The regiochemistry of reduction of mono-ethyl fumarate and maleate using a ruthenium BINAP catalyst

The regiochemistry of the reduction of mono-ethyl fumarate using bis(carboxylato){2,2′-bis(diphenylphosphino)-[R]-1,1-binapthyl}-ruthenium(II) (Ru[BINAP]) in H₂/CH₃OD is reported and occurs opposite to the regiochemistry observed in the reduction of tiglic acid. Reduction of mono-ethyl maleate with D₂/CH₃OD is very sluggish but produces meso-dideuteriosuccinic acid with high stereoselectivity. Reduction of mono-ethyl maleate with Ru[BINAP](O₂CR)₂ and H₂/CH₃OD results in mono-ethyl succinate-d₁ with nearly complete loss of regiochemistry.     

A convenient synthesis of pseudoglycosides via a Ferrier-type rearrangement using metal-free H3PO4 catalyst

A mild and efficient synthesis of pseudoglycals has been developed using a metal-free catalytic system. Phosphoric acid proved to be an excellent catalyst for conversion of 2,4,6-tri-O-acetyl-d-glycal to 2,3-unsaturated O-glycosides. A wide range of alcohols including naturally bioactive compounds could be coupled with the glycal to give the desired products in good to excellent yields and with high levels of α-selectivity.     

The mechanism of asymmetric reduction catalyzed by a C2 symmetric bis-amino alcohol catalyst

By means of¹H,¹³C,¹¹B NMR, polar transfer DEPT135, DEPT90 and 2D NMR experiments, IR, etc, the structure of the diaminodihydroxyl ligand and its derivatives used in the asym-metric reduction of prochiral ketones were detected. The catalysts derived from the ligand and borane formedin situ were also studied and the structure transformations in solution were monitored. The structure of the catalyst was proved to be a new type of dual-centered catalyst — bisoxazaborolidine.     

A convenient short synthesis of 7-oxo-PGI2

A 5-step synthesis of the title compound via selective hydroxylation of Δ₆-PGI₁ derivative is presented including stereochemistry and conformational analysis of intermediates.     

Application of MerCO as a chiral catalyst in asymmetric synthesis: asymmetric borane reduction of ketones

The borane reduction of aryl methyl ketones catalyzed by MerCO [(1R,2S,3R)-3-mercaptocamphan-2-ol] produced 1-aryl ethyl alcohols in 92% e.e. at 50°C in toluene. Significant temperature and solvent effects were observed in this reaction.     

A convenient route to chiral γ-lactones via asymmetric hydrogenation of γ-ketoesters using the RuCl3-BINAP-HCl catalytic system

A convenient one-step synthesis of chiral γ-lactones has been performed. The method is based on enantioselective hydrogenation of γ-ketoesters using the RuCl₃-BINAP-HCl catalytic system. Chiral γ-lactones (91-99% ee) have been isolated in 57-88% yield.     

Conceptually new chiral tertiary C2 symmetric diamines in asymmetric synthesis

New chiral diamines were prepared, based on the cyclohexane diamine core. The two different substituents on each nitrogen allow this heteroatom to become a stereogenic center upon chelation with a metal, such as lithium. The enantioselective addition of MeLi to imines, with ee's up to 68%, illustrates the validity of this concept.     

Selective catalytic reduction of NO by C2H2 over Ce-Al2O3 catalyst with rate-determining step of NO oxidation

Ce-Al2O3 catalysts prepared by co-precipitation are investigated both in NO oxidation by O2 and in selective catalytic reduction of NO by C2H2(C 2 H 2-SCR).It is found that C2H2-SCR is initiated and controlled by NO oxidation to NO 2 over Al2O3.Ce loading on Al2O3 is almost inactive for NO oxidation below 350 C,since NO2 strongly adsorbs on cerium oxide,leading to the active sites being blocked,which was characterized by temperature-programmed desorption of NO and NO 2 and Fourier transform infrared spectroscopy after NO+O 2 coadsorption over the samples.However,in the case of C2H2-SCR,Ce loading on Al 2 O 3 significantly improves the reaction by accelerating the NO oxidation step in the temperature range of 250-450 C,since the nitrate species produced by NO 2 adsorption is an active intermediate required by C2H 2-SCR.     

