纳米催化剂在CO_(2)加氢制甲醇中的研究进展北大核心CSCD

为减缓温室效应,将CO_(2)转换成高附加值的甲醇是减少CO_(2)排放的有效途径,而高效催化剂是CO_(2)加氢制甲醇反应规模化的关键.可调控合成的具有量子尺寸效应的纳米催化剂在该反应上具有独特的优势.因此我们深入探讨了反应机理,综述了纳米材料在CO_(2)加氢制甲醇中的研究进展,最后给出了高效催化剂可能的发展方向.     

The Lewis acid-catalyzed nazarov reaction of 2-(n-methoxycarbonylamino)-1,4-pentadien-3-ones

[reaction: see text] A highly efficient carbonylative Suzuki-Miyaura coupling reaction of lactam-derived vinyl triflates and alkenylboronic acids afforded 2-(N-methoxycarbonylamino)-1,4-pentadien-3-ones as suitable substrates for the Nazarov reaction. The most competent Lewis acids for the Nazarov reaction were Cu(OTf)(2) (2 mol %) and Sc(OTf)(3) (3 mol %) in DCE, which provided the Nazarov products in excellent yield. As both the carbonylative coupling and the subsequent Nazarov reaction were high yielding, the overall methodology is a concise and efficient route to [1]pyrindine systems.     

Copper-catalyzed tandem reaction of isocyanides with N-(2-haloaryl)propiolamides for the synthesis of pyrrolo[3,2-c]quinolin-4-ones

The copper-catalyzed tandem reaction of isocyanides with N-(2-haloaryl)propiolamides is very efficient for the synthesis of pyrrolo[3, 2-c]quinolin-4-ones. Highly reactive cyclic organocopper intermediates were proposed to be generated in the copper-catalyzed formal [3 + 2] cycloaddition reaction of isocyanides with triple bonds. Intramolecular trapping of the organocopper intermediates can lead to aryl C-C bond formation, which offered an efficient method for constructing fused pyrrole structures.     

Synthesis of biaryls via decarboxylative Pd-catalyzed cross-coupling reaction

[reaction: see text] A simple and efficient route to biaryls via Pd-catalyzed decarboxylative cross-couplings of arene carboxylic acids and aryl iodides is reported. The PdCl2/AsPh3 catalytic system in the presence of Ag2CO3 in DMSO was found to be particularly efficient to perform this transformation. This reaction can be extended to the synthesis of various biaryls, including sterically hindered biaryls, with yields ranging from 58% to 90%.     

An efficient synthesis of peri-hydroxy aromatic compounds via a strong-base-induced

An efficient synthesis of peri-hydroxy aromatic compounds has been accomplished via a strong-base-induced [4+2] cycloaddition of homophthalic anhydrides with alpha-sulfinyl-substituted derivatives of enolizable enones. The unsubstituted enones did not undergo an efficient [4+2] cycloaddition reaction with homophthalic anhydrides, presumably due to their enolization under the basic reaction conditions. The sulfinyl group not only promotes the cycloaddition reaction but also undergoes in situ elimination under the reaction conditions to afford the peri-hydroxy aromatic compounds in a single step. The application of this methodology for the synthesis of a key intermediate of antitumor antibiotic fredericamycin A is described. PM3 calculations of various 2-substituted cyclopentenones as well as the mechanism of the cycloaddition are also discussed.     

Baeyer-Villiger oxidation in supercritical CO2 with potassium peroxomonosulfate supported on acidic silica gel

Supercritical carbon dioxide (scCO2) is an efficient reaction medium to perform the Baeyer-Villiger oxidation with hydrated silica-supported potassium peroxomonosulfate (h-SiO2.KHSO5) under flow-through conditions. Hydration modulates the reactivity of the active surface by softening the acidity of the KHSO4 present in the supported reagent. The reaction in scCO2 is much more efficient than in n-hexane under similar conditions, which is attributed to better transport and solvating properties of the supercritical medium with regard to n-hexane.     

