On the synthesis and structure of monoaryllead and diaryllead acetates RPb(OCOCH3)3 and R2Pb(OCOCH3)2

Anhydrous monoaryllead triacetates ArPb(OAc)₃ (Ar = Ph, p-Tolyl, o-Tolyl, 2,5-Xylyl; OAc = OCOMe) were prepared by arylation of Pb(OAc)₄ with ArSn(C₄H₉-n)₃ in the presence of Hg(OCOCF₃)₂. The procedure was adapted for the synthesis of diaryllead diacetates Ar₂Pb(OAc)₂ (Ar = Ph, p-Tolyl, o-Tolyl, p-ClC₆H₄, o-ClC₆H₄) and afforded products with higher purity than other procedures. The crystal structures of PhPb(OAc)₃, Ph₂Pb(OAc)₂ and (o-Tolyl)₂Pb(OAc)₂ were determined by X-ray diffraction. PhPb(OAc)₃ and (o-Tolyl)₂Pb(OAc)₂ are monomeric. The pentagonal bipyramid around Pb in PhPb(OAc)₃, like the trapezoidal bipyramid around Pb in (o-Tolyl)₂Pb(OAc)₂, is heavily distorted, the OAc groups being unsymmetrically chelating. Lead in Ph₂Pb(OAc)₂ is in a distorted octahedral environment. One OAc group is bridging, linking the molecular units to infinite chains, the other OAc group is symmetrically chelating. IR, ¹H, ¹³C and ²⁰⁷Pb NMR spectroscopic data are reported. The structures of p-TolPb(OAc)₃, o-TolPb(OAc)₃ and 2,5-XylPb(OAc)₃ are inferred to be similar to that of PhPb(OAc)₃, and the structure of (o-ClC₆H₄)₂Pb(OAc)₂ is inferred to be similar to that of (o-Tolyl)₂Pb(OAc)₂.     

Catalytic oxidation of alcohols with allyl diethyl phosphate and palladium acetate

Allyl diethyl phosphate (ADP) was found to function as a stoichiometric hydrogen acceptor in a catalytic oxidation reaction of alcohols with Pd(OAc)₂. A variety of acyclic primary and secondary alcohols were oxidized in good yields and under mild conditions to the corresponding aldehydes and ketones, in the presence of Na₂CO₃ or K₂CO₃. Simple aliphatic primary alcohols yielded esters, exclusively. Polar ligand solvents (DMF, DMSO) were found to accelerate the reaction. Slow, but high yield reactions were encountered in THF and acetonitrile as solvents. The reactivity of several other allyl systems serving as H-acceptors, and several Pd compounds serving as catalysts, in the above oxidation reaction, was evaluated. It has been experimentally demonstrated (H-NMR) that ADP is capable of generating a π-allyl-Pd complex using a Pd(0) complex. Consequently, a catalytic cycle was proposed for the above oxidation reaction.     

肉桂醛催化选择加氢反应中双金属的协同效应

对既含有ＣＣ键又含有ＣＯ键的分子,ＣＣ键的选择加氢意义重大［１］．α,β不饱和醛选择加氢成饱和醛就属于此类．钯是已知的可在温和条件下将α,β不饱和醛选择加氢生成饱和醛最有效的催化剂之一．人们曾研究了不同钯化合物催化剂对α,β不饱和醛中ＣＣ的双键选择加...     

Anchimeric assistance in solvolysis of an organosilicon chloride and acetate

The compound (Me₃Si)₃CSiMeClI reacts with Hg(OAc)₂ in AcOH to give (Me₃Si)₂C(SiMe₂OAc)₂, under conditions in which the chloride (Me₃Si)₃CSiMe₂Cl is inert. Similarly, (Me₃Si)₂C(SiMe₂OAc)₂ reacts with CF₃CO₂H to give (Me₃Si)₂C[SiMe₂(O₂CCF₃)]₂ under conditions in which (Me₃Si)₃CSiMe₂OAc is inert. The results can be accounted for in terms of anchimeric assistance by the neighbouring acetoxy or trifluoroacetoxy group to the breaking of the Si---Cl or Si---OAc bond.     

