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Search for "stability" in Full Text gives 1380 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Chemoenzymatic synthesis of macrocyclic peptides and polyketides via thioesterase-catalyzed macrocyclization
Beilstein J. Org. Chem. 2024, 20, 721–733, doi:10.3762/bjoc.20.66
- stability, etc. Emerging research methods on bioinformatics, computational modeling, deep learning, protein engineering, and high-throughput screening will accelerate the pace of enzyme discovery to provide a broader platform of tools for employing chemoenzymatic strategies [64][87][88][89]. More
SOMOphilic alkyne vs radical-polar crossover approaches: The full story of the azido-alkynylation of alkenes
Beilstein J. Org. Chem. 2024, 20, 701–713, doi:10.3762/bjoc.20.64
- ]. On the other hand, the nature of the alkene might be limited as it would strongly influence the oxidation potential of the carbon radical and the stability of the resulting carbocation. Recently, we reported the first successful application of an RPC strategy for the azido-alkynylation of styrenes
Organic electron transport materials
Beilstein J. Org. Chem. 2024, 20, 672–674, doi:10.3762/bjoc.20.60
- orthogonal processing. One of the biggest challenges with n-type materials is air stability. This is explained by the redox potentials of water (−0.66 V vs standard calomel electrode (SCE)) and oxygen (+0.024 V vs SCE, +0.57 V vs SCE) [2][3]. Therefore, it has been observed that once the overpotential
HPW-Catalyzed environmentally benign approach to imidazo[1,2-a]pyridines
Beilstein J. Org. Chem. 2024, 20, 628–637, doi:10.3762/bjoc.20.55
- is known for its chemical and thermal stability. Herein, we report a straightforward approach to the GBB-3CR using HPW as catalyst in ethanol under microwave (μw) heating. This convenient environmentally benign methodology is broad in scope, provides the heterobicyclic products in high yields (up to
- green catalyst with greater chemical and thermal stability in comparison to other heteropolyacids [43]. HPW has been shown to catalyze MCRs in the synthesis of heterocyclic compounds with high efficiency and chemoselectivity (Figure 2), including functionalized benzo[c]chromeno[2,3-a]phenazine [44
Possible bi-stable structures of pyrenebutanoic acid-linked protein molecules adsorbed on graphene: theoretical study
Beilstein J. Org. Chem. 2024, 20, 570–577, doi:10.3762/bjoc.20.49
- the potential energy surface, a curved conformation (conformation 2 in Figure 1d) exists. Our previous results suggested that conformation 2 is a metastable state. The relative stability of these conformations is known to vary depending on the surrounding environment, e.g., solvents and solutes [9
- ]. Actually, the presence of solutes consisting of water and proteins improves the stability of conformation 2. This stabilization is explained partly by the formation of hydrogen bonds between water molecules and PASE. Conformation 2 increases the number of sites where hydrogen bonds can form with water
- molecules because the chain portion of PASE turns upward. Therefore, the stabilization energy of hydrogen-bond formation is greater in conformation 2 than in conformation 1. To improve the stability of conformation 2, hydration effects by electrostatic interactions between PASE and the solvent are also
Switchable molecular tweezers: design and applications
Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45
Ligand effects, solvent cooperation, and large kinetic solvent deuterium isotope effects in gold(I)-catalyzed intramolecular alkene hydroamination
Beilstein J. Org. Chem. 2024, 20, 479–496, doi:10.3762/bjoc.20.43
- tackle catalyst stability by changing the chloride scavenger [23] or adding other coordinating moieties [24][25]. Hartwig et al. have argued that a Brønsted acid generated in situ from metal triflates may be the “real” catalyst promoting some alkene functionalizations [26]. Therefore, the possibility of
- other in the NMR spectrum. Although we observed reaction inhibition in a number of instances with [JPhosAu(NCCH3)]SbF6 we have never yet observed the formation of this byproduct. On the one hand, this is a testament to the high stability of gold supported by JPhos, on the other hand, it suggests as yet
- utilizing a dinuclear gold phosphine. These enhancements are likely correlated with increased catalyst stability. The earliest reports of alkene hydroamination revealed NHC’s and JPhos (t-Bu2)P(o-biphenyl) as the most active ligands [12][13][14], but this was in comparison to Ph3P which has since been
