The development of new monometallic bifunctional catalysts with Lewis acid and Lewis base properties, and their application in asymmetric cyanation reactions

Bifunctional catalysts can drastically improve the efficiency of asymmetric processes with respect to enantioselectivity and/or conversion rate. A new type of chiral bifunctional catalyst has been developed recently in the Shibasaki group that contains both Lewis acid and Lewis base moieties. These monometallic and bifunctional phosphinoyl-containing catalysts are able to coordinate both nucleophilic and electrophilic substrates in the transition state. Several successful applications of this new catalytic concept in the field of asymmetric cyanation reactions have already been reported, for example, the asymmetric hydrocyanation of aldehydes and imines as well as the asymmetric Reissert reaction. The development and principle of this catalytic concept as well as main applications thereof are reviewed in this article.     

Facile preparation and reactivity of bifunctional ionic liquid-supported hypervalent iodine reagent: a convenient recyclable reagent for catalytic oxidation

Novel, efficient, and recyclable bifunctional catalysts bearing ionic liquid supported (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) and iodoarene moieties were developed and used for environmentally benign catalytic oxidation of alcohols. The reactions using peracetic acid as a green and practical co-oxidant afforded the corresponding carbonyl compounds in high yields under mild conditions and convenient work-up. Furthermore, these ionic liquid supported bifunctional catalysts could be simply recovered and reused.     

A Recyclable Trinuclear Bifunctional Catalyst Derived from a Tetraoxo Bis‐Zn(salphen) Metalloligand

A tetraoxo bis‐Zn(salphen) supramolecular host can bind various divalent metal salts, thereby providing access to trinuclear bifunctional systems that incorporate both Lewis acid sites and dynamically bound nucleophilic anions. The formation of these trinuclear species was investigated and their stability features were also determined. The application of these trinuclear complexes as bifunctional catalysts was evaluated in the formation of cyclic organic carbonates from epoxides and CO₂. The catalytic data, in combination with control experiments, clearly demonstrate that these trinuclear compounds show much higher recycling potential compared to various control compounds and they can be used in up to five cycles without an observable loss in activity. Furthermore, this new recyclable catalytic system does not require any additives and can be applied under solvent‐free conditions.     

Bifunctional asymmetric catalysis: a tandem nucleophile/Lewis acid promoted synthesis of beta-lactams

[reaction: see text]. We describe a superior procedure for the catalytic, asymmetric synthesis of beta-lactams using a bifunctional catalyst system consisting of a chiral nucleophile and an achiral Lewis acid.     

氮氧双功能salen催化剂在酮的不对称硅氰化反应中的应用

通过在催化剂的不同位置同时引入LALB（Lewis acid/Lewis base）双功能基团（包括氮氧偶极基团和金属钛中心）来改善其催化活性和立体控制能力,合成基于salen骨架结构的新型氮氧双功能催化剂.在相对温和的条件下成功的将该类双功能催化剂应用于酮的不对称硅氰化反应,表现出了中等程度的选择性和非常高的反应活性...     

Un nouveau polymère catalyseur bifonctionnel: Le polyvinyl-5 (6)benzimidazoleméthanethiol Synthèse et catalyse de l'hydrolyse de l'acétate de p-nitrophényle

We describe the preparation of a new macromolecular chain bearing a repetitive bifunctional group benzimidazolemethanethiol (cysteine enzyme-like polymer). The catalytic properties of the polymer (PNPA hydrolysis) are compared with the esterolytic activity of the isolated bifunctional group as a simple model molecule. In both cases there is a cooperative effect (bifunctional catalysis) between the thiol function and the heterocyclic nitrogen. The polymer has a high catalytic activity near the neutrality point (pH 7 to 8).     

