- Photosensitized Electron-Transfer Reaction of 3-Aryl-2-methyloxaziridine: Direct Deoxygenation from the Isomeric Arylnitrone
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Photosensitized electron-transfer reactions of 3-aryl-2-methyloxaziridines gave mainly the corresponding benzaldehydes, whereas the isomeric nitrones gave imines as well as aldehydes.Deoxygenation of the nitrone occurred via the nitrone cation radical under the reaction conditions.An aryl substituent effect on the reaction and isomerizations of both cation radicals are also discussed.
- Iwano, Yasunori,Kawamura, Yasuhiko,Miyoshi, Hiroki,Yoshinari, Toshifumi,Horie, Tokunaru
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- Synthesis of N-methyl imines in the presence of poly(N-vinylpyridine) as a reusable solid base catalyst by a mechanochemical process
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The synthesis of N-methyl imines was performed in the presence of catalytic amounts of poly(4-vinylpyridine) in high yields and rapidly at room temperature by a ball milling process. This new method has some advantages including good yields for relatively unreactive carbonyl compounds and short reaction times as well as being green in terms of avoiding the use of toxic reagents and solvents. The major advantage of this process is that the catalyst can be easily regenerated and reused several times without any significant loss of activity.
- Khaligh, Nader Ghaffari,Abbo, Hanna S.,Titinchi, Salam J. J.
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- Stable carbamate pathway towards organic-inorganic hybrid perovskites and aromatic imines
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Methyl ammonium methyl carbamate (MAC), formulated as CH3NH3+CH3NHCO2-, was synthesized by reacting liquid methylamine with supercritical CO2, and its structure was refined by single-crystal X-ray diffraction. MAC is a white crystalline salt and is as reactive as methylamine, and is a very efficient alternative to toxic methylamine. We were able to produce hybrid perovskite MAPbI3 (MA = methyl ammonium) by grinding MAC with PbI2 and I2 at room temperature, followed by storing the mixed powder. Moreover, this one-pot method is easily scalable for the large-scale synthesis of MAPbI3 in a small vessel. We have also investigated the reactivity of MAC towards aromatic aldehydes in the absence of solvent. The solventless reactions afforded imines as exclusive products with over 97% yield, which show higher selectivity than the methylamine-based synthesis. Complete conversions were typically accomplished within 3 h at 25 °C. The results of this study emphasize the importance of solid carbamates such as MAC to develop an environmentally friendly process for the synthesis of various amine-based materials on the industrial scale.
- Hur, Nam Hwi,Kim, Sun Joo,Lee, Byeongno,Lee, Kyu Hyung,Lim, Byung Wook,Nam, Wonwoo,Park, Hee Sun,Park, Young Jun
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p. 38055 - 38062
(2020/11/02)
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- Enantioselective Reductive Coupling of Imines Templated by Chiral Diboron
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We herein report a general, practical, and highly efficient method for asymmetric synthesis of a wide range of chiral vicinal diamines via reductive coupling of imines templated by chiral diboron. The protocol features high enantioselectivity and stereospecificity, mild reaction conditions, simple operating procedures, use of readily available starting materials, and a broad substrate scope. The method signifies the generality of diboron-enabled [3,3]-sigmatropic rearrangement.
- Chen, Dongping,Li, Kaidi,Tang, Wenjun,Xu, Guangqing,Xu, Ronghua,Zhou, Mingkang
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supporting information
p. 10337 - 10342
(2020/07/04)
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- Epoxide-Mediated Stevens Rearrangements of α-Amino-Acid-Derived Tertiary Allylic, Propargylic, and Benzylic Amines: Convenient Access to Polysubstituted Morpholin-2-ones
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A new strategy has been established for the synthesis of polysubstituted morpholin-2-ones through Stevens rearrangements of tertiary amines via in situ activation with epoxides. A range of α-amino acid-derived tertiary allylic, propargylic, and benzylic amines reacted with epoxides in the presence of zinc halide catalysts to afford structurally diverse allyl-, allenyl-, and benzyl-substituted morpholin-2-ones, respectively, in moderate-to-good yields with high regioselectivity. The process involves [2,3]- and [1,2]-Stevens rearrangements of quaternary ammonium ylide intermediates and constitutes a very convenient method to prepare polysubstituted morpholin-2-ones through tandem formation of C?N, C?O, and C?C bonds. Moreover, replacing epoxides with aziridines permitted the synthesis of polysubstituted piperazin-2-ones.
