Poly(1,4-butyl-bis-vinylpyridinium) borohydride as a new stable and efficient reducing agent in organic synthesis

The unstable sodium borohydride is stabilized on modified poly(4-vinylpyridinium), and it is used as an efficient and regenerable polymer-supported borohydride reagent for the reduction of a variety of carbonyl compounds, such as aldehydes, ketones, α,β-unsaturated carbonyl compounds, α-diketones and acyloins, in good to excellent yields.     

Poly(n-butyl-4-vinylpyridinium) borohydride as a new stable and efficient reducing agent in organic synthesis

Sodium borohydride is stabilized on poly(n-butyl-4-vinylpyridinium) chloride, and it is used as an efficient and regenerable polymer-supported borohydride reagent for the reduction of a variety of carbonyl compounds, such as aldehydes, ketones, α,β-unsaturated carbonyl compounds, α-diketones, and acyloins.     

聚合物支载的硼氢化钠还原剂系统对苯乙酮的不对称还原

聚合物支载硼氢负离子还原剂Na^+[P-COO(BH~3)]^-中的活泼氢原子能用于酮的不对称还原。该试剂中加入带手性碳的羧酸或醇, 反应后生成的还原系统还原苯乙酮。     

Triphenylphosphine as reducing agent for copper(II)-catalyzed AGET ATRP

Triphenylphosphine(TPP) was used as reducing agent to continuously generate the Cu(I) activator in copper(II)-catalyzed activators generated by electron transfer atom transfer radical polymerization(AGET ATRP). For example, the polymers prepared with a molar ratio of [MMA]0/[EBi B]0/[Cu Cl2]0/[PMDETA]0/[TPP]0 = 500/1/0.1/0.5/0.5 had controlled molecular weights and low molecular weight distribution(Mw/Mn) values(~1.2). TPP as a commercial reducing agent provides a convenient copper-catalyzed AGET ATRP procedure for the preparation of well-defined polymers.     

Ovalbumin-stabilized gold nanoclusters with ascorbic acid as reducing agent for detection of serum copper

Ovalbumin-stabilized gold nanoclusters(OVA@AuNCs) were prepared with ascorbic acid as a reducing agent. This strategy could realize the synthesis of water-soluble OVA@AuNCs within 20 min. The asprepared fluorescent probe showed a red fluorescence emission at 630 nm. Moreover, the properties of the OVA@AuNCs were characterized by transmission electron microscope, dynamic light scattering,ultraviolet-visible spectroscopy, fluorescent spectroscopy. Based on the surface electron density decrease-induced fluorescence quenching mechanism, the OVA@AuNCs provided high sensitivity and selectivity for sensing copper ions. A good linear relationship was obtained between the fluorescence intensity of OVA@AuNCs and the concentration of copper ions in the range of 5.0-100.0 μmol/L(R~2=0.999) with a detection limit of 640 nmol/L Furthermore, the rat serum copper contents were determined by using the OVA@AuNCs based assay, indicating great potential of fluorescent probes for application in biological and clinical analysis.     

New and efficient catalysts for enantioselective borohydride reduction of ketones and imines

Optically active aldiminato cobalt(II) complexes have been found to catalyze the enantioselective reduction of ketones with sodium borohydride affording the corresponding optically active secondary alcohols in high chemical yields with high enantioselectivities. The enantioselective borohydride reduction is also applicable to not only C=O bonds in aromatic ketones but also to C=N bonds in aromatic imines.     

Isolation and structural characterization of the first thermally robust and air stable Cr(4+) bent-metallocene complex

The first thermally robust and air stable bent-sandwich chromocene complex with chromium in the +4 oxidation state has been isolated and fully characterized.     

AgOTf-catalyzed one-pot reaction of 2-alkynylbenzaldehyde, amine, and sodium borohydride

One-pot reactions of 2-alkynylbenzaldehydes, amines, and sodium borohydride catalyzed by AgOTf under mild conditions provide a facile protocol for the concise synthesis of 1,2-dihydroisoquinoline derivatives.     

A novel positively thermo-sensitive hydrogel based on ethylenediaminetetraacetic dianhydride and piperazine: Design, synthesis and characterization

A new positively thermo-sensitive hydrogel was designed and synthesized by a condensation polymerization reaction of ethylenediaminetetraacetic dianhydride（EDTAD） and piperazine（PA） to give poly（ethylenediaminetetraacetic dianhydride-copiperazine） （PEP）.The obtained polymers’ structure was characterized by FTIR and ¹³C NMR.The backbone of the polymer linked by amide bond and abundant of carboxyl groups as pendant group could form strong intermolecular and intramolecular hydrogen bond at lower temperature and dissociate at higher temperature,resulting in the polymer with thermo-sensitivity.The aqueous solution of PEP at lower temperature（<20℃） showed micro-gel formation and transformed to transparent solution at higher temperature（>40℃）.Transition temperature shifted to higher value with the increasing of concentration.The hydrogel exhibited reversible phase transition and the transmittance change was not weakened by multiple temperature changes.     

