- Iridium-catalyzed coupling of simple primary or secondary amines, aldehydes and trimethylsilylacetylene: Preparation of propargylic amines
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The coupling of amines, aldehydes and trimethylsilylacetylene was found to be promoted in the presence of a catalytic amount of [IrCl(cod)]2; 1:1:1 or 1:2:2 coupling products were obtained by allowing primary amine to react with aldehyde and trimethylsilylacetylene.
- Sakaguchi, Satoshi,Mizuta, Tomoya,Furuwan, Masuyuki,Kubo, Takashi,Ishii, Yasutaka
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- Synthesis, Characterization, and Photocatalytic Application of Type-II CdS/Bi2W2O9 Heterojunction Nanomaterials towards Aerobic Oxidation of Amines to Imines
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A series of new type-II CdS/Bi2W2O9 heterojunction nanomaterials is prepared by a two stage process. Initially, phase-pure Bi2W2O9, with orthorhombic crystalline structure, is prepared by a facile combustion-synthesis route. The combustion-synthesized Bi2W2O9 is subsequently modified by CdS nanoparticles using a hydrothermal route. The CdS/Bi2W2O9 heterojunctions are characterized using XRD, XPS, FTIR spectroscopy, UV/Vis DRS, PL, and FESEM and HRTEM studies. The occurrence of ultrafine CdS nanoparticles, with diameters of 8–15 nm, well-dispersed over BWO plates, is inferred from microscopic characterization studies. The two crystalline phases exhibit microscopic close contact across grain boundaries, facilitating the transfer of excitons. The heterojunction materials exhibit improved visible-light absorption, enhanced charge-carrier separation, and suitable band-alignment characteristics of a type-II heterojunction. The CdS/Bi2W2O9 heterojunctions are evaluated as visible-light-active photocatalysts for the aerobic oxidation of amines to imines. Structurally and functionally diverse amine molecules are oxidized to the corresponding imines, with excellent selectivity, in a short span of time.
- Bhoi, Yagna Prakash,Mishra, Braja G.
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- Cyclometalated Half-Sandwich Iridium(III) Complexes: Synthesis, Structure, and Diverse Catalytic Activity in Imine Synthesis Using Air as the Oxidant
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Four air-stable cyclometalated half-sandwich iridium complexes 1-4 with C,N-donor Schiff base ligands were prepared through C-H activation in moderate-to-good yields. These complexes have been well characterized, and their exact structure was elaborated on by single-crystal X-ray analysis. The iridium(III) complexes 1-4 showed good catalytic activity in the imine synthesis under open-flask conditions (air as the oxidant) from primary amine oxidative homocoupling, secondary amine dehydrogenation, and the cross-coupling reaction of amine and alcohol. Substituents bonded on the ligands of the iridium complexes displayed little effect on the catalytic efficiency. The stability and good catalytic efficiency of the iridium catalysts, mild reaction conditions, and substrate universality showed their potential application in industrial production.
- Li, Rong-Jian,Ling, Chun,Lv, Wen-Rui,Deng, Wei,Yao, Zi-Jian
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p. 5153 - 5162
(2021/05/04)
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- Fe2Mn(μ3-O)(COO)6 Cluster Based Stable MOF for Oxidative Coupling of Amines via Heterometallic Synergy
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The direct catalytic oxidative coupling of amines is one of the attracting methods for the synthesis of a variety of pharmaceutical or industrial needed imines. Numerous earth-abundant manganese based salts, oxides, and complexes have been applied in this reaction. However, these compounds suffered from difficult separation, large catalyst loading, complicated reactivation or indeterminate activity. Considering the facts that metal-organic frameworks (MOFs) with crystalline structure, precise composition, and enormous surface area have superior performance in heterogeneous catalytic reactions, herein, we introduced Mn into [Fe3(μ3-O)(CH3COO)6], one of the precursors for the preparation of stable MOFs, and got [Fe2Mn(μ3-O)(CH3COO)6] cluster. After ligand replacement with biphenyl-3,4’,5-tricarboxylic acid (BPTC), heterometallic cluster-based [Fe2Mn(μ3-O)(BPTC)2(DMF)2(H2O)] (1) was obtained. As expected, 1 is stable and able to catalyze the homo- or cross-coupling of amines effectively and selectively with 0.9 mol% catalyst loading at room temperature. Control experiments indicated that the catalytic activity of 1 mainly stems from Mn sites and that Fe synergistically contributes to the stability. Additionally, 1 is recyclable and can be reused easily for at least 8 runs without obvious decrease in catalytic ability. To our knowledge, 1 should be the first heterometallic cluster-based MOF with defined structure suitable for the synthesis of diverse imines from oxidative coupling of amines under mild conditions, which may shed light on the easy preparation of effective heterogeneous catalysts for organic synthesis.
- Wang, Ying-Xia,Wang, Hui-Min,Meng, Pan,Song, Dong-Xia,Qi, Zhikai,Zhang, Xian-Ming
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p. 2983 - 2989
(2021/08/30)
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- Confined pyrolysis of a dye pollutant for two-dimensional F,N,S tri-doped nanocarbon as a high performance oxidative coupling reaction catalyst
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Nanocarbon materials as metal-free catalysts for the oxidative coupling of primary amines to imines suffer from high catalyst loading, low reaction rate and high oxygen demand. Doping heteroatoms in nanocarbons is realized as an effective strategy to improve the catalytic activity, however, the doping of fluorine has been rarely studied. Here we synthesized a F,N,S tri-doped hierarchical nanocarbon (FNSHC) by pyrolyzing a fluorine-containing azo-sulphonate dye (acid red-337, a pollutant in wastewater) confined in a layered double hydroxide (LDH). The LDH-confined synthetic method is beneficial to the formation of a two-dimensional porous structure with a large specific surface area (~1432 m2 g-1) and high fluorine content, enabling remarkable catalytic performance (98% yield in 4 h at 2 wt% catalyst loading under open-air conditions) and high recyclability, outcompeting current metal-free carbocatalysts. The conversion of environmental pollutants into heteroatom-doped carbon materials provides a new green strategy for the design and synthesis of functional carbon catalysts.