Systematische untersuchungen über das verhalten von organozinnverbindungen gegenüber flüssigem schwefeldioxid II. Reaktionen von arylstannanen mit flüssigem SO2

The behaviour of tetraarylstannanes, R₄Sn (R = C₆H₅CH₂, C₆H₅, o-, m-, p-CH₃C₆H₄), towards SO₂ under various conditions has now been studied in detail. Compared to aliphatic tetraorganostannanes, the variability of the reaction products is much less, so that in nearly all cases only disulfinates, R₂Sn(O₂SR)₂, are formed. The aromatic tin(IV) mono-, di- and tri-sulfinates are also obtained by metathetical reaction between the corresponding organotin halides and sodium sulfinates. A unique feature of triaryltin chlorides, R₃SnCl (R = C₆H₅, o-, m-, p-CH₃C₆H₄), is their disproportionation in liquid SO₂ leading to disulfinates, R₂Sn(O₂SR)₂, and dichlorides, R₂SnCl₂. (p-CH₃C₆H₄)₂SnCl₂, under more efficient conditions, also accepts SO₂ forming (p-CH₃C₆H₄SO₂)₂SnCl₂. The structural investigations of the newly prepared compounds are carried out on the basis of their IR and ¹H NMR spectra.     

无金属参与的二乙酸碘苯促进吲哚C3—H乙酸化反应

研究了无金属参与的二乙酸碘苯和吲哚的C3—H乙酸化反应, 通过对取代基效应、 温度以及二乙酸碘苯用量等因素的考察, 建立了反应的最佳条件: 反应温度60 ℃, 乙酸(HOAc)为溶剂. 在无需任何添加剂条件下, 以中等到良好的收率获得一系列C3位乙酸化的吲哚衍生物. 采用红外光谱、 核磁共振波谱、 高分辨质谱及X射线单晶衍射分析对目标化合物进行了结构表征, 并推测了可能的反应机理. 该催化体系对于克量级规模反应均能获得很好的结果.     

The effects of catalyst composition on the catalytic production of dimethyl carbonate

The synthesis of dimethyl carbonate (DMC) by oxidative carbonylation of MeOH has been studied in the presence of various catalyst systems. The effect of catalyst composition on the catalytic activity and product composition is investigated. A three-component catalyst system composed of PdCl₂(PPh₃)₂, Cu(OMe)₂ and Me₄NCl shows synergy effects in terms of the MeOH conversion (26%) and DMC selectivity (95%). The reaction performed in the presence of a single-component catalyst PdCl₂(PPh₃)₂ produces dimethoxy methane (DMM) as a major product with selectivity over 90%, while the addition of Me₄NCl or Cu(OMe)₂ to PdCl₂(PPh₃)₂ results in the increase of DMC selectivity from 2% to 60%.     

电石制备过程中不同含钙化合物与焦炭的反应行为研究

针对粉状原料-氧热法电石生产新工艺的需求,通过程序升温法研究了多种粉状含钙原料与粉状焦炭直接反应制备电石的过程。结果表明,升温过程中CaCO3释放的CO2、Ca(OH)2和电石渣释放的H2O对焦炭的量和质的影响很小,CaCO3、Ca(OH)2和电石渣均可直接用于电石生产,电石生成反应自1 450℃开始,1 740℃左右达到峰值。CaSO4与焦炭在920℃左右反应形成CaS,在研究的温度范围内CaS不与焦炭反应。     

Double annulations of dihydroxy- and diacetoxy-dialkynylbenzenes. An efficient construction of benzodifurans

An efficient synthetic route to construct disubstituted benzodifurans from dihydroxy- or diacetoxy-dialkynylbenzenes utilizing Cs₂CO₃ or Pd(OAc)₂/Cs₂CO₃ promoted double annulations is described. The scope for the reaction in the presence of a catalytic amount of Pd(OAc)₂ is more general. In addition, it was observed that NaOH-promoted reaction of diacetoxy-dialkynylbenzenes may directly afford in THF/MeOH/H₂O at 80 °C benzodifurans through hydrolysis and double cyclization in a one-pot manner. However, in most cases, the reaction is less selective affording a mixture of the double cyclization products and monocyclization–hydrolysis products.     

On the formation of the interlayer between Ni-P coating and AZ33 magnesium alloy substrate by means of in situ SEM observation

Pre-treatment process is the key step for electroless plating. Once a suitable pre-treatment film is in place, the desired metals can be plated. In this paper, Ni-P coating was successfully prepared on AZ33 magnesium alloy with Mg（OH）2 pre-treatment film by electroless plating. To investigate the role of MgF2 in Ni-P coating, the deposition procedures between Mg（OH）2 pre-treatment film and Mg（OH）2-MgF2 pre-treatment film （a traditional process） were compared. The surface morphology variations of coatings were observed with scanning electron microscopy and the compositions were analyzed by energy dispersive spectrometry. The results showed that during the plating, both MgF2 and Ni-P deposited at the initial stage, and MgF2 distributed in the bottom of the coating, forming a transitional interlayer with Ni- P. According to the heat quench test, a poor adhesion of the coating mainly occurred between the MgF2 and Ni-P coating.     