Synthesis of 2,2-difluoro-1,3-diketone and 2,2-difluoro-1,3-ketoester derivatives using fluorine gas
Beilstein J. Org. Chem. 2024, 20, 460–469, doi:10.3762/bjoc.20.41
- present in many agrochemical and pharmaceutical products owing to the beneficial properties imparted such as increased metabolic stability, lipophilicity and bioavailability of the bioactive entity [1][2][3]. In 2018, 30% of FDA approved drugs contained at least one fluorine atom, with an average of 2.7
Enhanced host–guest interaction between [10]cycloparaphenylene ([10]CPP) and [5]CPP by cationic charges
Beilstein J. Org. Chem. 2024, 20, 436–444, doi:10.3762/bjoc.20.38
- -conjugated molecules, CPPs with shorter conjugations have lower oxidation potentials than larger CPPs, and the first and the second oxidation potentials of [5]CPP are by 0.69 and 0.51 V lower than those of [10]CPP, respectively [43]. The other is the stability of the CPP dications. Since the dications are
- . However, the low solubility and stability of the dication in polar solvents prevented confirmation of the solvent effect. To clarify the additional interaction in the complex, the electrochemical analysis of the [10]CPP⊃[5]CPP2+[B(C6F5)4–]2 was examined by using cyclic voltammetry, which was performed in
- transition corresponds to the CT band. The structure and stability of [10]CPP⊃[5]CPP2+ were estimated by DFT calculations at the ωB97-XD/6-31G* level of theory. Three isomeric structures were optimized, of which complex 1, with two CPPs aligned in parallel, is the most thermodynamically stable (Figure 5a
Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles
Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36
- nanocompounds, instead picking graphene oxide (GO), due to its unique morphology and high chemical stability (Scheme 20) [112]. The graphene oxide was decorated with CuBr nanoparticles, which had already shown great catalytic potential, forming the GO–CuBr complex that was utilized for the synthesis of BIMs
- greatly diminished the conversion rates of BIMs, while replacing SDS with different surfactants had no effect on the reaction profile. Even though a large amount of 0.5 g of the LASSC nanocatalyst was employed, it displayed impressive stability, since it could be retrieved and reused upwards of 11 times
Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters
Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35
- Carlos R. Azpilcueta-Nicolas Jean-Philip Lumb Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada 10.3762/bjoc.20.35 Abstract Due to their ease of preparation, stability, and diverse reactivity, N-hydroxyphthalimide (NHPI) esters have found
- -hydroxyphthalimide (NHPI) esters (3) have emerged as convenient alternatives to Barton esters (Scheme 1) due in part to their ease of synthesis and greater stability (N–O BDE ≈ 75 kcal/mol) [28]. Their use as radical precursors was first described by Okada and colleagues in 1988 [29], who showed that C(sp3)-centered
Facile approach to N,O,S-heteropentacycles via condensation of sterically crowded 3H-phenoxazin-3-one with ortho-substituted anilines
Beilstein J. Org. Chem. 2024, 20, 336–345, doi:10.3762/bjoc.20.34
- ). This is also the basic compound used in the transformations that are studied in this work due to the high kinetic stability and good solubility ensured by the tert-butyl groups. The largest positive charge of the C(1)–C(2)–C(3) segment is concentrated at the C(2) atom. The charge at the other
- the geometry without imposing symmetry restrictions, followed by analyzing the stability of the DFT wave function. The images of the molecular structures in Figure 1 and Figure S6, Supporting Information File 1, were obtained using the Chemcraft program [35]. DFT-calculated molecular geometry (B3LYP/6
- and 6. Relative stability of the tautomers 7 and 7a,b of quinoxaline[2,3-b]phenoxazine calculated at the DFT B3LYP/6-311++G(d,p) level. Preparation of quinoxaline[2,3-b]phenoxazine (7) from 2-amino-3H-phenoxazin-3-one (8) [10] and 2-ethoxy-3H-phenoxazin-3-one (9) [11], respectively. Triphenodioxazine
Synthesis of π-conjugated polycyclic compounds by late-stage extrusion of chalcogen fragments
Beilstein J. Org. Chem. 2024, 20, 287–305, doi:10.3762/bjoc.20.30
- the organic product along with inorganic species [41][42][43][44]. Over the years, many efforts were thus devoted to the synthesis of thiepine derivatives with increased thermal stability, with the aim to disfavor the formation of the transient thianorcaradiene intermediate as a way to prevent the
