Merrifield树脂负载的L-脯氨酰L-苏氨酸二肽催化剂的合成及其对不对称Aldol反应的催化性能

制备了Merrifield树脂负载的L-脯氨酰L-苏氨酸二肽催化剂.将制备的催化剂用于催化直接不对称Aldol反应,并探索了溶剂、表面活性剂、催化剂用量、底物等不同条件对其催化性能的影响.结果表明,该催化剂在Tween-20水溶胶束中有很高的催化活性和较好的立体选择性,Aldol反应中部分产率达到85%以上,e.e.值达到78%,且该催化剂具有一定的重复使用性能.     

甲醇气相法制乙酸的Rh／Ys催化剂微观结构与性能关系研究

甲醇气相法制乙酸的Ｒｈ／Ｙｓ催化剂微观结构与性能关系研究柳忠阳，潘平来，彭文庆，袁国卿（中国科学院化学研究所，北京１０００８０）我们曾报道过以聚偏二氯乙烯碳化基为载体的Ｐｈ／Ｙｓ铑催化剂，该催化剂在催化甲醇羰基化制备乙酸的反应中，不仅具有可比拟于均相...     

辛可宁季铵盐的合成及催化不对称烷基化研究

探索了辛可宁季铵盐的通用合成方法, 确定辛可宁与取代苄溴在四氢呋喃中回流为最优反应途径, 合成了11个羟基保留的辛可宁季铵盐, 收率57%~88%, 并合成了4种羟基保护季铵盐, 羟基成醚过程在生成季铵盐前后均可进行, 总收率62%~71%; 羟基酯化只能在生成季铵盐之后进行, 总收率78%. 本文共合成了15个季铵盐(Cn-1~Cn-15), 其中5个为新化合物, 另有4个的合成方法未见文献报道. 选用该类季铵盐催化剂催化二苯亚甲基甘氨酸叔丁酯的不对称苄基化反应, 结果发现, 催化剂苄基具有4-Br取代或羟基成醚均有助于提高反应产物的对映选择性. Cn-9可得到最优的反应结果, 产率93%, e.e.值91%.     

新型层状晶态聚(苯乙烯-苯乙烯基膦酸)-磷酸锌铵有机聚合物-无机杂化材料的合成与表征

将苯乙烯-苯乙烯基膦酸共聚物、 二水合醋酸锌和磷酸二氢铵在温和的条件下反应, 通过调节无机磷酸盐和有机膦酸的比例, 合成了一系列有机聚合物-无机杂化材料聚(苯乙烯-苯乙烯基膦酸)-磷酸锌铵. 通过FTIR, TG, XRD, SEM和TEM等手段对其进行表征并测试了其催化性能. 结果表明, 聚(苯乙烯-苯乙烯基膦酸)-磷酸锌铵是一种新型层状晶态的有机聚合物-无机杂化材料, 具有较高的热稳定性和特殊的多孔结构. 将其作为催化剂载体, 以芳香二胺作为连接基团, 轴向固载手性Salen Mn(Ⅲ)制备了多相催化剂, 并用于非功能化烯烃的不对称环氧化反应. 催化实验结果表明, 该催化剂在以m-CPBA/NMO为氧化体系催化α-甲基苯乙烯和茚的反应中显示出优良的催化性能, 如催化茚的e.e.值可达99%, 并且可以回收利用, 循环使用8次仍具有较好的催化活性, 具有潜在的工业应用价值.     

有机催化丙二酸酯与β-硝基烯烃的不对称 Michael加成反应

将金鸡纳生物碱衍生物用于催化丙二酸酯和β-硝基芳基乙烯的不对称Michael加成反应。考察溶剂、温度及催化剂用量对反应催化性能的影响。结果表明,最佳催化条件为5 mol%催化剂1e,甲苯为溶剂,0℃反应。得到了86～93%的化学产率和最高达99%ee的对映选择性。     

氢对气相甲醇羰基化催化体系的影响

 主要讨论了氢对甲醇气相羰基化催化体系的影响．采用多孔碳化聚偏二氯乙烯小球负载金属镍催化体系，在不同进气条件下进行甲醇羰基化反应，得到不同氢含量时催化剂的活性和稳定性数据，以及氢对催化体系的微扰数据，并对催化剂的表面形态用SEM进行了表征，以评价氢的影响．从三个方面分析了氢对气相甲醇羰基化催化体系的影响，认为适量存在的氢对长时间保持催化剂活性是有利的．     

