Copper-Catalyzed Amination of Aryl Halides with Aqueous Ammonia under Mild Conditions

A Cu(I) generated in situ from CuSO₄·5H₂O/sodium ascorbate catalyzed cross‐coupling reaction of aryl halides with aqueous ammonia for the synthesis of primary aromatic amines has been developed. Key to the success included the application of aqueous ammonia under a homogeneous condition.     

Copper‐Catalyzed Oxidative Amination and Allylic Amination of Alkenes

Enamines and enamides are useful synthetic intermediates and common components of bioactive compounds. A new protocol for their direct synthesis by a net alkene C? H amination and allylic amination by using catalytic Cu^II in the presence of MnO₂ is reported. Reactions between N‐aryl sulfonamides and vinyl arenes furnish enamides, allylic amines, indoles, benzothiazine dioxides, and dibenzazepines directly and efficiently. Control experiments further showed that MnO₂ alone can promote the reaction in the absence of a copper salt, albeit with lower efficiency. Mechanistic probes support the involvement of nitrogen‐radical intermediates. This method is ideal for the synthesis of enamides from 1,1‐disubstituted vinyl arenes, which are uncommon substrates in existing oxidative amination protocols.     

Tandem Oxidation Process Using Ceric Ammonium Nitrate: Three-Component Synthesis of Trisubstituted Imidazoles Under Aerobic Oxidation Conditions

By combining a ceric ammonium nitrate (CAN)–catalyzed aerobic oxidation of α-hydroxy ketones with a subsequent three-component condensation reaction using aldehydes and ammonium acetate, highly substituted imidazole derivatives can be assembled. This reaction is an important approach for the synthesis of highly substituted imidazole derivatives and was carried out in good to excellent yields in ethanol as an environmentally benign solvent.     

Ecofriendly and Efficient One-Pot Procedure for the Synthesis of Quinazoline Derivatives Catalyzed by an Acidic Ionic Liquid Under Aerobic Oxidation Conditions

A three-component condensation reaction between 2-aminobenzophenone derivatives, formaldehyde or aromatic aldehydes, and ammonium acetate efficiently provides substituted quinazolines in a one-pot reaction in the presence of Brönsted acidic ionic liquid, 1-methylimidazolium triflouroacetate ([Hmim]TFA), in conjunction with aerobic oxidation. The ionic liquid was separated from the reaction mixture by simple extraction and was recycled three times without considerable loss in activity.     

Novel and Selective Method for the Aerobic Oxidation of Benzylic Alcohols in the Absence of Metal Catalyst

A metal-free aerobic oxidation of benzylic alcohols to the corresponding benzylaldehyde derivatives was accomplished using proton ionic liquids (pyridium nitrate) as catalyst in a nonsolvent system with excellent conversion and selectivity. The catalyst could be recycled with no other polluted emission in this reaction procedure.      

Heterogeneously Porous γ‐MnO2‐Catalyzed Direct Oxidative Amination of Benzoxazole through CH Activation in the Presence of O2

Oxidative amination of azoles through catalytic C? H bond activation is a very important reaction due to the presence of 2‐aminoazoles in several biologically active compounds. However, most of the reported methods are performed under homogeneous reaction conditions using excess reagents and additives. Herein, we report the heterogeneous, porous γ‐MnO₂‐catalyzed direct amination of benzoxazole with wide range of primary and secondary amines. The amination was carried under mild reaction conditions and using molecular oxygen as a green oxidant, without any additives. The catalyst can easily be separated by filtration and reused several times without a significant loss of its catalytic performance. Of note, the reaction tolerates a functional group such as alcohol, thus indicating the broad applicability of this reaction.     

Synthesis of Benzimidazoles via Iron-Catalyzed Aerobic Oxidation Reaction of Imine Derivatives with o-Phenylenediamine

A simple and efficient protocol for preparing benzimidazoles via Fe(NO₃)₃ · 9H₂O-catalyzed aerobic oxidation reaction of imine derivatives with o-phenylenediamine. This process uses air as an economical and green oxidant, tolerates a wide range of substrates, and affords the targeted benzimidazoles in moderate to excellent yields.     

