Light‐Sensitive and Recoverable N‐Heterocyclic Carbene Copper(I) Complex in Homogeneous Catalysis

The synthesis of a light‐responsive N‐heterocyclic carbene copper(I) complex by introducing a nitrobenzospiropyran unit into the carbene ligand was developed. The solubility of this complex was controlled through reversible conversion between its netural and ionic states using ultraviolet light irradiation. Taking advantage of such a light‐sensitive property facilitated its recovery and reuse in copper(I)‐catalyzed homogeneous oxidation and “click” reactions.

     

Versatile Phosphite Ligands Based on Silsesquioxane Backbones

Silsesquioxanes are employed as ligand backbones for the synthesis of novel phosphite compounds with 3,3′‐5,5′‐tetrakis(tert‐butyl)‐2,2′‐dioxa‐1,1′‐biphenyl substituents. Both mono‐ and bidentate phosphites are prepared in good yields. Two types of silsesquioxanes are employed as starting materials. The monophosphinite 1 and the monophosphite 2 are prepared from the thallium silsesquioxide derived from a completely condensed silsesquioxane framework (c‐C₅H₉)₇Si₇O₁₂SiOTl. The diphosphite 3 is synthesized starting with the incompletely condensed monosilylated disilanol (c‐C₅H₉)₇Si₇O₉(OSiMePh₂)(OH)₂. For monophosphite 2 , the corresponding trans‐[PtCl₂( 2 )] complex 4 is characterized by NMR spectroscopy as well as by X‐ray crystallography, as the first example of a completely condensed oxo‐functionalized silsesquioxane framework. The coordination of the bidentate ligand 3 towards Pd, Mo and Rh is studied, both by NMR spectroscopy as well as by X‐ray crystallography. Various modes of coordination are shown to be possible. The molecular structures for the complexes trans‐[PdCl₂( 3 )] ( 5 ), cis‐[Mo(CO)₄( 3 )] ( 6 ) and the dinuclear complex [{Rh(μ‐Cl)(CO)}₂(κ²‐ 3 )] ( 7 ) have been determined. In the rhodium‐catalyzed hydroformylation of 1‐octene high activities, with turnover frequencies of up to 6800 h⁻¹, are obtained with these new nanosized phosphorus ligands.     

Alternating Copolymerization of Cyclohexene Oxide and CO2 Catalyzed by Zinc Complexes with New 3‐Amino‐2‐cyanoimidoacrylate Ligands

New 3‐amino‐2‐cyanoimidoacrylate ligands with varying steric demands have been synthesized. Zinc acetate complexes of these ligands catalyze the copolymerisation of CO₂ and cyclohexene oxide, showing high activities (TOF up to over 200 h⁻¹).     

A Practical Method for Targeted Library Design Balancing Lead‐like Properties with Diversity

Choosing the right compounds to synthesise from large virtual combinatorial libraries is a current challenge for the pharmaceutical industry. Herein we describe a highly optimised method that aligns lead‐like properties with compound diversity. The methods are illustrated by considering a two‐dimensional library based on the interesting spirocyclic bis‐azetidine template.

     

Ruthenium Phenylindenyl Complex as an Efficient Transfer Hydrogenation Catalyst

An efficient and green protocol for the transfer hydrogenation of carbonyl and imine compounds is presented. The transformations are catalysed by the inexpensive and easily synthesised complex [RuCl(PPh₃)(3‐phenylindenyl)]. Its catalytic activity was compared to that of the most commonly encountered ruthenium complexes in transfer hydrogenation reactions involving several protypical substrates.     

Alternating Copolymerization of Carbon Dioxide and Cyclohexene Oxide and Their Terpolymerization with Lactide Catalyzed by Zinc Complexes of N,N Ligands

For the alternating copolymerization of CO₂ and cyclohexene oxide, a variety of zinc acetate complexes with new aminoimidoacrylate ligands has been synthesized and tested as catalysts. All complexes catalyzed the reaction and structure‐activity investigations revealed that the highest activities and selectivities were reached when the ligand’s aromatic rings were 2,6‐substituted by alkyl groups of different size (isopropyl versus methyl) and when the ligand backbone embodied an electron‐withdrawing cyano group. Furthermore, these complexes catalyzed the terpolymerization of CO₂, cyclohexene oxide and lactide to give poly(cyclohexyl carbonate‐co‐lactide) and the composition of the polymer was adjustable by the monomer feed.     

均相催化剂研究进展

综述了国内外均相催化的最新进展，包括均相催化氧化、烯烃聚合均相催化、加氢均相催化、均相催化多相化新进展及均相催化机理等。     

Ligand-based virtual screening, parallel solution-phase and microwave-assisted synthesis as tools to identify and synthesize new inhibitors of mycobacterium tuberculosis

In an attempt to identify new inhibitors of the growth of Mycobacterium tuberculosis (MTB), the causative agent of tuberculosis, a procedure for the generation, design, and screening of a ligand-based virtual library was applied. This used both an in silico protocol centered on a recursive partitioning (RP) model described herein, and a pharmacophoric model for antitubercular agents previously generated by our research group. Two candidates emerged from databases of commercially available compounds, both characterized by a minimum inhibitory concentration (MIC) of 25 microg mL(-1). Based on these compounds, two series of derivatives were synthesized by both parallel solution-phase and microwave-assisted synthesis, leading to enhanced antimycobacterial activity. During both the design and synthesis, attention was focused on the efficient allocation of available resources with the aim of reducing the overall costs associated with calculation and synthesis.     

