10.1016/j.tetlet.2020.151775
The research presents a transition-metal-free approach for the synthesis of 1,3-diynes and related molecules through Glaser- and Cadiot-Chodkiewicz-type coupling reactions. The study utilizes terminal alkynes or 1,1-dibromo-1-alkenes as reactants and explores the efficiency of molecular iodine as a catalyst in aqueous medium to achieve the desired 1,3-diynes in moderate to good yields. Terminal alkynes (such as phenylacetylene) as starting materials for the synthesis of 1,3-diynes. Piperidine as a base in the reactions. The reaction conditions demonstrate a significant functional group tolerance in water, and the scope of the metal-free method for synthesizing 1,3-enynes has been investigated. The research also includes control experiments to establish a plausible reaction mechanism, which is further supported by gas chromatography-mass spectrometry (GC-MS) analysis. The findings reveal that the process likely involves a radical pathway and is influenced by the presence of aerial oxygen. The study is significant as it offers an eco-friendly and cost-effective method for C-C bond forming reactions, which are essential in the synthesis of complex molecules for pharmaceuticals, materials science, and other applications.
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.
10.1002/1522-2675(20010613)84:6<1504::AID-HLCA1504>3.0.CO;2-G
The research focuses on developing new base-labile protecting groups for the synthesis of oligoribonucleotides, addressing the challenges posed by the 2'-OH function in RNA assembly. The study involved synthesizing various carbonochloridates from hydroxy compounds, such as β-hydroxybenzenepropanenitrile and 2,2-bis(4-nitrophenyl)ethanol, which were then introduced at the 5'-O position of thymidine to create model nucleosides. Kinetic studies were conducted to evaluate the deprotection rates of these groups using bases like DBU, piperidine, and Et3N, with analyses performed via HPLC to determine half-lives and cleavage mechanisms. The results indicated that the newly synthesized protecting groups, particularly the 1-(2-cyano-1-phenylethoxy)carbonyl and 2-(4-nitrophenyl)ethoxycarbonyl, demonstrated promising compatibility for temporary protection during RNA synthesis.
10.1007/BF00773086
The research focuses on the search for new drugs with antiviral activity, specifically targeting unsaturated lactones. The purpose of the study was to synthesize and test various chemical compounds based on substituted lactones for their potential antiviral properties. The researchers conducted several chemical transformations to create new systems containing heterocyclic rings such as lactone and lactam. Key chemicals used in the process included 3-cyano-4,5,5-trimethyl-A3-buten-elide, amines, bromine, 3-acetyl-4,5,5-trimethyl-A3-butenolide, piperidine, thiourea, aniline, and a-monostearin, among others. The synthesized compounds were then tested for their antiviral activity, and the results indicated that three compounds (V, X, and XI) showed activity and selectivity against the herpes virus, with compound XI also displaying an inhibiting effect against the Venezuelan equine encephalitis virus. The study concluded that while some of the synthesized compounds exhibited moderate antiviral activity, others were found to be toxic to chick embryo fibroblast cultures, suggesting a need for further research and refinement in the development of these potential antiviral drugs.
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.
10.1016/S0040-4020(01)81902-5
The study explores the efficient hydration of nitriles using the RuH2(PPh3)4 catalyst, converting them into corresponding amides under neutral conditions with only 1-2 equivalents of water. This method is advantageous due to its simplicity, high efficiency, and mild reaction conditions. The study extends this principle to transform ?-ketonitriles into ene-lactams, which are versatile intermediates for synthesizing piperidine and hydroquinoline ring systems. The efficiency of these reactions is demonstrated through the short-step synthesis of (-)-pumiliotoxin C, a toxic skin alkaloid produced by Central American frogs. The study also investigates the catalytic activities of various metal complexes in these transformations, finding RuH2(PPh3)4 to be the most effective. Additionally, the study explores the conversion of ene-lactams into ?-dioxylactams and further into ?-substituted lactams using different nucleophiles in the presence of TiCl4, providing a useful method for the stereoselective synthesis of cyclic amines.