水热合成的MoO3-SnO2催化剂催化氧化二甲醚的性能研究

采用无沉淀剂水热法一步合成了MoO₃-SnO₂复合金属氧化物催化剂,通过调变Mo/Sn物质的量比,考察了催化剂上活性组分MoO_x分散程度对二甲醚（DME）低温氧化生成甲酸甲酯（MF）反应性能的影响。当Mo/Sn=1∶2,反应条件为150℃时,催化剂表现出较好的催化性能,DME转化率为22.0%,MF选择性达到77.6%。实验中采用TEM、XRD、Raman、FT-IR、NH₃-TPD及H₂-TPR等表征对催化剂晶体结构及表面性质进行了分析。结果发现,Mo/Sn物质的量比变化会对催化剂晶体结构产生显著影响,钼氧化物在SnO₂表面形成不同分散程度的MoO_x结构,这种钼氧化物结构的变化进一步影响了催化剂表面的酸性及氧化还原性,是造成催化性能差异的主要原因。     

Enantioselective reduction of aliphatic ketones using NaBH4 and TarB-NO2, a chiral boronic ester

High enantioselectivities are obtained using a tartaric acid-derived boronic ester (TarB-NO₂) in combination with NaBH₄ for the asymmetric reduction of aliphatic ketones. The resulting alcohols are obtained in enantiomeric excesses ranging from 56% to 94%.     

Novel chiral C2-symmetric multidentate aminophosphine ligands for use in catalytic asymmetric reduction of ketones

A series of novel chiral C₂-symmetric multidentate aminophosphine ligands have been successfully synthesized by Schiff-base condensation of bis（o-formylphenyl）phenylphosphane and easily available monoprotected（1R,2R）-diaminocyclohexane.The catalytic properties of these ligands were investigated in Ir-catalyzed asymmetric transfer hydrogenation of various aromatic ketones,giving the corresponding optical active alcohols with up to 98%conversion and good ee under mild reaction conditions.     

V2O5/赤铁矿催化剂结构及其NH3选择性催化还原NOx性能

以水热合成针铁矿为前驱体浸渍偏钒酸铵,分别于300,400和500℃空气中焙烧,制备了不同活性组分负载量的V₂O₅/赤铁矿（V/H）催化剂,用于氨选择性催化还原（SCR）脱硝。采用X射线衍射、透射电子显微镜、比表面积分析仪、程序升温还原及程序升温脱附等方法对催化剂结构进行了表征,并用标气配制模拟烟气进行了脱硝实验。结果表明,300℃煅烧3%V/H催化剂当烟气温度为250-300℃时NO转化率均可达95%以上;当配气中单独加入水蒸气或低浓度SO₂（0.01%）时,V/H催化脱硝的活性不受影响;当系统加入高浓度的SO₂（0.03%与0.05%）或同时添加H₂O与SO₂时,SCR脱硝效率下降,其机制可能是SO₂在催化剂表面竞争吸附所致,停止添加后,催化活性迅速恢复。     

低温燃烧法制备Mn-CeO_x催化剂及其NH_3-SCR脱硝性能

通过低温燃烧法(LCS)制备了不同金属硝酸盐与柠檬酸物质的量比的系列Mn-CeO_x(LCS)锰铈催化剂,将其与共沉淀法(CP)制备的Mn-CeO_x(CP)锰铈催化剂相对比,结合XRD、XPS、FESEM和H2-TPR等技术表征,对其NH_3-SCR脱硝催化性能进行了研究。结果表明,金属硝酸盐与柠檬酸的物质的量比是影响Mn-CeO_x(LCS)催化剂脱硝性能的重要因素。虽然两种催化剂中的锰氧化物组分均为无定型,但相较于Mn-CeO_x(CP),Mn-CeO_x(LCS)表面具有较高的锰含量与Oα/(Oα+Oβ)比,其脱硝催化性能也较高;同时,Mn-CeO_x(LCS)锰铈催化剂上有更多的多级孔,有利于气体在催化剂上的吸附和反应。硝酸盐与柠檬酸物质的量比为36∶22的Mn-CeO_x(LCS)锰铈催化剂在80-180℃下脱硝率可达75%-100%;即使通入SO2,180℃下的脱硝率仍可稳定于74%。     

过渡金属对选择性催化还原脱硝CeO_2@TiO_2催化剂低温活性的促进作用

采用过渡金属M(M=Mn、Co、Fe和Cu)掺杂改性自发沉积策略制备的非晶态CeO_2@TiO_2催化剂,考察M-CeO_2@TiO_2选择性催化还原NO_x的低温活性,并通过XRD、TEM、N2吸附-脱附、H2-TPR、NH3-TPD及in-situ FT-IR等表征手段研究M-CeO_2@TiO_2的结构、表面性质以及低温NH3-SCR反应过程。结果表明,M-CeO_2@TiO_2具有更优异的低温氧化还原能力以及更多的表面酸量,且Cu掺杂对CeO_2@TiO_2选择性催化还原NO_x低温活性具有最为显著的促进作用。Cu-CeO_2@TiO_2催化剂在低温NH3-SCR反应过程中同时存在E-R机理和L-H机理,但是由于"快速SCR"使得L-H机理反应起关键作用。     