- Chen, Sian,Hu, Yajing,Li, Fang-Fang,Liu, Sijie,Peng, Ping,Wang, Haining,Yu, Ao,Yu, Bingzhe
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p. 7839 - 7847
(2020/11/30)
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- Air-Stable Half-Sandwich Iridium Complexes as Aerobic Oxidation Catalysts for Imine Synthesis
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Several N,O-coordinate half-sandwich iridium complexes, 1-5, containing constrained bulky β-enaminoketonato ligands were prepared and clearly characterized. Single-crystal X-ray diffraction characterization of these complexes indicates that the iridium center adopts a distorted octahedral geometry. Complexes 1-5 showed good catalytic efficiency in the oxidative homocoupling of primary amines, dehydrogenation of secondary amines, and the oxidative cross-coupling of amines and alcohols, which furnished various types of imines in good yields and high selectivities using O2 as an oxidant under mild conditions. No distinctive substituent effects of the iridium catalysts were observed in these reactions. The diverse catalytic activity, broad substrate scope, mild reaction conditions, and high yields of the products made this catalytic system attractive in industrial processes.
- Deng, Wei,Fan, Xiao-Nan,Ou, Hui-Dan,Yao, Zi-Jian
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supporting information
(2020/04/02)
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- Uniform Cu/chitosan beads as a green and reusable catalyst for facile synthesis of iminesviaoxidative coupling reaction
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A nonprecious metal and biopolymer-based catalyst, Cu/chitosan beads, has been successfully prepared by using a software-controlled flow system. Uniform, spherical Cu/chitosan beads can be obtained with diameters in millimeter-scale and narrow size distribution (0.78 ± 0.04 mm). The size and morphology of the Cu/chitosan beads are reproducible due to high precision of the flow rate. In addition, the application of the Cu/chitosan beads as a green and reusable catalyst has been demonstrated using a convenient and efficient protocol for the direct synthesis of iminesviathe oxidative self- and cross-coupling of amines (24 examples) with moderate to excellent yields. Importantly, the beads are stable and could be reused more than ten times without loss of the catalytic performance. Furthermore, because of the bead morphology, the Cu/chitosan catalyst has greatly simplified recycling and workup procedures.
- Bunchuay, Thanthapatra,Chantiwas, Rattikan,Chutimasakul, Threeraphat,Intanin, Apichai,Na Nakhonpanom, Pakamon,Tantirungrotechai, Jonggol,Tirdtrakool, Warinda
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p. 21009 - 21018
(2020/06/22)
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- Site-specific catalytic activities to facilitate solvent-free aerobic oxidation of cyclohexylamine to cyclohexanone oxime over highly efficient Nb-modified SBA-15 catalysts
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The development of highly active and selective heterogeneous catalysts for efficient oxidation of cyclohexylamine to cyclohexanone oxime is a challenge associated with the highly sensitive nitrogen center of cyclohexylamine. In this work, dispersed Nb oxide supported on SBA-15 catalysts are disclosed to efficiently catalyze the selective oxidation of cyclohexylamine with high conversion (>75%) and selectivity (>84%) to cyclohexanone oxime by O2without any addition of solvent (TOF = 469.8 h?1, based on the molar amount of Nb sites). The role of the active-site structure identity in dictating the site-specific catalytic activities is probed with the help of different reaction and control conditions and multiple spectroscopy methods. Complementary to the experimental results, further poisoning tests (with KSCN or dehydroxylation reagents) and DFT computational studies clearly unveil that the surface exposed active centers toward activation of the reactants are quite different: the surface -OH groups can catch the NH2group from cyclohexylamine by forming a hydrogen bond and lead to a more facile cyclohexylamine oxidation to desired products, while the monomeric or oligomeric Nb sites with a highly distorted structure play a key role in the dissociation of O2molecules beneficial for insertion of active oxygen species into cyclohexylamine. These catalysts exhibit not only satisfactory recyclability for cyclohexylamine oxidation but also efficiently catalyze the aerobic oxidation of a wide range of amines under solvent-free conditions.
- Ding, Wei,Mao, Liqiu,Peng, Haoyu,Yin, Dulin,Zhong, Wenzhou
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p. 3409 - 3422
(2020/06/09)
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- Selective one-pot synthesis of asymmetric secondary amines via N-alkylation of nitriles with alcohols
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The synthesis of asymmetric secondary amines (ASA) is commonly achieved by N-alkylation of primary amines with alcohols. Here, we investigated the ASA synthesis via the direct amination of alcohols with nitriles, which avoids the synthesis, separation and purification of the primary amines in a first step. Specifically, the ASA synthesis via N-alkylation of butyronitrile (BN) with primary (n-propanol, iso-butanol and n-octanol) and secondary (2‐propanol, 2‐butanol and 2‐octanol) alcohols was studied on SiO2-supported Co, Ni and Ru catalysts. Competitive BN hydrogenation‐condensation reactions formed dibutylamine (the symmetric secondary amine) and tertiary amines as main secondary products. On Co/SiO2, the ASA selectivities for BN/primary alcohol reactions were between 49 and 58% at complete BN conversion, forming dibutylamine and tertiary amines as byproducts. For BN/secondary alcohol reactions, Co/SiO2 formed selectively (ASA + dibutylamine) mixtures containing 78–85% of ASA, thereby showing that the alcohol amination with nitriles is an attractive alternative route for the synthesis of valuable asymmetric secondary amines.
- Segobia,Trasarti,Apesteguía
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p. 178 - 185
(2019/11/13)
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- Rhodium complex containing ortho-carborane benzimidazole structure and preparation method and application thereof
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The invention relates to a rhodium complex containing an ortho-carborane benzimidazole structure and a preparation method and application thereof. The preparation method of the rhodium complex includes the following steps that 1), an n-BuLi solution is added into an ortho-carborane solution for reaction at room temperature for 30-60 minutes; 2), benzimidazole bromide is added into the mixed solution for reaction at room temperature for 6-8 hours; 3), then [Cp*RhCl2]2 is added into the mixed solution for reaction at room temperature for 3-5 hours, and the rhodium complex is obtained after aftertreatment. The rhodium complex is used for catalyzing autoxidation coupling of primaryaliphaticamine to prepare imine compounds. Compared with the prior art, the synthesis process is simple and greenand has excellent selectivity and high yield, and the prepared rhodium complex has the advantages of stable physical and chemical properties and thermal stability, can catalyze the autoxidation coupling of primaryaliphaticamine to prepare the imine compounds under the condition of air as an oxidant, and has excellent catalytic activity.
