Ir-catalyzed asymmetric allylic alkylation using chiral diaminophosphine oxides: DIAPHOXs. Formal enantioselective synthesis of (−)-paroxetine

An Ir-catalyzed asymmetric allylic alkylation using chiral diaminophosphine oxide is described. Asymmetric allylic alkylation of terminal allylic carbonates proceeded using 5 mol % of Ir catalyst, 5 mol % of DIAPHOX 1i, 10 mol % of NaPF₆, 10 mol % of LiOAc, and N,O-bis(trimethylsilyl)acetamide (BSA), affording the corresponding branched products in excellent yield and in up to 95% ee. The developed catalytic asymmetric reaction was successfully applied to a formal enantioselective synthesis of (−)-paroxetine.     

Highly stereoselective peptide modifications through Pd-catalyzed allylic alkylations of chelated peptide enolates

Deprotonation of peptides in the presence of zinc chloride gives rise to highly reactive nucleophiles that can be subjected to palladium-catalyzed allylic alkylation reactions. Excellent diastereoselectivities are obtained that are nearly independent of the allylic substrate used. By using this protocol, highly functionalized side chains can also be incorporated in excellent yields and selectivities. The stereochemical outcome of the reaction is exclusively controlled by the peptide chain as long as terminal pi-allyl-palladium complexes are involved. Probably, there is a threefold coordination, at least, of the deprotonated peptide chain to the chelating zinc ion. In such metal peptide complexes, one face of the generated enolate is shielded by the side chain of the adjacent amino acid, thus directing the electrophilic attack onto the opposite face. This behavior explains why an S amino acid always generates an R amino acid (and the other way round).     

明胶大分子的照相性质研究——Ⅰ.明胶中的蛋氨酸砜及亚砜的测定

应用氨基酸分析仪对十六种国外明胶(大部分为IAG明胶)的氨基酸含量进行了测定,其中重点进行了蛋氨酸及其氧化产物含量的测定。测试结果表明:明胶中蛋氨酸含量随不同样品变化较大,亚砜含量一般较少,所有照相胶都含有砜,绝大多数胶样含有亚砜。     

基质辅助激光解吸电离-飞行时间质谱表征6氟双酚A芳香环状聚醚酮(砜)

应用基质辅助激光解吸电离飞行时间质谱,在不同阳离子剂的存在下,对6氟双酚A聚芳醚酮(砜)环状低聚物的结构进行了确认,研究了环状化合物对金属离子的选择性及激光质谱表征含氟环状低聚物的适宜条件.     

Synthesis of polymers in aqueous solutions: Synthesis of polysulfide by reaction of bis(4‐mercaptophenyl) sulfide with bis(4‐chloro‐3‐nitrophenyl) sulfone using various bases in aqueous solutions

The polycondensation of bis(4‐mercaptophenyl) sulfide (BMPS) with bis(4‐chloro‐3‐nitrophenyl) sulfone (BCNPS) was examined using various organic or inorganic bases in mixed solvents of N‐methyl‐2‐pyrrolidone (NMP) with water or in plain water. The reaction of BMPS with BCNPS proceeded smoothly to give the corresponding polysulfide in mixed solvents of NMP with water at 60 °C using 1,8‐diazabicyclo[5.4.0]undecene‐7 as a base, although the rate of the reaction decreased gradually as the water in the solvent increased. Polysulfide can also be obtained by reaction in plain water using appropriate organic bases such as tripropylamine (TPA) or quinoline. The polysulfide with a number‐average molecular weight of 45,100 was synthesized in 62% yield when the reaction of BMPS with BCNPS was performed using TPA as a base at 60 °C for 48 h in plain water. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3399–3404, 2000     

Physical aging of poly(ether sulfone)-modified epoxy resin

The physical aging process of 4,4′-diaminodiphenylsulfone (DDS) cured diglycidyl ether bisphenol-A (DGEBA) blended with poly(ether sulfone) (PES) was studied by differential scanning calorimetry (DSC) at four aging temperatures between T_g-50°C and T_g-10°C. At aging temperatures between T_g-50 and T_g-30°C, the experimental results of epoxy resin blended with 20 wt% of PES showed two enthalpy relaxation processes. One relaxation process was due to the physical aging of PES, the other relaxation process was due to the physical aging of epoxy resin. The distribution of enthalpy relaxation process due to physical aging of epoxy resin in the blend was broader and the characteristic relaxation time shorter than those of pure epoxy resin at the above aging temperatures (between T_g-50 and T_g-30°C). At an aging temperature between T_g-30 and T_g-10°C, only one enthalpy relaxation process was found for the epoxy resin blended with PES, the relaxation process was similar to that of pure epoxy resin. The enthalpy relaxation process due to the physical aging of PES in the epoxy matrix was similar to that of pure PES at aging temperatures between T_g-50 and T_g-10°C. © 1997 John Wiley & Sons, Inc.     

Poly(arylene ether)s,poly(arylene thioether)s,and poly(arylene sulfone)s derived from a dihydroxy(imidoarylene) monomer

Novel poly(arylene ether)s, poly(arylene thioether)s, and poly(arylene sulfone)s were synthesized from the dihydroxy(imidoarylene) monomer 1 . The syntheses of poly(arylene ether)s were carried out in DMAc in the presence of anhydrous K₂CO₃ by a nucleophilic substitution reaction between the bisphenol and activated difluoro compounds. Poly(arylene thioether)s were synthesized according to the recently discovered one-pot polymerization reaction between a bis(N,N′-dimethyl-S-carbamate) and activated difluoro compounds in the presence of a mixture of Cs₂CO₃ and CaCO₃. The bis(N,N′-dimethyl-S-carbamate) 3 was synthesized by the thermal rearrangement reaction of bis(N,N′-dimethylthiocarbamate) 2 , which was synthesized from 1 by a phase-transfer catalyzed reaction. The poly(arylene thioether)s were further oxidized to form poly(arylene sulfone)s, which would be very difficult, if not impossible, to synthesize by other methods. All of the polymers described have extremely high T_gs and thermal stability as determined from DSC and TGA analysis. Poly(arylene sulfone)s have the highest T_gs and they are in the range of 298–361°C. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1201–1208, 1998     

New sulfonated engineering polymers via the metalation route. II. Sulfinated/sulfonated poly(ether sulfone) PSU Udel and its crosslinking

New mixed sulfinated/sulfonated polysulfone PSU Udel has been produced by partial oxidation of sulfinated PSU with NaOCl. From the mixed sulfinated/sulfonated PSU, thin crosslinked polymer films have been produced by S-alkylation of the residual sulfinate groups with α,ω-diiodoalkanes having 4–10  (CH₂) units. The advantages of the partial oxidation process using NaOCl are as follows: (1) The desired oxidation degree can be adjusted finely. (2) No side reactions take place during oxidation. (3) The partially oxidized polymers is stable at ambient temperature. By variation of the oxidation degree of the sulfinated/sulfonated prepolymer and by variation of the chain length of the diiodo crosslinker, crosslinked membranes with a large range of properties in terms of ionic conductivity, swelling, and permselectivity have been produced. The partially oxidized polymers have been characterized by redox titration, ¹H-NMR, and FTIR. The crosslinked membranes have been characterized in terms of ionic conductivity (resistance), permselectivity, and swelling in dependence on ion-exchange capacity and oxidation degree of the prepolymers. In addition, the thermal stabilities of the membranes have been determined by TGA, and FTIR spectra have been recorded on the crosslinked films. Selected membranes show low ionic resistances, low swelling, and good temperature stability which makes them promising candidates for application in (electro)membrane processes. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1441–1448, 1998