Efficient and Facile Three-Component Reaction for the Synthesis of 2-Amine-4,6-diarylpyrimidine Under Solvent-Free Conditions

An efficient and convenient multicomponent reaction for the preparation of 2-amine-4,6-diarylpyrimidine by aromatic aldehydes, aromatic ketones, and guanidine carbonate in the presence of sodium hydroxide under solvent-free conditions is reported. The short reaction time coupled with the simplicity of the reaction procedure make this method one of the most efficient methods for the synthesis of this class of compounds.     

An efficient [2 + 2 + 1] synthesis of 2,5-disubstituted oxazoles via gold-catalyzed intermolecular alkyne oxidation

The first efficient intermolecular reaction of gold carbene intermediates generated via gold-catalyzed alkyne oxidation has been realized using nitriles as both the reacting partner and the reaction solvent, offering a generally efficient synthesis of 2,5-disubstituted oxazoles with broad substrate scope. The overall reaction is a [2 + 2 + 1] annulation of a terminal alkyne, a nitrile, and an oxygen atom from an oxidant. The reaction conditions are exceptionally mild, and a range of functional groups are easily tolerated. With complex and/or expensive nitriles, only 3 equiv could be sufficient to achieve serviceable yields in the absence of any solvent and using only 1 mol % BrettPhosAuNTf(2) as the catalyst.     

Synthesis of aryl substituted quinones as β-secretase inhibitors: Ligand-free direct arylation of quinones with aryl halides

The simple ligand-free direct arylation of quinones with aryl halides applying Pd(OAc)₂ as a catalyst in accordance with Heck reaction was studied. This reaction provided a simple and efficient synthetic approach to efficient inhibitors of β-secretase aryl-substituted quinones.     

Quantum topological resolution of catalyst proficiency

The purpose of this exploratory investigation is to characterize, contrast, and explain the differences between efficient Ni(π‐allyl)₂ and inefficient Pd(π‐allyl)₂ systems in the catalyzed cross‐coupling of alkanes. Within the framework of the quantum theory of atoms in molecules, we have created quantum topology phase diagrams (QTPDs) for nonisomeric species by the creation of aggregate‐isomers; simple sum rules are introduced to ensure that the Poincaré‐Hopf relation is obeyed. We show that the catalyzed reaction cycles can be represented as a directed QTPD where each species of the main reaction cycle forms a closed loop. The topological position of the unwanted side products relative to the main reaction cycle for each catalyst is also considered. We find the more efficient Ni(π‐allyl)₂ catalyst produces a reaction cycle on the QTPD that contains no “missing” topologies, preferentially proceeding to desired product at 94% yield, while avoiding wasteful side‐product pathways, disconnected from the major pathway by “missing” topologies. The converse is true for the less efficient Pd(π‐allyl)₂ catalyst, whose reaction pathway markedly bifurcates to final yields of 56% and 44% for product and side‐product, respectively. We subsequently used our nearest neighbor ring‐critical point approach to show that the species of the main reaction cycle of the efficient Ni(π‐allyl)₂ catalyst facilitates the desired chemical transformation whilst more effectively barring the formation of unwanted side product, with respect to the inefficient Pd(π‐allyl)₂ catalyst. The findings from the QTPD analysis are in agreement with traditional energetic‐barrier interpretations of reaction pathway preference. © 2015 Wiley Periodicals, Inc.     

Regioselective Ring Opening of Styrene Oxide Catalyzed by MoO2(acac)2

The ring-opening reaction of styrene oxide with various nitrogen, oxygen, and carbon nucleophiles catalyzed by MoO₂(acac)₂ was described. The corresponding ring-opening compounds with nearly 100% regioselectivities were obtained under mild conditions in moderate to good yields. MoO₂(acac)₂ is a highly efficient catalyst for the ring opening of styrene oxide. The reaction serves as a simple and efficient method for the synthesis of 1,2-bifunctional compounds.     

Synthesis of 1-methyl-3-oxo-7-oxabicyclo[2.2.1]hept-5-ene-2-carboxylic acid methyl ester

A simple and efficient method for the preparation of 1-methyl-3-oxo-7- oxabicyclo[2.2.1]hept-5-en-2-carboxylic acid methyl ester (1) is described. The first step is a highly regioselective Diels-Alder reaction between 2-methylfuran and methyl-3-bromo- propiolate. A remarkably difficult ketal hydrolysis reaction was effected by treatment with HCl, a simple reagent that was shown to be more efficient, in this case, than commonly used more elaborate methods.     

