Reactivity of Primary Phosphines and Primary Phosphine Sulfides towards Imines

Reactivity of primary phosphines with two stoichiometric equivalents of imine results in the formation of bis-α-aminophosphines ( 2 a – e ), which can be subsequently oxidized in the presence of S₈ or H₂O₂ to generate air stable bis-α-aminophosphine sulfides ( 2 b – m(S/O) ). To elucidate the mechanism of this three-component reaction, Hammett analysis, kinetic isotope effect (KIE), and trapping experiments were performed. Ultimately a P(V)–P(III) tautomerization is invoked, followed by nucleophilic attack by the P(III) species to generate the desired products.     

Domino nucleophilic trifluoromethylations of alkyl perfluorodithioesters

Under nucleophilic initiation, alkyl perfluorodithioesters react with trifluoromethyl(trimethyl)silane in a domino process beginning with a thiophilic addition-β-elimination of fluoride ion which leads to a perfluoroketenedithioacetal. Further addition-elimination steps eventually gives a mixture of mono, bis- and tris(trifluoromethyl) vinyl sulfides. Although they are difficult to separate, these new compounds were fully characterized by ¹⁹F NMR and mass spectrometry.     

1-烯丙基-3-甲基咪唑离子液体单体与丙烯腈共聚行为的研究

以1-烯丙基-3-甲基咪唑盐酸盐([AMIM]Cl)作为离子液体单体,偶氮二异丁腈作为引发剂,二甲基亚砜为溶剂,实现了与丙烯腈(AN)在不同反应条件下的自由基共聚合.研究了AN/[AMIM]Cl二元共聚合的动力学,得到了相应的竞聚率数据(rAN=8.11,r[AMIM]Cl=0).用1H-NMR、GPC、DSC、TGA等手段对共聚物进行了表征.通过对AN/[AMIM]Cl二元共聚及AN/IA/[AMIM]Cl三元共聚的研究发现,[AMIM]Cl在与丙烯腈共聚时具有双重作用,一部分离子单体进入到共聚物的分子链中调节其亲水性及可纺性,剩下的大部分留在纺丝液中可显著降低纺丝液的黏度,从而使高分子量高固含量纺丝液的纺制成为可能,有望得到高性能的碳纤维原丝.     

The application of nanostructured transition metal sulfides as anodes for lithium ion batteries

With wide application of electric vehicles and large-scale in energy storage systems, the requirement of secondary batteries with higher power density and better safety gets urgent. Owing to the merits of high theoretical capacity, relatively low cost and suitable discharge voltage, much attention has been paid to the transition metal sulfides. Recently, a large amount of research papers have reported about the application of transition metal sulfides in lithium ion batteries. However, the practical application of transition metal sulfides is still impeded by their fast capacity fading and poor rate performance. More well-focused researches should be operated towards the commercialization of transition metal sulfides in lithium ion batteries. In this review, recent development of using transition metal sulfides such as copper sulfides,molybdenum sulfides, cobalt sulfides, and iron sulfides as electrode materials for lithium ion batteries is presented. In addition, the electrochemical reaction mechanisms and synthetic strategy of transition metal sulfides are briefly summarized. The critical issues, challenges, and perspectives providing a further understanding of the associated electrochemical processes are also discussed.     

Photoconductive Polysilanes Bearing Charge-photogenerating Groups Based on Carbazole. 1 Synthesis via the Reductive Coupling of Diorganodichlorosilanes with Sodium

In order to prepare photoconductive organic materials with high charge-photogenerating quantum yield and high charge-carrier mobility, it was attempted to synthesize (9-carbazolyl)methyldichlorosilane, 1a , methyl-3-(9-carbazolyl)propyldichlorosilane, 1b , and methyl-4-(9-carbazolyl)phenyldichlorosilane, 1c and to homo- and copolymerize them with classical diorganodichlorosilanes in a Wurtz-type polymerization with sodium in the presence of polar additives. 1b did not homo- or copolymerize in these conditions. Low molecular weight homopolymers and copolymers with dimethyldichlorosilane and methylphenyldichlorosilane were easily obtained with 1c . Side reactions involving the ring-opening of tetrahydrofuran (THF) and occurring in the reaction of the Grignard derivative of 9-(4-bromophenyl)carbazole and methyltrichlorosilane in THF did not allow the isolation of 1c in a pure form. © 1997 John Wiley & Sons, Ltd.     