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Paragraph 0049-0052
(2019/08/20)
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- Flower-like Bi2O2CO3-mediated selective oxidative coupling processes of amines under visible light irradiation
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The photocatalytic selective transformation of amines is a green and cost-effective technology to obtain value-added products in chemical industry. In this work, a series of bismuth-based photocatalysts including Bi2MoO6, Bi2WO6, Bi5O7Cl, Bi5O7Br, Bi5O7I, BiPO4, BiVO4, Bi2O3 and various morphology Bi2O2CO3 (flower-like, sponge-like, plate-like and spherical)were synthesized and employed in the aerobic oxidative coupling of benzylamine. It is found that flower-like Bi2O2CO3 exhibited the highest photocatalytic activity, in which a 100% conversion of benzylamine with 99.0% selectivity of N-benzylidenebenzylamine was obtained at room temperature. Moreover, the photocatalytic oxidative coupling processes of various aromatic and aliphatic amines were further investigated, and excellent yields and selectivities of corresponding products are attained. Then, based on characterization results (XRD, SEM, BET and XPS, etc.)of catalyst, high photocatalytic activity of flower-like Bi2O2CO3 is attributed to thin nanopetals, low band gap, the morphology and large specific surface area. Finally, a possible reaction mechanism is proposed for the photocatalytic oxidative coupling of benzyl amine.
- Bai, Peng,Tong, Xinli,Wan, Jun,Gao, Yiqi,Xue, Song
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p. 257 - 265
(2019/05/17)
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- Highly selective oxidation of amines to imines by Mn2O3 catalyst under eco-friendly conditions
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Enhancing the selectivity of imines for the oxidative self-coupling of primary amines was found to be challenging in the heterogeneous catalysis. Three different manganese oxides (M-3, M-4, M-5) were synthesized by controlling the calcination temperature using a simple template-free oxalate route. The prepared manganese oxides were systematically characterized using XRD, N2 sorption, SEM, TEM, XPS, H2-TPR techniques. M-4 gave 96.2% selectivity of imine at 100% conversion of benzylamine, which was far more superior than other existing protocols. Mn3+/Mn4+ ratio was found to affect the selectivity of the imines. The probable reaction pathway for amines oxidation catalyzed by manganese oxides was proposed for the first time.
- Chen, Fushan,Yang, Tao,Zhao, Songlin,Jiang, Taotao,Yu, Lu,Xiong, Houfeng,Guo, Chuankun,Rao, Yufang,Liu, Yan,Liu, Liu,Zhou, Jian,Tu, Pengxiang,Ni, Jun,Zhang, Qunfeng,Li, Xiaonian
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supporting information
p. 2282 - 2286
(2019/09/30)
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- Unprecedented Copper(II) Complex with a Topoquinone-like Moiety as a Structural and Functional Mimic for Copper Amine Oxidase: Role of Copper(II) in the Genesis and Amine Oxidase Activity
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Copper amine oxidase (CAO), consisting of the topoquinone (TPQ) cofactor, catalyzes the oxidation of primary amines to aldehyde. We have successfully addressed this issue through isolation of a copper complex which mimics the active-site structure as well as the function of CAO. This inimitable complex, consisting of two TPQ-like side-arms, formed by ambient aerial oxidation of a precursor Schiff base complex, is the most efficient homogeneous catalyst for quantitative oxidation of primary benzylic amines to corresponding secondary imines under ambient conditions within 30 min. The longstanding contention of actual involvement of Cu(II) in the catalysis is resolved through quenching experiments of Cu(II) superoxo species and detailed density functional theory studies.
- Jangir, Ritambhara,Ansari, Mursaleem,Kaleeswaran, Dhananjayan,Rajaraman, Gopalan,Palaniandavar, Mallayan,Murugavel, Ramaswamy
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p. 10940 - 10950
(2019/11/13)
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- Oxygen-free water-promoted selective photocatalytic oxidative coupling of amines
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A novel photocatalytic selective oxidative transformation of amines to imines using water as a primary oxidant is achieved under oxygen-free conditions. In the presence a single 1%Pt?TiO2-500 catalyst, the photocatalytic oxidative coupling of benzylamine to N-benzylidenebenzylamine has been efficiently performed using water as an oxidant, in which a 99.8% conversion and a 92.5% selectivity were obtained at room temperature; meanwhile, a certain amount of hydrogen was detected that confirms the simultaneous occurrence of water splitting reaction. Further investigations revealed that the introduction of the Pt element facilitates the formation of O-holes on the surface of TiO2, which efficiently promotes the generation of active oxygen species from water and the following oxidative coupling of benzylamine. Then, the photocatalytic oxidative coupling of various aromatic and aliphatic amines with water as the primary oxidant were also studied, and excellent conversion and high selectivities to corresponding products were attained. Based on the control experiment and the catalytic principle, a possible reaction mechanism is proposed for the oxidative coupling of benzylamine with water as the primary oxidant.
- Bai, Peng,Tong, Xinli,Gao, Yiqi,Guo, Pengfei
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p. 5803 - 5811
(2019/10/23)
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- Selective aerobic oxidation of halides and amines with an inorganic-ligand supported zinc catalyst
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A practical, efficient and environmentally benign catalytic protocol for the oxidative cross-coupling reaction of halides with amines, oxidative self-coupling of amines and oxidation of halides was developed with inorganic-ligand supported ZnPOM (NH4)4[ZnMo6O18(OH)6] using molecular oxygen. This method mainly utilizes an inorganic polymolybdate ligand to support the Zn2+ ion, avoiding the use of complicated organic ligands.
