One-pot oxidant-free dehydrogenation-Knoevenagel tandem reaction catalyzed by a recyclable magnetic base-metal bifunctional catalyst

A new base-metal bifunctional catalyst NH-Pd(0)@MNP was prepared via a facile procedure and fully characterized. The as-prepared catalyst was used as an efficient relay catalyst for the one-pot oxidant-free dehydrogenation-Knoevenagel condensation tandem reaction from benzyl alcohol in H₂O under mild conditions and generated benzalmalononitriles with yield up to 96%. Meanwhile, the catalyst could be easily recovered from the reaction system by an external magnetic field, and is reusable with little loss of activity up to 6 runs (<5%).     

负载离子对型酞菁钴双功能硫醇氧化催化剂

将分别带有正、负电荷基团的季铵盐酞菁钴ＣｏＰＣ「Ｎ（ＣＨ３）３Ｉ」４和碘酸盐菁然ＣｏＰｃ（ＳＯ３Ｎａ）４溶解在一起,负载在由水滑石热分解而成的ＭｇＡｌ复合氧化物碱性载体上,制成负载离子对型酞菁钴催化剂,其所具有的碱经性双功能的特征能够有效地催化１－辛硫醇氧化,当这两种酞菁钴配合物的摩尔比为１时,催化活性最高,并且稳定性也有较明显的改善,这种双功能催化剂体系具有酶催化的特点,即遵循双底物（１－Ｃ８Ｈ     

Novel synthesis of rod‐coil block copolymers by combination of coordination polymerization and ATRP

Combination of coordination polymerization and atom transfer radical polymerization (ATRP) was applied to a novel synthesis of rod‐coil block copolymers. The procedure included the following steps: (1) monoesterification reaction of ethylene glycol with 2‐bromoisobutyryl bromide yielded a α‐bromo, ω‐hydroxy bifunctional initiator, (2) CpTiCl₃ (bifunctional initiator) catalyst was prepared from a mixture of trichlorocyclopentadienyl titanium (CpTiCl₃) and bifunctional initiator. Coordination polymerization of n‐butyl isocyanate initiated by such catalyst provided a well‐defined macroinitiator, poly(n‐butyl isocyanate)‐Br (PBIC‐Br), and (3) ATRP method of vinyl monomers using PBIC‐Br provided rod (PBIC)‐coil block copolymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4037–4042, 2007     

Application of the Lewis acid-Lewis base bifunctional asymmetric catalysts to pharmaceutical syntheses: stereoselective chiral building block syntheses of human immunodeficiency virus (HIV) protease inhibitor and beta3-adenergic receptor agonist

Chiral building block syntheses of promising drugs were achieved using two types of catalytic stereoselective cyanosilylations of aldehydes promoted by Lewis acid-Lewis base bifunctional catalysts 1 and 2 as the key steps (diastereoselective cyanosilylation of amino aldehyde and enantioselective cyanosilylation). In the first part of this article, syntheses of chiral building blocks (6) of Atazanavir (3: human immunodeficiency virus (HIV) protease inhibitor) using the bifunctional catalyst 2 are discussed. The reaction of Boc-protected phenylalaninal 21 in the presence of 1 mol% catalyst 2 selectively afforded the anti isomer 22 as the major product (diastereomeric ratio=97 : 3), which was successively converted to the corresponding epoxide 6 in six steps. In the second part, we describe a chiral building block synthesis of beta(3)-adrenergic receptor agonists. The enantioselective cyanosilylation of 3-chlorobenzaldehyde (38) with 9 mol% catalyst 1 gave the chiral cyanohydrin 39, which was converted to beta-hydroxyethylamine 40 by reduction. Moreover, the chiral ligand of catalyst 1 could be recovered without column chromatography and reused without decreasing its activity.     

