N‐Benzyl DABCO Tribromide–Promoted Oxidative Coupling of Benzyl Cyanides: A Convenient Procedure for the Synthesis of α, α′‐Dicyanostilbenes

A convenient and efficient procedure was developed for preparing α,α′‐icyanostilbenes through the oxidative coupling reaction of benzyl cyanide derivatives using N‐benzyl DABCO tribromide as the oxidative bromination reagent in the presence of K₂CO₃ as a base.     

Calcium and magnesium chlorides-catalyzed oxidative esterification of aromatic aldehydes

An interesting procedure for the oxidative esterification of aromatic aldehydes has been developed. By using catalytic amount of CaCl₂ or MgCl₂, various methyl benzoates were isolated in good yields with hydrogen peroxide as the terminal oxidant.     

Effect of quenching on the methane coupling reaction

The effect of reaction mixture quenching on C₂ product formation in the methane coupling reaction on La₂O₃/CaO is disclosed. For reaction with the mixture (vol. %): 54.5 CH₄, 9.1 O₂ and 36.4 N₂ at 973 K, quenching of products results in a two-fold decrease in C₂ product yield. The results give evidence that in methane oxidative coupling methyl radical formation can occur in the gas phase to an extent comparable with that on the catalyst surface. The effect described must be taken into account in the case of an industrial application of methane oxidative coupling, too, because quenching is a regular procedure in the high temperature oxidative processes.     

Baeyer-Villiger oxidation of cyclic ketones utilizing potassium peroxydisulfate(K_2S_2O_8) or sodium perborate(NaBO_3) in acidic media

The efficient, green, facile, mild and straightforward conversion procedure for the oxidation of cyclic ketones to lactones at room temperature utilizing potassium peroxydisulfate (K₂S₂O₈) in acidic media is satisfactory to high yields without using traditional chlorinated solvents is reported. This oxidative reagent is cheap and friendly environmental procedure for industrial purposes than use of organic peracids.     

I2/Fe(NO3)3·9H2O-catalyzed oxidative synthesis of aryl carboxylic acids from aryl alkyl ketones and secondary benzylic alcohols

An interesting and convenient procedure for the oxidative transformation of aryl alkyl ketones and secondary benzylic alcohols to aryl carboxylic acids has been developed. By using iodine and Fe(NO₃)₃·9H₂O as the catalysts, DMSO and oxygen as the oxidants, the desired aryl carboxylic acids were synthesized in moderate to excellent yields (up to 91%).     

Copper‐Catalyzed Aerobic Oxidative C?H and C?C Functionalization of 1‐[2‐(Arylamino)aryl]ethanones Leading to Acridone Derivatives

Efficient copper‐catalyzed aerobic oxidative C? H and C? C functionalization of 1‐[2‐(arylamino)aryl]ethanones leading to acridones has been developed. The procedure involves cleavage of aromatic C? H and acetyl C? C bonds with intramolecular formation of a diarylketone bond. The protocol uses inexpensive Cu(O₂CCF₃)₂ as catalyst, pyridine as additive, and economical and environmentally friendly oxygen as the oxidant, and the corresponding acridones with various functional groups were obtained in moderate to good yields.     

An Efficient Procedure for the Mild Oxidative Cleavage of Alkene-3-Ols: Application to the Preparation of 2-Alkoxy-2-(3,4,5-Trimethoxyphenyl)- Acetaldehyde

A new procedure for the oxidative cleavage of alken-3-ols to α-alkoxy aldehydes has been developed using a combination of OsO₄/Et₃N/KIO₄/di-benzo-18-crown-6-ether in benzene/water. This extremely mild method has been applied to several 2-alkoxy-2-(3,4,5-trimethoxyphenyl)acetaldehydes.     

Oxidative dehydrogenation of propane on the VO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/CeZrO/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> supported catalyst

The oxidative dehydrogenation of propane on a supported vanadium catalyst was studied (the support was a complex oxide system consisting of a ceria–zirconia solid solution deposited on γ-Al₂O₃ (CeZrO/γ-Al₂O₃)). A comparative analysis of the properties of the support and the catalyst prepared on its basis was performed. The support and catalyst were characterized by the BET method, scanning electron microscopy, X-ray diffraction analysis, and Raman spectroscopy. The catalytic properties of the catalyst and support were studied in propane oxidation at 450 and 500°C with pulse feeding of the reagent. The effect of propane on the support was found to improve the oxidative properties of the latter. This behavior of the support is related to the preparation procedure, which leads to the formation on its surface of the crystalline phase of the ceria–zirconia solid solution and amorphous ZrO₂ and Al₂O₃ phases and/or their solid solution. Similar processes occur with the catalyst support during the oxidative dehydrogenation, giving rise to additional active centers (CeVO₄).     