- Wang, Jingjing,Zhai, Yongyan,Wang, Ying,Yu, Han,Zhao, Wenshu,Wei, Yongge
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supporting information
p. 13323 - 13327
(2018/10/15)
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- Cultivation of a Cu/HMPC catalyst from a hyperaccumulating mustard plant for highly efficient and selective coupling reactions under mild conditions
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Cu-containing activated carbon (eco-catalyst, Cu/HMPC, where 'C' defines 'carbon') was derived from a metal-hyperaccumulating mustard plant (HMP) by a simple chemical activation method. Transmission electron microscopy/selected area diffraction (HRTEM/SAED) results revealed that the Cu/HMPC has mainly three types of morphology [sheet-like morphology (2D), hollow-spheres (3D) and needle-like structures (1D)] which are interconnected. HRTEM-SAED, Raman and X-ray photoelectron spectroscopy (XPS) results confirmed the existence of Cu oxide species in Cu/HMPC. Content of Cu in Cu/HMPC was determined to be 1.03 wt%. The quality of graphitization in Cu/HMPC was discussed by using Raman and XRD results. The BET surface area of Cu/HMPC was determined to be 620.8 m2 g-1. The Cu/HMPC actively transformed a wide range of amines to imines under very mild reaction conditions. The catalyst Cu/HMPC gave products in excellent yields (98-61%) with very high TON/TOF values (1512/339-833/35 h-1). To the best of our knowledge, this is the most efficient Cu-based heterogeneous eco-catalyst for the synthesis of imines among those reported to date. The Cu can be recovered from used Cu/HMPC by a simple HCl treatment. Versatility, heterogeneity and reusability of Cu/HMPC were tested. A possible mechanism has been proposed.
- Gopiraman, Mayakrishnan,Wei, Kai,Zhang, Ke-Qin,Chung, Ill-Min,Kim, Ick Soo
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p. 4531 - 4547
(2018/02/09)
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- Efficient Rare-Earth-Based Coordination Polymers as Green Photocatalysts for the Synthesis of Imines at Room Temperature
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Five new rare-earth coordination polymers (CPs) were designed in order to offer a remarkable platform that contains light-harvesting antennas and catalytic active centers to achieve solar-energy conversion as green alternatives in the synthesis of imines. These five new spirobifluorene-containing Ln-CPs, named [Er3(Hsfdc)3(sfdc)3(H2O)]·xH2O (RPF-30-Er), [Ln(Hsfdc)(sfdc)(EtOH)]·S (RPF-31-Ln, where Ln = La, Nd, and Sm and S = H2O or EtOH), and [Ho(Hsfdc)(sfdc)(H2O)] (RPF-32-Ho) (RPF = rare-earth polymeric framework and H2sfdc = 9,9′-spirobi[9H-fluorene]-2,2′-dicarboxylic acid), have been solvothermally synthesized, and their structural features can be described as follows: (i) RPF-30-Er shows a 3D framework in which the inorganic trimers (secondary building units) are cross-linked by Hsfdc- and sfdc2- linkers displaying a pcu topology. (ii) The isostructural RPF-31-Ln series of materials, together with RPF-32-Ho, exhibit a 1D network of chains growing along the a axis with a ribbon-of-rings topology type. The photocatalytic activity of the RPF-n materials was tested in the oxidative coupling of amines using molecular oxygen and air as oxidizing agents under warm light. Among the materials investigated, RPF-31-Nd was chosen to further investigate the approach in the selectivity of different amine derivates.
- Aguirre-Díaz, Lina M.,Snejko, Natalia,Iglesias, Marta,Sánchez, Félix,Gutiérrez-Puebla, Enrique,Monge, M. ángeles
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p. 6883 - 6892
(2018/06/26)
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- Cobalt-Catalyzed Selective Hydrogenation of Nitriles to Secondary Imines
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The first example of cobalt-catalyzed selective hydrogenation of nitriles to secondary imines is reported. The results demonstrate the significantly different selectivity compared with the previously reported cobalt catalytic system during the nitrile hydrogenation. A variety of aromatic and aliphatic nitriles are hydrogenated to the corresponding secondary imines.
- Li, Huaifeng,Al-Dakhil, Abdullah,Lupp, Daniel,Gholap, Sandeep Suryabhan,Lai, Zhiping,Liang, Lan-Chang,Huang, Kuo-Wei
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supporting information
p. 6430 - 6435
(2018/10/15)
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- Synthesis of [LAl(μ-S)2AlL] (L?=?HC(CMeNAr)2, Ar?=?2,6-Et2C6H3) with the insertion of sulfur into the Al–H bonds of LAlH2 and its application in catalysis
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Two aluminum complexes [LAl(μ-S)2AlL] (1) and [LAl(SeH)2] (2) were synthesized in good yield by reacting one equivalent of LAlH2 (L?=?HC(CMeNAr)2, Ar?=?2,6-Et2C6H3) with one equivalent of S and with two equivalents of Se without any catalysts, respectively. Complexes 1 and 2 have been characterized by 1H and 13C NMR, elemental analyses, and single crystal X-ray structural analysis. Furthermore, the good catalytic activity of 1 as bimetallic Lewis acid catalyst for the addition reaction of TMSCN to aldehydes and aldimine condensation reactions, respectively, were investigated.
- Zhong, Mingdong,Liu, Ying,Liu, Xin,Ma, Xiaoli,Yang, Zhi
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supporting information
p. 182 - 185
(2017/05/24)
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- Selective Hydrogenation of Nitriles to Secondary Imines Catalyzed by an Iron Pincer Complex
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Selective hydrogenation of nitriles to secondary imines catalyzed by an iron complex, the pincer complex (iPr-PNP)Fe(H)Br(CO), in the presence of catalytic base, is reported. A wide range of (hetero)aromatic and aliphatic nitriles are hydrogenated to the corresponding secondary imines under mild conditions.
- Chakraborty, Subrata,Milstein, David
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p. 3968 - 3972
(2017/06/19)
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- Aerobic oxidation of amines to imines catalyzed by a ruthenium complex under solvent-free conditions
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A ruthenium complex [Et3NH]2[Ru(dipic)Cl3] showed high efficiency in the homo-coupling of primary amines and cross-coupling of benzylamine with anilines and aliphatic amines to the corresponding imines under air and solvent-free conditions. This protocol is an atom-economical green process and tolerates various substrates bearing both electron-donating and electron-withdrawing substituents.
