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Search for "oxygen" in Full Text gives 1262 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Germanyl triazoles as a platform for CuAAC diversification and chemoselective orthogonal cross-coupling
Beilstein J. Org. Chem. 2024, 20, 3198–3204, doi:10.3762/bjoc.20.265
- extensive scope across a range of benign solvent conditions [7][8][9][10]. In addition, the CuAAC reaction uses inexpensive Cu catalysts [11], is insensitive towards oxygen and water [12][13], and consistently delivers high yields and (where relevant) enantioselectivities [8][9][10][14][15][16][17][18][19
Multicomponent reactions driving the discovery and optimization of agents targeting central nervous system pathologies
Beilstein J. Org. Chem. 2024, 20, 3151–3173, doi:10.3762/bjoc.20.261
- biomolecules like DNA and lipids. Lipid peroxidation and membrane disruption can cause random cross-linking, resulting in cell death and the fragmentation of proteins and enzymes. Elevated concentrations of reactive oxygen species (ROS) from various molecular processes contribute to the oxidation of proteins
- antioxidant properties were determined by oxygen radical absorbance capacity assay (ORAC-FL), expressed as Trolox equivalents (TE) and using fluorescein as probe. Additionally, the study investigated the ability of the compounds to activate the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathway in
- oxazepane scaffold 11 (Scheme 11). Replacing the nitrogen in the bioactive lactam 11 (γ-secretase inhibitor in AD therapy) with an oxygen should reduce the hydrogen bond donating (HBD) ability of the compounds. The method employs readily available starting materials, resulting in the desired compounds in a
Surprising acidity for the methylene of 1,3-indenocorannulenes?
Beilstein J. Org. Chem. 2024, 20, 3144–3150, doi:10.3762/bjoc.20.260
- compounds tend to deprotonate to form highly stable anions. The air stability of TBF conforms to that model. In contrast, although the dianion of BFC can be generated with tert-butoxide under inert atmosphere, in the presence of water it quenches and exposed to oxygen it oxidizes to form the diketone
- titrations the moisture and oxygen contents in argon were always under 10 ppm during measurements. Triflic acid (Aldrich, 99+%) and phosphazene base P2-Et (165535-45-5, Aldrich, ≥98%) were used to prepare the acidic and basic titrant solutions, respectively. Acetonitrile (Romil 190 SpS far UV/gradient
Hypervalent iodine-mediated intramolecular alkene halocyclisation
Beilstein J. Org. Chem. 2024, 20, 3113–3133, doi:10.3762/bjoc.20.258
- , the intramolecular HVI-mediated halocyclisation of alkenes using carbon, oxygen, nitrogen or sulfur nucleophiles. Herein, we describe the examples reported in the literature, which are organised by the different halogens involved and the internal nucleophiles. Keywords: cyclisation; halogenation
- reductive ligand coupling (RLC) pathway would be suppressed due to reduced fluxionality of the carboxylate ligand on I(III). These important findings are expected to enhance the use of aryl iodane(III)-dicarboxylates for constructing fluorinated azaheterocycles with improved selectivity and control. Oxygen
- internal oxygen nucleophile and fluoride then sequentially attack the activated alkene, to either form 5- or 6-membered furan or pyran heterocycles depending on the chain length in the substrate. The pyran ring is only formed from the alcohol starting material, presumably because the oxygen is reactive
Advances in the use of metal-free tetrapyrrolic macrocycles as catalysts
Beilstein J. Org. Chem. 2024, 20, 3085–3112, doi:10.3762/bjoc.20.257
- electrophilic CO2, leading to the formation of 18-IV. The negatively charged oxygen in 18-IV is then responsible for removing the chloride atom leading to the major isomer as a final product. The results of this study suggest that nonplanarity or distortion of the tetrapyrrolic macrocyclic core is not a
- photochemistry, porphyrins are mainly used for the generation of singlet oxygen (1O2) or other reactive oxygen species. Porphyrins in the triplet excited state can relax to the ground state by transferring energy to molecular oxygen (triplet state) forming 1O2 (Figure 13b) [67]. Photosensitized singlet oxygen
