- A metallopeptoid as an efficient bioinspired cooperative catalyst for the aerobic oxidative synthesis of imines
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Enzymatic catalysis is largely based on intramolecular cooperativity between a metal center and functional organic molecules located on one scaffold. Inspired by this concept we have designed the metallopeptoid trimer BT, which is a unique intramolecular cooperative oxidation catalyst incorporating two catalytic centers, phenanthroline-copper and TEMPO, as well as one non-catalytic benzyl group. Herein we explore the capability of BT to act as an efficient catalyst for the oxidative synthesis of imines, which are versatile intermediates in the fine chemicals and pharmaceutical industries. We demonstrate that BT, combined with CuI, can catalyze the production of benzyl, aryl, heteroaryl, allylic and aliphatic imines from various alcohols and amines with a turn-over-number up to 45 times higher than this achieved when phenanthroline, copper and TEMPO are mixed in solution. Moreover, in low catalyst(s) loading, BT enables transformations that are not possible when a mixture of the individual catalysts is employed.
- Chandra Mohan, Darapanani,Sadhukha, Arghya,Maayan, Galia
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- Synthesis of new azepino[3,4,5-cd]indole derivatives
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New 2-oxoazepino[3,4,5-cd]indole derivatives were formed by the reaction of the tosylate SKandF 98339 with N-alkyl and N-arylidenepropylamines in moderate yield.
- Hayes,Hayler,Walsgrove,Wicks
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Read Online
- Selectively catalytic epoxidation of α-pinene with dry air over the composite catalysts of Co-MOR(L) with Schiff-base ligands
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Twelve bi-/tridentate Schiff-base ligands (L1-L12) have been designed, synthesized and coordinated with ion-exchanged Co-MOR (Mordenite) forming a series of Co-MOR(L) composite catalysts, for which various analyzes and characterizations are conducted. Selectively catalytic epoxidation of α-pinene with dry air over Co-MOR(L) catalysts has been carried out, where uses TBHP in small amounts as the initiator. Among these Co-MOR(L) catalysts, Co-MOR(L8) exhibits the best activity for the titled reaction to obtain 85.8 mol% conversion and 90.8% selectivity of epoxide. Some factors such as the structure of ligands, the oxidants, the solvents, the catalyst amount, the reaction temperature and time play important roles in controlling the epoxidation. The recyclable stability of the Co-MOR(L8) catalyst is confirmed. The studies on the electrochemical behaviors of Co species in Co-MOR(L8) reveal the importance of reversible change between Co oxidation states for the epoxidation.
- Lu,Lei,Wei,Ma,Zhang,Hu,Zhou,Xia
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- Gating the photochromism of an azobenzene by strong host-guest interactions in a divalent pseudo[2]rotaxane
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The ability of an E-configured azobenzene guest to undergo photoisomerisation is controlled by the presence of a complementary host. Addition of base/acid allowed for a weakening/strengthening of the interactions in the divalent pseudo[2]rotaxane complex and hence could switch on/off photochromic activity.
- Lohse, Mirko,Nowosinski, Karol,Traulsen, Nora L.,Achazi, Andreas J.,Von Krbek, Larissa K. S.,Paulus, Beate,Schalley, Christoph A.,Hecht, Stefan
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- Transimination reactions in [b-3C-im][NTf2] ionic liquid
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Compared to conventional molecular solvents, the ionic liquid [b-3C-im][NTf2] was found to promote transimination reactions with up to ~100-fold rate enhancement. This rate effect observed at ambient temperature might be explained by the fact that the ionic liquid displays weak Lewis acidity with very low, if any, nucleophilicity and its imidazolium cation is expected to interact by associating with, and thus electrophilically activating, the CN bond of the starting imine, leading to increased stabilization of the polar, charged intermediate species and ultimately, rapid product formation. Moreover, the presence of 1 mol% Sc(OTf)3 in [b-3C-im][NTf2] further facilitates the transimination reactions studied.
- Chen, Chao-Wen,Tseng, Ming-Chung,Hsiao, San-Kai,Chen, Wen-Hao,Chu, Yen-Ho
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- Facile and efficient method for preparation of Schiff bases catalyzed by P2O5/SiO2 under free Solvent conditions
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A simple and convenient method for the preparation of Schiff bases is developed. In this method, the Schiff base compounds were prepared from the reaction of carbonyl compounds with primary amines. In this reaction, P 2O5/SiO2 have catalyzed the Schiff base formation in dry media under solvent-free conditions. Advantages of this method are use of an inexpensive and efficient catalyst, high yields of products, short reaction times, and simplicity of the reaction and workup.
- Naeimi, Hossein,Sharghi, Hashem,Salimi, Fariba,Rabiei, Khadijeh
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- Electrochemical, Iodine-Mediated α-CH Amination of Ketones by Umpolung of Silyl Enol Ethers
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The electrochemical, oxidative Umpolung reaction of silyl enol ethers utilizing simple iodide salts for the synthesis of α-amino ketones is described. The products were isolated in excellent yields of up to 100percent, and various functionalized starting materials were accepted in an undivided electrochemical cell design. Moreover, a sensitivity assessment to ensure an improved reproducibility of the reaction and cyclic voltammetry experiments were performed to postulate a plausible reaction mechanism on their basis.