Iron-Catalyzed Highly Efficient Aerobic Oxidative Synthesis of Benzimidazoles,Benzoxazoles, and Benzothiazoles Directly from Aromatic Primary Amines Under Solvent-Free Conditions in the Open Air

Solvent-free oxidative synthesis of benzimidazoles, benzoxazoles, and benzothiazoles from aromatic primary amines and o-phenylenediamine, o-aminophenol, and o-aminothiophenol has been achieved by using Fe(NO₃)₃ and TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxyl). This reaction can use air as an economical and green oxidant, and a wide variety of derivatives were obtained in good to excellent yields. The reaction mechanism was proposed and this method provides a direct, practical, and efficient approach for the preparation of substituted benzimidazoles, benzoxazoles, and benzothiazoles.     

Air Stable Iridium Catalysts for Direct Reductive Amination of Ketones

Half-sandwich iridium complexes bearing bidentate urea-phosphorus ligands were found to catalyze the direct reductive amination of aromatic and aliphatic ketones under mild conditions at 0.5 mol % loading with high selectivity towards primary amines. One of the complexes was found to be active in both the Leuckart–Wallach (NH₄CO₂H) type reaction as well as in the hydrogenative (H₂/NH₄AcO) reductive amination. The protocol with ammonium formate does not require an inert atmosphere, dry solvents, as well as additives and in contrast to previous reports takes place in hexafluoroisopropanol (HFIP) instead of methanol. Applying NH₄CO₂D or D₂ resulted in a high degree of deuterium incorporation into the primary amine α-position.     

Cu-Catalyzed Desulfonylative Amination of Benzhydryl Sulfones

A new method for the synthesis of benzhydryl amines from the reaction of readily available sulfone derivatives with amines is described. The Cu-catalyzed desulfonylative amination not only provides structurally diverse benzhydryl amines in good yields, but is also applicable to iterative and intramolecular aminations. Control experiments suggested that the formation of a Cu-carbene intermediate generated from the sulfone substrate, which represents a new route for desulfonylative transformations.     

Aerobic Oxidation of 2,3,6-Trimethylphenol with Reusable Homogenized Copper Catalysts

The oxidation of 2,3,6-trimethylphenol(TMP) can produce both 2,3,5-trimethyl-1,4-benzoquinone(TMQ) and 2,3,5-trimethyl-1,4-hydroquinone(TMHQ) as important intermediates of vitamin E. With a soluble and porous polymer of intrinsic microporo-sity(PIM-1), we developed a highly active and reusable CuO@PIM-1 catalyst for the aerobic oxidation of TMP to TMQ and TMHQ. The CuO@PIM-1 catalyst is high active and selective for the aerobic oxidation of TMP, and TMQ and TMHQ can be obtained in yields of 81% and 19%, respectively. The CuO@PIM-1 catalyst has both advantages of homogeneous and heterogeneous and the CuO@PIM-1 catalyst showed a higher activity than homogeneous(CuCl₂) and heterogeneous(supported CuO) catalysts. Moreover, CuO@PIM-1 catalyst can be recovered easily and reused at least 5 times without deactivation.     

Simple Copper Catalysts for the Aerobic Oxidation of Amines: Selectivity Control by the Counterion

We describe the use of simple copper‐salt catalysts in the selective aerobic oxidation of amines to nitriles or imines. These catalysts are marked by their exceptional efficiency, operate at ambient temperature and pressure, and allow the oxidation of amines without expensive ligands or additives. This study highlights the significant role counterions can play in controlling selectivity in catalytic aerobic oxidations.     

壳聚糖固载的四苯基钴卟啉催化空气氧化环己烷

 将金属卟啉吸附固载到壳聚糖上,在室温下制备了壳聚糖四苯基钴卟啉催化剂,并用紫外光谱技术测定了四苯基钴卟啉的固载量. 在未加入任何溶剂和还原剂的条件下,研究了壳聚糖四苯基钴卟啉催化空气氧化环己烷的性能. 在418 K和0.8 MPa的空气压力下,壳聚糖四苯基钴卟啉能够很好地催化空气氧化环己烷,环己烷转化率为11%,相应的主产物环己醇和环己酮的选择性为87%,转化数为2.9×105,与未固载的四苯基钴卟啉相比,其催化性能大大提高,环己烷转化率和转化数分别提高了10倍和27倍. 研究结果表明: 壳聚糖对四苯基钴卟啉不仅有明显的保护作用,使之免遭氧化破坏,而且还有重要的助催化作用.     