A chemoselective desulfurization method via homogeneous nickel catalysis

Isopropylmagnesium bromide in the presence of bis-(triphenylphosphino)- nickel(II) chloride reduces vinyl sulfides stereospecifically to the corresponding olefins without overreduction - a process which serves as a key step in the synthesis of the sex pheromone of the Douglas fir tussock moth.     

Synthesis and copolymerizations of 3,3-difluorocyclobutene-1-carbonitrile

3,3-Difluorocyclobutene-1-carbonitrile (DFCB) was synthesized via cycloaddition of 1-chloro-2,2-difluoroethylene and acrylonitrile, followed by dehydrochlorination with 1,4-diazabicyclo[2.2.2]octane in tetrahydrofuran. Unlike cyclobutene-1-carbonitrile, this monomer did not homopolymerize either under radical or anionic conditions. As an electron-poor monomer it copolymerized in the presence of free radicals with electronrich monomers such as styrene in good yield. It also copolymerized with electron-poor monomers such as acrylonitrile, although in lower yields. The extent of incorporation of DFCB in the copolymers also depended on the electronic characteristics of the comonomers: high incorporation occurred with electron-rich monomers, low incorporation with electron-poor monomers. One extremely electron-poor monomer, trimethyl ethylenetricarboxylate, did not copolymerize with DFCB.     

Ring-opening polymerizations of cyclic olefins

A ziegler-type catalyst system consisting of tungsten hexachloride and alkyl or aryl tin compounds was found to polymerize cyclopentene and other cyclic olefins through a ring-opening mechanism. This catalyst system also polymerized α-olefins such as ethylene and 1-octene. An attempt was made to copolymerize cyclopentene and ethylene. Other catalyst systems were also employed for ring-opening polymerizations with limited success.     

Thermodynamics of Addition Polymerization Processes

The polymerizability of compounds such as 1,l-disubstituted ethylenes, aldehydes, ketones, isocyanates, and five- and six-membered ring compounds is determined largely by thermodynamic considerations. The transition from non-polymerizability to polymerizability, correspondlng to a change in the sign of ΔG, is often quite sharp. Factors which generally make the free energy of polymerization more negative, and which therefore favor polymerization, are low temperature, high pressure, and high monomer concentration. Additional driving force is sometimes available if the monomer is in the supercooled (glassy) state rather than the crystalline state, or if the polymer crystallizes on formation. Alkyl substituents have an unfavorable effect on polymerizability; halogen substituents have a favorable effect. Many monomers which do not homopolymerize for thermodynamic reasons will copolymerize with a second monomer to the extent of forming copolymers containing 50 or even 66 mol per cent of the first monomer.     

1,3-Butadienyl-thiocyanate in der Diels-Alder-Reaktion mit anschliessender [3,3]-sigmatroper Umlagerung

1,3-Butadienyl Thiocyanates in the Diels-Alder Reaction Followed by a [3,3]-Sigmatropic Shift (E)- and (Z)-1,3-Butadienyl thiocyanates 3 , 4 , and 12–15 have been synthesized selectively. Their use as dienes for Diels-Alder reactions followed by a [3,3]-sigmatropic shift to obtain an isomeric isothiocyanate has been studied. The butadienyl thiocyanates are, unfortunately, not very reactive in Diels-Alder reactions. This disadvantage can be overcome, if a trapping reaction with EtOH is added to the two-step sequence. This sequence allows to get good yields of the O-ethyl thiocarbamates 18–23 , even if the first two reactions have not favorable equilibrium constants.     