- stability. Conversely, selenepine 28c and selenepine Se-oxide 29c were quantitatively converted into the seco-HBC 31 by thermal activation at 200 °C for 5 min, as evidenced by UV–visible absorption and HPLC monitoring. SO-extrusion from thiepine S-oxide 29b was also successfully triggered in the solid state
- , as well as the oxidation state of the embedded chalcogen atom, allows controlling the stability of the heteropine, and thus its propensity to undergo thermal extrusion. Although beyond the scope of this review, it is noteworthy that the authors successfully converted the selenepine Se-oxide 29c into
Unveiling the regioselectivity of rhodium(I)-catalyzed [2 + 2 + 2] cycloaddition reactions for open-cage C70 production
Beilstein J. Org. Chem. 2024, 20, 272–279, doi:10.3762/bjoc.20.28
- medical applications) and improving their stability, among other desirable properties. The most common reactions used to functionalize fullerenes are Diels–Alder and 1,3-dipolar cycloadditions and Bingel–Hirsch cyclopropanations [19][20]. In most cases, functionalization occurs while preserving the carbon
Substitution reactions in the acenaphthene analog of quino[7,8-h]quinoline and an unusual synthesis of the corresponding acenaphthylenes by tele-elimination
Beilstein J. Org. Chem. 2024, 20, 243–253, doi:10.3762/bjoc.20.24
- for compounds containing a quinoline fragment in various fields of research. At the same time, quinoline bases are a popular platform for the molecular design of polycyclic systems with receptor properties; they easily form proton complexes with high stability and selectivity [5][6]. This, in turn
Photochromic derivatives of indigo: historical overview of development, challenges and applications
Beilstein J. Org. Chem. 2024, 20, 228–242, doi:10.3762/bjoc.20.23
- + cations (500 equiv). At the same time, addition of TBA+ cations showed just a minimal impact on the stability of the Z-form comparable with the effect of counter anions and solvent polarity. In 2021, Tsubaki and co-workers synthesized bridged N,N′-dialkyl-substituted indigos 13 and studied their thermal
- '-dinitrobenzoylindigo 18b were provided by de Melo and co-workers in 2020 using modern femtosecond spectroscopic techniques as well as TD-DFT calculations [60]. In 1989, Takahashi and co-workers reported an important study of geometry and conformational stability of indigo and its N,N'-disubstituted derivatives [61][62
- zwitterionic resonance structures (Figure 3) increases in the excited state of indigo. This partial redistribution of charges, in turn, increases the electrostatic repulsion between the carbonyl groups in the Z-form (Figure 12) resulting in the larger energy gap between HOMO and LUMO and reduced stability for
Optimizations of lipid II synthesis: an essential glycolipid precursor in bacterial cell wall synthesis and a validated antibiotic target
Beilstein J. Org. Chem. 2024, 20, 220–227, doi:10.3762/bjoc.20.22
- disaccharide synthesis alongside C6-protected acceptors (2a or 2b in Figure 2) [10][11][14][15][37][38]. More recently, an innovative one-pot glycosylation approach using a (2,6-dichloro-4-methoxyphenyl)(2,4-dichlorophenyl)-protected glycosyl acceptor has been developed, demonstrating satisfactory stability
Chiral phosphoric acid-catalyzed transfer hydrogenation of 3,3-difluoro-3H-indoles
Beilstein J. Org. Chem. 2024, 20, 205–211, doi:10.3762/bjoc.20.20
- excellent yield and enantioselectivity. Keywords: asymmetric organocatalysis; chiral Brønsted acid; 3,3-difluoroindoline; Hantzsch ester; transfer hydrogenation; Introduction The introduction of fluoro atoms into organic molecules can alter their lipophilicity, solubility, metabolic stability, and
Comparison of glycosyl donors: a supramer approach
Beilstein J. Org. Chem. 2024, 20, 181–192, doi:10.3762/bjoc.20.18
- rotation values were measured with a PU-07 automatic digital polarimeter (Russia) at 28 °C in a jacketed glass cell (10 cm length). Special precautions were made to ensure the stability of the instrument and the temperature within the measuring compartment of the instrument and the cell, which was
- measurement of the quartz standards (to monitor the instrument stability). Each measurement at a particular concentration was repeated 10 times, then averaged and plotted against concentration. The standard deviations were calculated by using the Student’s distribution (95% probability) and did not exceed 1