- Strehl, Julia,Hilt, Gerhard
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supporting information
p. 5968 - 5972
(2020/08/12)
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- Nucleophilic Imines and Electrophilic o-Quinone Methides, a Three-Component Assembly of Assorted 3,4-Dihydro-2 H-1,3-benzoxazines
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A one-pot method for joining three separate components leading to an assortment of N-substituted 3,4-dihydro-2H-1,3-benzoxazines is described. The method involves the addition of a Grignard reagent to an o-OBoc salicylaldehyde in the presence of an imine. With a variety of components, 15 examples are presented, including the diastereoselective incorporation of chiral imines.
- Chen, Peishan Kc,Wong, Yuk Fai,Yang, Derek,Pettus, Thomas R. R.
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supporting information
p. 7746 - 7749
(2019/10/11)
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- Bi-functional catalyst of porous N-doped carbon with bimetallic FeCu for solvent-free resultant imines and hydrogenation of nitroarenes
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The efficient and stable catalyst applied to the transformation of amines into the corresponding imines and hydrogenation of nitroarenes under mild reaction conditions is reported. The catalytic performance of porous N-doped carbon with FeCu (FeCu@NPC) catalyst are tested by aromatic alcohol-based N-alkylated of amines with solvent-free and hydrogenation of nitroarenes via N2H4·H2O. The results proved that the yield of these two reactions are all over 99.9% under optimum condition. Moreover, the synergistic effect of the catalyst for N-alkylated reaction was investigated through the kinetic study. The catalyst can be easily separated from reaction system by an external magnetism, and can be recycled and reutilized for at least 4 runs with conversions are all over 75%. The study of the catalyst indicated that it was suitable for the reactions in industry. Hence, the catalysis process by the inexpensive metals-based catalyst is green and sustainable.
- Wang, Kaizhi,Gao, Wenbing,Jiang, Pengbo,Lan, Kai,Yang, Ming,Huang, Xiaokang,Ma, Lei,Niu, Fang,Li, Rong
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- Visible-Light-Driven Photocatalytic Oxidation of Organic Chlorides Using Air and an Inorganic-Ligand Supported Nickel-Catalyst Without Photosensitizers
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Engineering photoredox-triggered chemical transformation via visible light has been an emerging area in organic synthesis. However, most of the well-established photocatalysts are based upon either transition metal complexes involved with noble metals and organic ligands or photosensitive organic dyes, the development of pure inorganic molecular photocatalysts that could provide better stability and durability is greatly retarded. Herein we discover that the Anderson polyoxometalate (POM) Na4[NiMo6O18(OH)6] (1), which consists of pure inorganic framework built from a central NiII core supported by six MoVIO6 inorganic scaffold/ligands, can be used as a powerful photocatalyst. Upon irradiation with visible light (>400 nm), the compound can catalyze, in high efficiency, a wide range of reactions, including the oxidative cross-coupling reaction of chlorides with amines, as well as oxidation of chlorides using molecular oxygen, affording various imines, aldehydes, and ketones, respectively in high selectivity and good yields. Owing to the robust inorganic framework, this catalyst exhibits excellent stability during the catalysis and reusability with little loss of the catalytic activity, thus providing an alternative without use of complicated organic ligands and expensive noble metal-based photosensitizers.
- Yu, Han,Wang, Jingjing,Zhai, Yongyan,Zhang, Mengqi,Ru, Shi,Han, Sheng,Wei, Yongge
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p. 4274 - 4279
(2018/09/10)
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- Dynamic Covalent Metathesis in the C=C/C=N Exchange between Knoevenagel Compounds and Imines
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Fast and reversible dynamic covalent C=C/C=N exchange takes place without catalyst in nonpolar solvents between barbiturate-derived Knoevenagel (Kn) compounds and imines. A detailed study of the reaction indicates that it proceeds by an associative organo-metathesis mechanism involving the formation of a four-membered ring azetidine intermediate by addition of the imine C=N group to the C=C bond of the Kn compound. This intermediate could be generated cleanly and stabilized at low temperature by condensation of the o,p-dinitrophenyl Kn derivative with the cyclic imine 1-azacyclohexene. It was characterized by extensive NMR and mass spectrometric studies. The process described represents a genuine dynamic covalent organo-metathesis through a four-membered ring adduct as intermediate. It paves the way for the exploration of a wide set of dynamic systems involving (strongly) polarized C=C bonds and various imines, extending also into covalent dynamic polymers and polymolecular assemblies.
- Gu, Ruirui,Flidrova, Karolina,Lehn, Jean-Marie
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p. 5560 - 5568
(2018/05/01)
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- One-Pot Reductive Allylation of Amides by Using a Combination of Titanium Hydride and an Allylzinc Reagent: Application to a Total Synthesis of (-)-Castoramine
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A one-pot direct reductive allylation protocol has been developed for the synthesis of secondary amines by using titanium hydride and an allylzinc reagent. This protocol is applicable to a broad range of substrates, including acyclic amides, benzamides, α,β-unsaturated amides, and lactams. The stereochemical outcome obtained from the reaction with crotylzinc reagent suggested that the allylation reaction proceeds through a six-membered cyclic transition state. A total synthesis of (-)-castoramine was accomplished by following this protocol for the highly stereoselective construction of contiguous stereocenters.