Effects of Solid Acid Supports on the Bifunctional Catalysis of Levulinic Acid to γ‐Valerolactone: Catalytic Activity and Stability

Heterogeneous transformation of levulinic acid (LA) to γ‐valerolactone (GVL) is regarded as a critical process of the lignocellulose‐based biorefinery system. Substantial progress on the catalytic conversion of LA to GVL has been continuously achieved recently. However, the traditional research paradigm typically emphasizes the metal‐catalyzed hydrogenation step, but lacks profound insights into the potential impacts of catalyst supports. Herein, an overview of the bifunctional catalytic system classified by representative solid acid supports for LA conversion to GVL is presented, and effects of critical factors on metal‐ and acid‐ catalyzed processes are discussed. Particularly, impacts of key issues on catalytic stability are thoroughly summarized and analyzed. Challenges and suggestions are also proposed from the perspective of increases in both catalytic activity and stability. This review potentially contributes to the rational design of high‐efficiency catalysts used in the biomass valorization for renewable energy production.     

Anthranilamide: a simple, removable ortho-directing modifier for arylboronic acids serving also as a protecting group in cross-coupling reactions

Anthranilamide (AAM) serves as a bifunctional modifier on the boron atom in catalytic transformations of arylboronic acids. It makes boronyl groups unreactive in Suzuki-Miyaura coupling and promotes Ru-catalyzed ortho-silylation. Suzuki-Miyaura coupling of AAM-modified bromophenylboronic acids with tolylboronic acid gave 1,1'-biaryl-4-boronic acid bearing AAM on the boron atom, which subsequently underwent Ru-catalyzed ortho-silylation at the 3-position by virtue of the ortho-directing effect of the AAM group.     

Cooperative thiourea-Brønsted acid organocatalysis: enantioselective cyanosilylation of aldehydes with TMSCN

We report a new thiourea-Br?nsted acid cooperative catalytic system for the enantioselective cyanosilylation of aldehydes with yields up to 90% and enantioselectivities up to 88%. The addition of an achiral acid was found to be crucial for high asymmetric induction. Mechanistic investigations using a combination of NMR, ESI-MS, and density functional theory computations (including solvent corrections) at the M06/6-31G(d,p) level of theory suggest that the key catalytic species results from the cooperative interaction of bifunctional thioureas and an achiral acid that form well-defined chiral hydrogen-bonding environments.     

One-pot cascade deacetalization and nitroaldol condensation over acid–base bifunctional ZIF-8 catalyst

Designing an elegant cascade catalyst is one of the challenging issues in catalyst research because the different or sometimes antagonistic active sites should catalyze the reaction in a consecutive manner without any adverse effects. In particular, complex synthetic methods have been envisaged to avoid unfavorable neutralization between acid and base sites in the preparation of acid–base bifunctional catalysts. In this work, acid–base bifunctional catalytic activity of ZIF-8 was evaluated for one-pot cascade deacetalization and nitroaldol condensation, and the reaction performance was compared with those of other metal–organic framework (MOF) catalysts. Although MOFs bearing strong Lewis acid sites on their metal nodes efficiently promoted the first deacetalization step, they were either totally ineffective (Cu-BTC, Fe-BTC, and MIL-53) or unsatisfactory (MIL-101 and UiO-66) to produce final product in the second base-catalyzed reaction step. On the other hand, ZIF-8 was more efficient at catalyzing the second nitroaldol condensation step, and the selectivity of the final product was substantially improved to as high as 56.4%. The enhanced selectivity clearly demonstrates the promising potential of ZIF-8 as a site-isolated acid–base bifunctional catalyst. However, the gradual catalyst deactivation, resulting from weakening of both acid and base sites during a reaction revealed by characterization of used catalyst, should be improved to extend its use to other versatile cascade or tandem reactions.     

Multifunctional hybrid organic-inorganic catalytic materials with a hierarchical system of well-defined micro- and mesopores

Novel layered zeolitic organic-inorganic materials (MWW-BTEB) have been synthesized by intercalation and stabilization of arylic silsesquioxane molecules between inorganic zeolitic MWW layers. The organic linkers are conformed by two condensed silyl-arylic groups from disilane molecules, such as 1,4-bis(triethoxysilyl)benzene (BTEB), which react with the external silanol groups of the zeolitic layers. The hybrids contain micropores within the inorganic layers and a well-defined mesoporous system in between the organic linkers. An amination post-treatment introduces basic groups in the organic linkers close to the acid sites present in the structural inorganic counterpart. Through this methodology it has been possible to prepare bifunctional acid-base catalysts where the acid sites are of zeolitic nature located in the inorganic building blocks and the basic sites are part of the organic structure. The resultant materials can act as bifunctional catalysts for performing a two-step cascade reaction that involves the catalytic conversion of benzaldehyde dimethylacetal into benzylidene malononitrile.     

