螺[4,4]-1,6-壬二烯骨架手性双膦配体的合成

从方便易得的原料出发,以钯催化的烯基三氟甲磺酸酯与二苯基膦氧化物的偶联反应为关键步骤,合成了螺[4,4]-1,6-壬二烯骨架的手性双膦配体1.其中,关键中间体5的拆分是通过半制备手性液相色谱实现的,并通过该化合物的X射线单晶衍射分析确定了其中螺碳原子的绝对构型.配体(S)-1的Rh(I)络合物在α-乙酰氨基肉桂酸的氢化中表现出中等的对映选择性(53%ee).配体(S)-1的Cu(I)络合物能以较好的反应活性实现苯乙酮的不对称氢化,产物的对映体过量可以达到67%.     

Rhodium catalyzed asymmetric Pauson-Khand reaction using SDP ligands

~~Rhodium catalyzed asymmetric Pauson-Khand reaction using SDP ligands1. Khand, I. U., Knox, G R., Pauson, P. L. et al., Organocobalt complexes, Part Ⅱ. Reaction of acetylenehexacarbonyldicobalt complexes, (R1C2R2)Co2(CO)6, with norbomene and its deri…     

Hydrogenation of heteroaromatic nitrogen compounds catalyzed by rhodium and iridium systems containing diphosphine ligands

The systems prepared in situ by addition of two equivalents of diphosphine [1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp) and 1,4-bis(diphenylphosphino)butane (dppb)] to M₂Cl₂(COE)₄ (M = Rh, Ir; COE = cyclooctene) showed to be efficient and regioselective precatalysts for the hydrogenation of quinoline, isoquinoline, 5,6- and 7,8-benzoquinoline and acridine, under mild reaction conditions (130°C and 4 atm H₂). The Rh systems showed to be more active than the corresponding Ir ones, except for the case of acridine, where an inversed tendency was observed (Ir > Rh).     

Probing the stereo‐electronic properties of cationic rhodium complexes bearing chiral diphosphine ligands by 103Rh NMR

¹⁰³Rh NMR represents a powerful tool to assess the global electronic and steric contribution of diphosphine ligands on [Rh(COD)(diphosphine)]⁺ complexes. In the case of DIOP, BINAP and MeDUPHOS, this approach proved to be more informative than classical CO‐stretching frequency measurements. After validation, this method has been extended to a set of seven diphosphines. ¹⁰³Rh NMR measurements on [Rh(COD)(diphosphine)]PF₆ lead to the following order of donor properties: dppe > MeBPE > MeDUPHOS > dppb > DIOP > BINAP > Tol‐BINAP. This trend has been validated by DFT in the case of DIOP, BINAP and MeDUPHOS. In conjunction, ³¹P NMR chemical shift has been shown to reflect the ring constraints of the Rh‐diphosphine scaffold. This contribution is a step towards a mechanistic investigation of the catalytic hydrogenation of unsaturated substrates by ¹⁰³Rh NMR and DFT. Copyright © 2010 John Wiley & Sons, Ltd.     

基于碳量子点修饰硅胶荧光法测定塑料制品中的双酚A

制备了碳量子点修饰的硅胶SiO2@CDs.在盐酸介质中KBrO3能够氧化碳量子点使其荧光发射峰减弱,而双酚A(BPA)对此氧化猝灭有明显抑制作用,据此建立了荧光法测定痕量双酚A的新方法,线性范围是20~500μg·L-1,检出限3σ为5.2μg·L-1.本文作者将该方法成功用于塑料制品中双酚A的测定,回收率在95%~104%之间.     

铑-双膦配合物的咬角效应对催化1-十二烯氢甲酰化反应的影响

研究了HRh(CO)(PPh₃)₃-双膦配体(BISBI，BDPX，BDNA和BINAP)体系在1-十二烯氢甲酰化反应中的催化性能。4种双膦配体具有不同的空间结构，因而有不同的咬角(bite angle)，它们与铑催化剂前体HRh(CO)(PPh₃)₃进行配体交换后，形成不同的催化活性物种。4种复合催化剂体系中，HRh(CO)(PPh₃)₃-BISBI(咬角为120°)对直链醛的形成具有很高的区域选择性，这可能是因为形成了有利于生成直链烷基-铑的ee构型催化活性物种，其它3种双膦配体与HRh(CO)(PPh₃)₃组成的复合催化剂体系区域选择性没有多少变化，是与它们具有较小的咬角有关(BINAP85°，BDPX90°，BDNA104°)。上述4种HRh(CO)(PPh₃)₃ -双膦体系与HRh(CO)(PPh₃)₃-PPh₃体系相比较，催化活性较低，这可能是因为双膦的螯合配位作用使催化活性物种较稳定 。     

A new type of chiral porphyrin: Organopalladium porphyrins with chiral chelating diphosphine ligands