- Zhang, Yuecheng,Lu, Fei,Huang, Rong,Zhang, Hongyu,Zhao, Jiquan
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supporting information
p. 10 - 13
(2016/04/26)
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- Colloid and nanosized catalysts in organic synthesis: XIV. Reductive amination and amidation of carbonitriles catalyzed by nickel nanoparticles
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Hydrogenation of carbonitriles catalyzed by nickel nanoparticles in the presence of primary amines led to the predominant formation of unsymmetrical secondary amines. In the presence of secondary amines hydrogenation of nitrites provided enamines as main products. Hydrogenation of nitriles in the presence of formamide or acetamide afforded formyl or acetyl derivatives of primary amines.
- Popov, Yu. V.,Mokhov,Shcherbakova
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p. 798 - 805
(2016/06/13)
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- Mechanistic insights into the oxidative dehydrogenation of amines to nitriles in continuous flow
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The oxidative dehydrogenation of various aliphatic amines to their corresponding nitrile compounds using RuO2/Al2O3 catalysts in air was successfully applied to a continuous flow reaction. Conversions of amines (up to >99%) and yields of nitriles (up to 77%) varied depending on reaction conditions and the amine utilised. The presence of water was found to be important for the activity and stability of the RuO2/Al2O3 catalyst. The Hammett relationship and in situ infrared spectroscopy were applied to divulge details about the catalytic mechanism of the oxidative dehydrogenation of amines over RuO2/Al2O3 catalysts.
- Corker, Emily C.,Ruiz-Martínez, Javier,Riisager, Anders,Fehrmann, Rasmus
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p. 5008 - 5015
(2015/11/03)
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- Eco-friendly copper sulfate-catalyzed oxidation of amines to imines by hydrogen peroxide in water
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Imines are very important compounds in organic synthesis, and therefore, their preparation under mild conditions has attracted much attention. In this study, it was found that copper sulfate effectively catalyzes the highly selective oxidation of benzylamines to the corresponding imines with H2O2 in water at room temperature for 1.5 h. This mild and eco-friendly oxidation method could be applied to the oxidation of alkylamines. Therefore, a convenient procedure for the oxidation of amines to the imines has been developed.
- Marui, Kuniaki,Nomoto, Akihiro,Ueshima, Michio,Ogawa, Akiya
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supporting information
p. 1200 - 1202
(2015/03/04)
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- Highly efficient aerobic oxidation of various amines using Pd3Pb intermetallic compounds as catalysts
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Intermetallic Pd3Pb supported on Al2O3 can act as a highly efficient heterogeneous catalyst for the oxidation of various amines including primary, secondary, aromatic, aliphatic, and cyclic amines. The Royal Society of Chemistry 2014.
- Furukawa, Shinya,Suga, Akifusa,Komatsu, Takayuki
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p. 3277 - 3280
(2014/03/21)
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- Tert-Butyl hydroperoxide (TBHP)-mediated oxidative self-coupling of amines to imines over a α-MnO2 catalyst
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We here demonstrate a simple, efficient and eco-friendly protocol for the direct synthesis of imines from amines via a facile α-MnO2 catalyzed-procedure at rt. Up to 13 benzylic, heterocyclic, and normal aliphatic imines were synthesized with 95-99% selectivity at 82-99% conversion. the Partner Organisations 2014.
- Zhang, Zhe,Wang, Feng,Wang, Min,Xu, Shutao,Chen, Haijun,Zhang, Chaofeng,Xu, Jie
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supporting information
p. 2523 - 2527
(2014/05/06)
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- Solventless oxidative coupling of amines to imines by using transition-metal-free metal-organic frameworks
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A highly efficient, simple, and versatile transition-metal-free metal-organic framework catalytic system is proposed for the oxidative coupling of amines to imines. The catalytic protocol features high activities and selectivities to target products; compatibility with a variety of substrates, including aliphatic amines and secondary amines; and the possibility to efficiently and selectively promote amine cross-coupling reactions. A high stability and recyclability of the catalyst is also observed under the investigated conditions. Insights into the reaction mechanism indicate the formation of a superoxide species able to efficiently promote oxidative couplings. Neat couple! A metal-organic framework with open 2,2'-bipyridine sites offers a new, simple, and green protocol for the selective synthesis of imines from oxidative coupling of various amines under mild solvent-free conditions in the absence of transition metals. In addition, this catalyst is also capable of catalyzing the cross-coupling of two different amines to synthesize asymmetrical imines with unprecedented selectivity.
- Qiu, Xuan,Len, Christophe,Luque, Rafael,Li, Yingwei
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p. 1684 - 1688
(2014/07/08)
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- ZnIn2S4: A photocatalyst for the selective aerobic oxidation of amines to imines under visible light
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Flowerlike nanospheres of ZnIn2S4 consisting of interweaving nanoflakes were prepared by a rapid microwave-assisted solvothermal method. The photocatalytic performance of ZnIn2S4 in the aerobic oxidation of amines to imines is for the first time revealed. As-prepared ZnIn2S4 showed high efficiency for the transformations of various amines into their corresponding imines under visible-light irradiation by using air as the oxidant. The photocatalytic performance of ZnIn2S4 in the selective oxidation of amines to their corresponding imines is much higher than that of graphitic C3N4 and CdS previously reported. A plausible mechanism involving the oxygenation of amines to form aldehydes, followed by the nucleophilic addition of the amines to afford the final imines is proposed. The use of a cheap, environmentally friendly inorganic semiconductor photocatalyst and solar energy makes this transformation green and sustainable.
