- 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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- Four-Electron Electrocyclic Ring-Opening/Intermolecular [4+2] Cycloadditions of α-Hydroxycyclobutenones: Stereoselective Synthesis of Multiple Substituted δ-Lactams
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A four-electron electrocyclic ring-opening/intermolecular [4+2] cycloaddition of α-hydroxycyclobutenones is reported. The reaction represents the first example for the intermolecular cycloaddition of the extensively studied enol-ketene intermediate, and provides a new synthetic route to multiply substituted δ-lactams in high stereoselectivity.
- Song, Peidong,Li, Qing,Wang, Congcong,Wu, Wenfa,Mao, Xu,Wang, Jiajia,Hu, Xiangdong
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supporting information
p. 1208 - 1212
(2016/04/26)
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- Synthetic communications reviews: Synthesis of primary amines by one-pot reductive amination of aldehydes
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We report here a novel, one-pot, two-step reductive amination of aldehydes for the atom-economical synthesis of primary amines. The amination step has been carried out with hydroxylammonium chloride and does not require the use of a base. In the subsequent reduction step, a metal zinc/hydrochloride acid system has been used. This method is applicable to both aliphatic and aromatic aldehydes. The operational simplicity, the short reaction times, and the mild reaction conditions add to the value of this method as a practical alternative to the reductive amination of aldehydes. Copyright
- Ayedi, Mohamed Ali,Le Bigot, Yves,Ammar, Houcine,Abid, Souhir,Gharbi, Rachid El,Delmas, Michel
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p. 2127 - 2133
(2013/07/25)
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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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- Application of sequential Cu(I)/Pd(0)-catalysis to solution-phase parallel synthesis of combinatorial libraries of dihydroindeno[1,2-c]isoquinolines
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Parallel solution-phase synthesis of combinatorial libraries of dihydroindenoisoquinolines employing a sequential Cu(I)/Pd(0)-catalyzed multicomponent coupling and annulation protocol was realized. The scope and limitations of the protocol with respect to the substitution pattern in the aryl ring of the indene core, as well as the N-substituent have been defined, revealing that the methodology is compatible with a wide-range of aliphatic linear, branched, and ester functionalized N-substituents. Unexpectedly, the formation of regioisomers featuring a 1,2,3-contiguous substitution pattern in the aromatic ring of the indene core was observed. Three distinct combinatorial libraries with a total of 111 of members were synthesized, and 80 highly substituted dihydroindenoisoquinolines structurally related to known medicinal agents including some consisting of mixtures of two regioisomers were made available for biological activity testing.
- Kumar, Sarvesh,Painter, Thomas O.,Pal, Benoy K.,Neuenswander, Benjamin,Malinakova, Helena C.
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body text
p. 466 - 477
(2011/11/06)
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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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- Activation of fluorescent protein chromophores by encapsulation
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(Figure Presented) Chromophores related to fluorescent proteins, when sequestered into the "octaacid" capsule, recover their fluorescence. The fluorescence recovery is related to the inhibition of torsional motions within the cavity, implicating the single-bond torsion as an important contributor to internal conversion within this important class of chromophores.
- Baldridge, Anthony,Samanta, Shampa R.,Jayaraj, Nithyanandhan,Ramamurthy,Tolbert, Laren M.
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supporting information; experimental part
p. 1498 - 1499
(2010/04/03)
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- A novel construction of 2-benzazepine scaffold based on TiCl 4-mediated tandem Mannich reaction - Aromatic electrophilic substitution
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A novel construction of 2-benzazepine derivatives based on TiCl 4-mediated tandem Mannich reaction of electron-rich benzyl iminium ions with alkenyl ethers and Friedel - Crafts-type alkylation is described. The protocol is amenable to provide the tricyclic furo[3,2-d][2]benzazepine and pyrano[3,2-d][2]benzazepine derivatives, respectively, with 2,3-dihydrofuran or 3,4-dihydro-2H-pyran as the substrates.
- Li, Liangxi,Li, Zhiming,Wang, Quanrui
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experimental part
p. 2754 - 2761
(2010/04/02)
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