Synthesis of Mg5(CO3)4(OH)2·4H2O with Flower-like Microstructure and Its Catalytic Activity for Transesterification of Dimethyl Carbonate with Phenol

A novel flower-like hydrated magnesium carbonate hydroxide,Mg_5(CO_3)_4(OH)_2·4H_2O,with micro-structure composed of individual thin nano-sheets was synthesized using a facile solution route without the use of template or organic surfactant.Reaction time has an important effect on the final morphology of the product.The micro-structure and morphology of Mg_5(CO_3)_4(OH)_2·4H_2O were characterized by means of X-ray diffractometry(XRD),field-emission scanning electron microscopy(FE-SEM).Brunauer-Emmett-Teller(BET)surface areas of the samples were also measured.The probable formation mechanism of flower-like micro-structure was discussed.It was found that Mg_5(CO_3)_4(OH)_2·4H_2O with flower-like micro-structure was a novel and efficient catalyst for the synthesis of diphenyl carbonate(DPC)by transesterification of dimethyl carbonate(DMC)with phenol.     

Tetrabutylammonium salts of tritransition-metal-substituted A-α-tungstogermanate:Halogen-free and single-component catalysts for the coupling reaction of carbon dioxide and epichlorohydrin

The green synthesis of chloropropylene carbonate via the coupling reaction of carbon dioxide and epichlorohydrin had been achieved using halogen-free and single-component catalysts tetrabutylammonium salts of tritransition-metal-substituted A-α-tungstogermanate [（n-C₄H₉）₄N]₃H₇GeW₉M₃（H₂O）₃O₃₇（M = Cu^Ⅱ,Ni^Ⅱ,Co^Ⅱand Mn^Ⅱ） without any solvent.The catalytic activity was significantly depended on the transition metal introduced in polyoxometalates.[（n-C₄H₉）₄N]₃H₇GeW₉Mn₃（H₂O）₃O₃₇ exhibited the highest catalytic activity with 94.9%conversion for epichlorohydrin and 98%selectivity for chloropropylene carbonate in 3 h.Plausible mechanism was proposed based on the results.     

Supported transition-metal catalysts for the C---C coupling reaction between ethene and diazoalkanes

The preparation of a series of immobilized transition-metal catalysts are reported. The catalysts were obtained by chemisorption of either rhodium(I) or iridium(I) complexes [MX(C₂H₄)₂]_n (M = Rh, Ir; X = Cl, OAc, acac, f₃-acac, f₆-acac) on SiO₂ or MgO supports. The oxides were also activated by SiCl₄ or TiCl₄ to give support materials in which the acidic nature of the surface is substantially increased. The activity of the immobilized catalysts was tested, particularly in the reaction of ethene with diphenyldiazomethane which yields a mixture of 1.1-diphenylpropene (8) and 1.1-diphenylcyclopropane (9). It was found that the most active and most selective (highest ratio 8:9) catalyst B1 was formed support material B (SiO₂ activated by SiCl₄) and [RhCl(C₂H₄)₂]₂ (1) and that both the activity and selectivity of B1 was comparable with that of complex 1 in solution. In contrast, the supported catalysts A2, D2 and A3, D3 obtained from [Rh(OAc)(C₂H₄)₂]₂ (2) and [Rh(acac)(C₂H₄)₂] (3) were less active than compounds 2 and 3 in solution. The immobilized catalysts A6, A7, D7 and E7, which were generated from the chloro- and acetatoiridium(I) complexes [IrCl(C₂H₄)₂]₂ (6) and [Ir(OAc)(C₂H₄)₂]₂ (7), possessed a lower activity than the rhodium counterparts. With diazoalkanes other than Ph₂CN₂, the activity of the supported catalyst B1 was partly higher and partly lower than that of complex 1 in the homogeneous phase.     

A practical synthesis of α-bromo/iodo/chloroketones from olefins under visible-light irradiation conditions

A practical synthesis of α-bromo/iodo/chloroketones from olefins under visible-light irradiation conditions has been developed.In the presence of PhI(OAc)₂ as promoter and under ambient conditions,the reactions of styrenes and triiodomethane undergo the transformation smoothly to deliver the corresponding a-iodoketones without additional photocatalyst in good yields under sunlight irradiation.Mea nwhile,the reactions of styrenes with tribromomethane and trichloromethane generate the desiredα-bromoketones and a-chloroketones in high yields by using Ru(bpy)₃Cl₂ as a photocatalyst under blue LED(450-455 nm) irradiation.     