新型双功能磁性纳米催化剂的制备与表征

传统酸性催化反应以稀硫酸为酸催化剂,虽然稀硫酸的催化活性很高,但由于稀硫酸极易腐蚀设备、不易与反应体系分离、易造成环境污染等缺点,如何用固体超强酸取代稀硫酸作为酸催化剂成为了研究的重点.对目前有关磁性固体超强酸的研究主要有SO42-/ZrO2/MFe2O4(M=Fe,Co,N i)[1~3]和     

Cooperative Acid–Base Effects with Functionalized Mesoporous Silica Nanoparticles: Applications in Carbon–Carbon Bond‐Formation Reactions

Acid–base bifunctional mesoporous silica nanoparticles (MSN) were prepared by a one‐step synthesis by co‐condensation of tetraethoxysilane (TEOS) and silanes possessing amino and/or sulfonic acid groups. Both the functionality and morphology of the particles can be controlled. The grafted functional groups were characterized by using solid‐state ²⁹Si and ¹³C cross‐polarization/magic angle spinning (CP/MAS) NMR spectroscopy, thermal analysis, and elemental analysis, whereas the structural and the morphological features of the materials were evaluated by using XRD and N₂ adsorption–desorption analyses, and SEM imaging. The catalytic activities of the mono‐ and bifunctional mesoporous hybrid materials were evaluated in carbon–carbon coupling reactions like the nitroaldol reaction and the one‐pot deacetalization–nitroaldol and deacetalization–aldol reactions. Among all the catalysts evaluated, the bifunctional sample containing amine and sulfonic acid groups (MSN–NNH₂–SO₃H) showed excellent catalytic activity, whereas the homogeneous catalysts were unable to initiate the reaction due to their mutual neutralization in solution. Therefore a cooperative acid–base activation is envisaged for the carbon–carbon coupling reactions.     

Synthesis of multifunctional polymer containing Ni‐Pd NPs via thiol‐ene reaction for one‐pot cascade reactions

Recently, acid–base bifunctional catalysts have been considered due to their abilities, such as the simultaneous activation of electrophilic and nucleophilic species and their high importance in organic syntheses. However, the synthesis of acid–base catalysts is problematic due to the neutralization of acidic and basic groups. This work reports a facial approach to solve this problem via the synthesis of a novel bifunctional polymer using inexpensive materials and easy methods. In this way, at the first step, heterogeneous poly (styrene sulfonic acid‐n‐vinylimidazole) containing pentaerythritol tetra‐(3‐mercaptopropionate) (PETMP) and trimethylolpropane trimethacrylate (TMPTMA) cross‐linkers were synthesized in the pores of a mesoporous silica structure using click reaction as a novel bifunctional acid–base catalyst. After that, Ni‐Pd nanoparticles supported on poly (styrenesulfonic acid‐n‐vinylimidazole)/KIT‐6 as a novel trifunctional heterogeneous acid–base‐metal catalyst was prepared. The prepared catalysts were characterized by various techniques like FT‐IR, TGA, ICP‐AES, DRS‐UV, TEM, FE‐SEM, EDS‐Mapping, and XRD. The synthesized catalysts were efficiently used as bifunctional/trifunctional catalysts for one‐pot, deacetalization‐Knoevenagel condensation and one‐pot, three‐step and a sequential reaction containing deacetalization‐Knoevenagel condensation‐reduction reaction. It is important to note that the synthesized catalyst showing high chemo‐selectivity for the reduction of nitro group, alkenyl double bond and ester group in the presence of nitrile. Moreover, it was found that the different nanoparticles including Ni, Pd, and alloyed Ni‐Pd showing different chemo‐selectivity and catalytic activity in the reaction.     