SiO_2微球负载的CeCl_3·7H_2O-NaI催化邻氨基苯硫酚与高位阻α,β-不饱和酮的Michael加成及其串联反应

以粒径为5μm的SiO2微球为载体,制备了CeCl3·7H2O-NaI/SiO2负载催化剂,用SEM、EDS和XRD对其结构进行表征,并考察了该催化剂对邻氨基苯硫酚和高位阻α,β-不饱和酮的Michael加成及Michael加成-胺酮缩合串联反应的催化性能.研究结果表明,该催化体系能够很好地催化邻氨基苯硫酚类亲核试剂与高位阻α,β-不饱和酮反应,得到中等及优良的产率;催化剂使用5次,其形貌不变,但金属铈有少量流失,致使其催化活性有所下降.研究还发现,该催化剂对该串联反应的催化模式为,既催化Michael加成又催化胺酮缩合反应.     

甲醇气相法羰基化合成乙酸的镍催化剂(YhNi)的研究

本文报导了一种新型的甲醇羰基化生产乙酸的镍催化剂.由于选用了由聚偏二氯乙烯热裂解制得的特殊碳化物为载体,所以该催化剂有大比表面积,孔径分布均匀,并有优良的热稳定性和机械强度,其催化甲醇羰基化的速率在相对温和的条件下达到582克乙酸/克镍/时,高于文献报导的镍金属催化剂.     

稻壳碳基固体酸催化剂的制备及在木糖脱水制备糠醛反应中的催化性能

以工业生产中碱法溶硅剩余的稻壳残渣为碳源,采用硫酸磺化法制备稻壳碳基固体酸催化剂,考察了其催化木糖脱水制备糠醛的性能.采用红外光谱、元素分析及表面酸浓度测定等手段对催化剂进行了表征.对固体酸催化剂的制备条件进行了优化,所得催化剂的表面酸浓度可达1.03 mmol/g.以木糖脱水制备糠醛为模型反应,考察了溶剂类别、反应温度和反应时间对固体酸催化剂催化性能的影响.实验结果表明,以二甲基亚砜(DMSO)为反应溶剂效果优于水,并且随着反应温度的升高和反应时间的延长,反应产率逐渐增加,最高可达75.8%.此外,还对催化剂的循环性能进行了研究,探讨了其失活原因和再生方法.     

碳氮复合材料负载镍甲醇羰基化催化剂的研究

通过碳化由偏氯乙烯和丙烯腈悬浮共聚得到的前体,制得碳氮复合材料,将其负载金属镍后即得气相甲醇羰基化反应的催化剂。分别采用扫描电镜(SEM)、氮气吸附、XPS、电子探针(EPMA)等方法对该材料及由其制得的催化剂进行表征,证明该催化剂中的镍呈高度分散的纳米粒子状态。采用固定床反应器对该催化剂进行催化性能测试,结果表明该催化剂在较低金属镍负载量及较温和的条件下即可具有较好的催化性能。该催化剂的最佳镍负载量为1.5%左右。     

新轴手性N,N-Dioxide Biscarbolin衍生物催化酮亚胺的不对称硅氢化反应

以L-色氨酸为原料合成了5个伯酰胺结构的轴手性双咔啉N—O催化剂N2,N2'-二氧-9,9'-二甲基-3,3'-取代甲酰胺-β-双咔啉(4A~4E),并用于不对称催化酮亚胺的还原反应.结果表明,催化剂的催化转化率较高(80%~98%),立体选择性(e.e.值)较好,其中催化剂N2,N2'-二氧-9,9'-二甲基-3,3'-环己基甲酰胺-β-双咔啉(4B)的催化转化率达到了98%,e.e.值达68%.     

