- Nitrogen Atom Transfer Catalysis by Metallonitrene C?H Insertion: Photocatalytic Amidation of Aldehydes
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C?H amination and amidation by catalytic nitrene transfer are well-established and typically proceed via electrophilic attack of nitrenoid intermediates. In contrast, the insertion of (formal) terminal nitride ligands into C?H bonds is much less developed and catalytic nitrogen atom transfer remains unknown. We here report the synthesis of a formal terminal nitride complex of palladium. Photocrystallographic, magnetic, and computational characterization support the assignment as an authentic metallonitrene (Pd?N) with a diradical nitrogen ligand that is singly bonded to PdII. Despite the subvalent nitrene character, selective C?H insertion with aldehydes follows nucleophilic selectivity. Transamidation of the benzamide product is enabled by reaction with N3SiMe3. Based on these results, a photocatalytic protocol for aldehyde C?H trimethylsilylamidation was developed that exhibits inverted, nucleophilic selectivity as compared to typical nitrene transfer catalysis. This first example of catalytic C?H nitrogen atom transfer offers facile access to primary amides after deprotection.
- Schmidt-R?ntsch, Till,Verplancke, Hendrik,Lienert, Jonas N.,Demeshko, Serhiy,Otte, Matthias,Van Trieste, Gerard P.,Reid, Kaleb A.,Reibenspies, Joseph H.,Powers, David C.,Holthausen, Max C.,Schneider, Sven
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supporting information
(2022/01/20)
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- AMINE-BORANES AS BIFUNCTIONAL REAGENTS FOR DIRECT AMIDATION OF CARBOXYLIC ACIDS
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The present invention generally relates to a process for selective and direct activation and subsequent amidation of aliphatic and aromatic carboxylic acids to afford an amide R3CONR1R2. That the process is capable of delivering gaseous or low-boiling point amines provides a major advantage over existing methodologies, which involves an intermediate of triacyloxyborane-amine complex [(R3CO2)3—B—NHR1R2]. This procedure readily produces primary, secondary, and tertiary amides, and is compatible with the chirality of the acid and amine involved. The preparation of known pharmaceutical molecules and intermediates has also been demonstrated.
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Paragraph 0008-0009; 0063-0064
(2022/03/04)
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- Aerobic oxidation of primary amines to amides catalyzed by an annulated mesoionic carbene (MIC) stabilized Ru complex
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Catalytic aerobic oxidation of primary amines to the amides, using the precatalyst [Ru(COD)(L1)Br2] (1) bearing an annulated π-conjugated imidazo[1,2-a][1,8]naphthyridine-based mesoionic carbene ligand L1, is disclosed. This catalytic protocol is distinguished by its high activity and selectivity, wide substrate scope and modest reaction conditions. A variety of primary amines, RCH2NH2 (R = aliphatic, aromatic and heteroaromatic), are converted to the corresponding amides using ambient air as an oxidant in the presence of a sub-stoichiometric amount of KOtBu in tBuOH. A set of control experiments, Hammett relationships, kinetic studies and DFT calculations are undertaken to divulge mechanistic details of the amine oxidation using 1. The catalytic reaction involves abstraction of two amine protons and two benzylic hydrogen atoms of the metal-bound primary amine by the oxo and hydroxo ligands, respectively. A β-hydride transfer step for the benzylic C-H bond cleavage is not supported by Hammett studies. The nitrile generated by the catalytic oxidation undergoes hydration to afford the amide as the final product. This journal is
- Yadav, Suman,Reshi, Noor U Din,Pal, Saikat,Bera, Jitendra K.
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p. 7018 - 7028
(2021/11/17)
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- Ru(ii)- And Ru(iv)-dmso complexes catalyze efficient and selective aqueous-phase nitrile hydration reactions under mild conditions
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New water-soluble ruthenium(ii)- and ruthenium(iv)-dmso complexes [RuCl2(dmso)2(NH3)(CH3CN)] (1), [RuCl2(dmso)3(CH3CN)] (2), and [RuCl2(dmso)3(NH3)]·PF6·Cl (3) have been synthesized and characterized using elemental analyses, IR, 1H and 31P NMR, and electronic absorption spectroscopy. The molecular structures of complexes 1-3 were determined crystallographically. The reactivity of complexes 1-3 has been tested for aqueous-phase nitrile hydration at 60 °C in air, and good efficiency and selectivity are shown for the corresponding amide derivatives. Best performance is achieved with complex 3. Amide conversions of 56-99% were obtained with a variety of aromatic, alkyl, and vinyl nitriles. The reaction tolerated hydroxyl, nitro, bromo, formyl, pyridyl, benzyl, alkyl, and olefinic functional groups. Amides were isolated by simple decantation from the aqueous-phase catalyst. A catalyst loading down to 0.0001 mol% was examined and turnover numbers as high as 990?000 were observed. The catalyst was stable for weeks in solution and could be reused more than seven times without significant loss in catalytic activity. The gram-scale reaction was also performed to produce the desired product in high yields. This journal is
- Dubey, Santosh Kumar,Kaur, Gurmeet,Rath, Nigam P.,Trivedi, Manoj
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p. 17339 - 17346
(2021/10/08)
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- Cu(II)-promoted oxidative C-N bond cleavage of N-benzoylamino acids to primary aryl amides
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A novel protocol for CuCl2-promoted oxidative C-N bond cleavage of N-benzoyl amino acids was developed. It is the first example of using accessible amino acid as an ammonia synthetic equivalent for the synthesis of primary aryl amides via CuCl2-promoted oxidative C-N bond cleavage reaction. The present protocol shows excellent functional group tolerance and provides an alternative method for the synthetic of primary aryl amides in 84-96% yields.
- Zhou, Liandi,Liu, Wei,Zhao, Yongli,Chen, Junmin
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- Deoxygenative hydroboration of primary, secondary, and tertiary amides: Catalyst-free synthesis of various substituted amines
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Transformation of relatively less reactive functional groups under catalyst-free conditions is an interesting aspect and requires a typical protocol. Herein, we report the synthesis of various primary, secondary, and tertiary amines through hydroboration of amides using pinacolborane under catalyst-free and solvent-free conditions. The deoxygenative hydroboration of primary and secondary amides proceeded with excellent conversions. The comparatively less reactive tertiary amides were also converted to the corresponding N,N-diamines in moderate yields under catalyst-free conditions, although alcohols were obtained as a minor product.
