Friedl(a)nder反应中催化体系的研究进展

综述了近几年来国内外Friedlander反应中催化体系的研究进展,其中涉及质子酸碱/Lewis酸碱催化、有机金属催化以及离子液体催化等,并讨论了部分反应机理.     

Friedl nder反应中催化体系的研究进展

综述了近几年来国内外Friedl nder反应中催化体系的研究进展,其中涉及质子酸碱／Lewis酸碱催化、有机金属催化以及离子液体催化等,并讨论了部分反应机理．     

Friedländer反应中催化体系的研究进展

综述了近几年来国内外Friedländer反应中催化体系的研究进展, 其中涉及质子酸碱/Lewis酸碱催化、有机金属催化以及离子液体催化等, 并讨论了部分反应机理.     

铱催化氧化反应的研究进展

铱催化氧化反应是一种合成含氧有机物的方法.综述了近年来铱催化氧化烃类、醇类、酚类、醚类、醛类、酮类及其它有机物的研究进展,并讨论了部分反应机理.     

纳米CoFe2O4催化剂催化转化乙醇制氢

采用溶胶-凝胶法制备了纳米CoFe_2O_4催化剂并用于乙醇裂解和部分氧化制氢反应. CoFe_2O_4催化剂对乙醇催化裂解反应表现出较低的催化活性, 其主要原因可能是催化剂表面积碳以及催化剂粒径的长大. 而纳米CoFe_2O_4催化剂对乙醇部分氧化制氢反应具有良好的催化性能. TPR和XRD结果表明尖晶石结构的CoFe_2O_4相在乙醇部分氧化反应过程中发生了结构变化, 部分生成了CoFe合金相. 另外, 催化剂的粒径没有明显增大. 推测纳米CoFe_2O_4催化剂具有良好催化性能是尖晶石结构的CoFe_2O_4和合金相的协同作用所致.     

钯催化卤代芳烃Ullmann偶合反应

Ullmann偶合反应是有机合成中构建碳—碳键最重要的方法之一. 综述了钯催化卤代芳烃Ullmann偶合反应的研究进展, 其中包括钯催化还原Ullmann偶合反应和钯催化氧化Ullmann偶合反应等两部分.     

α-氰醇立体选择性合成新进展

总结了近十年来立体选择性合成α-氰醇的最新进展, 包括金属配合物催化的醛、酮类底物的立体选择性氢氰化和硅氰化反应, 不含金属的有机小分子催化剂催化的醛、酮类底物的立体选择性硅氰化反应以及生物催化的立体选择性氢氰化反应. 另外对部分反应中涉及的机理也作了介绍.     

过渡金属催化的炔烃复分解反应

综述了过渡金属均相催化的炔烃复分解反应进展,主要分为两部分：一是炔烃复分解反应在炔烃合成中的应用,即从六、七十年代Mortreux催化剂的发现能均相催化炔烃的歧化反应,经过一系列的条件改造,合成了炔醚和二芳基乙炔等化合物,并提出了可能的两种机理：金属卡宾和金属卡拜机理;金属钼和钨的卡拜络合物相继合成,发现此类络合物能够催化官能化的二炔的复分解反应,合成一系列的大环化合物。二是炔烃复分解反应在合成高聚物中的应用,即钙和钨的卡拜络合物被用来催化ROMP和ADIMET反应合成高聚物,改良了的Mortreux催化剂也能催化高聚物的生成,这些高聚物在发光器件、有机"塑料"激光、液晶显示器上都有应用。     

丰产金属催化烯基金属试剂的不对称烯基化反应研究进展

烯丙位手性中心不仅广泛存在于天然产物和药物活性分子中, 也是有机合成中的重要合成砌块. 过渡金属催化烯基金属试剂作为亲核试剂的不对称加成或偶联反应是构建这一结构非常有吸引力的策略之一. 在众多金属催化剂中, 铁钴镍铜等丰产金属由于其独特的催化活性以及低毒性、环境友好等优点而被用来代替铑钯等稀有金属应用于此类不对称烯基化反应中, 并取得了显著的成果. 基于此, 本文将综述丰产金属催化的烯基金属试剂参与的不对称烯基化反应研究进展. 主要包括: (1)钴催化的不对称烯基化反应, (2)镍催化的不对称烯基化反应, (3)铜催化的不对称烯基化反应以及(4)其他丰产金属催化的不对称烯基化反应等四部分.     