- Ye, Lin,Li, Zhaohui
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p. 2540 - 2543
(2015/04/14)
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- Synthesis of anti-2,3-dihydro-1,2,3-trisubstituted-1H-naphth [1,2-e][1,3]oxazine derivatives via multicomponent approach
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A series of anti-2,3-dihydro-1,2,3-trisubstituted-1H-naphth [1,2-e][1,3]oxazine derivatives 6 were exclusively obtained in high yields for the first time through multicomponent reactions (MCRs) of 2-naphthol, aromatic aldehydes and electron rich primary amines in ethanol at room temperature using CCl3COOH as catalyst. The same reaction could be conducted effectively in solvent-free medium at 100 °C. The stereochemistry of the two hydrogens connected to C-2 and C-4 (1,3) positions of the oxazine ring are identified as anti-orientation by single crystal XRD, COSY and NOESY analysis.
- Borah, Ruli,Dutta, Arup Kumar,Sarma, Parishmita,Dutta, Champak,Sarma, Bipul
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p. 10912 - 10917
(2014/03/21)
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- Synthesis of n-butylamine from butyronitrile on Ni/SiO2: Effect of solvent
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The effect of solvent on Ni(10.5percent)/SiO2 activity and selectivity for the liquid-phase hydrogenation of butyronitrile to butylamines was studied at 373 K and 13 bar using ethanol, benzene, toluene and cyclohexane as solvents. In ethanol, a protic solvent, the Ni catalyst yielded n-butylamine (84percent) and dibutylamine (16percent). When non-polar solvents, such as cyclohexane, toluene or benzene, were used, the solvent-catalyst interaction strength determined the selectivity to n-butylamine: the stronger the solvent-catalyst interaction the higher the n-buylamine production. The yield to n-butylamine in non-polar solvents varied between 39percent (cyclohexane) and 63percent (benzene).
- Segobia, Darío J.,Trasarti, Andrés F.,Apesteguía, Carlos R.
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p. 2272 - 2279
(2015/04/16)
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- Hydrogenation of nitriles to primary amines on metal-supported catalysts: Highly selective conversion of butyronitrile to n-butylamine
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The selective liquid-phase hydrogenation of butyronitrile to n-butylamine was studied in a batch reactor on Co(9.8%)/SiO2, Ni(10.5%)/SiO 2, Cu(9.2%)/SiO2, Pt(0.27%)/SiO2, Pd(0.33%)/SiO2, and Ru(1.8%)/SiO2 catalysts. At 373 K and 13 bar (H2), the initial butyronitrile conversion rate (rBN0, mmol/h g) followed the order Ni > Co > Pt > Ru > Cu > Pd. Cu/SiO 2 and Pd/SiO2 did not form n-butylamine and rapidly deactivated during the progress of the reaction. Pt/SiO2 produced mainly dibutylamine and only minor amounts of n-butylamine and tributylamine. In contrast, Ru/SiO2 formed preponderantly n-butylamine but also produced significant amounts of dibutylamine and butylidene-butylamine, an intermediate in the formation pathway of the secondary amine. The highest yield to n-butylamine was obtained on Ni/SiO2 (84%). Co/SiO2 was initially highly selective to n-butylamine but with the progress of the reaction the butylamine concentration in the reaction mixture diminished because it partially reacted with the solvent (ethanol) to form N-ethylbutylamine. In an attempt to reduce the formation of byproducts, Ni/SiO2 and Co/SiO2 catalysts were tested at lower temperatures and higher H 2 pressures. Butyronitrile was selectively converted to n-butylamine on Co/SiO2 at 343 K and 25 bar, yielding 97% of n-butylamine, similarly to the highest yields reported on Raney Co catalysts.
- Segobia,Trasarti,Apesteguía
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- PHOSPHO-AMINO PINCER-TYPE LIGANDS AND CATALYTIC METAL COMPLEXES THEREOF
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The present invention provides phospho-amino pincer-type ligands, metal complexes thereof, and catalytic methods comprising such metal complexes.
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Page/Page column 10
(2013/02/27)
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- Chemical reactivity and skin sensitization potential for benzaldehydes: Can Schiff base formation explain everything?
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Skin sensitizers chemically modify skin proteins rendering them immunogenic. Sensitizing chemicals have been divided into applicability domains according to their suspected reaction mechanism. The widely accepted Schiff base applicability domain covers aldehydes and ketones, and detailed structure-activity-modeling for this chemical group was presented. While Schiff base formation is the obvious reaction pathway for these chemicals, the in silico work was followed up by limited experimental work. It remains unclear whether hydrolytically labile Schiff bases can form sufficiently stable epitopes to trigger an immune response in the living organism with an excess of water being present. Here, we performed experimental studies on benzaldehydes of highly differing skin sensitization potential. Schiff base formation toward butylamine was evaluated in acetonitrile, and a detailed SAR study is presented. o-Hydroxybenzaldehydes such as salicylaldehyde and the oakmoss allergens atranol and chloratranol have a high propensity to form Schiff bases. The reactivity is highly reduced in p-hydroxy benzaldehydes such as the nonsensitizing vanillin with an intermediate reactivity for p-alkyl and p-methoxy-benzaldehydes. The work was followed up under more physiological conditions in the peptide reactivity assay with a lysine-containing heptapeptide. Under these conditions, Schiff base formation was only observable for the strong sensitizers atranol and chloratranol and for salicylaldehyde. Trapping experiments with NaBH3CN showed that Schiff base formation occurred under these conditions also for some less sensitizing aldehydes, but the reaction is not favored in the absence of in situ reduction. Surprisingly, the Schiff bases of some weaker sensitizers apparently may react further to form stable peptide adducts. These were identified as the amides between the lysine residues and the corresponding acids. Adduct formation was paralleled by oxidative deamination of the parent peptide at the lysine residue to form the peptide aldehyde. Our results explain the high sensitization potential of the oakmoss allergens by stable Schiff base formation and at the same time indicate a novel pathway for stable peptide-adduct formation and peptide modifications by aldehydes. The results thus may lead to a better understanding of the Schiff base applicability domain.