Synthesis, structure and reactivity of [(CF3)3GePt(PPh3)2]2Hg

The reaction of Pt(PPh₃)_n (n = 3 or 4) with [(CF₃)₃Ge]₂Hg or (CF₃)₃GeHgPt(PPh₃)₂Ge(CF₃)₃ (I) gives a stable diplatinum complex [(CF₃)₃GePt(PPh₃)₂]₂Hg (II). X-Ray analysis has established that compound II contains a Ge---Pt---Hg---Pt---Ge chain of C₂ symmetry. Both of the Pt atoms have distorted square-planar coordinations. The bond lengths are: Pt---Hg, 2.630(2) and 2.665(2) Å; Ge---Pt, 2.410(4) and 2.407(4) Å.

Compound II reacts with dihydrogen in THF solution under mild conditions to give mercury and the hydride (CF₃)₃GePt(PPh₃)₂H. On interaction of II with R₂Hg organomercurials (R = Cl, Et, GeEt₃, Ge(CF₃)₃, Ge(C₆F₅)₃) an unknown reaction takes place: Pt(PPh₃)₂ moieties migrate from the polymetallic grouping into the substrate with the formation of the corresponding RHgPt(PPh₃)₂R complexes or their demercuration products, R₂Pt(PPh₃);, (R = Cl, Et). The latter react further with complex I formed in the first step of the process to give Hg and (CF₃)₃GePt(PPh₃)₂R. The reaction schemes are discussed.     

Stereoselective Palladium-catalyzed Cross-coupling of (2-Amido-1-phenylpropyl)zinc Compounds with Aryl Bromides

A controllable diastereoselective C(sp²)―C(sp³) Negishi coupling reaction of secondary benzylic zinc reagents with aryl bromides to form medicinally important 2-arylphenylethylamines was demonstrated. In the presence of Pd(OAc)₂ and 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl(S-phos), open-chain(2-amido-1-phenylethyl)zinc reagent bearing a β-NHAc or NHCHO group undergoes coupling reaction to give syn-1-arylphenylethylamine mainly, whereas the zinc reagent bearing a sterically hindered β-amido group, for example NHCOC(CH₃)₂OTBS undergoes the coupling reaction to yield anti-1-arylphenylethylamines with a configuration inversion. In addition, a working mechanism for the stereoselective Negishi cross-coupling was also proposed.     

金属氧化物和盐催化剂上尿素与甲醇合成碳酸二甲酯

在高压釜中采用金属氧化物和盐作为催化剂由尿素与甲醇合成碳酸二甲酯。结果表明,含有结晶水的金属盐比无结晶水金属盐和金属氧化物具有更好的催化活性。采用羟基化合物与硝酸锌组成的二元催化剂,其催化活性显著高于单一催化剂;羟基与硝酸锌之间具有协同催化作用。其中,硝酸锌与SiO2组成的二元催化剂活性最高;硝酸锌与SiO2的质量比为2时,DMC收率可达4.5%。     

两个基于氢键构筑的超分子镁配合物的合成、 晶体结构及荧光性质

以5,6-苯并咪唑二酸(H₃bidc)为有机配体, 在水热条件下通过控制反应温度得到了2个镁配合物[Mg(Hbidc)(H₂O)₄](1) 和 [Mg(Hbidc)(H₂O)₅]·4H₂O(2). 通过单晶及粉末X 射线衍射、 红外光谱、 元素分析和热重分析对配合物进行了表征. 结果表明, 配合物1和2均为单核分子, 分别以不同的堆积方式通过氢键构筑成三维超分子结构. 值得注意的是, 配合物2的结构中捕获了由氢键连接的环状四聚体水簇(H₂O)₄. 配合物1和2的电荷布居分析结果与晶体结构的讨论一致. 此外, 固体荧光分析表明, 配合物1和2在室温下具有较强的蓝光发射.     

A new route for isoquinolines catalyzed by palladium

3-Bromopyridine-4-carbaldehyde is tethered with suitably electron withdrawing group substituted alkenes via Heck coupling followed by aldol reaction in dioxane at 150 °C under a catalytic system of Pd(OAc)₂/PPh₃/NaOAc to afford the corresponding isoquinolines in good yields.     

醋酸酮催化二硫醚与四氢呋喃的氧化偶联反应

研究了醋酸酮催化二硫醚与四氢呋喃以氧化偶联反应构建C—S键。 结果表明,在醋酸酮(10%摩尔分数)、二硫醚(0.5 mmol)、四氢呋喃(2 mL)和双氧水(35%,2倍化学计量),反应温度120 ℃条件下,二硫醚与四氢呋喃能够顺利地发生氧化偶联反应,生成相应的C—S键化合物,合成硫醚类化合物产率中等到良好。 该反应以双氧水为氧化剂,具有环境友好等特性。