Synthesis of multi-functional epoxides derived from limonene oxide and its application to the network polymers

Bio-based multi-functional epoxides (1) such as bis-, tri-, and tetra-epoxides were synthesized by ene-thiol reactions between limonene oxide and polyhydric thiols. A cross-linking reaction of 1 with branched polyethyleneimine (BPEI) afforded the corresponding network polymers 2 with relatively high thermal resistance in high yields.     

Tetravalent metal complexes as a new family of catalysts for copolymerization of epoxides with carbon dioxide

New tetravalent metal complexes with a trianionic [ONNO]-tetradentate ligand and an ancillary chloride ligand were synthesized as catalysts for the copolymerization of epoxides with carbon dioxide (CO(2)). All of the titanium, zirconium, germanium, and tin complexes were found to copolymerize epoxides with CO(2). In particular, the copolymerization of propylene oxide with CO(2) gave the almost-completely alternating copolymers by using titanium or germanium complexes. These results are the first example of the copolymerization using tetravalent metal complexes as a main component of catalysts.     

Novel Catalytic CO(2) Incorporation Reaction: Nickel-Catalyzed Regio- and Stereoselective Ring-Closing Carboxylation of Bis-1,3-dienes

Novel nickel-catalyzed carboxylation of bis-1,3-dienes using carbon dioxide (CO2) was investigated. In the presence of catalytic amounts of Ni(acac)2 and PPh3, various bis-1,3-dienes smoothly reacted with CO2 and an organozinc reagent (Et2Zn, Me2Zn, or Ph2Zn) under mild conditions. This catalytic carboxylation process was accompanied by carbocyclization of bis-1,3-diene followed by alkylation by an organozinc reagent to afford cyclic carboxylic acid derivatives in high yields with high regio- and stereoselectivities.     

A highly efficient, green, rapid, and chemoselective oxidation of sulfides using hydrogen peroxide and boric acid as the catalyst under solvent-free conditions

We report boric acid as a highly efficient and eco-friendly catalyst for the selective oxidation of sulfides to sulfoxides or sulfones, in excellent yields under solvent-free conditions, using 30% hydrogen peroxide as an oxidant. Various sulfides possessing functional groups such as alcohol, ester, and aldehyde are successfully and selectively oxidized without affecting sensitive functionalities.     

Synthesis of Diacyl Sulfides by Phase Transfer Catalysis

The symmetrical monothioanhydrides or diacyl sulfides have been synthesized by several methods. They are formed by acylation of free monothioacids or their anions¹, by acylation of potassium² or lithium³ sulfide, from the reaction of monothiocarboxylic acids with dicyclohexylcarbodiimide⁴ or by treatment of trimethylsilyl thiocarboxylates with acyl chlorides⁴. The recent publication about diacyl disulfides synthesis using phase transfer catalysis⁵ promted us to communicate our own results applying this technique to the preparation of the closely related diacyl sulfides. These compounds may be obtained by a more simple procedure than the published methods and in very high yields by the reaction of acylchlorides (1) with sodium sulfide nonahydrate in a solid-liquid system consisting of dichloromethane, the mentioned salt and hexadecyltributylphosphonium bromide as a phase transfer catalyst.     

Design, synthesis and characterization of novel biodegradable macrodiols based on poly（DL-lactic acid） and poly（p-dioxanone）

Integrating poly(lactic acid)(PLA),glycolic acid(GA) and ethylene glycol(EG) will hopefully result in a novel copolymer that combines such advantages as fastened and controllable release rate and improved flexibility together with good biocompatibility.In this study,p-dioxanone(PDO) was employed to copolymerize with DL-lactide(LA) via ring-opening melt polymerization using Sn(Oct)_2 as an initiator and ethylene glycol as a co-initiator.The obtained degradable macrodiols(HO-P(LA-co-PDO)-OH) were just such...     