- Natsch, Andreas,Gfeller, Hans,Haupt, Tina,Brunner, Gerhard
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p. 2203 - 2215
(2013/01/15)
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- Oxidations and oxidative couplings catalyzed by triazolylidene ruthenium complexes
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A series of "RuII(η6-arene)" complexes with 1,2,3-triazolylidene ligands have been prepared and fully characterized. The molecular structure of one of the new complexes has been determined by means of X-ray diffractrometry. The new complexes have been tested in a set of catalytic reactions involving alcohols and amines as substrates, including (i) base-free oxidation of benzylic alcohols to benzaldehydes, (ii) homocoupling of amines to form imines, and (iii) oxidative coupling of amines and alcohols to form amides. The results show the high versatility of the catalysts used and illustrate the application potential of 1,2,3-triazolylidene ligands in the design of effective homogeneous catalysts.
- Prades, Amparo,Peris, Eduardo,Albrecht, Martin
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experimental part
p. 1162 - 1167
(2011/05/04)
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- Polyethylene glycol clicked Co(ii) Schiff base and its catalytic activity for the oxidative dehydrogenation of secondary amines
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Copper catalyzed [3+2] cycloaddition "click method" provided an efficient and high yielding immobilization of cobalt(ii) Schiff base to the azido-functionalized MeOPEG5000; whereas the direct reaction between MeOPEG5000 and Co(ii) Schiff base did not produce any immobilization. The prepared catalyst was tested for the oxidative dehydrogenation of various secondary amines using TBHP as oxidant and could be easily recovered by precipitation with diethyl ether at the end of the reaction.
- Khatri, Praveen K.,Jain, Suman L.,Sivakumar K.,Sain, Bir
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experimental part
p. 3370 - 3374
(2011/06/25)
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- An effective method to prepare imines from aldehyde, bromide/epoxide, and aqueous ammonia
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A three-component reaction of aldehydes, alkyl bromides, and ammonia to form imines was studied. Aqueous ammonia was applied as the nitrogen source and solvent in the reaction. For the aromatic aldehyde, the product yields are good to excellent and the reaction conditions are mild to be compatible with a range of functional groups. The reaction of aldehydes and aqueous ammonia with epoxides was also studied and imines bearing a vicinal hydroxyl group can be obtained efficiently and regioselectively. And studies showed that this method allows the synthesis of primary amines and especially 1,2-amino alcohol selectively in high yield. It is proposed that the reaction pathway might involve a key intermediate of hydrobenzamide.
- Huang, Jing-Mei,Zhang, Jue-Fei,Dong, Yi,Gong, Wen
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supporting information; experimental part
p. 3511 - 3514
(2011/06/22)
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- Investigations into the mechanism of the liquid-phase hydrogenation of nitriles over Raney-Co catalysts
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The co-hydrogenation of acetonitrile and butyronitrile over Raney-Co was investigated in order to obtain insight into the mechanism underlying the formation of secondary amines. Acetonitrile was reduced much faster to the corresponding primary amine due to stronger adsorption on the catalyst surface. In parallel, dialkylimines were formed and subsequently converted to secondary amines. It is suggested that the dialkylimines are formed by reaction of partially hydrogenated intermediate species on the cobalt surface with amines. In this respect, n-butylamine was found to react much faster than ethylamine. The stronger inductive effect of the butyl chain is thought to facilitate nucleophilic attack of the amine at the α-C-atom of the surface species. By comparing the C2 and C4 balance for dialkylimines and dialkylamines, it was found that direct hydrogenation of the dialkylimine cannot be the only way of dialkylamine formation. Instead, it is suggested that alkyl group transfer occurs by reaction of a monoalkylamine with a dialkylimine and cross-transfer between two dialkylimines.
- Schaerringer, Peter,Mueller, Thomas E.,Lercher, Johannes A.
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p. 167 - 179
(2008/09/17)
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- Reactions of poly(hexafluoropropylene oxide) perfluoroisopropyl ketone with various amines
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The reaction of poly(hexafluoropropylene oxide) perfluoroisopropyl ketone, perfluoroethyl perfluoroisopropyl, or bis-perfluoroisopropyl ketone with various amines has been studied and the products identified. A comparison of the reactivity of the ketones with different amines is made and identified by mass spectroscopy. The reaction of diethyl amine with all three ketones leads to two unexpected products and the mechanism of their formation is considered.
- Howell, Jon L.,Friesen, Chadron M.,Laugesen, Krista L.,van der Ende, Alice E.
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p. 178 - 184
(2008/09/17)
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- A new supported rhodium catalyst for selective hydrogenation of nitriles to primary amines
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Nitriles are converted to primary amines with high selectivity using a newly developed alumina-supported rhodium catalyst. The high selectivity is obtained without any additives, which are often used to prevent the formation of higher amines. The catalyst is active under mild conditions In various solvents, which makes it specifically suitable for use in pharmaceutical applications or for other substrates that can react with additives like strong acids or bases.
- Witte, Peter T.
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p. 468 - 474
(2008/09/19)
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- Benzo-21-crown-7/secondary dialkylammonium salt [2]pseudorotaxane- and [2]rotaxane-type threaded structures
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We demonstrate that secondary dialkylammonium salts can thread through the cavity of benzo-21-crown-7 to form [2]pseudorotaxanes with binding constants (527-1062 M-1 in acetone) higher than the corresponding values (135-261 M-1 in acetone) of the analogous complexes with their traditionally used host, dibenzo-24-crown-8. Based on this new benzo-21-crown-7/secondary dialkylammonium salt recognition motif, a [2]rotaxane was successfully prepared. The formation of these threaded structures was confirmed by proton NMR spectroscopy, electrospray ionization mass spectrometry, and X-ray single crystal analysis.
- Zhang, Chuanju,Li, Shijun,Zhang, Jinqiang,Zhu, Kelong,Li, Ning,Huang, Feihe
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p. 5553 - 5556
(2008/09/17)
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- Microwave-assisted direct transformation of amines to ketones using water as an oxygen source
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Retro-reductive animations, direct transformations of amines to ketones, were catalyzed by Pd/C in water under microwave irradiation. The Royal Society of Chemistry 2005.
- Miyazawa, Akira,Tanaka, Kan,Sakakura, Toshiyasu,Tashiro, Masashi,Tashiro, Hideki,Surya Prakash,Olah, George A.