- Itabashi, Suguru,Shimomura, Masashi,Sato, Manabu,Azuma, Hiroki,Okano, Kentaro,Sakata, Juri,Tokuyama, Hidetoshi
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supporting information
p. 1786 - 1790
(2018/07/03)
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- Transition-Metal-Controlled Inorganic Ligand-Supported Non-Precious Metal Catalysts for the Aerobic Oxidation of Amines to Imines
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Most state-of-art transition-metal catalysts usually require organic ligands, which are essential for controlling the reactivity and selectivity of reactions catalyzed by transition metals. However, organic ligands often suffer from severe problems including cost, toxicity, air/moisture sensitivity, and being commercially unavailable. Herein, we show a simple, mild, and efficient aerobic oxidation procedure of amines using inorganic ligand-supported non-precious metal catalysts 1, (NH4)n[MMo6O18(OH)6] (M=Cu2+; Fe3+; Co3+; Ni2+; Zn2+, n=3 or 4), synthesized by a simple one-step method in water at 100 °C, demonstrating that the catalytic activity and selectivity can be significantly improved by changing the central metal atom. In the presence of these catalysts, the catalytic oxidation of primary and secondary amines, as well as the coupling of alcohols and amines, can smoothly proceed to afford various imines with O2 (1 atm) as the sole oxidant. In particular, the catalysts 1 have transition-metal ion core, and the planar arrangement of the six MoVI centers at their highest oxidation states around the central heterometal can greatly enhance the Lewis acidity of catalytically active sites, and also enable the electrons in the center to delocalize onto the six edge-sharing MO6 units, in the same way as ligands in traditional organometallic complexes. The versatility of this methodology maybe opens a path to catalytic oxidation through inorganic ligand-coordinated metal catalysis.
- Yu, Han,Zhai, Yongyan,Dai, Guoyong,Ru, Shi,Han, Sheng,Wei, Yongge
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supporting information
p. 13883 - 13887
(2017/10/13)
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- Dual Heterogeneous Catalyst Pd-Au@Mn(II)-MOF for One-Pot Tandem Synthesis of Imines from Alcohols and Amines
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A new Mn(II) metal-organic framework (MOF) 1 was synthesized by the combination of 4,4,4-trifluoro-1-(4-(pyridin-4-yl)phenyl)butane-1,3-dione (L) and Mn(OAc)2 in solution. 1 features a threefold-interpenetrating NbO net containing honeycomb-like channels, in which the opposite Mn(II)···Mn(II) distance is 23.5075(10) ?. Furthermore, 1 can be an ideal platform to support Pd-Au bimetallic alloy nanoparticles to generate a composite catalytic system of Pd-Au@Mn(II)-MOF (2). 2 can be a highly active bifunctional heterogeneous catalyst for the one-pot tandem synthesis of imines from benzyl alcohols and anilines and from benzyl alcohols and benzylamines.
- Chen, Gong-Jun,Ma, Hui-Chao,Xin, Wen-Ling,Li, Xiao-Bo,Jin, Fa-Zheng,Wang, Jing-Si,Liu, Ming-Yang,Dong, Yu-Bin
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p. 654 - 660
(2017/01/13)
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- Aerobic oxidative coupling of alcohols and amines towards imine formation by a dicopper(I,I) catalyst
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A dicopper(I,I) complex [Cu2(L1) (Cl)2] (1), bearing a Cu2Cl2 core spanned by a naphthyridine–diimine ligand is synthesized by the treatment of CuCl with 2,7–bis(N–mesitylmethylimino)–1,8–naphthyridine (L1). The catalytic efficacy of 1 is assessed for aerobic oxidative synthesis of imines from alcohols and amines. The title complex is found to be an excellent catalyst for a wide variety of alcohols and amines. Kinetic experiments revealed the involvement of both copper ions in the aerobic oxidation process. The general utility of naphthyridine based ligands to favour a possible bimetallic pathway for a catalytic reaction is demonstrated here.
- Dutta, Indranil,De, Subhabrata,Yadav, Sudhir,Mondol, Ranajit,Bera, Jitendra K.
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p. 117 - 124
(2017/09/30)
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- Monocyclic β-lactam and unexpected oxazinone formation: synthesis, crystal structure, docking studies and antibacterial evaluation
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Novel monocyclic β-lactam derivatives bearing aryl, phenyl and heterocyclic rings were synthesized as possible antibacterial agents. Cyclization of imines (3h, 3t) with phenylacetic acid in the presence of phosphoryl chloride and triethyl amine did not afford the expected β-lactams. Instead, highly substituted 1,3-oxazin-4-ones (4h, 4t) were isolated as the only product and confirmed by single crystal X-ray analysis of 4t. The results of antibacterial activity showed that compound 4l exhibited considerable antibacterial activity with MIC and MBC values of 62.5 μg/mL against Klebsiella pneumoniae. Cytotoxicity assay on Chinese Hamster Ovary (CHO) cell line revealed non-cytotoxic behavior of compounds 4d, 4h, 4k and 4l up to 200 μg/mL conc. Molecular docking was performed for compound 4l with penicillin binding protein-5 to identify the nature of interactions. The results of both in silico and in vitro evaluation provide the basis for compound 4l to be carried as a potential lead molecule in the drug discovery pipeline against bacterial infections.