Design and synthesis of a tridentate ligand for asymmetric bifunctional catalysis

Covalent attachment of a quinine moiety to a Schiff base ligand through an ester linkage generates a novel tridentate ligand that gives a new Lewis acid-Lewis base (LA-LB^∗) bifunctional catalyst having a mixture of the LA configurations. The LB^∗-dependent asymmetric bifunctional catalysis was demonstrated using the addition of diethylzinc to 2-methoxybenzaldehyde as a test reaction and the substrate scope of the new catalyst was illustrated using aromatic aldehydes.     

Bifunctional Catalysts for Reversible Oxygen Evolution Reaction and Oxygen Reduction Reaction

Metal-air batteries (MABs) and reversible fuel cells (RFCs) rely on the bifunctional oxygen catalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Finding efficient bifunctional oxygen catalysts is the ultimate goal and it has attracted a great deal of attention. The dilemma is that a good ORR catalyst is not necessarily efficient for OER, and vice versa. Thus, the development of a new type of bifunctional oxygen catalysts should ensure that the catalysts exhibit high activity for both OER and ORR. Composites with multicomponents for active centers supported on highly conductive matrices could be able to meet the challenges and offering new opportunities. In this Review, the evolution of bifunctional catalysts is summarized and discussed aiming to deliver high-performance bifunctional catalysts with low overpotentials.     

3,3-二取代3-吲哚-3'-基氧化吲哚的立体选择性合成

以10 mol%(R,R)-环己二胺衍生的手性双功能硫脲叔胺(4b)为催化剂,3'-吲哚-3-氧化吲哚与α-氨基砜为原料,经3'-吲哚-3-氧化吲哚与原位生成的N-Boc芳香醛亚胺的不对称Mannich反应,合成了20个3,3-二取代3-吲哚-3'-基氧化吲哚类化合物(3a~3t),分离收率54%~98%,dr值90∶10~99∶1,其结构经~1H NMR,~(13)C NMR和HR-MS(ESI-TOF)表征。     

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.     

Cobalt Incorporated Graphitic Carbon Nitride as a Bifunctional Catalyst for Electrochemical Water-Splitting Reactions in Acidic Media

Non-noble metal-based bifunctional electrocatalysts may be a promising new resource for electrocatalytic water-splitting devices. In this work, transition metal (cobalt)-incorporated graphitic carbon nitride was synthesized and fabricated in electrodes for use as bifunctional catalysts. The optimum catalytic activity of this bifunctional material for the hydrogen evolution reaction (HER), which benefitted at a cobalt content of 10.6 wt%, was promoted by the highest surface area and conductivity. The activity achieved a minimum overpotential of ~85 mV at 10 mA/cm² and a Tafel slope of 44.2 mV/dec in an acidic electrolyte. These values of the HER were close to those of a benchmark catalyst (platinum on carbon paper electrode). Moreover, the kinetics evaluation at the optimum catalyst ensured the catalyst flows (Volmer–Heyrovsky mechanism), indicating that the adsorption step is rate-determining for the HER. The activity for the oxygen evolution reaction (OER) indicated an overpotential of ~530 mV at 10 mAcm⁻² and a Tafel slope of 193.3 mV/dec, which were slightly less or nearly the same as those of the benchmark catalyst. Stability tests using long-term potential cycles confirmed the high durability of the catalyst for both HER and OER. Moreover, the optimal bifunctional catalyst achieved a current density of 10 mAcm⁻² at a cell voltage of 1.84 V, which was slightly less than that of the benchmark catalyst (1.98 V). Thus, this research reveals that the present bifunctional, non-noble metallic electrocatalyst is adequate for use as a water-splitting technology in acidic media.     