- frameworks (COF), have been extensively studied as photosensitizers of singlet oxygen and photoredox catalysts [87][88][89][90]. However, using metal-free porphyrins as photoredox catalysts for C–C or C–heteroatom bond formation is an area which has recently started to be explored. In 2016, Gryko and co
Advances in radical peroxidation with hydroperoxides
Beilstein J. Org. Chem. 2024, 20, 2959–3006, doi:10.3762/bjoc.20.249
- development of efficient synthetic approaches to implement organic peroxide functionality in various substrates is a timely task. From the synthetic point of view, organic peroxides are one of the best sources of oxygen atoms for a variety of oxygenation reactions [6]. Hydroperoxides (especially TBHP), acyl
- tendency to recombine with C-centered radicals and add to unsaturated bonds with the formation of new carbon–oxygen bonds. However, alkoxy radicals, which are always present in such systems, are involved not only in the formation of ROO radicals but also in hydrogen atom transfer (HAT) processes and β
- in Kwon’s review [34]. Cu-catalyzed oxygen atom transfer with TBHP were discussed in the review [35]. The review by Xiao considered visible light-driven C–C bond cleavage enabled with organic peroxides [36]. This comprehensive review summarizes all ever published studies on radical peroxidation with
Synthesis of fluorinated acid-functionalized, electron-rich nickel porphyrins
Beilstein J. Org. Chem. 2024, 20, 2954–2958, doi:10.3762/bjoc.20.248
- ; perfluorinated aliphatic carboxylic acids; porphyrin synthesis; Introduction Metal porphyrins are prosthetic groups in a number of essential biomolecules, including hemoglobin, chlorophyll, and cytochromes, supporting processes such as oxygen transport, photosynthesis, and electron transfer [1][2][3][4][5
- phenyl group of the porphyrin and the perfluoroalkyl chain. The oxygen atom, especially in the 2-position, should even improve the electronic properties of the porphyrin. Results and Discussion Our synthesis started with the readily available fluorinated symmetric diols HO–CH2–(CF2)n–CH2–OH (n = 2,4,6
Recent advances in transition-metal-free arylation reactions involving hypervalent iodine salts
Beilstein J. Org. Chem. 2024, 20, 2891–2920, doi:10.3762/bjoc.20.243
- upon binding of the enolate molecule to iodine either through a carbon–iodine or an oxygen–iodine bond. Both intermediates, I and II, are in rapid equilibrium with each other and further undergo two different types of reactions: [1,2]-ligand coupling and [2,3]-rearrangement (Scheme 2). Either of these
- copper catalyst afforded nearly better results for the arylated products. In 2022, Linde et al., demonstrated a conventional approach for achieving arylations of nitrogen- and oxygen nucleophiles via SNAr reaction, using o-fluorinated diaryliodonium salts 40, which enabled access to a greater range of
- strong C–N bond. The ring opening incorporated nitrogen, oxygen, sulfur, carbon, and halogen-containing nucleophiles and their derivatives. The substrate scope was examined with numerous aryl groups on iodonium salts 40 and the progress of aryl migration happens fruitfully by considering electronic
N-Glycosides of indigo, indirubin, and isoindigo: blue, red, and yellow sugars and their cancerostatic activity
Beilstein J. Org. Chem. 2024, 20, 2840–2869, doi:10.3762/bjoc.20.240
- (4a) initially resulted in the glycosylation of the oxygen atom to give intermediate A (−20 °C, 1.5 h). Extension of the reaction time (20 °C, 12 h) afforded N-indigoglycoside 5a which was isolated in 35% yield. The product contained an α-rhamnosyl moiety with 4C1 conformation. The formation of the
- product can be explained by rearrangement of the rhamnosyl group from the oxygen to the nitrogen atom. Oxidative debenzylation of 5a afforded 5b in high yield. Unfortunately, all attempts to remove the pivaloyl protective groups failed. On the other hand, employment of tri-O-acetyl-α-ʟ-rhamnosyl
- inhibition of colony formation were observed. Likewise, a concentration-dependent decrease of both the basal and ATP-linked oxygen consumption rate and of the capacity of oxidative respiration were observed at the mitochondrial level in the presence of compound β-33b. In addition, the morphology of the