CuBr-catalyzed direct indolation of tetrahydroisoquinolines via cross-dehydrogenative coupling between sp3 C-H and sp2 C-H bonds

A novel and efficient C-C bond formation method was developed via the cross-dehydrogenative coupling (CDC) reaction of indoles and tetrahydroisoquinolines catalyzed by copper bromide in the presence of an oxidizing reagent, tert-BuOOH. The CDC reaction provides a simple and efficient catalytic method to construct indolyl tetrahydroisoquinolines via a combination of sp3 C-H bond and sp2 C-H bond followed by C-C bond formation.     

Synthesis of β-keto-sulfones using ionic liquid [TPA][Pro] as an efficient and reusable reaction medium

Facile and an efficient synthesis of β-keto-sulfones is described by the reaction of α-haloketone with sodium alkyl/aryl sulphinates in ionic liquid [TPA][Pro] as an efficient and reusable reaction medium to afford the corresponding β-keto-sulfones in excellent yields.     

(BeDABCO)2Pd2Cl6 (1‐benzyl‐4‐aza‐1‐azoniabicyclo[2.2.2]octane chloride) as a highly active catalytic system for the Stille cross‐coupling reaction under microwave irradiation

An efficient catalytic system using (BeDABCO)₂Pd₂Cl₆ was developed for the Stille cross‐coupling reaction. The substituted biaryls were produced in excellent yields in short reaction times using a catalytic amount of this catalyst in DMF at 120 °C. The ionic character of homogeneous catalyst and microwave irradiation and also DMF as microwave‐active polar solvent gave higher yields and shorter reaction times than conventional heating. Benzyl DABCO as an efficient ligand and also a quaternary ammonium salt had an efficient stabilizing effect on the Pd(0) species. Copyright © 2013 John Wiley & Sons, Ltd.     

A new ketone synthesis by palladium-catalyzed cross-coupling reactions of esters with organoboron compounds

[reaction: see text] The palladium-catalyzed coupling reaction of 2-pyridyl esters with organoboron compounds is described. The reaction is compatible with various functional groups and proceeds under mild reaction conditions. The coordination of the nitrogen atom to Pd is a key step for efficient reaction.     

Zinc-mediated ring-expansion and chain-extension reactions of beta-keto esters

[Chemical reaction: see text] The reaction of cyclic beta-keto esters with CF3CO2ZnCH2I provided the corresponding ring-expanded products in moderate to good yields. Although alpha-substituted acyclic beta-keto esters reacted with much less efficient, chain-extension reaction of simple beta-keto esters also proceeded effectively to generate gamma-keto esters in high yields.     

Potassium dihydrogen phosphate catalyzed one-pot synthesis of 2,4,5-triaryl-1H-imidazoles

<正>A simple and efficient method has been developed;benzil/benzoin undergoes smooth condensation with various substituted aldehyde and ammonium acetate in the presence of potassium dihydrogen phosphate(KH_2PO_4) under mild reaction conditions to afford the corresponding trisubstituted imidazole in excellent yields.The method for synthesis of product,the reaction mixture was reflux in ethanol for 40-90 min.The present method is simple,efficient,and cost-effective.     

Direct C-H bond arylation of 2-hydroxybenzaldehydes with arylboronic acids via ligand-free palladium catalysis

A mild and efficient ligand-free palladium-catalyzed direct C-H bond arylation reaction was developed to afford 2-hydroxybenzophenones in good to excellent yields from easily available 2-hydroxybenzaldehydes and arylboronic acids. The given reaction provided one of the easiest pathways for accessing 2-hydroxybenzophenones, and a variety of functional groups could be tolerated in this process.     

Multicomponent approach to unique 1,4-diazepine-2-amines

Isocyanide-based multicomponent reaction (IMCR) of 1,3-diaminopropane with carbonyl compounds has been developed as an efficient strategy for the synthesis of 1,4-diazepine-2-amines. Brønsted and Lewis acids are able to promote the reaction, and TMSCl has been found to be the most efficient among them. The IMCR is applicable to a variety of carbonyl compounds and isocyanides.