TiO2-CeO2催化剂湿式氧化苯酚的活性研究

采用共沉淀法制备了湿式氧化降解苯酚的TiO2-CeO2催化剂，测定了反应过程中不同反应时间的COD去除率，结果表明，当Ti、Ce摩尔比为3：1时，在150℃、总压5MPa（其中氧分压4．5MPa）时，所制备的催化剂活性最高，反应90分钟COD去除率可以达到71％．对催化剂进行了比表面积、XRD和XPS测试，结果表明，高效的催化剂具有较多的活性位、催化剂粉末体系Ce的变价特性以及大量的表面吸附氧．     

Direct Catalytic Decarboxylative Amination of Aryl Acetic Acids

The decarboxylative coupling of a carboxylic acid with an amine nucleophile provides an alternative to the substitution of traditional organohalide coupling partners. Benzoic and alkynyl acids may be directly aminated by oxidative catalysis. In contrast, methods for intermolecular alkyl carboxylic acid to amine conversion, including amidate rearrangements and photoredox‐promoted approaches, require stoichiometric activation of the acid unit to generate isocyanate or radical intermediates. Reported here is a process for the direct chemoselective decarboxylative amination of electron‐poor arylacetates by oxidative Cu catalysis. The reaction proceeds at (or near) room temperature, uses native carboxylic acid starting materials, and is compatible with protic, electrophilic, and other potentially complicating functionality. Mechanistic studies support a pathway in which ionic decarboxylation of the acid generates a benzylic nucleophile which is aminated in a Chan–Evans–Lam‐type process.     

TiO_2-CeO_2催化剂湿式氧化苯酚的活性研究

采用共沉淀法制备了湿式氧化降解苯酚的TiO2-CeO2催化剂,测定了反应过程中不同反应时间的COD去除率,结果表明,当Ti、Ce摩尔比为3∶1时,在150℃、总压5MPa(其中氧分压4.5MPa)时,所制备的催化剂活性最高,反应90分钟COD去除率可以达到71%.对催化剂进行了比表面积、XRD和XPS测试,结果表明,高效的催化剂具有较多的活性位、催化剂粉末体系Ce的变价特性以及大量的表面吸附氧.     

Aerobic Oxidation of Alcohols Catalyzed by a New ZnO-Supported Copper Oxide Nanocatalyst in Aqueous Media

ZnO-supported copper oxide nanocatalyst is reported as an efficient recyclable catalyst for the aerobic oxidation of alcohols in the presence of oxygen as the oxidant. The catalyst was prepared by coprecipitation method and characterized by x-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM) analysis. A variety of primary and secondary alcohols were oxidized into the corresponding carbonyl compounds in good to excellent yields. The catalyst can be recovered by simple filtration and recycled up to five consecutive runs without significant decrease in the catalytic activity.     

Supported Palladium Oxide Nanoparticles in SBA‐15 as a Heterogeneous Catalyst for the Aerobic Oxidation of Alcohols

Palladium nanoparticles were first synthesized through the thermal decomposition method and subsequently immobilized on ordered mesoporous silica material, SBA‐15, to afford PdO/SBA‐15 catalyst. The synthesized catalyst was characterized by X‐ray diffraction, nitrogen adsorption‐desorption measurement, transmission electron microscopy, and inductively coupled plasma atomic emission spectrometry. The catalytic activity was tested for the aerobic oxidation of alcohols. Easy recovery, high yeilds and relatively short reaction times were observed for the mentioned catalyst.     

Highly Chemoselective Aerobic Oxidation of Amino Alcohols into Amino Carbonyl Compounds

The direct oxidation of unprotected amino alcohols to their corresponding amino carbonyl compounds has often posed serious challenges in organic synthesis and has constrained chemists to adopting an indirect route, such as a protection/deprotection strategy, to attain their goal. Described herein is a highly chemoselective aerobic oxidation of unprotected amino alcohols to their amino carbonyl compounds in which 2‐azaadamantane N‐oxyl (AZADO)/copper catalysis is used. The catalytic system developed leads to the alcohol‐selective oxidation of various unprotected amino alcohols, carrying a primary, secondary, or tertiary amino group, in good to high yield at ambient temperature with exposure to air, thus offering flexibility in the synthesis of nitrogen‐containing compounds.     

Practical Approach for Synthesis of 2-Amino-benzoxazole in Water

A practical copper-catalyzed amination of benzoxazole with secondary amine in water has been developed. This reaction has proved to be effective to some cyclic amines, and the substituted group of nitrogen has a great impact on the amination reaction. A copper-catalyzed/ amine-induced ring opening of the benzoxazole and recyclization/oxidation mechanism was also proposed.