Novel chiral dendritic diphosphine ligands for Rh(I)-catalyzed asymmetric hydrogenation: remarkable structural effects on catalytic properties

[reaction: see text] A series of dendritic ligands with a chiral diphosphine located at the focal point have been synthesized through coupling of pyrphos 2 with Fréchet-type polyether dendron 3. The relationship between the primary structure of the dendrimer and its catalytic properties was established in the Rh-catalyzed asymmetric hydrogenation of alpha-acetamido cinnamic acid 4. A remarkable structural effect on catalytic activity was observed.     

Synthesis of Dendritic BINAP Ligands and Their Applications in Asymmetric Hydrogenation

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A recyclable dendritic osmium catalyst for homogeneous dihydroxylation of olefins

A series of osmate (OsO₄²⁻) core dendrimers was prepared by an ion-exchange technique through the mixing of K₂OsO₄ and a bis(quaternary ammonium bromide) core dendrimer, which consisted of poly(benzyl ether) dendron. By employing an osmate core dendrimer as a homogeneous catalyst, dihydroxylation reactions of olefins proceeded rapidly, and the dendritic osmium catalyst was recovered by reprecipitation and then reused. Furthermore, a dendritic effect on the recyclability of a catalyst was observed. In the case of asymmetric dihydroxylation reactions, the corresponding diol was obtained in a high chemical yield with a fair enantiomeric excess (ee). In this case, not only the dendritic osmium catalyst but also the chiral ligand could be recovered by reprecipitation and reused efficiently up to five times.     

新型树状结构手性联二萘酚衍生物的合成及催化性能研究

报道了树状结构的手性联二萘酚(BINOL)配体的合成及其在二乙基锌对醛的不对称加成反应中的应用.(R)-2,2′-二羟基-1,1′-联萘-3,3′-二羧酸与末端为氨基的Frechet聚芳醚型树状分子经缩合反应,以中等产率得到0～3代的树状分子配体,用¹HNMR,IR和MALDI-TOF质谱进行了结构表征.这些树状手性配体与Ti(OPrⁱ)₄在无水甲苯溶液中形成的配合物是二乙基锌对醛不对称加成反应的高效催化剂,树状分子载体的体积对催化剂的对映选择性没有明显的影响.以邻氯苯甲醛为底物时,反应的对映选择性随树状分子代数的增加而有所提高.     

Recent advances in the application of chiral phosphine ligands in Pd-catalysed asymmetric allylic alkylation

One of the most powerful approaches for the formation of simple and complex chiral molecules is the metal-catalysed asymmetric allylic alkylation. This reaction has been broadly studied with a great variety of substrates and nucleophiles under different reaction conditions and it has promoted the synthesis of new chiral ligands to be evaluated as asymmetric inductors. Although the mechanism as well as the active species equilibria are known, the performance of the catalytic system depends on the fine tuning of factors such as type of substrate, nucleophile nature, reaction medium, catalytic precursor and type of ligand used. Particularly interesting are chiral phosphines which have proved to be effective asymmetric inductors in several such reactions. The present review covers the application of phosphine-donor ligands in Pd-catalysed asymmetric allylic alkylation in the last decade.     

Synthesis of New Chiral Phosphine Ligands and Their Application in Asymmetric Hydrogenation of Ketones

The design of new chiral ligands is the key in the development of transition metal catalyzed asymmetric synthesis. Many chiral diphosphine ligands have been prepared and applied in asymmetric catalytic reactions with excellent enantioselectivities. Among the chiral diphosphine ligands that have been reported, the atropisomeric C2-symmetric phosphines with a biaryl scaffold initiated by Noyori and co-workers with BINAP were found to have the widest application in the transition metal catalyze…     

Synthesis of Dendritic Schiff Base Ligands for Titanium Catalyzed Enantioselective HDA Reaction of Danishelfsky‘ s Diene with Aldehydes

A new type of dendritic NOBIN derived Schiff base ligands has been synthesized and applied to titanium catalyzed hetero-Diels-Alder reaction of Danigheifsky‘ s diene and aldehydes, affording the corresponding 2-substituted 2,3-dihydro-4H-pyran-4-one in good yields and moderate enantioselectivities (up to 59.2% ee). It was found that the size of dendron attached to the tridentated ligands has slight impact on the enantioselectivtty of the reaction and the second generation of dendritic ligand exhibited the best enantioselectivity.     