Mechanochemical difluoromethylations of ketones
Beilstein J. Org. Chem. 2024, 20, 2799–2805, doi:10.3762/bjoc.20.235
- by these findings, we now explored difluoromethylation reactions with compounds bearing less nucleophilic functional groups. Ketones caught our particular attention as they contain a weak nucleophilic carbonyl oxygen adjacent to an electrophilic carbonyl carbon. Previous studies have focused on
- with the generation of difluorocarbene from TMSCF2Br and KFHF. This is followed by a nucleophilic attack of the oxygen atom of ketone 1 on the difluorocarbene. Subsequently, a protonation–deprotonation sequence occurs, which can either be intermolecular, involving a molecule of HF, or intramolecular
- isolating the low-boiling non-polar products. Mechanistic studies suggested that in situ-generated difluorocarbene reacts with the ketone oxygen, followed by intermolecular protonation/deprotonation. Although the process has still synthetic limitations, also acyclic ketones can now be converted into
C–C Coupling in sterically demanding porphyrin environments
Beilstein J. Org. Chem. 2024, 20, 2784–2798, doi:10.3762/bjoc.20.234
- substrates in their void. Keywords: C–C coupling; conformational analysis; nonplanar porphyrin; Pd-catalysis; porphyrin; Introduction Porphyrins are tetrapyrrolic macrocycles that perform essential processes in nature, such as oxygen transport in hemoglobin and photosynthesis [1]. Porphyrins are often
- described as planar 18π aromatic macrocycles; however, molecular structure analysis frequently reveals nonplanar ring distortion [2][3]. In fact, porphyrins with nonplanar ring distortions are vital for many natural processes to occur, e.g., nonplanarity can alter oxygen affinity of the metal iron core [4
Interaction of a pyrene derivative with cationic [60]fullerene in phospholipid membranes and its effects on photodynamic actions
Beilstein J. Org. Chem. 2024, 20, 2732–2738, doi:10.3762/bjoc.20.231
- safer control of Vm. Keywords: liposome; π–π interaction; reactive oxygen species; superoxide radical anion; Introduction The [60]fullerene (C60) is known as an excellent electron acceptor [1][2] and is commonly used in organic solar cell applications [3]. Taking advantage of the fact that C60 can be
- photoinduced generation of reactive oxygen species (ROS) [8]. In our more recent study, the reversal of Vm after stopping photoirradiation of our triad molecule was associated with the renewal of the plasma membrane through endocytosis in living cells [6]. These results suggested that the photoinduced change
- generation of ROS by catC60 in the absence or presence of PyBA. As spin trapping reagents for the singlet oxygen (1O2), hydroxyl radical (•OH) and superoxide radical anion (O2•–); 2,2,6,6,-tetramethyl-4-piperidone (4-oxo-TEMP), 3,4-dihydro-2,3-dimethyl-2H-pyrrole 1-oxide (DMPO), and 5-(diethoxyphosphoryl)-5
Synthesis of spiroindolenines through a one-pot multistep process mediated by visible light
Beilstein J. Org. Chem. 2024, 20, 2722–2731, doi:10.3762/bjoc.20.230
- argon atmosphere to prevent the interaction of oxygen or reactive oxygen intermediates, which are not always compatible with the substrates, as well as the key intermediates. Moreover, BrCCl3 and its reduced form (chloroform) can be easily removed from the reaction mixture thanks to their low boiling
Computational design for enantioselective CO2 capture: asymmetric frustrated Lewis pairs in epoxide transformations
Beilstein J. Org. Chem. 2024, 20, 2668–2681, doi:10.3762/bjoc.20.224
- H2 over CO2 becomes crucial for effective CO2 reduction [7]. Additionally, the strength of the interaction between the catalyst and the resulting system after hydride transfer presents a limitation. The formation of a robust LA–oxygen interaction may impede proton transfer to the basic oxygen atom
- oxygen atoms [6][7]. Carbon capture and utilisation (CCU) technologies involve the extraction of CO2 from the atmosphere of the Earth to generate value-added chemicals, which can serve as platform chemicals in other chemical processes [20][21]. This is achieved by inserting CO2 as a C1 building block
