室温下3-喹啉硼酸催化的羧酸酰胺化反应

使用3-喹啉硼酸作为催化剂,催化脂肪类羧酸与胺直接脱水形成酰胺键.在室温条件下,该催化剂对多数脂肪族羧酸和伯胺/仲胺的反应表现出较好的催化活性,得到中等至较好收率的酰胺产物.对于具有挑战性的芳香酸及杂环芳香酸底物,在升高温度的条件下该催化剂也展示出较好的催化性能.

催化直接酰胺化反应研究进展

对近年来的酰胺键形成方法,尤其是符合绿色化学理念的催化直接酰胺化法进展进行了综述。总结了催化直接酰胺化的相关催化剂,包括金属盐类催化剂、硼化合物催化剂等。

酸和胺直接缩合制备酰胺的进展

酰胺键的合成是有机化学中非常重要和有意义的反应之一。国内外学者已对酰胺键的形成进行了长期研究,目前合成酰胺的底物和方法多种多样,然而,这些合成方法存在各种各样的资源浪费和环境污染问题。羧酸和胺之间的催化脱水缩合反应是合成相应酰胺的最理想方法,利用羧酸和胺在催化剂作用下直接缩合形成酰胺,避免了使用活化试剂带来的诸多问题。近年来以硼类和过渡金属为主体的催化剂得到广泛研究,并取得了一系列成果。本文主要介绍了以羧酸和胺为底物,同时符合绿色化学理念的催化合成方法,通过对这些催化剂催化性能的总结与分析,阐述了各种催化剂的优缺点。其中硼化合物催化的直接酰胺化反应是研究较多、前景最为诱人的方法,因此基于硼类化合物的特殊结构,设计更具活性的此类催化剂将是今后研究发展的方向。

铯催化吲哚衍生物N-酰胺化反应制备吲哚-1-芳(烷)基甲酰胺化合物

以5.0 mol%Cs OH·H2O作为催化剂,吲哚衍生物和芳(烷)基异氰酸酯发生N-酰胺化反应,以较高产率制备了一系列吲哚-1-芳(烷)基甲酰胺化合物.该方法对不同的吲哚衍生物和芳(烷)基异氰酸酯均具有较好的适用性,反应均能以较高的产率获得相应的目标产物.与已有方法相比,本方法具有反应条件温和、底物适用范围广、操作简便以及产率高等优点,为吲哚-1-芳(烷)基甲酰胺化合物的制备提供有效的路径.

Cobalt-catalyzed redox-neutral synthesis of isoquinolines: C–H activation assisted by an oxidizing N–S bond

A redox‐neutral avenue to access isoquinolines has been realized by a Co（III）‐catalyzed C–H activa‐tion process. Starting from readily available N‐sulfinyl imine substrates and alkynes, the reaction occurred via N–S cleavage with broad substrate scope and functional group compatibility in the presence of cost‐effective cobalt catalysts.

Accelerating photocatalytic hydrogen evolution and pollutant degradation by coupling organic co-catalysts with TiO_2

Accelerating the separation efficiency of photoexcited electron-hole pairs with the help of highly active co-catalysts has proven to be a promising approach for improving photocatalytic activity. Thus far, the most developed co-catalysts for semiconductor-based photocatalysis are inorganic materials;the employment of a specific organic molecule as a co-catalyst for photocatalytic hydrogen evolution and pollutant photodegradation is rare and still remains a challenging task. Herein, we report on the use of an organic molecule, oxamide (OA), as a novel co-catalyst to enhance electron- hole separation, photocatalytic H2 evolution, and dye degradation over TiO2 nanosheets. OA-modified TiO2 samples were prepared by a wet chemical route and demonstrated improved light absorption in the visible-light region and more efficient charge transport. The photocatalytic performance of H2 evolution from water splitting and rhodamine B (RhB) degradation for an optimal OA-modified TiO2 photocatalyst reached 2.37 mmol g^–1 h^–1 and 1.43 × 10^-2 min^-1, respectively, which were 2.4 and 3.8 times higher than those of pristine TiO2, respectively. A possible mechanism is proposed, in which the specific π-conjugated structure of OA is suggested to play a key role in the enhancement of the charge transfer and catalytic capability of TiO2. This work may provide advanced insight into the development of a variety of metal-free organic molecules as functional co-catalysts for improved solar-to-fuel conversion and environmental remediation.

