10.1002/ejoc.200600968
The research investigates the impact of ring substituents and leaving groups on the kinetics of SNAr (Nucleophilic Aromatic Substitution) reactions involving 1-halogeno- and 1-phenoxy-nitrobenzenes with aliphatic amines in acetonitrile. The study reports rate constants for the reactions, comparing them with previously reported data for more strongly activated compounds. The reactants included a series of 1-chloro-, 1-fluoro-, and 1-phenoxy-nitrobenzenes activated by CF3 or CN groups or by ring-nitrogen with n-butylamine, pyrrolidine, or piperidine. The experiments utilized spectrophotometric kinetic measurements, with the concentration of amine in large excess of the parent concentration, observing first-order kinetics. The study also analyzed the effects of changing the leaving group from chloride to fluoride and to phenoxide, and of the amine from n-butylamine to pyrrolidine and to piperidine on the reaction kinetics. The analyses included evaluating rate constants, examining steric effects, ground-state stabilisation, and base catalysis, with results indicating reduced reactivity with decreasing ring activation and specific steric effects leading to rate-retardation.
10.1016/j.tetlet.2008.01.026
The study presents the development of a polystyrene-immobilized pyrrolidine (compound 4) as an efficient, reusable, and stereoselective organocatalyst for the asymmetric Michael addition of cyclohexanone to nitroolefins. The catalyst, when combined with trifluoroacetic acid (TFA), enabled the reaction to proceed with high yields (up to >99%) and excellent diastereoselectivities (up to >99:1 dr) and enantioselectivities (up to >99% ee). The purpose of the chemicals used was to facilitate a carbon-carbon bond-formation reaction, which is a crucial process in organic synthesis. The study highlights the environmental friendliness and efficiency of the organocatalyst, as it can be recovered and recycled through simple filtration for more than 10 consecutive trials without significant loss of catalytic activity.
10.1016/S0040-4020(01)92361-0
The research focuses on the amidinoethylation of amino compounds, a new reaction that involves the addition of amines to the C=C double bond of various N,N'-substituted-propenamidines. The purpose of this study was to explore the synthesis of 3-amino-substituted-N,N'-substituted-propanamidines, which are not easily accessible through classical synthetic methods. The researchers found that the most nucleophilic amines, such as piperidine, morpholine, and pyrrolidine, added under mild conditions, while aliphatic and aromatic amines required more drastic conditions. The conclusions drawn from the study illustrate the activation of the C=C double bond of propenamidines by the conjugated amidine function, providing a new class of Michael acceptors for amino compounds. The chemicals used in the process include a variety of amines, such as piperidine, morpholine, pyrrolidine, cyclohexylamine, diisopropylamine, and aromatic amines, as well as solvents like acetonitrile, dimethylformamide, and ethylene glycol dimethylether, and catalysts such as acetic acid and SnCl4.
10.1134/S107036322001020X
The research aims to develop an efficient method for synthesizing novel pyrrolidine derivatives with potential antimicrobial properties using microwave-assisted techniques. The study focuses on synthesizing 1-acetyl-2-benzylpyrrolidine-2-carboxylic acid and its derivatives, starting from 2-benzyl-tert-butylpyrrolidine-1,2-dicarboxylate. Key chemicals used in the synthesis include n-butyl lithium, benzyl bromide, acetic anhydride, sodium bicarbonate, and various reagents for esterification and amidation. The microwave-assisted method proved to be more efficient than conventional synthesis, yielding higher product yields and shorter reaction times. The antimicrobial activity of the synthesized compounds was tested against various bacterial and fungal strains, with compounds 5c and 5f showing significant antibacterial and antifungal properties. The study concludes that microwave-assisted synthesis is a superior approach for producing these compounds and that modifications to the pyrrolidine ring can enhance their antimicrobial efficacy, suggesting potential applications in pharmaceuticals.
10.1021/acscatal.5b01726
The research focuses on the efficient synthesis of nitrones through the direct condensation of N-substituted hydroxylamine hydrochlorides with aromatic or aliphatic aldehydes, catalyzed by pyrrolidine. The study employs theoretical calculations, spectroscopic analysis, and experimental procedures to demonstrate that pyrrolidine not only liberates the hydrochloride of the hydroxylamine but also catalyzes the reaction via iminium activation. Additionally, a cooperative effect between pyrrolidine and pyrrolidinium chloride is found to facilitate several steps of the catalytic cycle through proton transfer, enhancing the nucleophilicity of the hydroxylamine. The experiments involve the use of various aldehydes and N-substituted hydroxylamine hydrochlorides, with reactions monitored by 1H NMR and optimized using different solvents and amounts of pyrrolidine. The analyses include DFT calculations to compare activation barriers and transition state geometries, providing insights into the reaction mechanism and the role of pyrrolidine as a catalyst. The research outcomes in mild reaction conditions, high yields, and simplified purification steps, aligning with green chemistry principles.
10.1002/anie.200801252
The research focuses on the development of a convenient synthesis method for pyrrolidines through amphiphilic allylation of imines with 2-methylenepropane-1,3-diols, utilizing a Pd catalyst and Et3B system. The study explores the reactivity of various aldimines, prepared from a wide range of amines and aldehydes, with 2-methylenepropane-1,3-diols to form pyrrolidines, marking the first example of such a synthesis using nonactivated 2-methylenepropane-1,3-diols as a zwitterionic carbon framework. The experiments involved in situ aldimine formation, followed by the addition of 2-methylenepropane-1,3-diol, Pd(OAc)2, nBu3P, and Et3B, and the reactions were conducted under a nitrogen atmosphere at 50°C. The reactants included aromatic and aliphatic aldehydes and amines, with the addition of halogens or acidic OH groups in some cases. The analyses used to characterize the products included techniques such as IR spectroscopy, 1H and 13C NMR spectroscopy, and HRMS, with the structure of one product confirmed by X-ray single-crystal analysis.
10.1039/c1ob06690k
The study presents a novel and efficient method for synthesizing 1,4-disubstituted imidazoles with complete regioselectivity. The researchers developed a protocol that involves an unusual double aminomethylenation of a glycine derivative to yield a 2-azabuta-1,3-diene, which then undergoes transamination/cyclization with an amine nucleophile to form the substituted imidazole. Key chemicals used in the study include aminoacetonitrile, which serves as the starting material for the azadiene synthesis, and various amines as nucleophiles for the cyclization step. The study also explores the use of different reagents such as dimethylformamide dimethylacetal (DMF·DMA) and pyrrolidine to enhance the reaction efficiency and lower the reaction temperature. The method is notable for its insensitivity to steric and electronic variations on the amine component, allowing for the preparation of a diverse range of imidazoles.
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