Peripherally palladated Ni(II) porphyrins have been prepared using enantiopure chiral chelating diphosphines as supporting ligands on the attached Pd(II) fragment. Both enantiomers of the following complexes have been obtained in good yields, using oxidative addition of the bromoporphyrin starting material 5-bromo-10,20-diphenylporphyrinatonickel(II) (NiDPPBr (1)) to the [Pd⁰L] complex generated in situ from Pd₂dba₃ and the chiral ligand L: [PdBr(NiDPP)(CHIRAPHOS)] (2a,b) [CHIRAPHOS = 2,3-bis(diphenylphosphino)butane], [PdBr(NiDPP)(Tol-BINAP)] (3a,b) [Tol-BINAP) = 2,2′-bis(di-p-tolylphosphino)-1,1′-binaphthyl] and [PdBr(NiDPP)(diphos)] [diphos = 1,2-bis(methylphenylphosphino)benzene] (4a,b). The induced asymmetry in the porphyrin was readily detected by ¹H NMR and CD spectroscopy. The porphyrin chiroptical properties are strongly dependent upon the structure of the chiral ligand, such that a monosignate CD signal, and symmetric and asymmetric exciton couplets were observed for 4a, 2b, and 3a,b, respectively.     

Phosphorus Ligands with a Large Cavity: Synthesis of Triethynylphosphines with Bulky End Caps and Application to the Rhodium‐Catalyzed Hydrosilylation of Ketones

Trialkynylphosphines substituted with bulky triarylsilyl groups at the alkyne termini were synthesized. The new phosphines P(C?CSiAr₃)₃ (Ar=3,5‐tBu₂‐4‐MeOC₆H₂, 3,5‐(Me₃Si)₂C₆H₃) are uncrowded near the phosphorus atom but bulky in the distal region. As a result, they contain a large cavity, at the bottom of which the phosphine lone‐pair electrons are located. The compounds are stable to oxidation by air and hydrolysis. DFT calculations suggested that the triethynylphosphines are good π‐acceptor ligands, comparable with P(OAr)₃. The trialkynylphosphines reacted with [{RhCl(cod)}₂] (P/Rh=1.1:1) to give selectively the monophosphine–rhodium complex [RhCl(cod)P(C?CSiAr₃)₃]. X‐ray crystal‐structure analysis revealed that the {RhCl(cod)} fragment is fully accommodated by the cavity of the phosphine ligand. Compared to the effect of analogues with smaller end caps and PPh₃, the trialkynylphosphines accelerated markedly the rhodium‐catalyzed hydrosilylation of ketones with a triorganosilane. It is proposed that the higher catalytic activity observed with the holey phosphines is a result of the preferential formation of a monophosphine–rhodium species.     

Chiral Phosphate in Rhodium‐Catalyzed Asymmetric [2+2+2] Cycloaddition: Ligand,Counterion, or Both?

Investigations based on NMR spectroscopy, mass spectrometry, and DFT calculations shed light on the metallic species generated in the rhodium‐catalyzed asymmetric [2+2+2] cycloaddition reaction between diynes and isocyanates with the chiral phosphate TRIP. The catalytic mixture comprising [{Rh(cod)Cl}₂], 1,4‐diphenylphosphinobutane (dppb), and Ag(S)‐TRIP actually gives rise to two species, both having an effect on the stereoselectivity. One is a rhodium(I) complex in which TRIP is a weakly coordinating counterion, whereas the other is a bimetallic Rh/Ag complex in which TRIP is a strongly coordinating X‐type ligand.     

Electrochemical determination of bisphenol A based on PHD/MWCNTs modified glassy carbon electrode

A novel electrochemical sensor for the determination of bisphenol A (BPA) was fabricated by block polyelectrolyte composite films, which composed of diblock polyelectrolyte poly (2-hydroxyethyl methacrylate)-b-poly (2-(dimethylamino) ethyl methacrylate) (PHEMA-b-PDMAEMA, noted as PHD in the later content) and multi-walled carbon nanotubes (MWCNTs). The tertiary amino groups of PDMAEMA can be protonated at physiological pH. The protonated PDMAEMA can thus interact with the negatively charged BPA through electrostatic attraction to increase the BPA sorption capacity and enhance the ability for highly sensitive detection of BPA. The PHD/MWCNTs composite films combine the electrocatalytic property of MWCNTs and the electrostatic attraction of protonated PHD. Because of the above-mentioned excellent property of the composite films, the PHD/MWCNTs/glassy carbon electrode exhibited good electrocatalytic activity to electrooxidation of BPA. The wide linear response range of the BPA sensor was from 4.56 × 10^?5 g L^?1 to 2.28 × 10^?2 g L^?1 with a lower detection limit of 2.28 × 10^?6 g L^?1 (S/N = 3) and high sensitivity 2442.86 μA L g^?1 cm^?2. The current reached the steady-state current with a shorter response time less than 4 s. The proposed method was successfully applied to determine BPA in real samples (PVC food package, milk, tap water and pond water) and satisfactory results were obtained. These results indicated that the block polyelectrolyte composite have potential applicability of the BPA sensor.     