- Aneja, Babita,Irfan, Mohammad,Hassan, Md. Imtaiyaz,Prakash, Amresh,Yadava, Umesh,Daniliuc, Constantin G.,Zafaryab, Md.,Rizvi, M. Moshahid A.,Azam, Amir,Abid, Mohammad
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p. 834 - 852
(2016/07/07)
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- Trans-Symmetric Dynamic Covalent Systems: Connected Transamination and Transimination Reactions
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The development of chemical transaminations as a new type of dynamic covalent reaction is described. The key 1,3-proton shift is under complete catalytic control and can be conducted orthogonally to, or simultaneous with, transimination in the presence of an amine to rapidly yield two-dimensional dynamic systems with a high degree of complexity evolution. The transamination-transimination systems are proven to be fully reversible, stable over several days, compatible with a range of functional groups, and highly tunable. Kinetic studies show transamination to be the rate-limiting reaction in the network. Furthermore, it was discovered that readily available quinuclidine is a highly potent catalyst for aldimine transaminations. This study demonstrates how connected dynamic reactions give rise to significantly larger systems than the unconnected counterparts, and shows how reversible isomerizations can be utilized as an effective diversity-generating element. Constant exchange: The development of chemical transaminations as a new type of dynamic covalent reactions is described (see figure). This study demonstrates how connected dynamic reactions give rise to significantly larger systems than the unconnected counterparts, and shows how reversible isomerizations can be utilized as an effective diversity-generating element.
- Schaufelberger, Fredrik,Hu, Lei,Ramstr?m, Olof
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supporting information
p. 9776 - 9783
(2015/06/30)
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- Factors influencing the regioselectivity of the oxidation of asymmetric secondary amines with singlet oxygen
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Aerobic amine oxidation is an attractive and elegant process for the α functionalization of amines. However, there are still several mechanistic uncertainties, particularly the factors governing the regioselectivity of the oxidation of asymmetric secondary amines and the oxidation rates of mixed primary amines. Herein, it is reported that singlet-oxygen-mediated oxidation of 1° and 2° amines is sensitive to the strength of the α-C-H bond and steric factors. Estimation of the relative bond dissociation energy by natural bond order analysis or by means of one-bond C-H coupling constants allowed the regioselectivity of secondary amine oxidations to be explained and predicted. In addition, the findings were utilized to synthesize highly regioselective substrates and perform selective amine cross-couplings to produce imines.
- Ushakov, Dmitry B.,Plutschack, Matthew B.,Gilmore, Kerry,Seeberger, Peter H.
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supporting information
p. 6528 - 6534
(2015/04/22)
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- Deep eutectic solvent catalyzed eco-friendly synthesis of imines and hydrobenzamides
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The urea-choline chloride-based deep eutectic solvent was found to be an efficient catalyst and reaction media for the additive-free synthesis of imines (Schiff bases) and hydrobenzamides by the reaction of aldehydes with amines and ammonia in good to high yields. Outstanding features of this protocol were the general and atom-economical reaction, absence of external catalysts and additives, simple workup, and availability and recycling of urea-choline chloride as a green solvent. Graphical abstract: (Chemical Equation Presented).
- Azizi, Najmedin,Edrisi, Mahtab
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p. 1695 - 1698
(2015/09/21)
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- Lanthanide coordination polymer constructed from 2,2′-bipyridyl-4,4′-dicarboxylic acid: Structure, catalysis and fluorescence
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Two new isostructural lanthanide coordination polymers (Ln-CPs) [Ln2(bpdc)3(DMF)2] (Ln = Tb for 1, Eu for 2) with two kinds of one-dimensional channels along the a axis, were synthesized by 2,2′-bipyridyl-4,4′-dicarboxylic acid (H2bpdc) under solvothermal conditions. With exposed Lewis acid Ln3+ centers, 1 as a heterogeneous catalyst shows good catalytic reactivity and selectivity for the Strecker reaction affording medium to excellent conversion yields. Luminescent studies illustrate that 1 and 2 show intensive green and red luminescence triggered by efficient antenna effect of ligands under UV light, respectively. Moreover, 1 exhibits sensitive fluorescent response to Cu2+ in DMF solution.
- Wang, Shengyan,Xu, Jianing,Zheng, Jifu,Chen, Xiaodong,Shan, Liang,Gao, Lijuan,Wang, Li,Yu, Miao,Fan, Yong
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supporting information
p. 81 - 86
(2015/09/15)
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- Selective aerobic oxidation of alcohols to aldehydes, carboxylic acids, and imines catalyzed by a Ag-NHC complex
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Silver NHC catalysts have been developed for the selective oxidation of alcohols to aldehydes or carboxylic acids in the presence of BnMe3NOH or KOH under dry air. The aerobic oxidation conditions are mild, and the yield is excellent. Further tandem catalysis enables the one-pot synthesis of imines in excellent yield. Only 0.1 mol % of the catalyst is required.