Perspectives on push–pull chromophores derived from click-type [2 + 2] cycloaddition–retroelectrocyclization reactions of electron-rich alkynes and electron-deficient alkenes
Beilstein J. Org. Chem. 2024, 20, 125–154, doi:10.3762/bjoc.20.13
Visible-light-induced radical cascade cyclization: a catalyst-free synthetic approach to trifluoromethylated heterocycles
Beilstein J. Org. Chem. 2024, 20, 118–124, doi:10.3762/bjoc.20.12
- an electron-withdrawing functional moiety into drug molecules would increase their metabolic stability [20], by avoiding, e.g., fast oxidation by cytochrome P450 oxidases [21]. In particular, the introduction of a trifluoromethyl group (–CF3) was shown to increase the metabolic stability of molecules
Optimizing reaction conditions for the light-driven hydrogen evolution in a loop photoreactor
Beilstein J. Org. Chem. 2024, 20, 74–91, doi:10.3762/bjoc.20.9
- actinometry. The system displayed exceptional stability, with operation sustained over 70 hours. A design of experiment (DOE) analysis was used to systematically investigate the influence of key parameters – photon flux, photocatalyst loading, stirring speed, and inert gas flow rate – on the hydrogen
- air or sampling mistakes. The long-term stability of the photocatalyst was initially tested in the loop photoreactor with a photocatalyst loading of 0.22 g L−1, a stirring speed of 560 rpm, a photon flux of 4.70 μmol s−1, and an inert gas flow rate of 75 mL min−1. Figure 9 shows the hydrogen
- evolution rate remained at this level for 70 hours of irradiation. These results prove the long-term stability of the systems, which is a prerequisite for any future application. Design of experiment analysis During design of experiment (DOE) analysis, the default linear and quadratic model were found to
Using the phospha-Michael reaction for making phosphonium phenolate zwitterions
Beilstein J. Org. Chem. 2024, 20, 41–51, doi:10.3762/bjoc.20.6
- , Figure S47). A similar oligomerization reaction has been reported for cyanoacrylates [40]. Apart from the adducts of these two very weak Michael acceptors, the zwitterionic species 2a–i described herein are quite stable. The stability of the zwitterions was evaluated exemplarily using the methyl acrylate
- adduct 2d. Stability studies were conducted in the solid state and in solution. When storing the zwitterion under ambient conditions for a duration of two months, minor decomposition can be observed. The proton NMR gives rise to new signals appearing at 6.81 ppm (dd, J = 14.5, J = 2.2 Hz) and 11.23 ppm
- phosphorus signal for 2d). Stability tests were also performed in two different deuterated solvents, CDCl3 and DMSO-d6. No air or moisture exclusion was applied. The tests were performed at room temperature and at 60 °C. 1H and 31P NMR spectra of the solutions were taken after 24, 48 and 72 h. At room
Facile access to pyridinium-based bent aromatic amphiphiles: nonionic surface modification of nanocarbons in water
Beilstein J. Org. Chem. 2024, 20, 32–40, doi:10.3762/bjoc.20.5
- below 0.1 mM (Figures S28 and S32, Supporting Information File 1), which is around 10 times lower than that of AA [12][13]. The increased stability against dilution likely arises from reduced electrostatic repulsion and increased anthracene-based π-stacking interactions due to the absence of o-alkoxy
- surface properties of the aromatic micelles (PA-R)n and their host–guest composites including nanocarbons in water. The ZP of self-assembled nanoparticles evaluates their structural stability in solution against aggregation through electrostatic repulsion [25]. Solutions of the micelles in Milli-Q water
- (0.5 mM based on PA-R) gave ZPs significantly varying with the attached side-chains. Aqueous solutions of (PA-CH3)n, (PA-OCH3)n, and (PA-OH)n provided ZPs of 7.3 mV, 18.8 mV, and 20.3 mV, respectively, suggesting an increase in stability upon introduction of the long hydrophilic side-chains (Table 1
Identification of the p-coumaric acid biosynthetic gene cluster in Kutzneria albida: insights into the diazotization-dependent deamination pathway
Beilstein J. Org. Chem. 2024, 20, 1–11, doi:10.3762/bjoc.20.1
- ) within 1 h. This property is probably due to the high stability of CmaA6. The high activity of CmaA6 makes it a useful tool for biochemical experiments and chemoenzymatic synthesis. Indeed, the discovery of CmaA6 allowed us to analyze the kinetics of the denitrification reaction catalyzed by AvaA7, which
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