10.1248/cpb.57.557
The research focuses on the synthesis and antimicrobial activity of novel 5-substituted-Nb-(2-oxo-2H-pyrano[2,3-b]quinoline-3-carbonyl)-3-phenyl-1H-indole-2-carbohydrazides, which are compounds containing indole and pyranoquinoline moieties. The study aims to develop compounds with potent antimicrobial and antituberculosis activity. The synthesis involved the reaction of ethyl 3-oxo-3-{2-[(5-substituted-3-phenyl-1H-indol-2-yl)carbonyl]hydrazinyl}propanoates with substituted-2-hydroxy-3-formylquinolines in the presence of piperidine as a catalyst in ethanol under reflux conditions. The synthesized compounds were characterized using IR, 1H-NMR, and mass spectrometry, and their structures were confirmed by spectral data. The experiments conducted to assess antimicrobial activity included antibacterial tests against Staphylococcus aureus, Escherichia coli, and Bacillus subtilus, antifungal tests against Aspergillus niger and Candida albicans, and antituberculosis tests against Mycobacterium tuberculosis (H37Rv). The compounds were compared with standard drugs Gentamycin, Nystatin, and Streptomycin for their activity, with the minimum inhibitory concentration (MIC) determined for the antituberculosis activity.
10.1021/ja406761j
The study presents a metal-free method for the direct hydrogenation of pyridines using homogeneous borane catalysts generated from alkenes and HB(C6F5)2 through an in situ hydroboration process. This approach yields a broad range of piperidines, which are important moieties found in many biologically active compounds, with high yields and excellent cis-stereoselectivities. The chemicals used in the study include various alkenes as catalyst precursors, HB(C6F5)2 as the borane catalyst, and different pyridine substrates as the reactants. The purpose of these chemicals is to facilitate a highly stereoselective hydrogenation reaction, which is a significant advancement as it overcomes challenges associated with catalyst deactivation and pyridine dearomatization, and provides an efficient and metal-free route to synthesize piperidines.
10.1002/ardp.19853180215
The research focuses on the synthesis and investigation of pyran derivatives, specifically benzodipyrandiones that are double fused with pyrimidine and pyrazole. The purpose of the study was to explore the chemical reactions and properties of these complex organic compounds. The researchers started with the Kostanecki method to synthesize benzodi-pyrandion from diacetylresorcin, which was then hydrolyzed to form a tetraketon. This intermediate reacted with CS2/KOH/DMS to yield 2,8-bisdimethylthiobenzodipyrandion, which was further transformed into various derivatives through reactions with piperidine, hydrazine, and benzamidin. The resulting compounds, including 3,7-diphenyl-benzo[1,2-b:5,4-b']di(pyrano[2,3-c]pyrazol)-4,6-dion, 4,8-diphenyl-benzo[1,2-b:5,4-b']di(pyrano[2,3-d]pyrimidin)-5,7-dion, and 3,7-Dibenzoyl-2,8-dipiperidino-benzo[1,2-b:5,4-b']dipyran-1,6-dion, were found to be poorly soluble in common solvents. The study concluded with the characterization of these compounds through melting point determination, yield calculation, and spectroscopic analysis, including infrared (IR) and proton nuclear magnetic resonance (1H-NMR) spectroscopy. The chemicals used in the process included diacetylresorcin, CS2, KOH, DMS, piperidine, hydrazine, benzamidin, and various solvents such as DMSO, aceton, and ethanol.
10.1055/s-0029-1219235
The study focuses on the synthesis and chemical reactivity of novel azaenamines that incorporate a tetrahydrobenzo[b]thiophene (THBT) moiety. These compounds are of interest due to their potential as selective HCV polymerase inhibitors and their diverse pharmacological activities, including antibacterial, immunomodulatory, anti-inflammatory, antidiabetic, antiplatelet activating factor, and antiviral properties. The researchers synthesized azaenamines containing the 4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate and -carboxamide moieties and investigated their reactivity, particularly in Michael addition reactions with α,β-unsaturated nitriles, condensation with malononitrile, and Mannich reactions with aldehydes and piperidine. The synthesized azaenamines served as valuable precursors for the synthesis of fused pyridazine derivatives, and the study aimed to develop an efficient route for these reactions, which were accelerated and yielded better results when conducted using microwave irradiation.
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