- Han, Lei,Xing, Ping,Jiang, Biao
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supporting information
p. 3428 - 3431
(2014/07/21)
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- Morphology-tuned exceptional catalytic activity of porous-polymer-supported Mn3O4 in aerobic sp3 C-H bond oxidation of aromatic hydrocarbons and alcohols
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Mn3O4 nanomaterials with different morphologies (sphere, nanowire, and octahedron) embedded into functionalized nanoporous polymers were developed by a facile one-pot solvothermal technique at different temperatures. These Mn3O4-based hybrid materials could behave as heterogeneous nanocatalysts to perform sp3 C-H bond oxidation of aromatic hydrocarbons and alcohols with molecular oxygen as an economic oxidant. Catalytic activity could be effectively tuned by changing the morphology of incorporated Mn3O4 in nanoporous polymer. These Mn3O4-based hybrid materials exhibited remarkable catalytic performance for sp3 C-H bond oxidation as compared with bare Mn3O4 nanoparticles. Mn3O4 with octahedral morphology in nanoporous polymer exhibited the highest catalytic activity on account of its more exposed crystallographic planes and edges. These Mn3O4-based nanocatalysts could be recycled and reused for consecutive catalytic cycles without a significant loss of catalytic activity. Exceptional crystal facets: Nanoporous-polymer-supported Mn3O4 nanocatalysts (Mn@DVTA, DVTA=divinyltriallyl) with different morphologies are developed to catalyze aerobic sp3 C-H bond oxidation of aromatic hydrocarbons and alcohols. Among the different nanocatalysts, those with octahedral crystallite morphology exhibit outstanding catalytic performance.
- Mondal, John,Borah, Parijat,Sreejith, Sivaramapanicker,Nguyen, Kim Truc,Han, Xiguang,Ma, Xing,Zhao, Yanli
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p. 3518 - 3529
(2015/04/16)
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- Metal-Ligand cooperation on a diruthenium platform: Selective imine formation through acceptorless dehydrogenative coupling of alcohols with amines
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Metal-metal singly-bonded diruthenium complexes, bridged by naphthyridine-functionalized N-heterocyclic carbene (NHC) ligands featuring a hydroxy appendage on the naphthyridine unit, are obtained in a single-pot reaction of [Ru2(CH3COO)2(CO)4] with 1-benzyl-3-(5,7-dimethyl-1,8-naphthyrid-2-yl)imidazolium bromide (BIN-HBr) or 1-isopropyl-3-(5,7-dimethyl-1,8-naphthyrid-2-yl)imidazolium bromide (PIN-HBr), TlBF4, and substituted benzaldehyde containing an electron-withdrawing group. The modified NHC-naphthyridine-hydroxy ligand spans the diruthenium unit in which the NHC carbon and hydroxy oxygen occupy the axial sites. All the synthesized compounds catalyze acceptorless dehydrogenation of alcohols to the corresponding aldehydes in the presence of a catalytic amount of weak base 1,4-diazabicyclo[2.2.2]octane (DABCO). Further, acceptorless dehydrogenative coupling (ADHC) of the alcohol with amines affords the corresponding imine as the sole product. The substrate scope is examined with 1 (BIN, p-nitrobenzaldehyde). A similar complex [Ru2(CO) 4(CH3COO)(3-PhBIN)][Br], that is devoid of a hydroxy arm, is significantly less effective for the same reaction. Neutral complex 1 a, obtained by deprotonation of the hydroxy arm in 1, is found to be active for the ADHC of alcohols and amines under base-free conditions. A combination of control experiments, deuterium labeling, kinetic Hammett studies, and DFT calculations support metal-hydroxyl/hydroxide and metal-metal cooperation for alcohol activation and dehydrogenation. The bridging acetate plays a crucial role in allowing β-hydride elimination to occur. The ligand architecture on the diruthenium core causes rapid aldehyde extrusion from the metal coordination sphere, which is responsible for exclusive imine formation. Ligand lends a hand: Metal-hydroxy/hydroxide and metal-metal cooperation is demonstrated for acceptorless dehydrogenation of alcohols to give aldehydes. The ligand architecture ensures rapid extrusion of the aldehyde from the metal core, resulting in the formation of the corresponding imine as the sole coupled product with amines (see scheme; DABCO=1,4-diazabicyclo[2.2.2]octane).
- Saha, Biswajit,Wahidurrahaman,Daw, Prosenjit,Sengupta, Gargi,Bera, Jitendra K.
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p. 6542 - 6551
(2014/06/09)
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- Pseudorotaxane orientational stereoisomerism driven by π-electron density
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Pseudo[2]rotaxane orientational isomers were formed in a stereocontrolled way by exploiting the electron-withdrawing (EW) or electron-donating (ED) effects of para-substituted dibenzylammonium axles threaded through the π-electron rich calixarene cavity, which allow the fine tuning of the weak π-π interactions.
- Gaeta, Carmine,Talotta, Carmen,Neri, Placido
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supporting information
p. 9917 - 9920
(2014/08/18)
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- Chitosan: A highly efficient renewable and recoverable bio-polymer catalyst for the expeditious synthesis of α-amino nitriles and imines under mild conditions
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Commercial chitosan-without any post-modification with active Bronsted or Lewis acid centers-was found to be a highly efficient renewable and recoverable bio-polymer catalyst for the rapid and convenient synthesis of α-amino nitriles or imines from aromatic aldehydes and amines under mild reaction conditions at room temperature in high to quantitative yields. The α-amino nitrile derivatives were prepared through the Strecker reaction using trimethylsilyl cyanide (TMSCN) and catalyzed by chitosan as a heterogeneous bifunctional organocatalyst.