- new intermediate (Min5) is stabilised, in which the oxygen of CO2 has attacked the electrophilic carbon of PO, and the oxygen atom of PO interacts with the LB. This mechanism is exclusive to phosphorus-containing FLPs, as nitrogen does not support this type of reactivity. Subsequently, the
Transition-metal-free decarbonylation–oxidation of 3-arylbenzofuran-2(3H)-ones: access to 2-hydroxybenzophenones
Beilstein J. Org. Chem. 2024, 20, 2655–2667, doi:10.3762/bjoc.20.223
- catalyzed by both dissolved oxygen and atmospheric oxygen [27], we envisaged that degassed THF solvent kept under inert atmosphere would not produce hydroperoxides, and hence the reaction will not proceed under such circumstances. To confirm this hypothesis, we degassed freshly distilled THF with Ar for 2 h
Efficient modification of peroxydisulfate oxidation reactions of nitrogen-containing heterocycles 6-methyluracil and pyridine
Beilstein J. Org. Chem. 2024, 20, 2599–2607, doi:10.3762/bjoc.20.219
- reactions was made. It has been suggested that a nucleophilic substitution of the peroxide oxygen atom occurs in peroxydisulfate [32]. Regarding phenols (Elbs reaction), there is also a nucleophilic substitution of the phenolate ion. For aromatic amines (Boyland–Sims reaction), a neutral nitrogen atom of
- oxidized more completely due to a more efficient consumption of the oxidant (APS). Previously, the oxidation of orotic acid was studied and it was found that the presence of oxygen in the reaction medium affects the yield of the sulfate derivative [37]. Under anaerobic conditions, a low yield of the
- peroxydisulfate ion, leading to the production of oxygen [39]: Oxygen accumulation is additionally achieved by hydrogen peroxide self-decay, which is known to be increased in alkaline conditions [40]: Additionally, it has been reported [41] that hydroxyl radicals, produced from the decomposition of H2O2, can
Base-promoted cascade recyclization of allomaltol derivatives containing an amide fragment into substituted 3-(1-hydroxyethylidene)tetronic acids
Beilstein J. Org. Chem. 2024, 20, 2585–2591, doi:10.3762/bjoc.20.217
- formation of an intramolecular hydrogen bond and the double bond is located in the furanone ring. In contrast to the aforementioned example the considered compounds 4 have an exocyclic enol fragment and the intramolecular hydrogen bond is connected to the carbonyl oxygen atom. Thus, the absence of
Transition-metal-free synthesis of arylboronates via thermal generation of aryl radicals from triarylbismuthines in air
Beilstein J. Org. Chem. 2024, 20, 2577–2584, doi:10.3762/bjoc.20.216
- , entry 2 vs entries 3 and 4). Under atmospheric oxygen, the yield of 3a decreased slightly (Table 1, entry 5). The reaction was investigated at 60 °C and 100 °C, and it was found that the reaction was most efficient at 80 °C (Table 1, entry 2 vs entries 6 and 7). We have previously succeeded in
- atmosphere and in the open-air. In the absence of oxygen, the color of the reaction mixture changed only slightly. In contrast, the reaction in air resulted in the formation of black and a small amount of white insoluble solid (probably metallic bismuth or bismuth oxide) [55], and 3a was successfully
- confirmed and characterized by the 1H NMR measurement of the crude reaction mixture (Scheme 4b) [48]. These results clearly showed that the thermal generation of aryl radicals from triarylbismuthines is one of the key factors for the transition-metal-free synthesis of arylboronates, and oxygen (air) would
A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis
Beilstein J. Org. Chem. 2024, 20, 2500–2566, doi:10.3762/bjoc.20.214
Photoredox-catalyzed intramolecular nucleophilic amidation of alkenes with β-lactams
Beilstein J. Org. Chem. 2024, 20, 2461–2468, doi:10.3762/bjoc.20.210
- their investigation of the hydrofunctionalization reaction of unsaturated amides and thioamides [28]. They have found that the oxygen atom of the amide group, rather than the nitrogen atom, acted as a nucleophile, leading to the formation of 2-oxazolines and 2-thiazolines. Another recent example of
- attack the radical cation A, giving the bicyclic radical intermediate B. Amide is an ambident nucleophile, and oxygen attack of radical cation A is also conceivable to give the corresponding imidate [28]. In our reaction, O-addition is disfavored due to the formation of an unsaturated four-membered ring