- An, Duk Keun,Jaladi, Ashok Kumar,Kim, Hyun Tae,Yi, Jaeeun
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supporting information
(2021/11/17)
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- Gram-Scale Preparation of Acyl Fluorides and Their Reactions with Hindered Nucleophiles
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A series of acyl fluorides was synthesized at 100 mmol scale using phase-transfer-catalyzed halogen exchange between acyl chlorides and aqueous bifluoride solution. The convenient procedure consists of vigorous stirring of the biphasic mixture at room temperature, followed by extraction and distillation. Isolated acyl fluorides (usually 7-20 g) display excellent purity and can be transformed into sterically hindered amides and esters when treated with lithium amide bases and alkoxides under mild conditions.
- Barbasiewicz, Micha?,Tryniszewski, Micha?
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- Nano-construction of CuO nanorods decorated with g-C3N4 nanosheets (CuO/g-C3N4-NS) as a superb colloidal nanocatalyst for liquid phase C[sbnd]H conversion of aldehydes to amides
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Herein, we describe an intelligent strategy to fabricate nanosheets of graphitic carbon nitride (g-C3N4) decorated with nanorods copper oxide (CuO NRs). Then, the catalytic activity of CuONRs/g-C3N4-NS was developed for the synthesis of primary amides in water. The morphology of CuO and its synergetics effect with nanosheets g-C3N4 a major role in the yield of products. Furthermore, hydroxylamine hydrochloride (NH2OH·HCl) due to availability and affordability was used as a suitable substitute for ammonia source. The findings demonstrate that this layer nanostructure is a superb catalyst for converting various derivatives of aldehyde to their corresponding amides. The current protocol can be useful criterion in the synthesis and stabilization of metal oxides and provides new insight in organic transformation.
- Mohammadi, Robabeh,Gholipour, Behnam,Alamgholiloo, Hassan,Rostamnia, Sadegh,Mohtasham, Hamed,Zonouzi, Afsaneh,Ramakrishna, Seeram,Shokouhimehr, Mohammadreza
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- Half-Sandwich Iridium Complexes Based on β-Ketoamino Ligands: Preparation, Structure, and Catalytic Activity in Amide Synthesis
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A series of β-ketoamino-based N,O-chelate half-sandwich iridium complexes with the general formula [Cp*IrClL] have been prepared in good yields. These air-insensitive iridium complexes showed desirable catalytic activity in an amide preparation under mild conditions. A number of amides with diverse substituted groups were furnished in a one-pot reaction with good-to-excellent yields through an amidation reaction of NH2OH·HCl with aldehydes in the presence of these iridium(III) precursors. The excellent catalytic activity, mild reaction conditions, and broad substrate scope gave this type of iridium catalyst potential for use in industry. All of the obtained iridium complexes were well characterized by different spectroscopy techniques. The exact molecular structure of complex 3 has been confirmed by single-crystal X-ray analysis.
- Wang, Yang,Guo, Wen,Guan, Ai-Lin,Liu, Shuang,Yao, Zi-Jian
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p. 11514 - 11520
(2021/07/31)
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- A Molecular Iron-Based System for Divergent Bond Activation: Controlling the Reactivity of Aldehydes
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The direct synthesis of amides and nitriles from readily available aldehyde precursors provides access to functional groups of major synthetic utility. To date, most reliable catalytic methods have typically been optimized to supply one product exclusively. Herein, we describe an approach centered on an operationally simple iron-based system that, depending on the reaction conditions, selectively addresses either the C=O or C-H bond of aldehydes. This way, two divergent reaction pathways can be opened to furnish both products in high yields and selectivities under mild reaction conditions. The catalyst system takes advantage of iron's dual reactivity capable of acting as (1) a Lewis acid and (2) a nitrene transfer platform to govern the aldehyde building block. The present transformation offers a rare control over the selectivity on the basis of the iron system's ionic nature. This approach expands the repertoire of protocols for amide and nitrile synthesis and shows that fine adjustments of the catalyst system's molecular environment can supply control over bond activation processes, thus providing easy access to various products from primary building blocks.
- Chatterjee, Basujit,Jena, Soumyashree,Chugh, Vishal,Weyhermüller, Thomas,Werlé, Christophe
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p. 7176 - 7185
(2021/06/30)
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- Amide bond formation in aqueous solution: Direct coupling of metal carboxylate salts with ammonium salts at room temperature
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Herein, we report a green, expeditious, and practically simple protocol for direct coupling of carboxylate salts and ammonium salts under ACN/H2O conditions at room temperature without the addition of tertiary amine bases. The water-soluble coupling reagent EDC·HCl is a key component in the reaction. The reaction runs smoothly with unsubstituted/substituted ammonium salts and provides a clean product without column chromatography. Our reaction tolerates both carboxylate (which are unstable in other forms) and amine salts (which are unstable/volatile when present in free form). We believe that the reported method could be used as an alternative and suitable method at the laboratory and industrial scales. This journal is
- Nielsen, John,Tung, Truong Thanh
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supporting information
p. 10073 - 10080
(2021/12/10)
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- A mild and selective Cu(II) salts-catalyzed reduction of nitro, azo, azoxy, N-aryl hydroxylamine, nitroso, acid halide, ester, and azide compounds using hydrogen surrogacy of sodium borohydride
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The first mild, in situ, single-pot, high-yielding well-screened copper (II) salt-based catalyst system utilizing the hydrogen surrogacy of sodium borohydride for selective hydrogenation of a broad range of nitro substrates into the corresponding amine under habitancy of water or methanol like green solvents have been described. Moreover, this catalytic system can also activate various functional groups for hydride reduction within prompted time, with low catalyst-loading, without any requirement of high pressure or molecular hydrogen supply. Notably, this system explores a great potential to substitute expensive traditional hydrogenation methodologies and thus offers a greener and simple hydrogenative strategy in the field of organic synthesis.
- Kalola, Anirudhdha G.,Prasad, Pratibha,Mokariya, Jaydeep A.,Patel, Manish P.
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supporting information
p. 3565 - 3589
(2021/10/12)
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- Method for preparing primary and secondary amide compounds
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The invention belongs to the field of organic chemical synthesis, and particularly relates to a method for preparing primary and secondary amide compounds. The method for preparing primary and secondary amide compounds comprises the following steps of carrying out catalytic reduction on an N-substituted amide compound at 30-130 DEG C by using a protic solvent as a reduction reagent and a dichloro(p-methyl isopropylbenzene) ruthenium (II) dimer complex as a catalyst to obtain a reaction solution after the reduction reaction is finished, and carrying out post-treatment on the reaction solution to obtain the corresponding primary amide compound or secondary amide compound. According to the method for preparing the primary and secondary amide compounds, the transfer hydrogenation reaction of nitrogen-oxygen and nitrogen-carbon bonds is realized, the reaction conditions are mild and simple, the substrate application range is wide, the operation is convenient, and the corresponding primary amide compound or secondary amide compound is obtained with high efficiency and high selectivity.