Synthesis and characterization of two zinc(II) macrocyclic Schiff-base complexes containing piperazine moiety, crystal structure of one complex

Two symmetrical and asymmetrical Zn(II) complexes of a pentadentate (N₅) macrocyclic Schiff-base ligands, were prepared via templated [1 + 1] cyclocondensation of 2,6-diacetylpyridine with two different amines containing piperazine moiety. The complexes have been characterized by a variety of methods including, IR, FAB mass spectrometry, elemental analysis and conductivity measurements. The crystal structure of the asymmetric complex, [ZnL¹Br]ClO₄ was determined by X-ray diffraction. It is shown that in the solid state the complex adopts a distorted pentagonal–pyramidal geometry, with the macrocycle in the pentagonal plane and the bromide ion in the axial position.     

An acrylated fullerene derivative for efficient and thermally stable polymer solar cells

The continuous microstructure evolution occurring in active layers of polymer-fullerene solar cells is one of the main causes for their device instability. With aim to tackle it, this work developed a new polymerizable fullerene acceptor, [6,6]-phenyl-C₆₁-butyl acrylate (PC₆₁BA). It was found that PC₆₁BA has similar light-absorption properties and HOMO and LUMO energy levels as [6,6]-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM), and can be converted into insoluble oligomers upon heating at 150 °C. Polymer-fullerene solar cells using poly(3-hexylthiophene) (P3HT) as donor and PC₆₁BA as acceptor exhibited an optimized efficiency of 3.54%, the performance comparable to P3HT/PC₆₁BM cells (optimized efficiency: 3.70%). But, the former possess much better thermal stability than the latter owing to aggregation suppression by the polymerized PC₆₁BA. These results indicate that PC₆₁BA, unlike most previous reported, is a unique polymerizable fullerene derivative that can be used alone as acceptor to achieve both efficient and thermally stable polymer solar cells.     

Me3SiCl-NaI-CH3CN as an efficient and practical reducing agent for benzylic alcohols

Secondary and tertiary benzylic alcohols are reduced conveniently tothe corresponding aryl alkanes by using Me₃SiCl-NaI-CH₃CN reagent in hexane. The reaction was successfully applied to a short step synthesis of (±)-ar-turmerone.     

Syntheses,Crystal Structures,Optical and Thermal Properties of Two New Zirconium Polyselenides (K8Zr6Se30) Containing One‐dimensional Anionic Chains

Two new ternary compounds with composition K₈Zr₆Se₃₀ were prepared by reacting zirconium powder in potassium polyselenide melts. Both compounds crystallize in the triclinic space group P1 with a = 12.391(1) Å, b = 14.897(2) Å, c = 15.253(2) Å, α = 73.149(9)°, β = 76.330(9)°, γ = 70.023(9)° and V = 2502.8(3) ų for I and a = 12.2793(8) Å, b = 14.887(1) Å, c = 22.512(2) Å, α = 72.714(7)°, β = 88.475(7)°, γ = 70.748(7)° and V = 3698.1(4) ų for II . Their structures consist of infinite linear one‐dimensional anionic chains running parallel to [110], which are connected by the potassium cations. The structural differences between both compounds originate from some disordering in one of the two crystallographically independent anionic chains of each compound, in which Se^2– anions are exchanged by Se₂^2– anions to some degree. The optical band gap was determined by UV/Vis reflectance spectra to 1.91 eV for I and 1.81 eV for II . Differential scanning calorimetry investigations show, that II decomposes reversibly at about 500 °C to K₂Se₃ and ZrSe₃. On cooling II is formed again. These results are confirmed by the direct reaction between K₂Se₃ and ZrSe₃ which leads directly to II .     