- Jin, You-Xiang,Yu, Bang-Kui,Qin, Si-Ping,Tian, Shi-Kai
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supporting information
p. 5169 - 5172
(2019/03/28)
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- Mechanosynthesis of N-methyl imines using recyclable imidazole-based acid-scavenger: In situ formed ionic liquid as catalyst and dehydrating agent
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1,1′-(1,4-Butanediyl)bis(imidazole) was prepared by a modified method and its application as an efficient promoter was demonstrated for the mechanosynthesis of N-methyl imines using ball milling as a non-conventional process under solvent-free conditions. In this new protocol design, the bis-imidazole acted as a recyclable acid-scavenging agent. This efficient approach to the N-methyl imines displays a combination of the synthetic virtues of a non-conventional condensation reaction with ecological benefits and convenience of a facile mechanosynthetic process. The current method has advantages such as reduced waste by avoiding solvent, exclusion of hazardous materials during the reaction, elimination of handling an anhydrous gas in an evacuated container or a solution of methylamine in ethanol, good yields for relatively unreactive benzaldehydes containing electron-donating substituents, short reaction times, and metal- and acid-free conditions. Furthermore, the promoter was easily regenerated and reused several times with no significant loss of activity.
- Khaligh, Nader Ghaffari,Ling, Ong Chiu,Mihankhah, Taraneh,Johan, Mohd Rafie,Ching, Juan Joon
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p. 194 - 199
(2018/12/04)
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- Unusually Reactive Cyclic Anhydride Expands the Scope of the Castagnoli-Cushman Reaction
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In the course of synthesizing and testing various "azole-including" cyclic anhydrides in the Castagnoli-Cushman reaction with imines, a remarkably reactive, pyrrole-based anhydride has been identified. It displayed a remarkably efficient reaction with N-alkyl and N-aryl imines, in particular, with "enolizable" α-C-H imines which typically fail to react with a majority of known cyclic anhydrides. The reactivity of this anhydride has been justified by an efficient resonance stabilization of its enol form. This finding expands the existing arsenal of highly reactive cyclic anhydrides and further confirms the importance of anhydride enolization for an efficient Castagnoli-Cushman reaction.
- Chizhova, Maria,Khoroshilova, Olesya,Dar'In, Dmitry,Krasavin, Mikhail
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p. 12722 - 12733
(2018/10/15)
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- Simple and efficient one-pot solvent-free synthesis of N-methyl imines of aromatic aldehydes
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A one-pot solvent-free synthesis of N-methyl imines in good to excellent yields was performed by grinding together aromatic aldehydes and methylamine hydrochloride in the presence of a base. The best yields were achieved when an excess of methylamine hydrochloride and inexpensive sodium hydrogen carbonate was used (usually in a molar ratio ArCHO/CH3NH2· HCl/NaHCO3 = 1:5:5), allowing the reaction to proceed for 1 h (in the case of aromatic aldehydes containing electron-withdrawing substituents) or overnight (in the case of electron-rich aldehydes). After a simple work-up (extraction with diethyl ether) the obtained products were mostly pure enough for spectral characterization. In this way, 31 N-methyl imines were prepared, among which eight were synthesized for the first time. Their structures were elucidated by spectral means (1H- and 13C-NMR, IR, MS) whenever it was possible. In the case of salicylaldehyde and 4-chlorobenzaldehyde, the synthesis of the corresponding imines was also conducted on a gram-scale with a 72% and 84% isolated yield, respectively. The present approach not only provides good to high yields, but also eliminates the disadvantages of the traditional synthesis of N-methyl imines, such as the use of hazardous solvents and more or less expensive catalysts and the necessity of work/handling with an anhydrous gas in pressurized containers.
- Radulovi?, Niko S.,Miltojevi?, Ana B.,Vuki?evi?, Rastko D.
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p. 257 - 270
(2013/05/09)
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- 4-Phenyl tetrahydroisoquinolines as dual norepinephrine and dopamine reuptake inhibitors
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Novel 4-phenyl tetrahydroisoquinolines that inhibit both dopamine and norepinephrine transporters were designed and prepared. In this Letter, we describe the synthesis, in vitro activity and associated structure-activity relationships of this series. We also report the ex vivo NET occupancy of a representative compound, 41.
- Pechulis, Anthony D.,Beck, James P.,Curry, Matt A.,Wolf, Mark A.,Harms, Arthur E.,Xi, Ning,Opalka, Chet,Sweet, Mark P.,Yang, Zhicai,Vellekoop, A. Samuel,Klos, Andrew M.,Crocker, Peter J.,Hassler, Carla,Laws, Mia,Kitchen, Douglas B.,Smith, Mark A.,Olson, Richard E.,Liu, Shuang,Molino, Bruce F.