A catalytic asymmetric synthesis of chiral glycidic acid derivatives through chiral dioxirane-mediated catalytic asymmetric epoxidation of cinnamic acid derivatives

A novel and practical asymmetric synthesis of chiral glycidic acid derivatives involving methyl (2R,3S)-3-(4-methoxyphenyl)glycidate ((2R,3S)-2a), a key intermediate for diltiazem hydrochloride (1), was developed. Treatment of methyl (E)-4-methoxycinnamate ((E)-3a) with chiral dioxirane, generated in situ from a catalytic amount (5 mol %) of an 11-membered C(2)-symmetric binaphthyl ketone (R)-7a, provided (2R,3S)-2a in 92% yield and 80% ee. Other cinnamic acid esters and amides were epoxidized by the use of the same procedure to give the corresponding chiral glycidic acid derivatives with up to 95% yield and 92% ee. Higher enantioselectivities in the asymmetric epoxidation of (E)-cinnamates than that of (E)-stilbene derivatives were observed and were proposed to be attributed to a dipole-dipole repulsion between oxygen atoms of an ester group in the cinnamates and those of the lactone moieties in the binaphthyl dioxirane.     

Mg掺杂In2O3-x催化剂光热催化CO2加氢

为提高光热催化CO₂加氢In₂O₃催化剂的催化活性,采用均相水热法制备Mg (OH)₂-In (OH)₃前驱体,通过高温煅烧和H₂-还原处理得到了富含氧空位的Mg掺杂In₂O_3-x(Mg-In₂O_3-x)催化剂。在300℃、常压、可见光照射条件下,CO₂加氢转化为CO的CO₂转化率可达31.20%,CO产生速率为14.22 mmol·g_cat^-1·h^-1,CO选择性为100%。相比于单一In₂O_3-x催化剂,Mg-In₂O_3-x催化剂光热催化CO₂转化率及CO产生速率明显提高,这归因于Mg成功掺杂到In₂O₃晶格中,促进In₂O₃表面氧空位的形成,进而对可见光响应效率大幅提高,并有效减缓光生电子-空穴的复合。     

Fischer-Tropsch synthesis over ruthenium-promoted Co/Al2O3 catalyst with different reduction procedures

The effect of reduction procedure on catalyst properties, activity and products selectivity of ruthenium-promoted Co/γ-Al2O3 catalyst in Fischer-Tropsch synthesis (FTS) was investigated. Catalyst samples were reduced with different reduction gas compositions and passivated before being characterized by TPR and XRD techniques. Different activity and product selectivity analyses were also performed. These results showed that the catalyst dispersion, particle size, and the degree of reduction changed with different reduction gas compositions, which were resulted from the water partial pressures in reduction process that give varying degrees of interaction with the support. It has been suggested that the FTS activity of cobalt catalyst was directly dependent on the catalyst reducibility. A reduction gas with a molar ratio of H2/He = 1 was used to prevent the formation of Co-support compound during catalyst reduction.     

Mg掺杂In2O3-x催化剂光热催化CO2加氢

为提高光热催化CO₂加氢催化剂In₂O₃的催化活性,采用均相水热法制备Mg(OH)₂-In(OH)₃前驱体,通过高温煅烧和H₂-还原处理得到了富含氧空位的Mg掺杂In₂O_3-x(Mg-In₂O_3-x)催化剂。在300℃、常压、可见光照射条件下,CO₂加氢转化为CO的CO₂转化率可达31.20%,CO产生速率为14.22 mmol·gcat^-1·h^-1,CO选择性为100%。相比于单一In₂O_3-x催化剂,Mg-In₂O_3-x催化剂光热催化CO₂转化率及CO产生速率明显提高,这归因于Mg成功掺杂到In₂O₃形晶格中,促进In₂O₃表面氧空位的形成,进而对可见光响应效率大幅提高,并有效减缓光生电子-空穴的复合。     

A comparison of palladium complexes of BINAP and diphenylphosphinooxazoline ligands in the catalytic asymmetric synthesis of cis-decalins

BINAP and a range of oxazoline-containing phosphinamine ligands were screened in the palladium-catalysed asymmetric intramolecular Heck cyclisation to form cis-decalins. Complexes formed from Pd₂(dba)₃ and BINAP gave cyclised products in up to 65% yield and 85% ee. The t-leucine-derived diphenylphosphinoferrocenyloxazoline ligand afforded our optimal enantioselectivity of 85% for the range of phosphinamine ligands tested. Variation of solvent and base appears to indicate that this system is sensitive to catalyst deactivation and that a combination of either toluene or N-methylpyrrolidine with potassium carbonate as base was required for acceptable catalytic activity. Catalysts prepared from palladium complexes of diphenylphosphinoaryloxazoline ligands were less reactive than the corresponding BINAP catalysts as the optimal yield obtained was 47%.