trimethylsilyl azide

The [3+2] cycloaddition between various nitriles and trimethylsilyl azide proceeds smoothly in the presence of a Cu^I catalyst in DMF/MeOH, to give the corresponding 5-substituted 1H-tetrazoles in good to high yields. The reaction most probably proceeds through the in situ formation of a copper azide species, followed by a successive [3+2] cycloaddition with the nitriles.