- Dekamin, Mohammad G.,Azimoshan, Mojtaba,Ramezani, Leila
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supporting information
p. 811 - 820
(2013/04/10)
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- General, green, and scalable synthesis of imines from alcohols and amines by a mild and efficient copper-catalyzed aerobic oxidative reaction in open air at room temperature
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A general, green, and scalable synthesis of the useful imines and a,b-unsaturated imines is successfully achieved by a low-loading and powerful, mild and efficient copper-catalyzed aerobic oxidative reaction of alcohols and amines in the open air at room temperature under base- and dehydrating reagent-free conditions. This practical reaction can use air as the economic and green oxidant, tolerates a wide range of substrates, can afford high yields of the target imines on a large scale, and produces water as the only by-product, and thus being the best imination method as yet using alcohols and amines directly.
- Tian, Haiwen,Yu, Xiaochun,Li, Qiang,Wang, Jianxin,Xu, Qing
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supporting information
p. 2671 - 2677,7
(2012/12/12)
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- Direct chemoselective allylation of inert amide carbonyls
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Direct allylation of inert amide carbonyls utilizing the Schwartz reagent afforded either substituted tertiary or secondary amines. A preactivation step was successfully avoided, which is generally a requisite to increase the electrophilicity of amides. The reaction exhibited remarkable functional group tolerance and proceeded even in the presence of methyl esters and nitro groups.
- Oda, Yukiko,Sato, Takaaki,Chida, Noritaka
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supporting information; experimental part
p. 950 - 953
(2012/04/18)
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- One-pot sequence synthesis of azetidin-2-one using diethyl chlorophosphate
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A simple and convenient synthesis of 2-azetidinone derivatives from the reaction of a pre-mixture of amines and aldehydes with carboxylic acids in the presence of diethyl chlorophosphate by [2+2] cycloaddition reaction is described. Separation and purification of imines as intermediates were not required. The methodology is convenient and good to excellent yields of products were obtained with simple purification.
- Zarei, Maaroof
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experimental part
p. 118 - 120
(2012/05/04)
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- Synthesis of structurally diverse 2-azetidinones via staudinger reaction on a solid support
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Trimellitic anhydride was attached to Merrifield resin and a ketene was generated from polymer-bound phthaloylglycine. Then this polymer reacted with imines in the presence of Vilsmeier reagent and triethylamine to afford the solid-phase-tethered β-lactam products. Selective cleavage of supported β-lactams by trifluoroacetic acid and methylhydrazine gave 4-carboxyphthalimido- and 3-amino-β-lactams, respectively. The trans-stereochemistry was found in all products.
- Jarrahpour, Aliasghar,Fadavi, Abdolhamid,Zarei, Maaroof
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experimental part
p. 320 - 327
(2011/05/14)
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- Assembly of a self-complementary monomer: Formation of supramolecular polymer networks and responsive gels
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Self-complementary monomer 1, which combines a macrotricyclic polyether and two dibenzylammonium ions together, was synthesized, and its self-assembly into supramolecular polymer networks by host-guest interactions was studied. For the purpose of comparative study, two model molecules 2 and 3 were also prepared. It was found that model molecule 2 and dibenzylammonium ion 4 form a 1:2 complex in solution and in the solid state, which afforded a model system for the investigation of the assembly behavior of monomer 1. Consequently, the 1H NMR spectrum of 1 in CD3CN showed characteristic proton signals similar to the model system, which suggested that 1 self-assembles into a supramolecular polymer network. Formation of the supramolecular polymer was further evidenced by the MALDI-TOF MS spectrum, viscometry, and dynamic light-scattering (DLS) experiments. Moreover, it was found that the decomposition and re-formation of the supramolecular polymer could be chemically controlled by the use of triethylamine and trifluoroacetic acid. Interestingly, the supramolecular polymer forms an organogel both in CD3CN and in 1:1 (v/v) CDCl3/CD3CN, and reversible thermo-and pH-induced gel-sol transitions were also found. The presented work will provide a new strategy for the construction of supramolecular polymers with specific structures and properties.
- Su, Yong-Sheng,Liu, Jia-Wei,Jiang, Yi,Chen, Chuan-Feng
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experimental part
p. 2435 - 2441
(2011/05/02)
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- A highly diastereoselective synthesis of α-hydroxy-β-amino acid derivatives via a Lewis acid catalyzed three-component condensation reaction
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A very efficient three-component synthesis of a series of syn α-hydroxy-β-amino esters, obtained in high diastereoselection and yield, was realized starting from an aldehyde, benzylamine, and the ketene silyl acetals derived from Ley's lactones. The synthetic protocol was optimized and the above compounds were obtained without the isolation of intermediates. The origin of the observed diastereoselection was investigated through a computational model of the key reaction step.
- Gassa, Federico,Contini, Alessandro,Fontana, Gabriele,Pellegrino, Sara,Gelmi, Maria Luisa
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experimental part
p. 7099 - 7106
(2010/12/24)
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- Structural-activity relationship study of highly-functionalized imidazolines as potent inhibitors of nuclear transcription factor-κB mediated IL-6 production
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We herein describe the synthesis and anti-inflammatory properties of a small library of imidazoline-based NF-κB inhibitors. The structure-activity relationship of various substituents on an imidazoline core structure was evaluated for the ability to inhibit NF-κB mediated IL-6 production. Optimization of the scaffolds was pursued by correlating luciferase-based NF-κB reporter assays with inhibition of IL-6 production in IL-1β stimulated human blood. Several derivatives were found to inhibit NF-κB mediated IL-6 production in the nanomolar range in IL-1β stimulated human blood.