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Paragraph 0035-0045
(2021/02/06)
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- The polyhedral nature of selenium-catalysed reactions: Se(iv) species instead of Se(vi) species make the difference in the on water selenium-mediated oxidation of arylamines
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Selenium-catalysed oxidations are highly sought after in organic synthesis and biology. Herein, we report our studies on the on water selenium mediated oxidation of anilines. In the presence of diphenyl diselenide or benzeneseleninic acid, anilines react with hydrogen peroxide, providing direct and selective access to nitroarenes. On the other hand, the use of selenium dioxide or sodium selenite leads to azoxyarenes. Careful mechanistic analysis and 77Se NMR studies revealed that only Se(iv) species, such as benzeneperoxyseleninic acid, are the active oxidants involved in the catalytic cycle operating in water and leading to nitroarenes. While other selenium-catalysed oxidations occurring in organic solvents have been recently demonstrated to proceed through Se(vi) key intermediates, the on water oxidation of anilines to nitroarenes does not. These findings shed new light on the multifaceted nature of organoselenium-catalysed transformations and open new directions to exploit selenium-based catalysis.
- Capperucci, Antonella,Dalia, Camilla,Tanini, Damiano
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supporting information
p. 5680 - 5686
(2021/08/16)
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- Cubic CuxZrO100-x as an efficient and selective catalyst for the oxidation of aromatics active methyl, alcohol, and amine groups
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The local structure of a supported active metal plays a vital role in determining the desired product's selectivity in heterogeneous catalysis. Herein, we have developed a simple protocol for the synthesis of Cu doped on cubic ZrO2 mixed metal oxide catalysts and used it for the selective oxidation of various functional groups. The catalyst was synthesized by varying the wt.% of Cu (1–20%) on ZrO2 by co-precipitation, followed by hydrothermal treatment. The X-ray diffraction pattern of the catalysts confirmed the formation of the cubic phase of ZrO2, and the growth of CuO occurred along the (1 1 1) plane. The microscopy analysis revealed the uniform distribution of Cu on the ZrO2 surface, while XPS analysis confirmed the presence of copper in the +2 oxidation state. The synthesized catalyst with 2 wt% loading of Cu on ZrO2 showed excellent liquid-phase oxidation properties and gave good to best conversion of active methyl groups, alcohols, and amines with high selectivities to corresponding ketones, aldehydes, and amides, respectively, under milder reaction conditions. Furthermore, the synthesized catalyst showed a broader substrate scope for the various substituted active methyl groups, alcohols, and amines with good conversion and selectivity.
- Bankar, Balasaheb D.,Advani, Jacky H.,Biradar, Ankush V.
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- Ruthenium(II) complexes bearing bidentate acylthiourea ligands for direct oxidation of amine α-carbon to amide
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In this study, the synthesis and structural characterization of ruthenium complexes supported by S,O-acylthiourea ligands (L1-L6) with different substituent groups as well as auxiliary ligands PPH3, CO, and Cl and their evaluation as catalysts for direct oxidation of the α-methylene group in amines were reported. Ru(II) complexes, Ru1-Ru6, were prepared from the reaction of the RuH(CO)Cl(PPh3)3 precursor and ligands L1-L6 having different electronic and steric properties. The ligands and complexes prepared were characterized by FT-IR, 1H–13C- and/or 31P NMR spectroscopic techniques. The molecular structures of Ru1 and Ru3 complexes with appropriate crystal quality were also confirmed by X-ray single crystal analysis. Solid-state structures of Ru1 and Ru3 revealed that the ruthenium center is surrounded by one carbonyl, one chloride, two PPh3 ligands, and the S,O-donor atoms from the acylthiourea ligand in bidentate monoanionic form. The catalytic activity of all complexes for the α-oxygenation reactions of primary benzylic amines to amides was investigated. Overall, all catalysts exhibited excellent activity and selectivity towards the formation of amide production under the present reaction conditions. In addition, both catalyst activation and product selectivity/formation were particularly dependent on the amount/type of base and oxygen.
- Aslan, Muhammed,Gumus, Ilkay
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- Visible-light-induced direct construction of amide bond from carboxylic acids with amines in aqueous solution
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A novel visible-light-promoted N-acylation for the synthesis of amides from easily available carboxylic acids with amines in the presence of I2 within 2.5 h in aqueous solution has been developed. Using sunlight as the visible light source greatly reduces the cost of experiments and produces almost no toxic effects. Hence, this study provides an alternative catalytic system for the construction of a wide range of amides with readily available materials. Moreover, the strategy was successfully applied in the preparation of N-(3-(2,6-dimethoxyphenoxy)-7-nitroquinoxalin-2-yl)benzohydrazide, which displayed a signification anti-proliferation effect on A549, MCF-7 and HCT116 cell lines.
- Wang, Jin,Hou, Huiqing,Hu, Yongzhi,Lin, Jin,Wu, Min,Zheng, Zhiqiang,Xu, Xiuzhi
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supporting information
(2021/02/09)
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- Visible light-mediated synthesis of amides from carboxylic acids and amine-boranes
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Here, a photocatalytic deoxygenative amidation protocol using readily available amine-boranes and carboxylic acids is described. This approach features mild conditions, moderate-to-good yields, easy scale-up, and up to 62 examples of functionalized amides with diverse substituents. The synthetic robustness of this method was also demonstrated by its application in the late-stage functionalization of several pharmaceutical molecules.
- Chen, Xuenian,Kang, Jia-Xin,Ma, Yan-Na,Miao, Yu-Qi
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supporting information
p. 3595 - 3599
(2021/06/06)
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- Method for preparing amide from carboxylic acid under irradiation of blue light by taking iridium and cobalt complexes as catalysts
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The invention relates to a method for preparing amide from carboxylic acid under the irradiation of blue light by taking iridium and cobalt complexes as catalysts, and belongs to the field of chemistry. The method comprises the following step of: by taking R substituted carboxylic acid and R1' and R2' substituted amines as raw materials, triphenylphosphine as a deoxidizing agent, [Ir(dF(CF3)ppy)2(dtbbpy)]PF6 as a photocatalyst and Co(dmgH)(dmgH2)Cl2 as a metal complex catalyst, reacting in dichloromethane in an inert atmosphere and under the irradiation of blue light to obtain an amide compound, wherein R is an aryl group, a heteroaryl group, a protected amino group, a substituted alkyl group, a substituted aryl group or a substituted protected amino group, R1' is a hydrogen group, a substituted alkyl group, a phenyl group or a substituted phenyl group, and R2' is a hydrogen group, a substituted alkyl group, a phenyl group or a substituted phenyl group.