Simple and Efficient Method for Obtaining Fluorene and Spirobifluorene Bromide Derivatives

A mild, simple, and efficient synthetic procedure for the preparation of 2-monobromo-, 2,7-dibromo-, and 2,2′,7,7′-tetrabromo-substituted spirobifluorene derivatives and their key intermediates, 2-monobromo- and 2,7-dibromo-substituted fluorene compounds, has been developed. The oxidative bromination of fluorene and spirobifluorene was achieved using NaBr/H₂O₂ as the bromine source. High conversion of the starting materials was achieved together with good selectivities under optimized reaction conditions.     

Lewis superacids derived from triflic and triflimidic acids and their use as catalysts in 1,6-diene cycloisomerisation

We have developed a procedure for the preparation of anhydrous metallic triflates and triflimidates of general formulae M(OTf)_n and M(NTf₂)_n based on the oxidative dissolution of metal powders in the presence of HOTf or HNTf₂, respectively. The method provides salts in anhydrous form, solvates with DMSO molecules, and constitutes a good complement to a previous method developed in our group based on an electrochemical procedure. We have compared the catalytic activity of various Sn(IV) salts in the reaction of cycloisomerisation of 1,6-dienes and identified that anhydrous Sn(IV) triflimidates are more active catalysts, as compared to anhydrous Sn(IV) triflate, or their hydrated forms usually obtained by conventional methods of preparation or purchased from chemical suppliers.     

Ru(III)-catalyzed oxidative reaction in ionic liquid: an efficient and practical route to 2-substituted benzothiazoles and their hybrids with pyrimidine nucleoside

An efficient, practical and environmentally benign synthesis of 2-substituted benzothiazoles was developed through RuCl₃-catalyzed oxidative condensation of 2-aminothiophenol with aldehyde in ionic liquid by using air as the oxidant. With this procedure, a series of 2-substituted benzothiazoles and benzothiazole/pyrimidine nucleoside hybrids with antimicrobial activities were efficiently prepared from easily accessible starting materials.     

An expedient synthesis of indolo[1,2-a]quinolines via Mn(OAc)3-mediated oxidative free radical cyclization and NaI/O2-assisted dealkoxycarbonylation/aerobic oxidation cascade

An expedient synthetic procedure of indolo[1,2-a]quinolines was developed using a sequential Cu-mediated N-arylation of indole, Mn(OAc)₃-mediated oxidative free radical cyclization, and NaI/O₂-assisted concomitant dealkoxycarbonylation/aerobic oxidation. The last step was replaced by a palladium-catalyzed decarboxylation/elimination protocol for the allyl ester derivatives.     

Molecular‐Level Insights into the Oxidative Degradation of Grafted Amines

The oxidative degradation of CO₂ adsorbents consisting of amine‐grafted pore‐expanded mesoporous MCM‐41 silica was investigated. The adsorbents were treated under flowing air at various temperatures, and the degree of deactivation was evaluated through the measurement of their CO₂ adsorption capacity prior and subsequent to exposure to air. To decipher the chemical structure of surface species upon air‐deactivation of grafted amines, a solvent extraction procedure was developed using a deuterated basic solution. The obtained solutions were analyzed by a variety of 1D and 2D NMR spectroscopy techniques, such as ²⁹Si, ¹³C, ¹H, [¹H,¹⁵N] HMBC, [¹H,¹³C] HMQC, COSY and DOSY. The surface species generated by oxidative degradation of amine‐grafted silica were found to contain functional groups such as imine, amide and carboxylic groups. Several structural units were conclusively demonstrated.     

Alkene and Alkyne Oxidative Cleavage Catalyzed by RuO4 in Environmentally Acceptable Solvents

Abstract

The application of CCl₄, C₆H₁₂, EtOAc, and Me₂CO as solvents for biphasic systems has been compared for oxidative cleavage of alkenes and alkynes by RuO₄ to carboxylic acids, using the RuCl₃ · nH₂O–IO(OH)₅ reagent for which an improved procedure is described. Cyclohexane is an effective and economic replacement for the environmentally unfriendly CCl₄; acetone and ethyl acetate are less effective.     