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p. 7219 - 7222
(2013/01/15)
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- Highly enantioselective synthesis of tetrahydroquinolines via cobalt(II)-catalyzed tandem 1,5-hydride transfer/cyclization
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A chiral catalyst prepared from N,N′-dioxide and Co(BF 4)2·6H2O was applied in the asymmetric hydride transfer initiated cyclization reaction, giving optically active tetrahydroquinolines in good yields with high enantioselectivities under mild reaction conditions. Meanwhile, in light of the absolute configuration of the product, a possible working model was proposed to explain the origin of the activation and asymmetric induction.
- Cao, Weidi,Liu, Xiaohua,Wang, Wentao,Lin, Lili,Feng, Xiaoming
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supporting information; scheme or table
p. 600 - 603
(2011/04/15)
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- Steric and electronic effects in capsule-confined green fluorescent protein chromophores
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The turn-on of emission in fluorescent protein chromophores sequestered in an "octaacid" capsule is controlled by stereoelectronic effects described by a linear free energy relationship. The stereochemical effects are governed by both the positions and volumes of the aryl substituents, while the electronic effects, including ortho effects, can be treated with Hammett σ parameters. The use of substituent volumes rather than A values reflects packing of the molecule within the confines of the capsule.
- Baldridge, Anthony,Samanta, Shampa R.,Jayaraj, Nithyanandhan,Ramamurthy,Tolbert, Laren M.
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supporting information; scheme or table
p. 712 - 715
(2011/04/15)
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- Gamma-lactams-A novel scaffold for highly potent and selective α7 nicotinic acetylcholine receptor agonists
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A novel class of α7 nicotinic acetylcholine receptor (nAChR) agonists has been discovered through high-throughput screening. The cis γ-lactam scaffold has been optimized to reveal highly potent and selective α7 nAChR agonists with in vitro activity and selectivity and with good brain penetration in mice.
- Enz, Albert,Feuerbach, Dominik,Frederiksen, Mathias U.,Gentsch, Conrad,Hurth, Konstanze,Mueller, Werner,Nozulak, Joachim,Roy, Bernard L.
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scheme or table
p. 1287 - 1291
(2009/10/02)
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- Cholinesterase inhibitors: SAR and enzyme inhibitory activity of 3-[ω-(benzylmethylamino)alkoxy]xanthen-9-ones
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In this work, we further investigated a previously introduced class of cholinesterase inhibitors. The removal of the carbamic function from the lead compound xanthostigmine led to a reversible cholinesterase inhibitors 3. Some new 3-[ω-(benzylmethylamino)alkoxy]xanthen-9-one analogs were designed, synthesized, and evaluated for their inhibitory activity against both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). The length of the alkoxy chain of compound 3 was increased and different substituents were introduced. From the IC50 values, it clearly appears that the carbamic residue is crucial to obtain highly potent AChE inhibitors. On the other hand, peculiarity of these compounds is the high selectivity toward BuChE with respect to AChE, being compound 12 the most selective one (6000-fold). The development of selective BuChE inhibitors may be of great interest to clarify the physiological role of this enzyme and to provide novel therapeutics for various diseases.
- Piazzi, Lorna,Belluti, Federica,Bisi, Alessandra,Gobbi, Silvia,Rizzo, Stefano,Bartolini, Manuela,Andrisano, Vincenza,Recanatini, Maurizio,Rampa, Angela
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p. 575 - 585
(2008/03/12)
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- Oxidation of secondary amines by molecular oxygen and cyclohexanone monooxygenase
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Cyclohexanone monooxygenase from Acinetobacter calcoaceticus catalyzed the oxidation of tertiary and secondary amines to N-oxides and nitrones, respectively. The formation of a hydroxylamine intermediate was involved with secondary amines as starting substrates.
- Colonna, Stefano,Pironti, Vincenza,Carrea, Giacomo,Pasta, Piero,Zambianchi, Francesca
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p. 569 - 575
(2007/10/03)
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- ACTIVATING ACTION OF THE IMMONIUM GROUP IN THE SUBSTITUTION OF ALKOXYL AND HALOGEN ATOMS BY THE ALKYLAMINO GROUP IN THE BENZENE RING
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The substitution of the alkoxy group in o-, p-, and m-alkoxybenzylidenedimethylimmonium iodides by the action of aliphatic amines was investigated.Only p-alkoxy derivatives enter into the reaction forming, after hydrolysis, p-alkyl- and p-dialkylaminobenzaldehydes.Substitution can also be realized in p-alkoxybenzaldehydes and Schiff bases in the presence of the amine hydrochloride.Similarly, the halogen atom in p-halogenobenzaldehydes is substituted by the aliphatic amine residue.Quantum-mechanical calculations of the energy of anionic localization and charge at the attacked carbon atom o f the benzene ring are consistent with the experimantal data.
- Yudin, L. G.,Blokhin, A. V.,Bundel', Yu. G.,Simkin, B. Ya.,Terenin, V. I.
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p. 2064 - 2068
(2007/10/02)
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