Bifunctional transition metal‐based molecular catalysts for asymmetric C?C and C?N bond formation

This paper describes the recent advances in the conceptually new bifunctional Ir and Ru catalysts for asymmetric catalytic reactions. These reactions include the enantioselective Michael addition of 1,3‐dicarbonyl compounds to cyclic enones and nitroalkenes, and the enantioselective direct amination of α‐cyanoacetates with diazoesters. The outcome of these reactions in terms of reactivity and selectivity was delicately influenced by the catalyst structures and the reaction conditions including the solvents used. Even with a 1 : 1 molar ratio of donors to acceptors, the reactions proceeded smoothly to give the corresponding chiral adducts with an excellent yield and enantiomeric excess (ee). Preliminary mechanistic studies showed that the key stage of the catalytic cycle is the interaction of the bifunctional catalyst with a pronucleophilic reagent that leads to stereoselective formation of C‐, O‐, or N‐bound complexes. The resulting protonated catalyst bearing metal‐bound nucleophiles readily reacts with electrophiles to provide C? C and C? N bond formation products in a highly stereoselective manner. © 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 9: 106–123; 2009: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20172     

Asymmetric Synthesis of Chromans Through Bifunctional Enamine-Metal Lewis Acid Catalysis

Cooperative enamine-metal Lewis acid catalysis has emerged as a powerful tool to construct carbon-carbon and carbon-heteroatom bond forming reactions. A concise synthetic method for asymmetric synthesis of chromans from cyclohexanones and salicylaldehydes has been developed to afford tricyclic chromans containing three consecutive stereogenic centers in good yields (up to 87 %) and stereoselectivity (up to 99 % ee and 11 : 1 : 1 dr). This difficult organic transformation was achieved through bifunctional enamine-metal Lewis acid catalysis. It is believed that the strong activation of the salicylaldehydes through chelating to the metal Lewis acid and the bifunctional nature of the catalyst accounts for the high yields and enantioselectivity of the reaction. The absolute configurations of the chroman products were established through X-ray crystallography. DFT calculations were conducted to understand the mechanism and stereoselectivity of this reaction.     

MOFs as multifunctional catalysts: one-pot synthesis of menthol from citronellal over a bifunctional MIL-101 catalyst

A bifunctional MOF catalyst containing coordinatively unsaturated Cr(3+) sites and palladium nanoparticles (Pd@MIL-101) has been used for the cyclization of citronellal to isopulegol and for the one-pot tandem isomerization/hydrogenation of citronellal to menthol. The MOF was found to be stable under the reaction conditions used, and the results obtained indicate that the performance of this bifunctional solid catalyst is comparable with other state-of-the-art materials for the tandem reaction: Full citronellal conversion was attained over Pd@MIL-101 in 18 h, with 86% selectivity to menthols and a diastereoselectivity of 81% to the desired (-)-menthol, while up to 30 h were necessary for attaining similar values over Ir/H-beta under analogous reaction conditions.     

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.     

Squaramide‐Catalyzed Asymmetric aza‐Friedel–Crafts/N,O‐Acetalization Domino Reactions Between 2‐Naphthols and Pyrazolinone Ketimines

N‐Boc ketimines derived from pyrazolin‐5‐ones were explored to develop an unprecedented domino aza‐Friedel–Crafts/N,O‐acetalization reaction with 2‐naphthols. The novel method requires a catalyst loading of only 0.5 mol % of a bifunctional squaramide catalyst, is scalable to gram amounts, and provides a new series of furanonaphthopyrazolidinone derivatives bearing two vicinal tetra‐substituted stereogenic centers in excellent yields (95–98 %) and stereoselectivity (>99:1 d.r. and 97–98 % ee ). A different reactivity was observed in the case of 1‐naphthols and other electron‐rich phenols, which led to the aza‐Friedel–Crafts adducts in 70–98 % yield and 47–98 % ee .     

A new reaction for the direct conversion of 4-azido-4-deoxy-D-galactoside into a 4-deoxy-D-erythro-hexos-3-ulose

[reaction: see text] A new one-step reaction has been developed for converting 4-azido-4-deoxy-d-galactoside into 4-deoxy-d-erythro-hexos-3-ulose by phosphoramidites and tetrazole. It is proposed that the new reaction proceeds via an intramolecular Staudinger reaction of the phosphite intermediate and a tetrazole-catalyzed elimination reaction of the resultant phosphorimidate. Tetrazole appears to be playing a unique role by acting as a bifunctional catalyst to facilitate the elimination reaction.     