Synthesis of 7,7’-Disubstituted BINAP and Their Application in Asymmetric Catalytic Reaction

The design of new chiral ligands plays a very important role in the development of transition metal catalyzed asymmetric synthesis. Many chiral diphosphine ligands have been prepared and applied in asymmetric catalytic reactions with excellent enantioselectivities. Among the chiral diphosphine ligands reported, BINAP was found to have been the widest application in the transition metal catalyzed reaction. Recently we have developed a novel oxovanadium (Ⅳ) complex catalyst for the oxidative …     

C2, Symmetric Dibenzosuberanes as Templates for the Chirality Determination of Helicenes and Their Applications as Optically Switchable Memory Device

We have recently developed a new type of chiral templates, dibenzosuberanes. Thess C₂, symmetric diaryl modifiers have been successfully applied to the synthesis of chiral triarylcarbenium ions. They can serve as catalysts in the asymmetric Mukaiyama aldol reactions with moderate enantioselectivities of up to 50% [1]. We have subsequently found that one major side reaction between the catalyst and the substrate-silyl ketene acetal which releases extra silyl-X species is responsible for the erosion of asymmetric induction. The dibenzosuberane scaffold was found essential to prevent this type of side reaction. For the selection of carbenium counter ions, we have resorted to the chloride in order to completely suppress the undesired silyl catalysis [2].     

手性羰基铁体系催化酮的不对称氢转移氢化

手性羰基铁络合物很少被用于芳香酮的不对称氢转移氢化.利用不同的羰基铁络合物与手性双胺双膦配体现场络合,形成手性胺膦铁催化体系.考察了它们对多种芳香酮的不对称氢转移催化氢化性能.结果表明,三核的手性胺膦铁簇合物是催化芳香酮不对称氢转移氢化的较好体系.当用三核的铁簇合物[Et₃NH]⁺[HFe₃(CO)₁₁]^-体系催化1,1-二苯基丙酮的氢化时,最高可获得98%的对映选择性.通过现场红外光谱测定,揣测羰基铁簇合物Fe₃(CO)₁₂在催化反应过程中保持三核的簇合物的簇骼不变.     

Synthesis of Novel Chiral Dibenzo [ a, c ] cycloheptadiene Bis(oxazoline) and Catalytic Asymmetric Reactions

Over the last decade, C2-symmetric chiral oxazoline metal complexes have been recognized as an effective classof chiral catalyst in a variety of transition metal catalyzed asymmetric reactions. [1] High catalytic activities and enantiomeric excesses have been obtained using C2-symmetric chiral ligands in conjunction with suitable transition metal ion, for example, the hydrosilylation of ketone, allylic alkylation, Michael addition, Diels-Alder cycloaddition, and cyclopropanation. Thus, the design and synthesis of new chiral oxazoline ligands have inspired many scientists to work with great efforts.     

Synthesis and application of peripherally alkyl-functionalized dendritic pyrphos ligands: Homogeneous-supported catalysts for enantioselective hydrogenation

A new series of dendritic ligands with a chiral diphosphine located at the focal point have been synthesized through coupling of (R,R)-3,4-bis(biphenylphosphino)pyrrolidine (pyrphos) with peripherally alkyl-functionalized benzoic acid dendrons. These ligands were employed in the Rh-catalyzed asymmetric hydrogenation of prochiral dehydroamino acids, exhibiting excellent catalytic activities and enantioselectivities. The second-generation dendritic catalyst could be recovered by simple liquid–liquid biphasic separation and reused four times without serious loss of its activity and selectivity.     

金属催化的不对称氢化反应研究进展与展望

手性过渡金属络合物催化的不对称氢化反应是合成光学活性化合物的重要方法. 本文从手性配体及手性催化剂、不对称催化新反应、新方法和新策略三个方面简要评述新世纪以来过渡金属催化的不对称氢化反应研究领域的新进展. 从新世纪初至今, 手性单磷配体得到了复兴, 出现了如MonoPhos、SiPhos、DpenPhos等高效单齿亚磷酰胺酯配体; 磷原子手性(P-手性)配体也得到了快速发展, 如BenzP*、ZhanPhos、TriFer等已成为新的高效手性双膦配体; 螺环骨架手性配体成为新世纪手性配体设计合成的亮点, 除了SiPhos、SIPHOX、SpinPHOX等高效手性螺环配体外, 手性螺环吡啶胺基磷配体SpiroPAP的铱催化剂成为目前最高效的分子催化剂. 不对称催化氢化新反应研究也取得了突破, 如非保护烯胺、杂芳环化合物及N-H亚胺的氢化等反应都实现了高对映选择性. 自组装手性催化剂、树枝状手性催化剂、铁磁性纳米负载的可回收手性催化剂, 以及“混合”配体手性催化剂等新方法和新策略也在不对称催化氢化反应中得到了应用. 然而, 手性过渡金属络合物催化的不对称氢化研究仍然充满挑战, 也期待新的突破.     