单原子分散含Ni复合氢氧化物的制备及POM反应研究

以共沉淀法合成的系列NiMgAl单原子分散复合氢氧化物(NMA-HTLC)为前驱物, 经过焙烧制得复合氧化物催化剂. 并考察了不同催化剂的焙烧温度、还原温度、反应温度对催化甲烷部分氧化反应的影响.     

Fast and non–derivative method based on high–performance liquid chromatography–charged aerosol detection for the determination of fatty acids from Agastache rugosa (Fisch. et Mey.) O. Ktze. seeds

This study utilised response surface methodology to optimise the conditions for the extraction of A. rugosa seeds oil (ARO). Single–factor experiment and response surface methodology (RSM) were performed to identify the extraction time, liquid–solid ratio and extraction temperature that provided the highest yield of ARO. The optimal extraction time, liquid–solid ratio and extraction temperature were 8 h, 4:1 mL/g and 55 °C. The fatty acids (FAs) content and oil yield obtained through the optimised impregnation–extraction process were 19.67 mg/g and 32.1%. These values matched well with the predicted values. Linolenic acid was identified to be the main active ingredient of ARO. The high–performance liquid chromatography–charged aerosol detection method presented here is fast and does not require derivatisation. Therefore, it could be used to quantitatively analyse the FAs present in ARO and applied to detect compounds with low or no ultraviolet response.     

Surface plasmon resonance imaging biosensors for aromatase based on a potent inhibitor and a specific antibody: Sensor development and application for biological material

Aromatase (ARO) is an enzyme with potential diagnostic significance. Aberrant expression of aromatase in tissues is associated with a number of pathological conditions, including tumor of the breast, ovary, testes, liver, adrenal cortex and uterus, as well as endometriosis. Two methods for the highly selective determination of ARO concentration in human tissues by using of two different biosensors co-operating with the surface plasmon resonance imaging technique (SPRI) have been developed. One of the developed biosensors contains immobilised rabbit polyclonal antibody specific for aromatase (Y-ARO), while the other contains immobilized ARO inhibitor-exemestane (E-ARO). Both biosensors specifically bound ARO from analyzed samples. The analytically useful dynamic response range of both biosensors is between 0.3 and 5.0 ng mL^?1. The detection limit (3S.D.) of both biosensors is 90 pg mL^?1. Standard deviation of both biosensors is 1%. Recoveries of ARO spikes are between 97 and 108% for both biosensors under model conditions and for real samples. Albumin and alkaline phosphatase are tolerated for both biosensors up to 10,000 fold excess.      

Heterologous expression, purification, reconstitution and kinetic analysis of an extended type II polyketide synthase.

BACKGROUND: Polyketide synthases (PKSs) are bacterial multienzyme systems that synthesize a broad range of natural products. The 'minimal' PKS consists of a ketosynthase, a chain length factor, an acyl carrier protein and a malonyl transferase. Auxiliary components (ketoreductases, aromatases and cyclases are involved in controlling the oxidation level and cyclization of the nascent polyketide chain. We describe the heterologous expression and reconstitution of several auxiliary PKS components including the actinorhodin ketoreductase (act KR), the griseusin aromatase/cyclase (gris ARO/CYC), and the tetracenomycin aromatase/cyclase (tcm ARO/CYC). RESULTS: The polyketide products of reconstituted act and tcm PKSs were identical to those identified in previous in vivo studies. Although stable protein-protein interactions were not detected between minimal and auxiliary PKS components, kinetic analysis revealed that the extended PKS comprised of the act minimal PKS, the act KR and the gris ARO/CYC had a higher turnover number than the act minimal PKS plus the act KR or the act minimal PKS alone. Adding the tcm ARO/CYC to the tcm minimal PKS also increased the overall rate. CONCLUSIONS: Until recently the principal strategy for functional analysis of PKS subunits was through heterologous expression of recombinant PKSs in Streptomyces. Our results corroborate the implicit assumption that the product isolated from whole-cell systems is the dominant product of the PKS. They also suggest that an intermediate is channeled between the various subunits, and pave the way for more detailed structural and mechanistic analysis of these multienzyme systems.     

Cr(salen) impregnated on silica for asymmetric ring opening reactions and its recovery via desorption/re-impregnation

The impregnation of Cr^III(salen) complexes on silica resulted in a heterogeneous catalyst for the asymmetric ring opening (ARO) reaction of epoxides with good selectivity and acceptable activity. As became apparent from a series of 10 successive batch tests in the ARO reaction of 1,2-epoxyhexane, leaching was limited, while catalytic activity and selectivity were acceptable. Though the support suffered from abrasion in the batch reactor, 80% of the catalyst was easily recoverable via simple extraction from the used solid catalyst and entirely transferable onto a fresh carrier via impregnation. It was shown that 80% of the leached catalyst at the end of the tests could be transformed into a fresh heterogeneous catalyst as well.     