New concepts for regio- and stereoselective bis- and triscyclopropanations of C60

The synthesis of isomerically multiple adducts of C(60) with a defined three-dimensional structure is still one of the most challenging tasks of exohedral fullerene chemistry. The inherent regioselectivity of successive additions of addends such as malonates to the fullerene's [6,6]-double bonds is only moderate. In most cases difficult-to-isolate mixtures of regioisomers are obtained. The regioselectivity can be significantly improved if multifunctional addends able to undergo two or more additions are allowed to react with C(60). Preorganization and minimization of strain energy within the addend skeleton reduce the number of sterically allowed addition patterns. Improved concepts for highly regio- and stereoselective bis- and triscyclopropanations of C(60) are described. Two examples of the bisadditions with complete regioselectivity leading to trans-2- and cis-2 are presented. Here, the two malonate binding sites are linked by rigid tetraphenylporphyrin and calix-[4]-arene spacers. Selective trisadditions were achieved with the easy-to-synthesize and easy-to-modify tripodal addends 5-7, where the malonates are held together by a focal aryl moiety. Another very elegant approach for bis- and trisadditions involves cyclo-[n]-alkylmalonates. Selection between addition patterns with and without rotational axes is possible by choosing the right combinations of the flexible alkyl chains connecting the malonates. If alkyl chains of identical lengths are used bis- and trisadducts such as 19-21 and 25 with rotational symmetry are formed with high regioselectivity. These addition patterns are avoided if cyclo-[n]-malonates containing alkyl chains of different lengths are employed. In this case adducts such as 26 and 27 with C(s)-symmetry are formed. The use of the chiral cyclo-[3]-malonate 28 allows for the regio- and stereoselective synthesis of the enantiomerically pure e,e,e-trisadducts 29 and 30 containing an inherently chiral addition pattern with C(3)-symmetry.     

Efficient synthetic methods for unsaturated 3,4,5-trimethoxybenzyl sulfides and ethers

Convenient and efficient procedures were developed for preparation of 3,4,5-trimethoxybenzyl sulfides and ethers containing vinyl, allyl, and propargyl groups proceeding from 3,4,5-trimethoxybenzyl alcohol, elemental sulfur, and thiourea in basic and basic-reductive systems (hydrazine hydrate?KОН?DMF, NaBH₄?EtOH, KОН?DMSO). The effective method of the synthesis of 1,1'-[disulfandiylbis(methylene)]bis-(3,4,5-trimethoxybenzene) consists in the reduction of the elemental sulfur to disulfide anion with hydrazine hydrate in the presence of KОН followed by the reaction with 3,4,5-trimethoxybenzyl chloride under the conditions of phase-transfer catalysis or in DMF.     

Efficient solvent-free selective monoalkylation of arylacetonitriles with mono-, bis-, and tris-primary alcohols catalyzed by a Cp*Ir complex

Our objectives were to develop catalytic atom-economic processes accessing and/or incorporating versatile functionality using aryl/heteroaryl acetonitriles as substrates. We report essentially solvent-free [Cp*IrCl2]2 catalyzed redox neutral processes whereby substituted acetonitriles react with primary alcohols to deliver monosubstituted aryl/heteroaryl acetonitriles in excellent yield. We further demonstrate that such processes can be achieved by conventional or microwave heating and that bis- and tris-primary alcohols are also processed efficiently.     

Self-immobilizing catalysts and cocatalysts for olefin polymerization

Homogeneous catalysts for olefin polymerization such as metallocene or half-sandwich complexes containing the metals titanium, zirconium and hafnium, or other transition-metal coordination complexes can be functionalized with alkenyl groups and have then the potential to copolymerize with olefins to give heterogeneous catalysts. In a similar manner metallacyclic metallocene complexes with a metal-carbon sigma bond allow the catalytic insertion of olefins into this bond and produce heterogeneous catalysts. It is also possible to functionalize the active species of the cocatalyst methylalumoxane (MAO) and use it for self-immobilization processes. The high excess of MAO that is necessary in homogeneous solution can be reduced by more than 90% with this method.