- Assessment of a reductive amination route to methyl(3-nitrobenzyl)amine hydrochloride
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During the development of a sodium borohydride mediated reductive animation of 3-nitrobenzaldehyde with methylamine, studies revealed that partial reduction of the nitro group occurred, and potentially dangerous azo- and azoxy-containing products were gen
- Connolly, Terrence J.,Constantinescu, Anton,Lane, Tim S.,Matchett, Michael,McGarry, Patrick,Paperna, Mariya
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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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- 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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- Mixed carboxylic-sulfonic anhydride in reaction with imines: A straightforward route to water-soluble β-lactams via a Staudinger-type reaction
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The first example of employing a mixed carboxylic-sulfonic anhydride in reaction with imines is reported. Unlike its well-studied isostere homophthalic anhydride, benzo[c][1,2]oxathiin-3(4H)-one 1,1-dioxide gave no product of a formal [4 + 2] cycloaddition and only followed an alternative reaction pathway toward β-lactams, presumably, via a formal [2 + 2] cycloaddition (a Staudinger-type reaction). Optimized reaction conditions involve the use of triethylamine as a base promoter, which also allows isolating the product β-lactam benzene sulfonic acids as respective triethylammonium salts by conventional column chromatography. The reaction shows some preference to trans-isomer formation; pure diastereomers can be isolated in some cases.
- Bakulina, Olga,Dar'In, Dmitry,Krasavin, Mikhail
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p. 3989 - 3998
(2018/06/08)
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- Thiazolidinones derived from dynamic systemic resolution of complex reversible-reaction networks
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A complex dynamic system based on a network of multiple reversible reactions has been established. The network was applied to a dynamic systemic resolution protocol based on kinetically controlled lipase-catalyzed transformations. This resulted in the formation of cyclized products, where two thiazolidinone compounds were efficiently produced from a range of potential transformations.
- Zhang, Yan,Ramstroem, Olof
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supporting information
p. 3288 - 3291
(2014/04/03)
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- Asymmetric synthesis of tetrahydropyridines via an organocatalytic one-pot multicomponent Michael/aza-Henry/cyclization triple domino reaction
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A low loading of a quinine-derived squaramide efficiently catalyzes the triple-domino Michael/aza-Henry/cyclization reaction between 1,3-dicarbonyl compounds, β-nitroolefins, and aldimines to provide tetrahydropyridines bearing three contiguous stereogeni
- Blümel, Marcus,Chauhan, Pankaj,Hahn, Robert,Raabe, Gerhard,Enders, Dieter
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supporting information
p. 6012 - 6015
(2015/01/08)
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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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- Efficient synthesis of new 4-arylideneimidazolin-5-ones related to the GFP chromophore by 2+3 cyclocondensation of arylideneimines with imidate ylides
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A 2+3 condensation of a wide assortment of Schiff bases, prepared from aromatic aldehydes and primary amines, with methyl (1-ethoxyethylideneamino) acetate allows convenient access to an extensive family of substituted 4-arylideneimidazolin-5-one analogues of the green fluorescent protein (GFP) chromophore. Georg Thieme Verlag Stuttgart · New York.
- Baldridge, Anthony,Kowalik, Janusz,Tolbert, Laren M.
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scheme or table
p. 2424 - 2436
(2010/09/06)
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- Reactions of N-Chloro-N-alkylbenzylamines with Amines in Acetonitrile. Origin of Steric Effect in Imine-Forming Elimination
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Reaction of N-chloro-N-alkylbenzylamines in which the alkyl group is Me, Et, i-Pr, sec-Bu, and t-Bu with MeNH2 and Et2NH in MeCN have been studied kinetically.The eliminations are quantitative and regiospecific, producing only N-benzylidenealkylamines.The relative rates of elimination for Me/Et/i-Pr/sec-Bu/t-Bu alkyl substituents are 1/0.6/0.4/0.3/0.1 with MeNH2 and 1/0.5/0.3/0.2/0.03 with Et2NH, respectively.Comparison with published data reveals that Charton's value for the imine-forming elimination decreases with the variation of the base-solvent from MeONa-MeOH to MeNH2-MeCN but increases when the base is changed from MeNH2 to Et2NH.For a given base, Hammett ρ and kH/kD values decrease and the ΔH(excit.) and ΔS(excit.) values increase with bulkier alkyl substituents.From these results, the origin of the steric effect in imine-forming elimination is attributed to the repulsive interaction between the alkyl group and the base in the transition state.