Phosphabarrelenes as ligands in rhodium-catalyzed hydroformylation of internal alkenes essentially free of alkene isomerization

Despite significant research efforts in the past, one of the remaining problems to be solved in industrially important hydroformylation is the chemoselective low-pressure hydroformylation of internal alkenes. We report here on a new class of phosphabarrelene/rhodium catalysts 2 that display very high activity towards hydroformylation of internal alkenes with an unusually low tendency towards alkene isomerization. Preparation of new phosphabarrelene ligands, studies of their coordination properties, as well as results obtained in the rhodium-catalyzed hydroformylation of cyclic and acyclic internal alkenes are reported.     

Measurement of bisphenol A and bisphenol B levels in human blood sera from healthy and endometriotic women

A sensitive HPLC method with fluorescence detection was developed for the determination of bisphenol A (BPA) and bisphenol B (BPB) in human blood serum. The detection limits of the method were 0.18 and 0.20 ng/mL for BPA and BPB, respectively. A single‐step liquid–liquid extraction was used for the pre‐treatment of serum samples. The recoveries of BPA and BPB spiked to sera were 85.6 and 87.7%, respectively. The analyses of sera from both healthy and endometriotic women emphasized the absence of bisphenols in all the control cases (11 women), whereas BPA was found in 30 sera (51.7%) and BPB was found in 16 sera (27.6%) in the group of 58 patients with endometriosis; in nine of such sera BPA and BPB were present simultaneously. Only relatively to the sera quantitated, BPA concentrations ranged from 0.79 to 7.12 ng/mL (mean concentration 2.91 ± 1.74 ng/mL), whereas BPB concentrations ranged from 0.88 to 11.94 ng/mL (mean concentration 5.15 ± 4.16 ng/mL). Therefore, the presence of at least one of the two bisphenols was verified in a percentage as high as 63.8% in the sera from endometriotic women, suggesting the existence of a relationship between endometriosis and BPA and/or BPB exposure. Indeed, it is well known that bisphenols can work as xenoestrogens, owing to their structural similarity to natural and synthetic estrogens (e.g. estradiol and dietilstilbestrol). However, further studies are necessary to confirm this hypothesis and to assess the actual dose at which exposures to bisphenols are able to increase the sensitivity of the endometriotic cells to estradiol. Copyright © 2009 John Wiley & Sons, Ltd.     

Stitching phospholanes together piece by piece: new modular di- and tridentate stereodirecting ligands

The modular one-pot synthesis of a large family of bi- and tridentate 2,5-dimethyl- and 2,5-diphenyl-substituted phospholanes employs air-stable chiral phospholanium chloride salts and primary amines or NH(4)Cl as starting materials. These were transformed into the C(2)-symmetric dimethyl- and diphenylphospholane ligands, which reacted with [Rh(cod)(2)]BF(4) (cod=1,5-cyclooctadiene) to yield the rhodium complexes [Rh(L)(cod)]BF(4) (L=bisphospholane ligands). The corresponding trisphospholane complexes, 11 and 12, were obtained in high yields (81 and 92%, respectively), and fully characterised by NMR spectroscopy, mass spectrometry and elemental analysis. Whilst in the C(3)-symmetric complex 11, containing the tridentate 2,5-dimethylphospholane, the ligand is bound symmetrically, different coordination behaviour was found for the diphenyl-substituted complex 12, in which the coordination of only two of the three phospholane moieties to the metal centre was observed. A DFT study at the B3PW91 level established minimum energy structures consistent with experimental findings in solution and in the solid state. The non-coordinated phospholane unit present in 12 allowed further modification of the complex through the coordination of Au(I)-X (X=Cl, C(6)F(5) and tris(trifluoromethyl)phenyl ((F)Mes)) fragments to the pendant phosphane. To investigate the potential of the new ligands, the enantioselective hydrogenation of a series of prochiral olefins as benchmark substrates, using isolated Rh complexes as catalysts, was studied. The substrates included methyl esters of three dehydro-α-acetamido acids and two itaconic acid derivatives. In general good to excellent enantioselectivities (of up to >99% ee) were observed. Ligand backbone modification by coordination of bulky Au-X substituents to the free phospholane unit in complex 12 led to an outstanding enhancement of the catalyst performance and there was a clear correlation between the properties of the complex periphery and the enantioselectivity.     

金-石墨烯修饰电极电化学检测塑料瓶中双酚A

在离子液体碳糊电极(CILE)表面上采用一步电还原法制备了纳米金(nAu)-石墨烯(GR)复合膜修饰电极(nAu-GR/CILE).研究了双酚A(BPA)在nAu-GR/CILE上的电化学行为,BPA的电极反应过程为受吸附控制的不可逆过程;采用示差脉冲伏安法研究了BPA氧化峰电流和浓度之间的关系,在0.08～400.0...     

Chiral diphosphine ligands based on camphor: synthesis and applications in asymmetric hydrogenations

The synthesis of a novel class of atropisomer chiral diphosphine ligands with a bornene framework is described. The new ligands showed in Rh catalyzed asymmetric hydrogenation of α- and β-enamides very high ee’s (more than 99%).