Rhodium-catalyzed asymmetric ring opening of oxabicyclic alkenes with organoboronic acids

The first rhodium(I)-catalyzed asymmetric addition of organoboronic acids to oxabicyclic alkenes is reported. This asymmetric ring-opening (ARO) reaction can proceed in high yield under very mild conditions with electronically diverse organoboronic acids, in a highly diastereoselective and enantioselective manner. [structure: see text]     

Synthesis of enantiopure β-amino alcohols via AKR/ARO of epoxides using recyclable macrocyclic Cr(III) salen complexes

A series of chiral macrocyclic Cr(III) salen complexes 1-8 were synthesized and characterized. These complexes were found to be highly active, regio-, diastereo-, and enantioselective catalysts in aminolytic kinetic resolution (AKR) of racemic trans-epoxides as well as asymmetric ring opening (ARO) of prochiral meso-epoxides with various anilines as nucleophiles at room temperature in 18-24 h. Excellent yields (>99% with respect to the nucleophile) with high enantioselectivity (ee, >99%) of chiral anti-β-amino alcohols was achieved with concomitant recovery of corresponding epoxides in high ee (up to >99%). The complex 1 also catalyzed the ARO of meso-epoxides to provide corresponding syn-β-amino alcohols in high yield (99%) and ee (up to 91%). Due to built-in basic sites in the catalyst, no external base (as an additive) was required to promote AKR and ARO reactions. The catalyst 1 was conveniently recycled several times with retention of its performance. The AKR of trans-stilbene oxide with aniline was successfully demonstrated at relatively higher scale (10 mmol) using the catalyst 1.     

Cr(salen) catalysed asymmetric ring opening of monocyclic terpene-epoxides

The racemic Cr^III(salen) complex was found to be an efficient catalyst for the asymmetric ring opening (ARO) with TMSN₃ of cyclic 1,2-epoxy-terpenes bearing C₄-substituents.     

AROHap: An effective algorithm for single individual haplotype reconstruction based on asexual reproduction optimization

In this paper, a method for single individual haplotype (SIH) reconstruction using Asexual reproduction optimization (ARO) is proposed. Haplotypes, as a set of genetic variations in each chromosome, contain vital information such as the relationship between human genome and diseases. Finding haplotypes in diploid organisms is a challenging task. Experimental methods are expensive and require special equipment. In SIH problem, we encounter with several fragments and each fragment covers some parts of desired haplotype. The main goal is bi-partitioning of the fragments with minimum error correction (MEC). This problem is addressed as NP-hard and several attempts have been made in order to solve it using heuristic methods. The current method, AROHap, has two main phases. In the first phase, most of the fragments are clustered based on a practical metric distance. In the second phase, ARO algorithm as a fast convergence bio-inspired method is used to improve the initial bi-partitioning of the fragments in the previous step. AROHap is implemented with several benchmark datasets. The experimental results demonstrate that satisfactory results were obtained, proving that AROHap can be used for SIH reconstruction problem.     

Cr(Salen)] as a 'bridge' between asymmetric catalysis,Lewis acids and redox processes

An overview focused on the synthesis, structural features and catalytic applications of chiral [Cr(Salen)] complexes is presented. Key aspects of modern organic chemistry such as Lewis acids, asymmetric catalysis and redox processes are strictly connected with chronium-Schiff base complexes. Among the asymmetric transformations mediated by [Cr(Salen)] complexes, Diels-Alder and hetero-Diels-Alder reactions, ARO of epoxides, kinetic resolution of meso-epoxides and Nozki-Hyama reactions are taken into account.     

Highly enantioselective catalytic asymmetric ring opening reaction employing the Daniphos ligand

A set of the recently published planar-chiral Daniphos diphosphine ligands, based on an arene chromium tricarbonyl scaffold, has been applied to the rhodium-catalyzed asymmetric ring opening (ARO) reaction of 1,4-dihydro-1,4-epoxynaphthalene with methanol as the nucleophile. Enantioselectivities of up to 97.5% ee at satisfactory conversions have been obtained. The most successful ligand showed to be a PPh₂/P(t-Bu)₂-substituted derivative. An X-ray structure of this ligand is presented and discussed.