Synthesis of dendritic catalysts and application in asymmetric transfer hydrogenation

Frechet-type core-functionalized chiral diamine-based dendritic ligands and hybrid dendritic ligands condensed from polyether wedge and Newkome-type poly(ether-amide) supported multiple ligands were designed and synthesized. The solubility of hybrid dendrimers was found to be finely controlled by the polyether dendron. The catalytic efficiency and recovery use of dendritic ruthenium complexes were compared in the transfer hydrogenation of acetophenone. The core-functionalized dendritic catalysts demonstrated much better recyclability, which verified the stabilizing effects of the bulky polyether wedge on the catalytically active complex. Moreover, the dendritic catalysts were applied in the asymmetric transfer hydrogenation of ketones, enones, imine, and activated olefin, and moderate to excellent enantioselectivitiy was achieved comparable to that of monomeric catalysts.     

手性二茂铁类配体在钯催化不对称反应中的应用

本文综述了近10 年来手性二茂铁类配体在钯催化不对称烯丙基取代反应,包括各种不同底物的烯丙基烷基化、烯丙基胺基化和烯丙基磺酰化反应中的应用,并对其在不对称Claisen 重排、不对称Diels-Alder 反应、不对称Heck 反应、不对称羰基化、不对称氢化硅烷化和不对称碳碳键断裂等反应中的应用进行了综述,对部分反应的机理和该领域的发展前景进行了讨论。     

Peptide Deravatives as New Chiral Ligands for Enantioselective Phenylacetylene Addition to Aldehydes

The asymmetric addition of alkynylzinc to aldehydes is an important method of synthesizing chiral propargyl alcohols, which are important precursors to many chiral organic compounds. Recently, many significant chiral ligands in this area have been disclosed.[1] Use of a short peptide as a catalyst would allow expansion beyond the (still uncharted) repertoire of single amino acids, while conserving the advantages of a small molecule catalyst. To the best of our knowledge,no results of peptide derivatives as chiral ligands in this reaction has been disclosed to date.[2] Herein, we report the initial results of peptide derivatives, which have been used directly as a chiral ligand in this reaction (Scheme 1).     

Suzuki-Miyaura reaction in water, conducted by employing an amphiphilic dendritic phosphine-palladium catalyst: a positive dendritic effect on chemical yield

A series of amphiphilic dendritic ligands with a phosphine core was synthesized by use of tris(4-hydroxyphenyl)phosphine oxide and poly(benzyl ether) dendron. The corresponding phosphine-palladium core dendrimers were applied as a catalyst to an aqueous-media Suzuki-Miyaura reaction. A positive dendritic effect on chemical yields of cross-coupling products was observed.     

Spiro Skeletons: A Class of Privileged Structure for Chiral Ligand Design

This Focus Review highlights the exciting results obtained in the area of asymmetric catalysis using spirobiindane‐ or spirobifluorene‐based chiral ligands. The spiro, mono, and bidentate ligands have been successfully applied in a wide range of transition‐metal‐catalyzed asymmetric reactions, including hydrogenations, carbon–carbon and carbon–heteroatom coupling reactions, with superior or comparable enantioselectivities to those obtained by using the related ligands bearing other backbones, thus proving that the spiro skeleton is a type of privileged structure for chiral ligand design. It is expected that the spiro concept for chiral ligand design will stimulate the future efforts to understand the features that account for their broad applicability and to apply this understanding to seek new privileged chiral ligands and catalysts.     

Synthesis of Dendrimer-supported Chiral Bis(oxazoline) Ligands and Their Applications in Aldol Reaction via Aqueous Media

Chiral bis(oxazoline) ligands have been applied in many enatioselective reactions. Recently, studies of the immobilization of bis(oxazoline) on both soluble and insoluble supports have been of great interest. Among the different methods to anchor the homogeneous catalysts, a soluble, polymer-supported catalyst usually achieves higher stereoselectivity and activity because the catalysis can be separated and recycled via simple methods such as solvent precipitation. Dendrimers are highly branche…     

Novel Schiff base ligands derived from Cinchona alkaloids for Cu(II)-catalyzed asymmetric Henry reaction

A new series of Schiff bases derived from Cinchona alkaloids were developed as chiral ligands for the copper(II)-catalyzed asymmetric Henry reaction. The optimized catalyst can promote the Henry reaction of both aromatic and aliphatic aldehydes with nitromethane or nitroethane. Those reactions can afford the chiral β-nitro alcohol adducts with high enantioselectivities.