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Paragraph 0103-0104
(2021/05/12)
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- Mechanochemical Synthesis of Primary Amides
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Ball milling of aromatic, heteroaromatic, vinylic, and aliphatic esters with ethanol and calcium nitride afforded the corresponding primary amides in a transformation that was compatible with a variety of functional groups and maintained the integrity of a stereocenter α to carbonyl. This methodology was applied to α-amino esters and N-BOC dipeptide esters and also to the synthesis of rufinamide, an antiepileptic drug.
- Gómez-Carpintero, Jorge,Sánchez, J. Domingo,González, J. Francisco,Menéndez, J. Carlos
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p. 14232 - 14237
(2021/10/20)
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- Direct Amidation of Esters by Ball Milling**
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The direct mechanochemical amidation of esters by ball milling is described. The operationally simple procedure requires an ester, an amine, and substoichiometric KOtBu and was used to prepare a large and diverse library of 78 amide structures with modest to excellent efficiency. Heteroaromatic and heterocyclic components are specifically shown to be amenable to this mechanochemical protocol. This direct synthesis platform has been applied to the synthesis of active pharmaceutical ingredients (APIs) and agrochemicals as well as the gram-scale synthesis of an active pharmaceutical, all in the absence of a reaction solvent.
- Barreteau, Fabien,Battilocchio, Claudio,Browne, Duncan L.,Godineau, Edouard,Leitch, Jamie A.,Nicholson, William I.,Payne, Riley,Priestley, Ian
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supporting information
p. 21868 - 21874
(2021/09/02)
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- Green and efficient Beckmann rearrangement by Cu(II) contained nano-silica triazine based dendrimer in water
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In this research, a Cu(II) contained nano-silica triazine based dendrimer was prepared, characterized, and utilized as a retrievable catalytic system (Cu(II)-TrDen@nSiO2) for green formation of primary amides in water at room temperature. The structure of nanoparticles was fully characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetry analysis (TGA). The results revealed that the nanoparticles have spherical morphology and an average size of around 40 nm. The analysis also illustrated that the copper nanoparticles had been successfully loaded on the nitrogen-rich dendritic structure with a uniform distribution. The inductively coupled plasma analysis showed that about 0.67 mmol/g of Cu was loaded on the Cu(II)-TrDen@nSiO2 support. Mild reaction conditions, excellent yields, environment-friendly synthesis, and easily prepared starting materials are the key features of the present method. The catalyst is easily removed from the reaction media using a simple filtration and can be re-used at least five times without any considerable loss of its catalytic activity.
- Bahreininejad, Mohammad Hasan,Moeinpour, Farid
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p. 893 - 901
(2021/01/12)
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- Process Development of the Copper(II)-Catalyzed Dehydration of a Chiral Aldoxime and Rational Selection of the Co-Substrate
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The access towards chiral nitriles remains crucial in the synthesis of several pharmaceuticals. One approach is based on metal-catalyzed dehydration of chiral aldoximes, which are generated from chiral pool-derived aldehydes as substrates, and the use of a cheap and readily available nitrile as co-substrate and water acceptor. Dehydration of N-acyl α-amino aldoximes such as N-Boc-l-prolinal oxime catalyzed by copper(II) acetate provides access to the corresponding N-acyl α-amino nitriles, which are substructures of the pharmaceuticals Vildagliptin and Saxagliptin. In this work, a detailed investigation of the formation of the amide as a by-product at higher substrate loadings is performed. The amide formation depends on the electronic properties of the nitrile co-substrate. We could identify an acceptor nitrile which completely suppressed amide formation at high substrate loadings of 0.5 m even when being used with only 2 equivalents. In detail, utilization of trichloroacetonitrile as such an acceptor nitrile enabled the synthesis of N-Boc-cyanopyrrolidine in a high yield of 92 % and with full retention of the absolute configuration.
- Gr?ger, Harald,Nonnhoff, Jannis
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- Method for efficiently synthesizing primary amide and N-methyl secondary amide compounds
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The invention discloses a method for efficiently synthesizing primary amide and N-methyl secondary amide compounds, which specifically comprises the following steps: adding metal amine borane MRNHBH3 into a reaction container filled with anhydrous THF (tetrahydrofuran) under anhydrous and anaerobic conditions, wherein M=Na or K, and R=H or Me; adding an ester compound R 'CO2R ''(R' is alkyl or aryl) and R'' is alkyl or aryl) into a reaction kettle, carrying out stirring reaction at room temperature, and carrying out post-treatment to obtain the pure target product primary amide compound or N-methyl secondary amide compound. The preparation method is simple to operate, low in toxicity, harmless, safe, reliable and suitable for large-scale production.
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Paragraph 0007; 0011
(2021/08/07)
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- Product selectivity controlled by manganese oxide crystals in catalytic ammoxidation
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The performances of heterogeneous catalysts can be effectively tuned by changing the catalyst structures. Here we report a controllable nitrile synthesis from alcohol ammoxidation, where the nitrile hydration side reaction could be efficiently prevented by changing the manganese oxide catalysts. α-Mn2O3 based catalysts are highly selective for nitrile synthesis, but MnO2-based catalysts including α, β, γ, and δ phases favour the amide production from tandem ammoxidation and hydration steps. Multiple structural, kinetic, and spectroscopic investigations reveal that water decomposition is hindered on α-Mn2O3, thus to switch off the nitrile hydration. In addition, the selectivity-control feature of manganese oxide catalysts is mainly related to their crystalline nature rather than oxide morphology, although the morphological issue is usually regarded as a crucial factor in many reactions.
- Hui, Yu,Luo, Qingsong,Qin, Yucai,Song, Lijuan,Wang, Hai,Wang, Liang,Xiao, Feng-Shou
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p. 2164 - 2172
(2021/09/20)
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- Efficient base-free hydrodehalogenation of organic halides catalyzed by a well-defined diphosphine-ruthenium(II) complex
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A base-free, robust catalytic system based on the diphosphine-ruthenium(II) complex cation has been developed for the hydrodehalogenation of a wide range of aryl- and alkyl-chlorides/bromides (27 examples) with molecule hydrogen. Notably, the reaction proceeds at 120 °C with low catalyst loading (0.1 mol%) and exhibits a good tolerance toward functional groups, such as amido, carboxyl, sulfonyl, methoxyl, ester groups. All dehalogenation products are confirmed by GC, GC–MS and NMR spectroscopy. Moreover, a mechanism for the diphosphine-ruthenium(II) complex cation catalyzed dehalogenation process has been proposed. This hydrodehalogenation methodology shows a potential application for the organic transformation and degradation of organic halides.