Polymer-supported enantioselective bifunctional catalysts for nitro-Michael addition of ketones and aldehydes

Introduction of an L-amino acid as a spacer and a urea-forming moiety in a polymer-supported bifunctional urea-primary amine catalyst, based on (1R, 2R)-(+)-1,2-diphenylethylenediamine, significantly improves the catalyst's activity and stereoselectivity in the asymmetric addition of ketones and aldehydes to nitroolefins. Yields and enantioselectivities, unprecedented for immobilized catalysts, were obtained with such challenging donors as acetone, cyclopentanone, and α,α-disubstituted aldehydes, which usually perform inadequately in this reaction (particularly when a secondary-amine-based catalyst is used). Remarkably, though in the examined catalysts the D-amino acids as spacers were significantly inferior to the L?isomers, for the chosen configuration of the diamine (match-mismatch pairs) the size of the side chain of the amino acid hardly influenced the enantioselectivity of the catalyst. These results, combined with the reactivity profile of the catalysts with substrates bearing two electron-withdrawing groups and the behavior of the catalysts' analogues based on tertiary (rather than primary) amine, suggest an enamine-involving addition mechanism and a particular ordered C-C bond-forming transition state as being responsible for the catalytic reactions with high enantioselectivity.     

Enantioselective formation of tert-alkylamines by desymmetrization of 2-substituted serinols

Novel enantioselective desymmetrization of 2-substituted 2-amino-1,3-propanediols has been established to generate asymmetric quaternary carbon centers comprising an amino group. Enantioselective as well as chemical conversion proved to be greatly dependent on the protecting group of the amino group in the substrate, desymmetrizing reagent, base, solvent, and naturally, catalyst. The highly effective desymmetrization has been implemented by using N-benzoylated substrates with benzoyl chloride and triethylamine in the presence of tetraphenylbisoxazoline (24)-CuCl(2) complex in THF at ambient temperature. An extensive survey of catalysts revealed that dimethylmalonate-bridged bisoxazoline-CuCl(2) complexes were superior. Among them, the tetraphenylbisoxazoline (24)-CuCl(2) complex turned out to work most efficiently with a wide array of the substrates. All the examined substrates, with the exception of 2-phenylserinol 36, were desymmetrized in the presence of 24-CuCl(2) complex to give high enantioselectivities ranging from 85 to 95 % ee. Complementary use of the diisopropylbisoxazoline (22)-CuCl(2) complex has remedied the mediocre desymmetrization of 36 to give a significantly improved enantioselectivity from 63 to 83 % ee.     

Polymer‐Supported Enantioselective Bifunctional Catalysts for Nitro‐Michael Addition of Ketones and Aldehydes

Introduction of an L ‐amino acid as a spacer and a urea‐forming moiety in a polymer‐supported bifunctional urea–primary amine catalyst, based on (1R, 2R)‐(+)‐1,2‐diphenylethylenediamine, significantly improves the catalyst’s activity and stereoselectivity in the asymmetric addition of ketones and aldehydes to nitroolefins. Yields and enantioselectivities, unprecedented for immobilized catalysts, were obtained with such challenging donors as acetone, cyclopentanone, and α,α‐disubstituted aldehydes, which usually perform inadequately in this reaction (particularly when a secondary‐amine‐based catalyst is used). Remarkably, though in the examined catalysts the D ‐amino acids as spacers were significantly inferior to the L isomers, for the chosen configuration of the diamine (match–mismatch pairs) the size of the side chain of the amino acid hardly influenced the enantioselectivity of the catalyst. These results, combined with the reactivity profile of the catalysts with substrates bearing two electron‐withdrawing groups and the behavior of the catalysts’ analogues based on tertiary (rather than primary) amine, suggest an enamine‐involving addition mechanism and a particular ordered C? C bond‐forming transition state as being responsible for the catalytic reactions with high enantioselectivity.     

New catalysts for the base-promoted isomerization of epoxides to allylic alcohols. Broadened scope and near-perfect asymmetric induction

Optically active (1S,3R,4R)-3-[N-(trans-2,5-dialkyl)pyrrolidinyl]methyl-2-azabicyclo-[2.2.1]heptanes were evaluated as catalysts for the enantioselective beta-elimination of meso-epoxides. The (2R,5R)-dimethylpyrrolidinyl-substituted catalyst 4 exhibited exceptionally high enantioselectivity and reactivity, and several substrates were rearranged with enantioselectivities of 98-99% ee. In addition, the use of 4 allowed the first successful, true catalytic rearrangement of the difficult substrates cyclopentene oxide (81%, 96% ee) and (Z)-4-octene oxide (80%, 91% ee).     