Hypervalent iodine-mediated cyclization of bishomoallylamides to prolinols
Beilstein J. Org. Chem. 2024, 20, 2455–2460, doi:10.3762/bjoc.20.209
- the alkene and the amide increased from two to three atoms. In the latter case, cyclization at the amide nitrogen to form the pyrrolidine ring was favored over cyclization at the amide oxygen. A DFT study was undertaken to rationalize the change in mechanism of this cyclization process. In addition
- amide at both the oxygen and the nitrogen, however, the ΔG‡ value for the latter was lower by 2.5 kcal·mol−1. This demonstrates a clear kinetic preference for formation of the five-membered ring over the seven-membered one [19]. Subsequent deprotonation of 11 leads to tertiary amide 12. Upon cyclization
- atoms separating the functional groups, cyclization at the amide oxygen occurs to generate five- and six-membered rings, respectively. However, when there is a three-carbon atom link, the corresponding seven-membered ring is not formed. Instead, cyclization at nitrogen occurs to generate a five-membered
Synthesis and conformational analysis of pyran inter-halide analogues of ᴅ-talose
Beilstein J. Org. Chem. 2024, 20, 2442–2454, doi:10.3762/bjoc.20.208
- 109.36°, respectively. However, there is a bond angle narrowing for the other analogues (Cl: 108.07°; Br: 107.94°; I: 107.78°). Finally, the angles involving the exo-anomeric oxygen (O1–C1–O5) are similar with a difference of about 1° between the larger (compound 17) and smaller (compound 14) angle. As
- ][62][63][64][65]. In our case, for compound 15, I4 interacts with H4 (d = 3.521 Å, a = 93.77°) and I4 also interact with the oxygen of the carbonyl of the acetate at C6 (I4···O, d = 3.147 Å; a = 179.70°) (Figure 4b and Table 7). This result is in line with hydrogen (C–I···H) and halogen (C–I···O
- , 17, and α-ᴅ-talose 18. ORTEP diagram showing 50% thermal ellipsoid probability (except for 18): carbon (gray), oxygen (red), fluorine (green), chlorine (orange), bromine (dark red), iodine (purple), and hydrogen (white). Packing arrangement of compound compound 15; a) View down the b axis; b
Phenylseleno trifluoromethoxylation of alkenes
Beilstein J. Org. Chem. 2024, 20, 2434–2441, doi:10.3762/bjoc.20.207
- oxygen atom which disfavors the episelenonium opening with the CF3O− anion in the closest position to the oxygen atom. It is noteworthy that the regioisomeric ratio of terminal alkenes (2e, 2i) evolved with the reaction time. The amount of the kinetic terminal regioisomer (anti-Markovnikov – 2e’, 2i
Evaluating the halogen bonding strength of a iodoloisoxazolium(III) salt
Beilstein J. Org. Chem. 2024, 20, 2401–2407, doi:10.3762/bjoc.20.204
- than prototypic iodolium 1OTf, the oxygen-bridged iodoxinium 4OTf exhibited improved performance and the polyfluorinated iodolium 2OTf was by far the most active. A previous study on gold activation by halogen bonding showed significantly higher activity when the weakly coordinating counteranion
- % conversion after already 4 h (≈55% after 2 h) and the oxygen-bridged iodoxinium 4BArF performed slightly better (≈70% after 2 h). For these two catalysts, a very slight sigmoidal curve shape was also observed. The polyfluorinated XB donor 2BArF performed the best, with ≈90% conversion after 2 h. The
- ). Halogen bonding dimer found in the crystal structure of 7Br. Ellipsoids are shown at 50% probability (carbon: grey, nitrogen: blue, oxygen: red, bromine: orange, iodine: purple) and hydrogen atoms are shown in standard ball-and-stick model (white). Halogen and hydrogen bonding is indicated dashed. 1H NMR
Synthesis, electrochemical properties, and antioxidant activity of sterically hindered catechols with 1,3,4-oxadiazole, 1,2,4-triazole, thiazole or pyridine fragments
Beilstein J. Org. Chem. 2024, 20, 2378–2391, doi:10.3762/bjoc.20.202
- planes of the cycles corresponds to 5°). These pairs (Figure 3) are bound in a supramolecular chain along the 0c axis owing to two H-bonds between the OH group of catechol and the oxygen atom of nitro-group (O1–H1···O4B (1−x, 1−y, −1+z): the H1···O4 distance is 2.46(1) Å, the O1···O4 distance is 2.886(3
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