Amine formylation with CO2 and H2 catalyzed by heterogeneous Pd/PAL catalyst

For the first time, Pd supported on natural palygorskite was developed for amine formylation with CO2 and H2. Both secondary and primary amines with diverse structures could be converted into the desired formamides at < 100 °C, and good to excellent yields were obtained.

Selective aerobic oxidation promoted by highly efficient multi-nitroxy organocatalysts

Selective oxidation with molecular oxygen as the sole oxidant under mild conditions is of crucialimportance for the long‐term sustainable exploitation of available feedstocks and the formation ofrequired intermediates for organic synthesis and industrial processes.Among the developed oxidationprotocols,innovative strategies using hydroxyimide organocatalysts in combination with metallicor metal‐free cocatalysts have attracted much attention because of the good activities andselectivities of such catalysts in the oxo functionalization of hydrocarbons.This method is based onthe reaction using N‐hydroxyphthalimide,which was first reported by Ishii’s group in the1990s.Although the important and wide‐ranging applications of such catalysts have been summarizedrecently,there are no reviews that focus solely on oxidation strategies using multi‐nitroxy organocatalysts,which have interesting properties and high reactivities.This review covers the concisesynthetic methods and mechanistic profiles of known multi‐nitroxy organocatalysts and summarizessignificant advances in their use in efficient aerobic oxidation.Based on a combination of experimentaland theoretical results,guidelines for the future rational design of multi‐nitroxy organocatalystsare proposed,and the properties of various model multi‐nitroxy organocatalysts are predicted.The present overview of the advantages,limitations,and potential applications of multi‐nitroxyorganocatalysts can provide useful tools for researchers in the field of selective oxidation.

Synthesis,characterization,and activity of a covalently anchored heterogeneous perylene diimide photocatalyst

The consecutive two‐photon photocatalytic behavior of perylene diimide(PDI)enables it to catalyze photoreduction reactions that are thermodynamically unfavorable via single‐photon processes.In this work,we developed a heterogeneous PDI photocatalyst by covalently binding PDI molecules on the surface of nanosilica.This photocatalyst structure overcomes the intrinsic limitation of the low solubility of PDI,but retains its consecutive two‐photon photocatalytic property.Detailed characterization of the photocatalyst by techniques such as thermogravimetric analysis,solid‐state nuclear magnetic resonance spectroscopy,and Fourier transform infrared spectroscopy indicated that the PDI molecules were anchored covalently on the surface of nanosilica.The obtained photocatalyst reduced aryl halides under visible‐light irradiation in polar organic solvent and in water.The present study provides a promising strategy to realize two‐photon activity of PDI in common solvents for photocatalytic applications.

Zirconium-hydride-catalyzed site-selective hydroboration of amides for the synthesis of amines:Mechanism,scope,and application

Developing mild and efficient catalytic methods for the selective synthesis of amines is a longstanding research objective.In this respect,catalytic deoxygenative amide reduction has proven to be promising but challenging,as this approach necessitates selective C-O bond cleavage.Herein,we report the selective hydroboration of primary,secondary,and tertiary amides at room temperature catalyzed by an earth-abundant-metal catalyst,Zr-H,for accessing diverse amines.Various readily reducible functional groups,such as esters,alkynes,and alkenes,were well tolerated.Furthermore,the methodology was extended to the synthesis of bio-and drug-derived amines.Detailed mechanistic studies revealed a reaction pathway entailing aldehyde and amido complex formation via an unusual C-N bond cleavage-reformation process,followed by C-O bond cleavage.

Ni-mediated C–N activation of amides and derived catalytic transformations

Amide, as a ubiquitous functional group, is essential in various aspects of chemistry and biology. Although the history of studying amide is rich and fruitful, the synthetic application of amide is very limited due to the inertness of amide C–N bond. Recently,significant advances have been achieved towards the nickel-mediated C–N activation of amides. This approach allows a facile generation of acyl-nickel intermediates, and a number of unique transformations have been designed and realized based on the amide C–N bond activation. Focused on the catalytic transformation, this review summarizes and categorizes the recent advances on the synthetic applications of Ni-mediated C–N bond activation of amides.