- Gao, Pengxiang,Liu, Qingbin,Liu, Yahuan,Ma, Ning,Wang, Zheng,Zhao, Ziwei
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- CuO-decorated magnetite-reduced graphene oxide: a robust and promising heterogeneous catalyst for the oxidative amidation of methylarenes in waterviabenzylic sp3C-H activation
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A magnetite-reduced graphene oxide-supported CuO nanocomposite (rGO/Fe3O4-CuO) was preparedviaa facile chemical method and characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), UV-vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), Brunauer-Emmett-Teller (BET) analysis, vibrating-sample magnetometry (VSM), and thermogravimetric (TG) analysis. The catalytic activity of the rGO/Fe3O4-CuO nanocomposite was probed in the direct oxidative amidation reaction of methylarenes with free amines. Various aromatic and aliphatic amides were prepared efficiently at room temperature from cheap raw chemicals usingtert-butyl hydroperoxide (TBHP) as a “green” oxidant and low-toxicity TBAI in water. This method combines the oxidation of methylarenes and amide bond formation into a single operation. Moreover, the synthesized nanocomposites can be separated from the reaction mixtures using an external magnet and reused in six consecutive runs without a noticeable decrease in the catalytic activity.
- Ebrahimi, Edris,Khalafi-Nezhad, Ali,Khalili, Dariush,Rousta, Marzieh
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p. 20007 - 20020
(2021/11/12)
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- Ring Opening/Site Selective Cleavage in N-Acyl Glutarimide to Synthesize Primary Amides
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A LiOH-promoted hydrolysis selective C-N cleavage of twisted N-acyl glutarimide for the synthesis of primary amides under mild conditions has been developed. The reaction is triggered by a ring opening of glutarimide followed by C-N cleavage to afford primary amides using 2 equiv of LiOH as the base at room temperature. The efficacy of the reactions was considered and administrated for various aryl and alkyl substituents in good yield with high selectivity. Moreover, gram-scale synthesis of primary amides using a continuous flow method was achieved. It is noted that our new methodology can apply under both batch and flow conditions for synthetic and industrial applications.
- Govindan, Karthick,Lin, Wei-Yu
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supporting information
p. 1600 - 1605
(2021/03/03)
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- Unlocking Amides through Selective C–N Bond Cleavage: Allyl Bromide-Mediated Divergent Synthesis of Nitrogen-Containing Functional Groups
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We report a new set of reactions based on the unlocking of amides through simple treatment with allyl bromide, creating a common platform for accessing a diverse range of nitrogen-containing functional groups such as primary amides, sulfonamides, primary amines, N-acyl compounds (esters, thioesters, amides), and N-sulfonyl esters. The method has potential industrial applicability, as demonstrated through gram-scale syntheses in batch and in a continuous flow system.
- Govindan, Karthick,Chen, Nian-Qi,Chuang, Yu-Wei,Lin, Wei-Yu
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supporting information
p. 9419 - 9424
(2021/11/30)
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- N-Ammonium Ylide Mediators for Electrochemical C-H Oxidation
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The site-specific oxidation of strong C(sp3)-H bonds is of uncontested utility in organic synthesis. From simplifying access to metabolites and late-stage diversification of lead compounds to truncating retrosynthetic plans, there is a growing need for new reagents and methods for achieving such a transformation in both academic and industrial circles. One main drawback of current chemical reagents is the lack of diversity with regard to structure and reactivity that prevents a combinatorial approach for rapid screening to be employed. In that regard, directed evolution still holds the greatest promise for achieving complex C-H oxidations in a variety of complex settings. Herein we present a rationally designed platform that provides a step toward this challenge using N-ammonium ylides as electrochemically driven oxidants for site-specific, chemoselective C(sp3)-H oxidation. By taking a first-principles approach guided by computation, these new mediators were identified and rapidly expanded into a library using ubiquitous building blocks and trivial synthesis techniques. The ylide-based approach to C-H oxidation exhibits tunable selectivity that is often exclusive to this class of oxidants and can be applied to real-world problems in the agricultural and pharmaceutical sectors.
- Saito, Masato,Kawamata, Yu,Meanwell, Michael,Navratil, Rafael,Chiodi, Debora,Carlson, Ethan,Hu, Pengfei,Chen, Longrui,Udyavara, Sagar,Kingston, Cian,Tanwar, Mayank,Tyagi, Sameer,McKillican, Bruce P.,Gichinga, Moses G.,Schmidt, Michael A.,Eastgate, Martin D.,Lamberto, Massimiliano,He, Chi,Tang, Tianhua,Malapit, Christian A.,Sigman, Matthew S.,Minteer, Shelley D.,Neurock, Matthew,Baran, Phil S.
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supporting information
p. 7859 - 7867
(2021/05/26)
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- Visible light bromide catalysis for oxazoline, pyrrolidine, and dihydrooxazine synthesesviaCsp3-H functionalizations
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A catalytic benzylic Csp3-H functionalization protocol is described here. This visible light-mediated process is centered on the utilization of a bromide catalyst and oxidant to generate a nitrogen (N)-centered radical for a site-selective hydrogen atom transfer (HAT) process. This strategy enabled the unconventional syntheses of a number of N-heterocycles dependent on the amide identity. We also discovered a nucleophilicity-dependent kinetic resolution for stereochemical differentiation of Csp3-H bonds that enabled the stereoselective synthesis ofcis- andtrans-oxazolines.
- Kaur, Navdeep,Ziegelmeyer, Elizabeth C.,Farinde, Olutayo N.,Truong, Jonathon T.,Huynh, Michelle M.,Li, Wei
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p. 10387 - 10390
(2021/10/14)
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- Room Temperature Hydrolysis of Benzamidines and Benzamidiniums in Weakly Basic Water
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Benzamidinium compounds have found widespread use in both medicinal and supramolecular chemistry. In this work, we show that benzamidiniums hydrolyze at room temperature in aqueous base to give the corresponding primary amide. This reaction has a half-life of 300 days for unsubstituted benzamidinium at pH 9, but is relatively rapid at higher pH's (e.g., t1/2 = 6 days at pH 11 and 15 h at pH 13). Quantum chemistry combined with first-principles kinetic modeling can reproduce these trends and explain them in terms of the dominant pathway being initiated by attack of HO- on benzamidine. Incorporation of the amidinium motif into a hydrogen bonded framework offers a substantial protective effect against hydrolysis.
- Yu, Li-Juan,Cullen, Duncan A.,Morshedi, Mahbod,Coote, Michelle L.,White, Nicholas G.