Oxidative C−H/C−H Cross‐Coupling Reactions between N‐Acylanilines and Benzamides Enabled by a Cp*‐Free RhCl3/TFA Catalytic System

By making use of a dual‐chelation‐assisted strategy, a completely regiocontrolled oxidative C?H/C?H cross‐coupling reaction between an N‐acylaniline and a benzamide has been accomplished for the first time. This process constitutes a step‐economic and highly efficient pathway to 2‐amino‐2′‐carboxybiaryl scaffolds from readily available substrates. A Cp*‐free RhCl₃/TFA catalytic system was developed to replace the [Cp*RhCl₂]₂/AgSbF₆ system generally used in oxidative C?H/C?H cross‐coupling reactions between two (hetero)arenes (Cp*=pentamethylcyclopentadienyl, TFA=trifluoroacetic acid). The RhCl₃/TFA system avoids the use of the expensive Cp* ligand and AgSbF₆. As an illustrative example, the procedure developed herein greatly streamlines the total synthesis of the naturally occurring benzo[c]phenanthridine alkaloid oxynitidine, which was accomplished in excellent overall yield.     

Biomimetic Decarboxylation of Carboxylic Acids with PhI（OAc）2 Catalyzed by Manganese Porphyrin [Mn（TPP）OAc]

Manganese（Ⅲ） meso-tetraphenylporphyrin acetate [Mn（TPP）OAc] served as an effective catalyst for the oxidative decarboxylation of carboxylic acids with （diacetoxyiodo）benzene [PhI（OAc）2] in CH2CI2-H2O（95：5, volume ratio）. The aryl substituted acetic acids are more reactive than the less electron rich linear carboxylic acids in the presence of catalyst Mn（TPP）OAc. In the former case, the formation of carbonyl products was complete within just a few minutes with 〉97% selectivities, and no further oxidation of the produced aldehydes was achieved under these catalytic conditions. This method provides a benign procedure owing to the utilization of low toxic（diacetoxyiodo） benzene, biologically relevant manganese porphyrins, and carboxylic acids.     

Self‐Assembly of Multi‐nanozymes to Mimic an Intracellular Antioxidant Defense System

In this work, for the first time, we constructed a novel multi‐nanozymes cooperative platform to mimic intracellular antioxidant enzyme‐based defense system. V₂O₅ nanowire served as a glutathione peroxidase (GPx) mimic while MnO₂ nanoparticle was used to mimic superoxide dismutase (SOD) and catalase (CAT). Dopamine was used as a linker to achieve the assembling of the nanomaterials. The obtained V₂O₅@pDA@MnO₂ nanocomposite could serve as one multi‐nanozyme model to mimic intracellular antioxidant enzyme‐based defense procedure in which, for example SOD, CAT, and GPx co‐participate. In addition, through assembling with dopamine, the hybrid nanocomposites provided synergistic antioxidative effect. Importantly, both in vitro and in vivo experiments demonstrated that our biocompatible system exhibited excellent intracellular reactive oxygen species (ROS) removal ability to protect cell components against oxidative stress, showing its potential application in inflammation therapy.     

Heterogeneous copper‐catalyzed oxidative coupling of oxime acetates with sodium sulfinates: An efficient and practical synthesis of β‐keto sulfones

An efficient and practical route to β‐keto sulfones has been developed through heterogeneous oxidative coupling of oxime acetates with sodium sulfinates by using an MCM‐41‐supported Schiff base‐pyridine bidentate copper (II) complex [MCM‐41‐Sb,Py‐Cu (OAc)₂] as the catalyst and oxime acetates as an internal oxidant, followed by hydrolysis. The reaction generates a variety of β‐keto sulfones in good to excellent yields. This new heterogeneous copper (II) catalyst can be easily prepared via a simple procedure from readily available and inexpensive reagents and exhibits the same catalytic activity as Cu (OAc)₂. MCM‐41‐Sb,Py‐Cu (OAc)₂ is also easy to recover and is recyclable up to eight times with almost consistent activity.     

CO2选择氧化低碳烷烃的研究进展

本文以低碳烷烃的选择催化氧化反应为对象，对几种CO₂选择氧化低碳烷烃的反应工艺进行了归纳总结，重点分析讨论了催化氧化反应中CO₂作为氧化剂的作用机制，并提出了研究展望。