- Cho, Bong Rae,Suh, Young Wook
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p. 2855 - 2858
(2007/10/02)
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- Reactions of N-Halogenobenzylmethylamines with Triethylamine in Acetonitrile. Effect of Leaving Group upon the Imine-forming Transition State
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Reactions of N-halogenobenzylmethylamines (1) and (2) with Et3N-MeCN have been investigated kinetically.Eliminations from (1) and (2) were quantitative and regiospecific, producing only benzylidenemethylamines.For the elimination reaction of (1) with Et3N, kH/kD 5.7, ρ 0.88, 9.1 kcal mol-1, and -42.4 cal mol-1 K-1 were determined.The transition-state structure is assessed as being highly symmetric with similar extents of Cβ-H and Nα-Cl bond cleavage, little carbanionic character, and significant ?-bond formation.The structure of the transition state changes only slightly with the change in the leaving group from Cl to Br.
- Cho, Bong Rae,Namgoong, Sung Keon,Kim, Tae Rin
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p. 853 - 856
(2007/10/02)
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- Reactions of N-(Arylsulfonoxy)-N-benzylmethylamines with Sodium Methoxide in Methanol
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Reactions of N-(arylsulfonoxy)-N-benzylmethylamines (1) with MeONa in MeOH have been investigated.The eliminations are quantitative, producing only benzylidenemethylamines.The reactions are first order in substrate and first order in base, and an E2 mechanism is evident.Comparison of the rate data reveals that the arenesulfonates are better leaving groups than halogens in imine-forming elimination.For elimination from 1, ρ = 1.14, kH?kD = 3.6, ρlg = 1.30, and β1g = -0.43 have been calculated.Differences in the transition-sate characters for imine-forming eliminations from ArCH2N(Cl)CH3 and 1 have been intepreted in terms of changes in the leaving-group properties and base strength.
- Cho, Bong Rae,Pyun, Sang Yong,Kim, Tae Rin
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p. 8041 - 8044
(2007/10/02)
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- Reactions of N-Chlorobenzylmethylamines with Secondary Amines in Acetonitrile. Effect of Base Strength upon the Imine-Forming Transition State
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Reactions of N-chlorobenzylmethylamines 1 with R2NH in MeCN have been investigated kinetically.Eliminations from 1 were quantitative and regiospecific, producing only benzylidenemethylamines.For the elimination reaction of 1 with Bu2NH, kH/kD = 8.8, ρ = 0.96, ΔH(excit.) = 7.6 kcal/mol, and ΔS(excit.) = -45.1 eu were determined.The transition state structure is assessed as being highly symmetrical with similar extents of Cβ-H and Nα-Cl bond cleavage, little carbanionic character, and significant ? bond formation.The kH/kD and ρ values first increase and then decrease with enhancing amine base strength.Comparison of these results with those for related olefin-forming eliminations provides insight into the transition state differences between imine- and olefin-forming eliminations.
- Cho, Bong Rae,Namgoong, Sung Keon,Bartsch, Richard A.
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p. 1320 - 1324
(2007/10/02)
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- Reactions of N-Halobenzylalkylamines with Sodium Methoxide in Methanol
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Reactions of N-halobenzylmethylamines 1 and 2 (X = Cl and Br) with MeONa-MeOH have been investigated.Eliminations from 1 were quantitative, producing only benzylidenemethylamines.Reaction of 2 with MeONa-MeOH produced benzylidenemethylamines and benzylmethylamines.The yield of benzylidenemethylamine increased with electron-withdrawing aryl substituents and increased base concentration and became quantitative when pentane was used as a solvent.The results are interpreted as competing bimolecular elimination and nucleophilic substitution by methoxide on bromine.Product studies for reaction of N-halobenzyl-tert-butylamines with MeONa-MeOH and EtSNa-MeOH establish that the substitution reaction is a general reaction pathway available for the N-haloamines.Transition states for eliminations from 1 and 2 are characterized by Hammett ρ and primary deuterium isotope effect values.
- Cho, Bong Rae,Yoon, Jong Chan,Bartsch, Richard A.
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p. 4943 - 4946
(2007/10/02)
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- Benzylamines: Synthesis and evaluation of antimycobacterial properties
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The synthesis of benzylamines with various N-alkyl chains and substituents in the aromatic system as well as their evaluation on Mycobacterium tuberculosis H 37 Ra are described. The most active compounds in this test, N-methyl-3-chlorobenzylamine (MIC 10.2 μg/mL), N-methyl-3,5-dichlorobenzylamine (93, MIC 10.2 μg/mL), and N-butyl-3,5-difluorobenzylamine (MIC 6.4 μg/mL), also exhibited a marked inhibitory effect on Mycobacterium marinum and Mycobacterium lufu used for the determination of antileprotic properties. The combination of 93 with aminosalicylic acid, streptomycin, or dapsone exert marked supra-additive effects on M. tuberculosis H 37 Ra.
- Meindl,Von Angerer,Schonenberger,Ruckdeschel
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p. 1111 - 1118
(2007/10/02)
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