A novel simple bifunctional catalyst for the direct aldol reaction

Direct aldol reactions of aldehydes and ketones can proceed smoothly in the presence of a catalytic amount of naphthol/sodium naphtholate(5 mol%) to afford the corresponding products with yields up to 98%.Such a bifunctional catalyst is more moderate than strong acid or base employed in direct aldol reactions.     

Pt/SAPO-11催化剂载体的改性对正十四烷临氢转化性能的影响

以Pt/SAPO-11双功能催化剂为基础,对催化剂载体进行柠檬酸、炭黑改性,以正十四烷为模型化合物,通过催化剂表征和反应评价,探索了催化剂载体的改性对正十四烷临氢转化性能的影响。结果表明,异构化产物以单甲基异构物为主,改性没有改变催化剂的酸强度,但使得酸浓度有所下降。通过柠檬酸调变催化剂的酸性使得催化剂的低温催化活性显著提高,采用炭黑扩孔改性,有效改善了催化剂的传质性能,提高了催化剂的单甲基异构体选择性。柠檬酸和炭黑改性的催化剂裂化产物均以C6为主,改性并没有改变SAPO-11分子筛的孔道限制效应,裂化产物呈现一定的择型效应,裂化产物分布呈现出不对称分布的特点。     

Direct asymmetric organocatalytic Michael reactions of alpha,alpha-disubstituted aldehydes with beta-nitrostyrenes for the synthesis of quaternary carbon-containing products

[reaction: see text] Direct asymmetric catalytic Michael reactions have been performed using chiral-amine/acid bifunctional catalysts. Performed with 0.3 equiv of (S)-(+)-1-(2-pyrrolidinylmethyl)pyrrolidine and 0.3 equiv of trifluoroacetic acid as the catalyst, the reaction of alpha,alpha-dialkylaldehydes with (E)-beta-nitrostyrene provided the alpha,alpha-dialkyl Michael products in up to 96% yield with up to 91% ee. With respect to enantioselectivity, l-proline was a poor catalyst of this class of Michael reactions.     

双官能团醇类化合物催化胺化反应的研究进展

本文综述了由双官能团醇类化合物催化胺化合成二元胺或环胺的研究进展,分别讨论了金属催化剂和固体酸催化剂对双官能团醇类化合物的不同作用机制,考察了反应物结构对 反应活性和选择性的影响,重点介绍了超临界氨流体在二元醇催化胺化反应中的应用,并指出了今后研究的方向.     

Rapid fluorescent screening for bifunctional amine-acid catalysts: efficient syntheses of quaternary carbon-containing aldols under organocatalysis

[reaction: see text] Direct catalytic aldol reactions of alpha,alpha-dialkylaldehyde donors and arylaldehyde acceptors have been performed using pyrrolidine-acetic acid bifunctional catalysts. This general and practical amine-acid combination was identified by screening catalysts using a new fluorescent detection system for carbon-carbon bond formation. Using 0.05 equiv of pyrrolidine and 0.25 equiv of acetic acid as catalyst, we obtained alpha,alpha-dialkylaldol product in 96% yield after 2 h at ambient temperature. Proline was a poor catalyst of this reaction.     

Sputtered nano-cobalt on H-USY zeolite for selectively converting syngas to gasoline

Selectively converting CO and H2 to gasoline product(isoparaffin and olefin) in one step still remains a great challenge. We demonstrate effective H-USY zeolite supported nano-cobalt bifunctional catalysts for this catalytic reaction, which are prepared by the novel physical sputtering process. Particles of the sputtered cobalt exist in nano-level and are well-dispersed on acid USY zeolite. Easy activation of the loaded nano-cobalt is also achieved in a low-temperature hydrogen reduction atmosphere. In the tandem catalytic reaction, the sputtered bifunctional Co/USY catalyst exhibits a much higher CO conversion and higher isoparaffin selectivity than the conventional impregnated one. Compared with H-Mor, H-Beta and other zeolites supported catalysts, H-USY zeolite supported cobalt catalyst shows the clearest promotional effect on the activity of FischerTropsch synthesis. The described synthesis herein provides a new pathway to solve the problem caused by the strong metal-support interaction(MSI) in heterogeneous catalysis.