- Kahlon, Daljinder K.,Lansdell, Theresa A.,Fisk, Jason S.,Tepe, Jetze J.
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experimental part
p. 3093 - 3103
(2009/10/02)
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- Silica gel supported sodium hydrogen sulfate as an efficient and reusable heterogeneous catalyst for the synthesis of imines in solvent-free conditions under microwave irradiation
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This synthesis of imines has been carried out efficiently by the condensation of carbonyl compounds with amines in the presence of silica gel supported sodium hydrogen sulfate (NaHSO4.SiO2) as a heterogeneous catalyst under microwave irradiation in solvent-free conditions. NaHSO4.SiO2 can be recovered and re-used up to ten times by simple washing with diethyl ether after each use and activated in an oven at 120°C for 1 h, thus rendering the process more economical.
- Gopalakrishnan, Mannathusamy,Sureshkumar, Purushothaman,Kanagarajan, Vijayakumar,Thanusu, Jeyaraman,Govindaraju, Ramalingam
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p. 299 - 303
(2007/10/03)
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- The simple and selective synthesis of 3-amino-2,2-difluorocarboxylic esters and difluoro-β-lactams using ethyl bromodifluoroacetate in the presence of rhodium catalyst
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Treatment of imines (5) with ethyl bromodifluoroacetate (1) and Et 2Zn in the presence of RhCl(PPh3)3 in anhydrous medium gave difluoro-β-lactams (7) in good to excellent yields, while 3-amino-2,2-difluorocarboxylic esters (6) were obtained in good yields by adding MgSO4·7H2O to the reaction medium.
- Sato, Kazuyuki,Tarui, Atsushi,Matsuda, Seiji,Omote, Masaaki,Ando, Akira,Kumadaki, Itsumaro
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p. 7679 - 7681
(2007/10/03)
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- Diastereochemical diversity of imidazoline scaffolds via substrate controlled TMSCI mediated cycloaddition of azlactones
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(Chemical Equation Presented) We report herein a trimethylsilyl chloride mediated substrate controlled 1,3-dipolar cycloaddition for the diastereoselective synthesis of either syn- or anti-imidazolines. This method provides scaffolds with four points of diversity and control over two stereocenters.
- Sharma, Vasudha,Tepe, Jetze J.
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p. 5091 - 5094
(2007/10/03)
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- Molecular sieves in ionic liquids as an efficient and recyclable medium for the synthesis of imines
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A great variety of imines were efficiently isolated in high yields from the reaction of aldehydes and amines in ionic liquids. The ionic liquids could be recovered and reused for at least five cycles without loss in the yields being a useful alternative to dichloromethane or diethyl ether, which are the commonly used solvents for this reaction.
- Andrade, Carlos Kleber Z.,Takada, Sayuri Cristina S.,Magalh?es Alves, Luana,Petrocchi Rodrigues, Juliana,Suarez, Paulo Anselmo Z.,Brand?o, Rodrigo Fleury,Soares, Valério Cassiano D.
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p. 2135 - 2138
(2007/10/03)
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- Regioselective cyclomanganation of Schiff bases. An unexpected effect of chloro substituents
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The synthesis of new metallacycles of benzyl-benzylidene-amines by using [MnMe(CO)5] as metallating agent is reported. The results described suggest that cyclomanganation takes place by the formation of a four-centered transition state, involving the C-H and Mn-Cacetyl bonds, in the acetyl coordination complex formed in the first step of the reaction. In this paper we describe the synthesis of new metallacycles by the cyclomanganation reaction of benzyl-benzylidene-amines by using [MnMe(CO)5] as metallating agent. These ligands can undergo metallation on different aromatic carbon atoms but no important differences have been found in the regioselectivity of the process, that can be related to the electronic effect of the substituents, and in all the cases studied the endo-cyclomanganated complexes of para-substituted imines have been obtained. The corresponding exo-metallacycles were obtained by reaction of [MnMe(CO)5] on the imine 2,6-Cl2C6H3CH=NCH2Ph and 2,4,6-Me3C6H2CH=NCH2Ph, derived from 2,6-dichlorobenzaldehyde and 2,4,6-trimethylbenzaldehyde, respectively. The results described suggest that the mechanism of the cyclomanganation is similar to that of cyclopalladation and it can be proposed that cyclomanganation takes place by the formation of a four-centered transition state, involving the C-H and Mn-Cacetyl bonds, in the acetyl coordination complex formed in the first step of the reaction.
- Albert, Joan,Cadena, J. Magali,Granell, Jaume,Solans, Xavier,Font-Bardia, Mercè
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p. 4889 - 4896
(2007/10/03)
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- Oxidation of N-benzylaldimines to N-benzylamides by MCPBA and BF3·OEt2
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N-Benzylamides were obtained from the corresponding N-benzylaldimines in high yields. N-Benzylaldimines are readily prepared from the corresponding aldehydes with benzylamine. This procedure involves the oxidation of N-benzylaldimines with MCPBA with BF3·OEt2. In this reaction, the reaction presumably follows an internal hydrogen abstraction to provide only N-benzylamide.