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.     

生物质合成气一步法合成LPG的实验研究

由生物质气化合成液体燃料(甲醇、二甲醇和低碳烃类),是理想的碳中性绿色燃料,将其用作城市交通和民用燃料,已经引起全世界的广泛关注.[1,2]     

Green chemistry of polyurethanes: The catalytic <Emphasis Type="Italic">n</Emphasis>-butylaminolysis of ethylene carbonate as a model chain-growth reaction in the formation of nonisocyanate polyurethanes

The kinetic regularities and the mechanism of the catalytic action of 1,5,7-triazabicyclo[4.4.0]dec-5-ene, which is the most active of the known catalysts for the formation of hydroxyurethanes from cyclocarbonates and amines, were studied using the example of the n-butylaminolysis of ethylene carbonate. In contrast with the noncatalytic reaction, which proceeds via two parallel pathways that involve one and two molecules of amine, the catalytic reaction follows a single pathway: the second molecule of amine is replaced by a molecule of the catalyst that accelerates the process in accordance with the mechanism of bifunctional catalysis. Different reaction pathways were studied by quantum chemical calculations based on the density functional method. It was shown that the high activity of 1,5,7-triazabicyclo[4.4.0]dec-5-ene results from the formation of a planar cation-like form of the catalyst. Moreover, the low-energy transition between the cation and the initial 1,5,7-triazabicyclo[4.4.0]dec-5-ene enables the catalyst to simultaneously be a good donor and acceptor of protons. This study presents a new way for finding among bifunctional organic compounds the catalysts that are even more active in the reaction of cyclocarbonates with amines.     

CoNi nanoparticles anchored inside carbon nanotube networks by transient heating:Low loading and high activity for oxygen reduction and evolution

Transitional metal alloy and compounds have been developed as the low cost and efficient bifunctional electrocatalysts for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).However,a high mass loading of these catalysts is commonly needed to achieve acceptable catalytic performance,which could cause such problems as battery weight gain,mass transport blocking,and catalyst loss.We report herein the preparation of fine CoNi nanoparticles(5-6 nm)anchored inside a nitrogendoped defective carbon nanotube network(CoNi@N-DCNT)by a transient Joule heating method.When utilized as an electrocatalyst for oxygen reduction and evolution in alkaline media,the CoNi@N-DCNT film catalyst with a very low mass loading of 0.06 mg cm^-2 showed excellent bifunctional catalytic performance.For ORR,the onset potential(Eonset)and the half-wave potential(E_1/2)were 0.92 V versus reversible hydrogen electrode(vs.RHE)and 0.83 V(vs.RHE),respectively.For OER,the potential at the current density(J)of 10 mA cm^-2(E₁₀)was 1.53 V,resulting in an overpotential of 300 mV much lower than that of the commercial RuO₂ catalyst(320 mV).The potential gap between E_1/2 and E₁₀ was as small as 0.7 V.Considering the low mass loading,the mass activity at E₁₀ reached at 123.2 A g^-1,much larger than that of the RuO₂ catalyst and literature results of transitional metal-based bifunctional catalysts.Moreover,the CoNi@N-DCNT film catalyst showed very good long-term stability during the ORR and OER test.The excellent bifunctional catalytic performance could be attributed to the synergistic effect of the bimetal alloy.     

Catalytic enantioselective construction of quaternary stereocenters by direct vinylogous Michael addition of deconjugated butenolides to nitroolefins

A direct vinylogous Michael reaction of γ-substituted deconjugated butenolides with nitroolefins has been developed with the help of a newly identified quinine-derived bifunctional catalyst, allowing the synthesis of densely functionalized products with contiguous quaternary and tertiary stereocenters in excellent yield with perfect diastereoselectivity (>20:1 dr) and high enantioselectivity (up to 99:1 er).