Wang Resin-supported Enantioselective Catalysts for the Asymmetric Michael Additions ofAcetone to β-Nitroolefins

Two Wang resin-supported (1R,2R)-(+)-1,2-DPEN(DPEN=diphenylethylenediamine) catalysts were synthesized from cyanuric chloride and trimesoyl chloride, respectively. These two catalysts were characterized by FTIR, TGA and elemental analysis. The results demonstrated that (1R,2R)-(+)-1,2-DPEN was successfully bonded to the surface of Wang resin through the amido linkage. Subsequently, the asymmetric Michael addition of acetone to β-nitrostyrene was employed to evaluate their catalytic performance. It was found that the catalyst generated from trimesoyl chloride exhibited much better catalytic behavior than our previously reported catalyst, likely attributed to the multiple hydrogen-bond interaction between β-nitrostyrene and amide group, which made the catalytic transition intermediates more stable. Under the optimal conditions, 76.1% β-nitrostyrene conversion and 93.8% enantioselectivity were obtained. Finally, the generality of this catalyst was examined with Michael additions of acetone to β-nitroolefins and excellent enantioselectivities(91.9% to 99.9%) were achieved.     

Growth of Single-Walled Carbon Nanotubes with Controlled Structure: Floating Carbide Solid Catalysts

Single-walled carbon nanotube (SWNT) horizontal arrays with specific chirality can be enriched using solid carbide catalysts on substrates. However, scale-up production by continuous loading of the solid catalysts onto the substrates is challenging. Described here is the preparation of a floating carbide solid catalyst (FSC) for the controlled growth of SWNTs. The FSC, titanium carbide (TiC) nanoparticle, was directly obtained in the carrier gas phase by decomposition and carbonization of the titanocene dichloride precursor at high temperature. By using the TiC nanoparticle FSC, both SWNT horizontal arrays and randomly distributed networks can be obtained. The chirality of the as-grown SWNTs were thermodynamically controlled to have fourfold symmetry. Further optimization of growth condition resulted in an abundance of (16,8) tubes with about a 74 % content. This FSC chemical vapor deposition (FSCCVD) method has potential for realizing mass growth of SWNTs with controlled structures.     

Bifunctional hydrogen-bond donors that bear a quinazoline or benzothiadiazine skeleton for asymmetric organocatalysis

Hydrogen-bond (HB)-donor catalysts that bear a 2-aminoquinazolin-4-(1H)-one or a 3-aminobenzothiadiazine-1,1-dioxide skeleton have been developed, and it has been shown that these catalyst motifs act similarly to other HB-donor catalysts such as thioureas. The highly enantioselective hydrazination of 1,3-dicarbonyl compounds was realized even at room temperature with up to 96% ee for 2-aminoquinazolin-4-(1H)-one-type catalysts, which were more effective than the corresponding urea and thiourea catalysts. In addition, benzothiadiazine-1,1-dioxide-type catalysts were shown to promote the isomerization of alkynoates to allenoates with high enantioselectivity. To overcome the problem that the products were obtained as mixtures with the starting alkynoates, we developed the tandem isomerization and cycloaddition of alkynoates for the synthesis of advanced chiral compounds such as bicyclo[2.2.1]heptenes and 3-alkylidene pyrrolidine without a significant loss of enantioselectivity.     

Phase-transfer catalyzed asymmetric arylacetate alkylation

Phenethyl arylacetates are alkylated under phase-transfer conditions with cinchona catalysts with alkyl halides in high yield with excellent enantioselectivity (84-99% ee) following recrystallization. Cinchonidine (CD) derived catalyst gave the (R)-product and cinchonine (CN) catalyst produced the (S)-product. The phenethyl (PE) ester group is removed, using ammonium formate and catalytic Pd/C, to give alkylated carboxylic acid products in high selectivity. The utility of the approach is demonstrated by a direct synthesis of (S)-naproxen^™.     

Application of a C2-symmetric copper carbenoid in the enantioselective hydrosilylation of dialkyl and aryl-alkyl ketones

We report excellent reactivity and enantioselectivity of a C(2)-symmetric copper-bound N-heterocyclic carbene (NHC) in the hydrosilylation of a variety of structurally diverse ketones. This catalyst exhibits extraordinary enantioselctivity in the reduction of such challenging substrates as 2-butanone and 3-hexanone. Even at low catalyst loading (2.0 mol %), the reactions occur in under an hour at room temperature and often do not require purification beyond catalyst and solvent removal. The scope of this transformation was investigated in the reduction of 10 aryl-alkyl and alkyl-alkyl ketones.