- An, Gwang-Il,Rhee, Hakjune
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p. 876 - 878
(2007/10/03)
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- Oxidative N-debenzylation of N-benzyl-N-substituted benzylamines catalyzed by horseradish peroxidase
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A report on the oxidative N-debenzylation of N-benyl-N-substituted benzylamines catalyzed by horseradish peroxidase was presented. A solution of benzylamine in benzene was added to a benzene solution of p-anisaldehyde in 100 ml flask over 10 minutes. Expulsion of proton and hydroxylation yielding α-hydroxylamines were followed by the formation of benzaldehydes and benzylamines.
- Kim, Sung Soo,Jung, Hwan
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p. 555 - 558
(2007/10/03)
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- Diazoketones as precursors in β-lactam synthesis. New insights into the mechanism of the photochemically induced Staudinger reaction
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Diazoketones 1-3, derived from suitably protected amino acids (Ala, Val and Tle), have been photochemically rearranged in the presence of imines leading exclusively to trans-arranged 4-aryl- and cinnamoyl-substituted β-lactams 17-33 with up to 84% yield. Selectivities were dependent on the steric demand of the amino acid side-chain ranging from 65:35 to 90:10. The relative configurations were proved by several X-ray crystal structures and comparison of NMR spectra. Further reactions of the azetidinones at position C-4 have been performed: electron-rich aryl substituents (e.g., 4-methoxyphenyl, furyl and thienyl) could be degraded to carboxylic acids 34 and 35 which were further transformed to acetoxy derivatives (compounds 36 and 37) in a Kolbe reaction of type II. The cinnamoyl group could be oxidized to the formyl group by ozonolysis (→38,39). The mechanism of the photochemically induced β-lactam formation is discussed in detail.
- Linder,Frey,Podlech
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p. 2566 - 2577
(2007/10/03)
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- Pyrroles from 1,2-cyclopropanediamines and aldehydes
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Mechanistic investigations by means of proton spectroscopy detected intermediates and uncovered the course of reactions in acetate-buffered [D4]methanol of primary cyclopropanediamines cis- and trans-2a with benzaldehyde (3a) or 2,2-dimethylpropanal (3b), of secondary cyclopropanediamines cis- and trans-2b with 3b, and of the ringmethylated cyclopropanediamine trans-14a and the aromatic aldehydes 3a and c. This study provided the basis of an expedient synthesis of pyrroles which takes place under exceptionally mild conditions. Irrespective of the configuration, primary (2a·2HBr) and secondary cyclopropanediammonium dibromides 2b and c·2HBr that are devoid of ring substituents react with aromatic aldehydes 3a, e-h, cinnamic aldehyde (3i), and 3b to afford 2-substituted (8a, b) and 1,2-disubstituted pyrroles (8c-i), respectively. The 3-substituted secondary transcyclopropanediammonium dibromides 24·2HBr furnish 1,2,4-trisubstituted pyrroles 25. While the primary 1-methylcyclopropanediammonium dibromide trans-14a·2HBr reacts regioselectively with 3a and c to produce only 2,3-substituted pyrroles 19a, c, the corresponding secondary dibromide trans-14c·2HBr gives rise to the formation of mixtures of 1,2,3- (22) and 1,2,5-trisubstituted pyrroles 23. The key step of pyrrole formation from 1,2-cyclopropanediamines and aldehydes is the ring expansion of intermediate monoiminium ions of type 5 via azomethine ylides (E,Z)-6 to yield dihydropyrrolium ions 7.
- Von Der Saal, Wolfgang,Reinhardt, Robert,Stawitz, Josef,Quast, Helmut
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p. 1645 - 1652
(2007/10/03)
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- Mechanistic and synthetic aspects of amine oxidations promoted by 3-methyl-5-ethyllumiflavinium perchlorate
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Preparative and kinetic aspects of the chemistry of 3-methyl-5-ethyllumiflavinium perchlorate (1) with primary and secondary amines have been investigated. Reactions of! with primary and secondary amines leads to rapid production of modestly stable C4a-adducts. The rates of these processes, determined by stopped-flow kinetic methods, parallel amine nucleophilicities. The C4a-adducts undergo benzylamine promoted elimination reactions to produce N-benzylaldimine products with rates that parallel reactivity profiles expected for E2-elimination processes. Finally, flavinium salt 1 serves as a catalyst for oxidations of primary and secondary amines under aerobic conditions.
- Hoegy, Susan E.,Mariano, Patrick S.
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p. 5027 - 5046
(2007/10/03)
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- A simple and inexpensive method for the preparation of imines and azadienes
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A number of imines and azadienes were prepared in high yield and good purity by using the condensation reactions of various aldehydes and ketones with amines over natural Algerian bentonite.
- Saoudi,Benguedach,Benhaoua
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p. 2349 - 2354
(2007/10/02)
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- Stereoselective Synthesis of Monocyclic &β-Lactams from the Reaction of Acid Chlorides/Mixed Anhydrides with Substituted Imines.
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Monocyclic β-lactams (IIa-f, IIIa, d) having the desired stereochemistry can be prepared from appropriate imines (Ia-f) on treatment with acid chlorides or mixed anhydrides in the presence of Et3N.These β-lactams are obtained in appreciable yields and also show some antimicrobial activity.
- Sharma, S. D.,Kaur, S.,Mehra, Usha
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p. 141 - 144
(2007/10/02)
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