Ru(Ⅱ)-catalyzed ortho-amidation and decarboxylation of aromatic acids: a versatile route to meta-substituted N-aryl benzamides

Carboxylate as a promising and valuable directing group has attracted a great deal of attention.However,employing it as a traceless direction group has rarely been reported.We developed the ruthenium-catalyzed amidation of substituted benzoic acids with isocyanates via directed C–H functionalization followed by decarboxylation to afford the corresponding metasubstituted N-aryl benzamides,in which the carboxylate serves as a unique,removable directing group.Notably,this protocol can provide an efficient alternative to access meta-substituted N-aryl benzamides,which are much more difficult to prepare than ortho-substituted analogues.

Effect of polyamide on selectivity of its supported Raney Ni catalyst

A newly-developed polyamide supported Raney Ni catalyst, which is suitable for use in fix-bed reactions with high selectivity, was studied in this paper. Selective hydrogenation of acetone to isopropanol was chosen as a probe reaction. It has been found that clean preparation of isopropanol could be achieved, that is to say, the two main byproducts(isopropyl ether and methyl-iso-butyl carbinol) could be eliminated with the newly-developed polyamide supported Raney Ni catalyst. The elimination of these side reactions was attributed to the adsorption effect of polyamide support and a model was proposed. The proposed model was further proved by hydroamination reaction of acetone. According to this model, catalyst support can play an important role in chemical reactions. Different products could be produced when different catalyst support is used, the main reaction and side reactions can even be reversed sometimes when the chemicals, active component of catalyst and reaction condition are the same. This model could help to improve catalytic selectivity of many Raney metal catalysts used routinely in chemical and oil refining industry, and is also useful for hydrogenation reactions in pharmaceutical and food industry.

Cu(Ⅱ)-catalyzed aerobic oxidative amidation of azoarenes with amides

A method for Cu(Ⅱ)-catalyzed dehydrogenative amidation of azoarene using air as the terminal oxidant was developed. Various amides, such as arylamides, alkylamides, lactams, and imides, are all effective amidation reagents and provide the desired products in moderate to excellent yields. Notably, good yields can also be obtained on a gram-scale with this amidation reaction.In this protocol of azoarene amidation, the catalyst(Cu(OAc)_2) and oxidant(air) are inexpensive and readily available, and the process is highly efficient and atom economical.

Copper-catalyzed direct oxidation and N-arylation of benzylamines with diaryliodonium salts

An efficient approach for the synthesis of N-arylated amides was developed via copper(Ⅱ) triflate-catalyzed direct oxidation of(aryl)methylamines to primary arylamides by air and subsequent N-arylation by diaryliodonium salts. Various substituted benzylamines could be applied in the reaction, providing a series of N-arylated amides in moderate to good yields. This method showed convenient, practical, and environment friendly advantages.

Iron-catalyzed aerobic oxidative amidation of tertiary amines with carboxylic acids

An oxidative amidation of tertiary amines with carboxylic acids has been developed in the presence of FeC13- 6H20 as catalyst and oxygen as oxidant. A variety of tertiary amides were obtained in good to excellent yields from inexpensive and readily available reagents. The possible reaction pathways were investigated.

A facile access for the C–N bond formation by transition metal-free oxidative coupling of benzylic C–H bonds and amides

Using 2,3-dichloro-5,6-dicyano-p-benzoquinone(DDQ)as the oxidant,we communicate an efficient oxidative C–N coupling of benzylic C–H bonds with amides to afford a series of amination products in good yields.A wide range of functional groups as well as various sulfonamides and carboxamides are well tolerated.Moreover,this reaction involves both the challenging C–H functionalization and C–N bond formation.

Ru-catalyzed highly enantioselective hydrogenation of a-keto Weinreb amides

Asymmetric hydrogenation of α-keto Weinreb amides has been realized with [Ru（（S）-Sunphos）（benzene）C1]C1 as the catalyst and CeC13·7H20 as the additive. A series of enantiopure -hydroxy Weinreb amides （up to 97% ee） have been obtained. Cata- lytic amount of CeC13·7H20 is essential for the high reactivity and enantioselectivity and the ratio of CeC13·7H20 to [Ru（（S）-Sunphos）（benzene）C1]C1 plays an important role in the hydrogenation reaction.