烯烃氢甲酰化反应催化剂的研究进展

综述了烯烃氢甲酰化反应的催化剂体系 ,通过对发展较成熟的烯烃氢甲酰化均相催化体系缺点的分析 ,引入近 2 0年来发展起来的水溶性膦配体和过渡性金属配位生成的水 /有机两相催化体系 ,对其催化机理、优点和最新发展动态进行了评述 ;最后重点介绍了负载水相催化体系的组成、优点、水溶性配体和已报道的此类催化剂。     

New Chiral Diphosphine Ligands Designed to have a Narrow Dihedral Angle in the Biaryl Backbone

A series of novel optically active diphosphine ligands, (4,4′‐bi‐1,3‐benzodioxole)‐5,5′‐diylbis(diarylphosphine)s ( 6 ), which are called SEGPHOS, has been designed and synthesized with dihedral angles in the Ru complexes being less than that in the corresponding BINAP‐Ru complex. The stereorecognition abilities of SEGPHOS‐Ru complex catalysts in the asymmetric catalytic hydrogenation of a wide variety of carbonyl compounds are superior to those observed with BINAP‐Ru complex catalysts.     

Rhodium‐Catalyzed Asymmetric 1,4‐Additions,in Water at Room Temperature,with In‐Flask Catalyst Recycling

Using the newly introduced designer surfactant polyethylene glycol ubiquinol sebacate (PQS), as the platform for micellar catalysis, non‐racemic BINAP has been covalently attached and rhodium(I) inserted to form PQS‐BINAP‐Rh. This species, the first example of a non‐racemically‐ligated transition metal catalyst‐tethered amphiphile, can be utilized for Rh‐catalyzed asymmetric conjugate addition reactions of arylboronic acids to acyclic and cyclic enones. These are performed in water at room temperature, while the catalyst can be recycled without its removal from water in the reaction vessel.     

Josiphos Ligands with an Imidazolium Tag and their Application for the Enantioselective Hydrogenation in Ionic Liquids

Josiphos ligands bearing an imidazolium moiety show high efficiency and reusability for the rhodium‐catalyzed enantioselective hydrogenation of methyl acetamidoacrylate (MAA) and dimethyl itaconate (DMI) in biphasic co‐solvent/ionic liquid combinations.     

Toward a Continuous‐Flow Synthesis of Boscalid®

A two‐step continuous‐flow protocol for the synthesis of 2‐amino‐4′‐chlorobiphenyl, a key intermediate for the industrial preparation of the fungicide Boscalid^® is described. Initial tetrakis(triphenylphosphine)palladium‐catalyzed high‐temperature Suzuki–Miyaura cross‐coupling of 1‐chloro‐2‐nitrobenzene with 4‐chlorophenylboronic acid in a microtubular flow reactor at 160 °C using the tert‐butanol/water/potassium tert‐butoxide solvent/base system provides 4′‐chloro‐2‐nitrobiphenyl in high yield. After in‐line scavenging of palladium metal with the aid of a thiourea‐based resin, subsequent heterogeneous catalytic hydrogenation is performed over platinum‐on‐charcoal in a dedicated continuous‐flow hydrogenation device. The overall two‐step homogeneous/heterogeneous catalytic process can be performed in a single operation providing the desired 2‐amino‐4′‐chlorobiphenyl in good overall yield and high selectivity.     

Highly Selective Copper‐Catalyzed Monoarylation of Aniline

A series of mono‐, bi‐ and tridendate ligands was investigated in the copper‐catalyzed monoarylation of aniline with p‐chloronitrobenzene. Excellent selectivities at high conversions were observed when bridged bisimidazolidenes as well as biphenyl‐bisalkylphosphines were employed. The X‐ray crystal structure of bis(tert‐butyl)biphenylphosphine‐copper complex indicates a significant binding of the metal center to the aryl moiety and, thus, an almost bidendate coordination mode. Chelating bisphosphines, glycol, phenanthroline or other mono‐ to tridendate ligands led to less selective or productive catalysts.     

Ferrocene Redox Controlled Reversible Immobilization of Ruthenium Carbene in Ionic Liquid: A Versatile Catalyst for Ring‐Closing Metathesis

A ferrocene‐tagged ruthenium carbene 15 that can be reversibly immobilized in an ionic liquid (IL) via the controlled oxidation and reduction of a ferrocene tag was prepared. This offers a new strategy which uses redox chemistry to control immobilization and to recycle both the catalyst and the IL. In this experiment, 11 recycles were performed for the ring‐closing metathesis (RCM) of a substrate using 16 as the catalyst in an ionic liquid (IL). More importantly, after the reaction was completed, the ruthenium catalyst was easily separated from the supporting IL by just adding decamethylferrocene (DMFc) to reduce the cationic ferrocene and then extracting it with benzene. Thus, this recycle system offers an easy way to recycle both the ruthenium catalyst and the IL.     

A Convenient High Activity Catalyst for the Sonogashira Coupling of Aryl Bromides

A mixture of Na₂PdCl₄, CuI and (t‐Bu)₃PH⁺BF₄⁻ (molar ratio 4 : 3 : 8) dispersed in H₂N(i‐Pr)₂⁺Br⁻ can be used as a “single source” precatalyst for the Sonogashira coupling of aryl bromides with various aryl‐ and alkylacetylenes in HN(i‐Pr)₂ solvent. Arylacetylenes require just 0.005 mol % of Pd catalyst at 80 °C, with TOFs ranging between 3,200 and 10,000 h⁻¹.