Unprecedented polymerization of trimethylene carbonate initiated by a samarium borohydride complex: mechanistic insights and copolymerization with epsilon-caprolactone

Poly(trimethylene carbonate) (PTMC) was synthesized through ring-opening polymerization by using a rare-earth borohydride initiator, [Sm(BH(4))(3)(thf)(3)]. This initiator shows a high activity to give high-molar-mass PTMCs with molar-mass distributions ranging from 1.2 to 1.4, and with a regular structure void of ether linkages. The polymers were characterized by (1)H and (13)C NMR spectroscopy, (1)H-(1)H COSY, (1)H-(13)C HMQC NMR spectroscopy, size-exclusion chromatography (SEC), viscosimetry, and MALDI-TOF MS analyses. A coordination-insertion mechanism was established based on detailed NMR characterizations, especially of the polymer chain end-functions. The monomer initially coordinates the samarium to give [Sm(BH(4))(3)(tmc)(3)], 1. The monomer then opens up through cleavage of the cyclic ester oxygen--acyl bond and inserts into the Sm--HBH(3) bond resulting in an alkoxide complex, [Sm{O(CH(2))(3)OC(O)HBH(3)}(3)], 2, or [Sm{O(CH(2))(3)OC(O)H}(3)], 2', which then propagates the polymerization of TMC to give the active polymer [Sm({O(CH(2))(3)OC(O)}(n)O(CH(2))(3)OC(O)HBH(3))(3)], 3 or [Sm(O(CH(2))(3)OC(O){O(CH(2))(3)OC(O)}(n)O(CH(2))(3)OC(O)H)(3)], 3'. Finally, acidic hydrolysis of 3 or 3' gives HO(CH(2))(3)OC(O)[O(CH(2))(3)OC(O)](n)O(CH(2))(3)OC(O)H, 4. This novel alpha-hydroxy,omega-formatetelechelic PTMC represents the first example of a formate-terminated polycarbonate. TMC and epsilon-caprolactone (CL) were copolymerized to afford both random PTMC-co-PCL and block PTMC-b-PCL copolymers that were characterized by (1)H NMR spectroscopy, SEC, and differential scanning calorimetry (DSC). The structure of the block copolymers depends on the order of addition of monomers: if CL is introduced first, dihydroxytelechelic HO-PTMC-b-PCL-OH polymers are formed, whereas introduction of TMC first or simultaneous addition of comonomers leads to hydroxyformatetelechelic HC(O)O-PTMC-b-PCL-OH analogues.     

复合还原剂NaBH~4/BiCl~3对α,β-不饱和腈的选择性还原

在95%乙醇溶剂中，NaBH~4/BiCl~3能选择性还原α,β-不饱和腈，同时探讨了该反应的还原机理。     

Metallocene Carbene Complexes and Related Compounds of Titanium,Zirconium, and Hafnium

The structure and creativity spectrum of transition-metal carbene complexes has been widened significantly by the bent metallocenes of titanium, zirconium, and hafnium. Proceeding from metal carbonyls and reactive (butadiene)-, (aryne)-, or (olefin) MCp₂ complexes, many new Fischer-type metaloxycarbene complexes of Zr, Hf, V, Nb, Cr, Mo, W, Mn, Re, Fe, Ru, Os, Co, Ni, and Rh have been synthesized. The incorporation of titanocene, zirconocene, or hafnocene fragments allows new types of carbene complexes to be prepared. For the (alkylidenamido)metallocene complexes , metallocene ylides , and binuclear (μ-alkynyl)metallocene compounds, some metalligand π bonding is indicated. Metallocene complexes with metallaoxirane units, , show similar chemical behavior to that of binuclear (μ-methylene)complexes . The methylene groups of zirconaoxirane complexes, which are derived from carbon monoxide, may be expelled as ethylene by thermally induced CC coupling. With metal hydrides, CH₂ transfer with insertion into the metal–hydride bond occurs. In one case, methylene insertion into a metal–carbon bond can even be observed. These reactions of Ti-group metallaoxiranes could be models for postulated intermediates in the Fischer–Tropsch synthesis.     

Synthesis and characterization of new thienylpyrrolyl-benzothiazoles as efficient and thermally stable nonlinear optical chromophores

The synthesis and full characterization of new chromophores with second-order nonlinearities containing thienylpyrrolyl and benzothiazolyl moieties are reported. The solvatochromic behavior of the compounds was investigated. The hyperpolarizabilities β of derivatives 4-6 were measured using hyper-Rayleigh scattering and thermogravimetric analysis (TGA) was used to evaluate their thermal stability. The experimental results indicate that strong nonlinearity is balanced by good thermal stability especially for chromophores 6b and 6c, making them good candidates for NLO applications.     

Application of an air stable Pd oxazoline complex for Heck, Suzuki, Sonogashira and related C-C bond-forming reactions

The novel complex trans-[PdCl₂(η¹-N-2-ethyl-2-oxazoline)₂] is shown to be an active and oxidatively robust catalyst for C-C bond-forming reactions (Heck, Sonogashira, Ullman, Suzuki), which can be carried out in air without rigorous solvent/substrate purification and in the absence of additional free ligand.