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supporting information
p. 13762 - 13767
(2021/10/12)
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- Systematic study on acylation of methyl 3-aminocrotonate with acid chlorides of aliphatic, aromatic and α, β-unsaturated acids: A comparative evaluation of the preference for regio- And stereoselectivity vis-à-vis 3-aminocrotononitrile
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Acylation of methyl 3-aminocrotonate 1a in benzene with a variety of aliphatic and aromatic acid chlorides including α, β-unsaturated acid chloride in the presence of an added organic base, (either pyridine or triethylamine) is reported. The preferred N, C-site selectivity in these reactions has been compared with the terminal selectivity of the products obtained previously on acylation of methyl 3-aminocrotononitrile 1b. A strong preference either for N- or C- selectivity in N, C-acylation has been observed for both 1a and 1b based on the choice of acid chlorides and added organic base. Interestingly, irrespective of the enamine 1a or 1b, acylation with α, β-unsaturated acid chlorides in the presence of triethylamine afforded 3,4-dihydropyridin-(2H)-one via [3.3] sigmatropic rearrangement of the corresponding intermediary N(E)-enamide. Accrued results show methyl 3-aminocrotonate to be a better precursor for preparation of enamides (N-acylated products) whereas 3-aminocrotononitrile is found to be a preferred choice for preparation of enaminones (C-acylated products). An attempt is made to offer a preliminary theoretical interpretation for observed site selectivity.
- Mahalanabis, Kumar K.,Mukherjee, Attreyee
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p. 291 - 302
(2021/09/28)
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- Does electrophilic activation of nitroalkanes in polyphosphoric acid involve formation of nitrile oxides?
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The mechanistic rationale involving activation of nitroalkanes towards interaction with nucleophilic reagents in the presence of polyphosphoric acid (PPA) was re-evaluated. Could nitrile oxide moieties be formed during this process? This experiment demonstrates that at least in some cases this could happen, as generated nitrile oxides were successfully intercepted as adducts of [3 + 2] cycloadditions. This journal is
- Aksenov, Alexander V.,Aksenov, Dmitrii A.,Aksenov, Nicolai A.,Kirilov, Nikita K.,Kurenkov, Igor A.,Nobi, Mezvah A.,Rubin, Michael,Skomorokhov, Anton A.,Sorokina, Elena A.
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p. 35937 - 35945
(2021/12/02)
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- Synthesis of Pentacoordinated Spiro[44]phosphoranes by Reaction of Cyclic Phosphazenyl Anions with Epoxides: Study of their P-Remote Functionalization and Hydrolysis
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The synthesis of a new family of pentacoordinated spiro[4.4]phosphoranes stabilized by the ortho-benzamide bidentate ligand (oBA, -C6H4-2-C(O)NH-) through reaction of C,Cortho-dilithiated phosphazenes with oxiranes is reported. Mixtures of epimers that differ in configuration at the phosphorus atom were obtained with moderate to high yields and diastereoselectivities. C3-Disubstituted derivatives could be separated, which provided access to enantiopure products arising from the reaction with (R)-2-phenyloxirane. Stereomutation was observed by heating the spirophosphoranes at 100 C. Directed ortholithiation of spirophoshoranes followed by electrophilic quench reactions including carbon-based and heteroatom-based electrophiles afforded derivatives functionalized in a remote position with respect to the phosphorus atom. Benzoic acid catalyzed hydrolysis of spirophosphoranes furnished ortho-(γ-hydroxyalkylphosphoryl)benzamides by cleavage of the P O and P N bonds with retention of the phosphorus configuration. In contrast, alkaline hydrolysis led to the formation of γ- hydroxyphosphinic acids and benzamide.
- García López, Jesús,Iglesias, María J.,López Ortiz, Fernando,Navarro, Yolanda,Sansores Peraza, Pablo M.
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- Cascade transformations of 1-r-ethynyl-9,10-anthraquinones with amidines: Expanding access to isoaporphinoid alkaloids
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The interaction of acetamidine and phenylamidine with peri-R-ethynyl-9,10-anthraquinones in refluxing n-butanol leads to the formation of cascade transformations products: addition/elimination/ cyclization—2-R-7H-dibenzo[de,h]quinolin-7-ones and(or) 2-R-3-aroyl-7H-dibenzo[de,h]quinolin-7-ones. The anti-inflammatory and antitumor properties of the new 2-R-7H-dibenzo[de,h]quinolin-7-ones were investigated in vivo, in vitro, and in silico. The synthesized compounds exhibit high anti-inflammatory activity at dose 20 mg/kg (intraperitoneal injection) in the models of exudative (histamine-induced) and immunogenic (concanavalin A-induced) inflammation. Molecular docking data demonstrate that quinolinones can potentially intercalate into DNA similarly to the antitumor drug doxorubicin.
- Alabugin, Igor V.,Baev, Dmitry Sergeevich,Krivenko, Ol’Ga Leonidovna,Sorokina, Irina Vasilievna,Tolstikova, Tatyana Genrikhovna,Vasilevsky, Sergey Francevich
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- Tuning acylthiourea ligands in Ru(II) catalysts for altering the reactivity and chemoselectivity of transfer hydrogenation reactions, and synthesis of 3-isopropoxy-1H-indole through a new synthetic approach
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Ru(II)-p-cymene complexes (1–3) containing picolyl based pseudo-acylthiourea ligands (L1-L3) were synthesized and characterized. The crystallographic study confirmed the molecular structures of all the ligands (L1-L3) and complex 3. The catalytic activity of the complexes was tested mainly towards TH of carbonyl compounds and nitroarenes. The influence of steric and electronic effects of the ligands on the chemoselectivity and reactivity were reported. The catalytic activity was enhanced and chemoselectivity was switched after tuning the ligands in the catalysts, compared to their corresponding unmodified Ru(II)-p-cymene complexes. The catalysis was extended to a broad range of substrates including some challenging systems like furfural, benzoylpyridine, benzoquinone, chromanone, etc. The strategy of tuning the bifunctional ligands in the catalysts for effective and selective catalysis worked nicely. Further, the catalysis was extended to one pot synthesis of 3-isopropoxyindole from 2-nitrocinnamaldehyde, the first synthetic route similar to Baeyer Emmerling indole synthesis. All the catalytic experiments exhibited high conversion and selectivity.
- Sathishkumar, Pushpanathan N.,Prabha, Padinhattath Sachind,Bhuvanesh, Nattamai S.P.,Karvembu, Ramasamy
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- Fe3O4@GlcA@Cu-MOF: A Magnetic Metal-Organic Framework as a Recoverable Catalyst for the Hydration of Nitriles and Reduction of Isothiocyanates, Isocyanates, and Isocyanides
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A novel magnetic metal-organic framework (Fe3O4@GlcA@Cu-MOF) has been prepared and characterized by spectroscopic, microscopic, and magnetic techniques. This magnetically separable catalyst exhibited high catalytic activity for nitrile hydration and the ability to reduce isothiocyanates, isocyanates, and isocyanides with excellent activity and selectivity without any additional reducing agent.