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p. 2104 - 2106
(2007/10/03)
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- Synthesis, properties, and redox ability of optically active 3-carbamoyl-1,6-dimethylpyrimido[4,5-c]pyridazine-5,7(1H,6H)-dione and related pyrimido-annulated pyridine analogues
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Optically active 3-carbamoyl-1,6-dimethylpyrimido[4,5-c]pyridazine-5,7(1H,6H)-dione (13a) and related pyrimido-annulated pyridine analogues (13b,c) were prepared via the corresponding 3-ethoxycarbonyl-1,6-dimethylpyrimido[4,5-c]pydazine-5,7(1H,6H)-dione (11a) and the related compounds (11b,c). The properties of 11a-c, 13a-c, and the related 1,3,6-trimethylpyrimido[4,5-c]pyridazine-5,7(1H,6H)-dione (18a) as well as 7-phenyl-and 3,7,8-trimethyl-pyrido[2,3-d]pyrimidine-2,4(3H,8H)-dione (18b,c) having no carbamoyl or ester function were studied by the UV-VIS spectra and redox potentials. Although pyridazine derivative (13a) was not reduced, pyridine derivatives (11b,c), (13b), and (18b) were reduced by Na 2S2O4 to give dihydrogenated compounds (20b,c), (21b), and (22b), respectively. The photo-induced oxidation reactions of 13a,b and 18a-c toward some amines under aerobic conditions were studied to give the corresponding imines in more than 100% yields [based on compounds 13a,b and 18a-c], suggesting that the oxidation proceeds in an autorecycling process.
- Naya, Shin-Ichi,Shibayama, Kohtaro,Nitta, Makoto
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p. 1393 - 1408
(2007/10/03)
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- An insight of the reactions of amines with trichloroisocyanuric acid
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The reaction between amines or α-aminoacids with trichloroisocyanuric acid is studied under various conditions: N,N-dichloroamines, nitriles and ketones can be obtained from primary amines, while free aminoacids undergo oxidative decarboxylation to the corresponding nitrile of one less carbon atom.
- De Luca, Lidia,Giacomelli, Giampaolo
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p. 2180 - 2184
(2007/10/03)
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- Photolysis of N-nitrosamines in neutral media
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The photolysis of N-nitrosamines in solutions of acetonitrile follows a first-order reaction with respect to the concentration of nitrosamine. Quantum yields are very low (≈0.1) and depend on the concentration of nitrosamine, with the observation of a linear correlation between the reciprocal of quantum yield and the reciprocal of nitrosamine concentration. For all the nitrosamines studied, the final product of the photolysis appears to be unique, alkylidenimine, which in the case of nitroso methyl benzyl amine undergoes a relatively rapid hydrolysis, giving rise to benzaldehyde, following second order kinetics. A provisional model consistent with the experimental results obtained in this work is proposed.
- Fiz,Usero,Casado
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p. 341 - 351
(2007/10/03)
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- A Facile Oxidation of Secondary Amines to Imines by Iodosobenzene or by a Terminal Oxidant and Manganese or Iron Porphyrins and Manganese Salen as the Catalysts
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The oxidation of secondary amines to imines by iodosobenzene or catalysed by either manganese(III) or iron(III) porphyrins, or by a manganese(III) salen complex with iodosobenzene as the oxygen donor has been investigated.Both aromatic and aliphatic amines can be oxidized smoothly to the corresponding imines with iodosobenzene as the oxidant and the elimination of hydrogen takes place towards the least substituted carbon.Manganese(III) and iron(III) porphyrins and manganese(III) salen are found to catalyse the oxidation of secondary amines to imines with iodosobenzene as the terminal oxidant.Those amines that are less reactive when iodosobenzene is the oxidant, can be converted to the imines in higher yields if a catalyst is added, compared with the uncatalysed reaction.By-products such as carbonyls and nitrones are found in some of these reactions.The manganese(III) salen complex is found to be the best catalyst, followed by manganese(III) porphyrin and iron(III) porphyrin.On the basis of Hammett plots, isotopic labelling studies and other experimental investigations the mechanisms for the uncatalysed and catalysed amine-to-imine oxidations are discussed.
- Larsen, Jan,Joergensen, Karl Anker
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p. 1213 - 1217
(2007/10/02)
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- Oxidative carbonylation of aliphatic amines catalysed by nickel-complexes
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The catalytic activity of some nickel-complexes in the dioxygen-induced oxidative carbonylation of amines has been studied.N,N'-substituted ureas were obtained in fairly low yields (maximum 55percent), instead of N,N'-oxamides expected on the basis of a p
- Giannoccaro, Potenzo,Nobile, Cosimo Francesco,Mastrorilli, Pietro,Ravasio, Nicoletta
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p. 251 - 258
(2007/10/02)
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- TRICHLOROSILANE-IMINE COMPLEXES. A NEW METHOD FOR THE REDUCTION OF IMINES TO AMINES
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It has been found that trichlorosilane adds regio-specifically to the carbon-nitrogen double bond of imines under mild conditions to yield hydrolytically unstable N-trichlorosilyl intermediates.The latter can be hydrolyzed in situ by alcoholic base to give the corresponding amines in moderate to good yields.Variously substituted aldo and keto imines, both alkyl and aryl, were tested to demonstrate the scope of the reaction.The facility of trichlorosilane addition appears to depend on the nature of the groups directly attached to the carbon-nitrogen double bond.Hydride trapping experiments suggest an intramolecular rather than intermolecular hydride transfer during the course of the reaction.
- Benkeser, Robert A.,Snyder, Dudley C.
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p. 107 - 115
(2007/10/02)
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- Reaction of Amines with Haloalkanes. 5. Dissolution of Copper Activated by Sulfur in n-Butylamine-Carbon Tetrachloride Solutions
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Earlier study has shown that oxygen causes the dissolution of copper metal in amine-haloalkane solutions.We have found that sulfur also activates copper metal for the dissolution process.A kinetic study has been made by using n-butylamine and CCl4 as reactants at 30 deg C.A mechanism involving an intermediate copper(I) sulfide film is proposed.
- Parodi, George A.,Miller, John G.
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p. 2968 - 2972
(2007/10/02)
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