- Ghorbani-Choghamarani, Arash,Taherinia, Zahra
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supporting information
p. 902 - 909
(2020/11/30)
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- Microwave preparation method of 2, 4-disubstituted oxazole compound
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The invention discloses a microwave preparation method of a 2, 4-disubstituted oxazole compound. The method comprises the following steps: carrying out heating reflux reaction on substituted carboxylic acid and thionyl chloride, after the reaction is finished, carrying out rotary evaporation to remove excessive thionyl chloride to obtain yellow transparent liquid substituted acyl chloride, and then adding dichloromethane to dilute for later use; dropwise adding substituted acyl chloride into ammonia water while stirring under an ice bath condition, removing the ice bath after the acyl chlorideis dropwise added, stirring at room temperature until a large amount of white solids appear in the solution, carrying out suction filtration after the reaction is finished, and drying to obtain substituted amide. Substituted amide, dichloromethane, triethylamine and an alpha-bromocarbonyl compound are loaded into a pressure reaction tank designed by CEM. The mixture is irradiated in a CEM DISCOVER 2.0 annular focusing single-mode microwave synthesizer. The mixture is cooled to room temperature by passing compressed air through a microwave chamber. The target compound is filtered after cooling, and the crude solid recrystallized with ethanol to obtain the 2, 4-disubstituted oxazole compound.
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Paragraph 0015-0016
(2020/11/25)
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- Weak coordinated nitrogen functionality enabled regioselective C-H alkynylationviaPd(ii)/mono-N-protected amino acid catalysis
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The exploration of weak coordinated amine derivative enabled regioselective C-H functionalization remains challenging due to the elusive achievement of reactivity and selectivity simultaneously. Herein, regioselective C-H alkynylation of various readily transformable nitrogen functionalities was developed with great efficiency, with the assistance of the mono-N-protected amino acid (MPAA) ligandviaPd(ii) catalysis proceedingvia5, 6 and 7-membered palladacycle intermediates.
- Liu, Bifu,Ouyang, Wensen,Nie, Jianhong,Gao, Yang,Feng, Kejun,Huo, Yanping,Chen, Qian,Li, Xianwei
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supporting information
p. 11255 - 11258
(2020/10/06)
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- Design, synthesis, and bioactivities of novel pyridazinone derivatives containing 2-phenylthiazole or oxazole skeletons
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A series of novel pyridazinone derivatives were designed and synthesized by replacing 4-(tert-butyl)phenyl moiety of pyridaben with 2-phenylthiazole or oxazole fragments via activity substructure connecting approach. The structures of all target compounds were characterized through NMR, MS, and elemental analysis. Bioassay results exhibit that most compounds showed potent bioactivities against Aphis fabae, Tetranychus urticae, Erysiphe graminis, and/or Puccinia polysora. Among the newly synthesized compounds, 2-(tert-butyl)-4-chloro-5-(((2-phenylthiazol-4-yl)methyl)thio)pyridazin-3(2H)-one (12b) displays remarkable insecticidal activity against A fabae. Its LC50 value (2.73 mg/L) is better than that of pyridaben (5.46 mg/L), although inferior to that of imidacloprid (0.51 mg/L). In addition to its extraordinary insecticidal activity, compound 12b also exerts 96.9% fungicidal activities against P polysora at 500 mg/L in vivo, significantly superior to that of pyridaben (50.0%), while slightly lower than that of tebuconazole (100%). This article discusses the synthesis, bioassay results, and structure-activity relationship of this series of novel pyridazinone derivatives.
- Dang, Mingming,Liu, Minhua,Huang, Lu,Ou, Xiaoming,Long, Chuyun,Liu, Xingping,Ren, Yeguo,Zhang, Ping,Huang, Mingzhi,Liu, Aiping
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p. 4088 - 4098
(2020/10/02)
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- Preparation method of 2, 4-disubstituted thiazole compound
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The invention discloses a preparation method of a 2, 4-disubstituted thiazole compound. The method comprises the following steps: carrying out heating reflux reaction on substituted carboxylic acid inthionyl chloride to obtain yellow transparent liquid, and adding dichloromethane to dilute for later use; in an ice bath, slowly dropwise adding the substituted acyl chloride solution into ammonia water while stirring, stirring at room temperature to separate out a white solid, and after the reaction is finished, carrying out suction filtration, washing and drying to obtain substituted amide; carrying out reflux on substituted amide and Lawesson in tetrahydrofuran, carrying out rotary evaporation to remove the solvent after the reaction is finished, and carrying out column purification on thecrude product to obtain substituted sulfamide. The preparation method comprises the following steps: putting substituted sulfamide, ethanol, triethylamine and an alpha-bromocarbonyl compound into a pressure reaction tank, putting the pressure reaction tank into an annular focusing single-mode microwave synthesizer for irradiation, and cooling with compressed air to obtain a target compound. Basedon microwave synthesis, the invention has the advantages of short reaction time, high yield, high heating speed, environment friendliness and the like, and provides a microwave synthesis method of a2, 4-disubstituted thiazole compound.
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Paragraph 0034; 0037-0038
(2020/11/23)
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- Ru-based complexes as heterogeneous potential catalysts for the amidation of aldehydes and nitriles in neat water
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Five novel heterogeneous mononuclear complex-anchored Ru(III) have been efficiently sono-synthesized and characterized by utilizing several analytical techniques. The assembled complexes could be utilized as effective, robust and recyclable (up to eight consecutive runs) catalysts for one-pot transformation of a vast array of nitriles and aldehydes to primary amides in H2O under aerobic conditions. Moreover, some unreported di- and tetra-amide derivatives were obtained also under the optimal conditions. The results of ICP/OES analysis demonstrated that there is no detected leaching of the recycled catalyst, which suggests the real heterogeneity of the present protocol. The present Ru-complexes exhibited superiority compared to other reported catalysts for amide preparation in terms of low catalyst load, short reaction time, low operating temperature, no hazardous additives required, and high values of TON (990) and TOF (1980 h11).
- Arafa, Wael Abdelgayed Ahmed
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supporting information
p. 1056 - 1064
(2020/11/09)
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- Half-sandwich ruthenium(II) complexes containing biphenylamine based Schiff base ligands: Synthesis, structure and catalytic activity in amidation of various aldehydes
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New half-sandwich ruthenium (II) complexes [η6?p-cymene)Ru (L1-3)Cl] (1–3) containing biphenylamine based Schiff base ligands (HL1-3) have been synthesized and characterized by analytical and spectroscopic methods. Additionally, the solid state structure of 2 has been determined by single crystal X-ray diffraction study. The complex 2 serves as a catalyst for the amidation of various aldehydes to amides in good yield.
- Nagalakshmi, Veerasamy,Nandhini, Raja,Brindha, Veerappan,Krishnamoorthy, Bellie Sundaram,Balasubramani, Kasthuri
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- Half-Sandwich Iridium Complexes for the One-Pot Synthesis of Amides: Preparation, Structure, and Diverse Catalytic Activity
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Several types of air-stable N,O-coordinate half-sandwich iridium complexes containing Schiff base ligands with the general formula [Cp*IrClL] were synthesized in good yields. These stable iridium complexes displayed a good catalytic efficiency in amide synthesis. A variety of amides with different substituents were obtained in a one-pot procedure with excellent yields and high selectivities through the amidation of aldehydes with NH2OHHCl and nitrile hydration under the catalysis of complexes 1-4. The excellent and diverse catalytic activity, mild conditions, broad substance scope, and environmentally friendly solvent make this system potentially applicable in industrial production. Half-sandwich iridium complexes 1-4 were characterized by NMR, elemental analysis, and IR techniques. Molecular structures of complexes 2 and 3 were confirmed by single-crystal X-ray analysis.
- Fan, Xiao-Nan,Deng, Wei,Liu, Zhen-Jiang,Yao, Zi-Jian
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p. 16582 - 16590
(2020/11/13)
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- Ruthenium(III) 2-(aminofluoreneazo)phenolate complexes: Synthesis, characterization, catalytic activity in amidation reaction and Fluorescence quenching studies
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A series of ruthenium(III)2-(aminofluoreneazo)phenolate complexes with general formula [RuCl(PPh3)2(L1-5)] (1–5) (L = 2-(aminofluoreneazo)phenolate ligands) have been synthesized. The characterization of the synthesized complexes was accomplished by elemental analysis, spectroscopic (FT-IR, UV–Vis, Fluorescence and EPR) and ESI-MStechniques. The catalytic performance of one of the synthesized complexes 3 for the amidation of aldehyde in the presence of NaHCO3/NH2OH·HCl has been evaluated. The fluorescence emission of complexes [RuCl(PPh3)2(L2)] (2) and [RuCl(PPh3)2(L3) (3)] are effectively quenched by 1,4-benzoquinone and 1,4-naphthoquinone in acetonitrile medium.
- Thirumal, Muniyappan,Venkatachalam, Galmari,Venkattappan, Anbazhagan
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- Nitromethane as a nitrogen donor in Schmidt-type formation of amides and nitriles
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The Schmidt reaction has been an efficient and widely used synthetic approach to amides and nitriles since its discovery in 1923. However, its application often entails the use of volatile, potentially explosive, and highly toxic azide reagents. Here, we report a sequence whereby triflic anhydride and formic and acetic acids activate the bulk chemical nitromethane to serve as a nitrogen donor in place of azides in Schmidt-like reactions. This protocol further expands the substrate scope to alkynes and simple alkyl benzenes for the preparation of amides and nitriles.
- Jiao, Ning,Liu, Jianzhong,Qiu, Xu,Song, Song,Wei, Jialiang,Wen, Xiaojin,Zhang, Cheng,Zhang, Ziyao
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supporting information
p. 281 - 285
(2020/01/28)
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- Direct Synthesis of N,N-Disubstituted Formamides by Oxidation of Imines Using an HFIP/UHP System
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The straightforward synthesis of N,N-disubstituted formamides using a combination of 1,1,1,3,3,3-hexafluoroispropanol (HFIP) and H2O2 is described. The unique features of HFIP allowed the utilization of a green oxidant such as H2O2, and the products, arising from an oxidation-rearrangement sequence, were obtained in good to high yields under smooth reaction conditions.
- Llopis, Natalia,Gisbert, Patricia,Baeza, Alejandro
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p. 11072 - 11079
(2020/10/12)
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- Cu(II)–metformin immobilized on graphene oxide: an efficient and recyclable catalyst for the Beckmann rearrangement
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Abstract: In this study, for the first time, the copper(II) nanoparticles (NPs) have been immobilized on metformin-functionalized graphene oxide and then its catalytic applications have been investigated in synthesis of amides from aldoximes (Beckmann rearrangement). The chemical structure of prepared catalyst has been characterized by various analyses like FT-IR, TGA, TEM, SEM, EDX, and ICP. All analyses confirm the successful and stable immobilization of copper NPs on functionalized graphene oxide. This synthesized heterogeneous nanocatalyst showed excellent catalytic activity with high product yields and short reaction times. Also, the suggested catalyst could be recycled ten times without a drastic decrease in its catalytic activity. Graphic abstract: [Figure not available: see fulltext.].
- Solaiman Hamed, Ahmed,Mohammad Ali, Ehab
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p. 701 - 714
(2019/11/03)
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- Discovery and characterization of an acridine radical photoreductant
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Photoinduced electron transfer (PET) is a phenomenon whereby the absorption of light by a chemical species provides an energetic driving force for an electron-transfer reaction1–4. This mechanism is relevant in many areas of chemistry, including the study of natural and artificial photosynthesis, photovoltaics and photosensitive materials. In recent years, research in the area of photoredox catalysis has enabled the use of PET for the catalytic generation of both neutral and charged organic free-radical species. These technologies have enabled previously inaccessible chemical transformations and have been widely used in both academic and industrial settings. Such reactions are often catalysed by visible-light-absorbing organic molecules or transition-metal complexes of ruthenium, iridium, chromium or copper5,6. Although various closed-shell organic molecules have been shown to behave as competent electron-transfer catalysts in photoredox reactions, there are only limited reports of PET reactions involving neutral organic radicals as excited-state donors or acceptors. This is unsurprising because the lifetimes of doublet excited states of neutral organic radicals are typically several orders of magnitude shorter than the singlet lifetimes of known transition-metal photoredox catalysts7–11. Here we document the discovery, characterization and reactivity of a neutral acridine radical with a maximum excited-state oxidation potential of ?3.36 volts versus a saturated calomel electrode, which is similarly reducing to elemental lithium, making this radical one of the most potent chemical reductants reported12. Spectroscopic, computational and chemical studies indicate that the formation of a twisted intramolecular charge-transfer species enables the population of higher-energy doublet excited states, leading to the observed potent photoreducing behaviour. We demonstrate that this catalytically generated PET catalyst facilitates several chemical reactions that typically require alkali metal reductants and can be used in other organic transformations that require dissolving metal reductants.
- MacKenzie, Ian A.,Wang, Leifeng,Onuska, Nicholas P. R.,Williams, Olivia F.,Begam, Khadiza,Moran, Andrew M.,Dunietz, Barry D.,Nicewicz, David A.
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