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Search for "acidity" in Full Text gives 289 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Multiswitchable photoacid–hydroxyflavylium–polyelectrolyte nano-assemblies
Beilstein J. Org. Chem. 2021, 17, 166–185, doi:10.3762/bjoc.17.17
- -assembly in this study: pelargonidin chloride (Flavy), 1-naphthol-3,6-disulfonate (1N36S, photoacid), and poly(allylamine). The photoacid hydroxy group acidity increases upon photoexcitation. Flavy can undergo different reactions as given in Scheme 1. Poly(allylamine) is present in the protonated form as a
Pentannulation of N-heterocycles by a tandem gold-catalyzed [3,3]-rearrangement/Nazarov reaction of propargyl ester derivatives: a computational study on the crucial role of the nitrogen atom
Beilstein J. Org. Chem. 2020, 16, 3059–3068, doi:10.3762/bjoc.16.255
- anion as a base (Figure 6). In fact, the abstraction of the hydrogen atom in the position adjacent to Au (C3) shows a low activation barrier (TS8, ΔG‡ = 12.6 kcal⋅mol−1) from the corresponding precomplex, leading to the formation of the intermediate XI and triflic acid. The high acidity of the latter
One-pot multicomponent green Hantzsch synthesis of 1,2-dihydropyridine derivatives with antiproliferative activity
Beilstein J. Org. Chem. 2020, 16, 2862–2869, doi:10.3762/bjoc.16.235
- ), 40 wt % PW on silica (Table 1, entry 9), a 30 wt % PW loading on montmorillonite K30 clay (Table 1, entry 11), and a 40 wt % PW loading on alumina (Table 1, entry 12). The study on the optimal reaction conditions shed a light on the acidity and the physical characteristics required for the reaction
Changed reactivity of secondary hydroxy groups in C8-modified adenosine – lessons learned from silylation
Beilstein J. Org. Chem. 2020, 16, 2854–2861, doi:10.3762/bjoc.16.234
- with the 3’-OH group, due its higher acidity [29]. For modified nucleosides, the preference of 2’-O-TBDMS formation in the presence of AgNO3 may not be given [29], and indeed, as already mentioned above, the C8-linker conjugated nucleoside derivative 7 (Scheme 1) shows the opposite behavior: the 3’-O
Activation of pentafluoropropane isomers at a nanoscopic aluminum chlorofluoride: hydrodefluorination versus dehydrofluorination
Beilstein J. Org. Chem. 2020, 16, 2623–2635, doi:10.3762/bjoc.16.213
- doped with chlorine atoms which causes a distortion of the structure resulting in the amorphicity and high Lewis acidity of the compound. The reactivity of ACF towards C–F bond activations was deeply investigated. For instance, the activation of fluoromethanes was observed at ACF in the presence of
- been found in a homogeneous phase, but germylium ions can promote such reaction pathways [58]. Nevertheless, the formation of the compounds 1, 10b, 11, and 12 can alternatively be initiated by the Lewis acidity of ACF itself, as outlined above without the presence of silane (see Scheme 3). Therefore
A proposed sustainability index for synthesis plans based on input provenance and output fate: application to academic and industrial synthesis plans for vanillin as a case study
Beilstein J. Org. Chem. 2020, 16, 2346–2362, doi:10.3762/bjoc.16.196
- , unitless), acidity-basicity potential (ABP, unitless), bioconcentration potential (BCP, unitless), persistence potential (PER, unitless), soil sorption coefficient (soil, Koc), half-life of solvent in environment (half-life, h), aquatic toxicity to fish (aqua, mg/L for 96 h), Q-phrase potential (Q-phrase
Chan–Evans–Lam N1-(het)arylation and N1-alkеnylation of 4-fluoroalkylpyrimidin-2(1H)-ones
Beilstein J. Org. Chem. 2020, 16, 2304–2313, doi:10.3762/bjoc.16.191
- 9d,e. Thus, the presence of the electron-withdrawing 4-fluoroalkyl group in pyrimidones 1 is a significant structural factor playing a major role in the overall success of the Chan–Evans–Lam reaction, most likely due to related increase in NH-acidity of the heterocyclic system. The ester group and
Regioselective cobalt(II)-catalyzed [2 + 3] cycloaddition reaction of fluoroalkylated alkynes with 2-formylphenylboronic acids: easy access to 2-fluoroalkylated indenols
Beilstein J. Org. Chem. 2020, 16, 2193–2200, doi:10.3762/bjoc.16.184
- literature [20][40]. The reaction of Int-1 with the alkynes 1 also gives Int-2b as a regioisomeric intermediate of Int-2a, leading to the 3-fluoroalkylated cobalt alkoxide Int-3b. Subsequently, the proton shift of the cobalt alkoxide Int-3b provides the allylcobalt species Int-4b because the acidity of the
Automated high-content imaging for cellular uptake, from the Schmuck cation to the latest cyclic oligochalcogenides
Beilstein J. Org. Chem. 2020, 16, 2007–2016, doi:10.3762/bjoc.16.167
- ]. Firstly, in comparison to simple guanidinium cations 2 (pKa 12.5) and ammonium cations 3 (pKa 10.5), the Schmuck cation has a lower pKa value of 7 to 8 due to the increased acidity of acylguanidiniums, which favors the formation of stronger hydrogen-bonded ion pairs (Figure 1, magenta part). Secondly, the
Synthesis of 3(2)-phosphonylated thiazolo[3,2-a]oxopyrimidines
Beilstein J. Org. Chem. 2020, 16, 1947–1954, doi:10.3762/bjoc.16.161
- -trifluoromethyl-2-thiouracil (1e) enhances the acidity of the N3H hydrogen by direct conjugation to the carbonyl moiety. As a result, 2-thiouracil 1e acts as an ambident nucleophile. Thus, the attack of the carbon atom attached to the chlorine by the N3 nitrogen atom is accompanied by the elimination of hydrogen
Selective preparation of tetrasubstituted fluoroalkenes by fluorine-directed oxetane ring-opening reactions
Beilstein J. Org. Chem. 2020, 16, 1936–1946, doi:10.3762/bjoc.16.160
- analysis and supported by HRMS. All three halogenated products were purified and isolated as a mixture (≈61% determined by NMR). The contrasting result observed with HBr/AcOH and TBAB/CSA highlighted the importance of the acidity of the medium on the reaction course of the ring-opening reaction (Scheme 5
Polarity effects in 4-fluoro- and 4-(trifluoromethyl)prolines
Beilstein J. Org. Chem. 2020, 16, 1837–1852, doi:10.3762/bjoc.16.151
- this weakens their interaction. Similar considerations can be applied to the acidity of the carboxylic group (Figure 6B), where the mutual orientation of the C–X dipole and the carboxylate -CO2− charge has an effect [74]. In diastereomeric fluoroprolines there is a large difference in the mutual
- orientation of the groups, while in the (trifluoromethyl)prolines the orientation is similar. This is reflected in the acidity values. Lipophilicity Another parameter, which may be sensitive to the orientation of the dipoles within a molecule is the lipophilicity. It is well known that single aliphatic
- conformation of the side chains. The positive end of the ammonium dipole is on the hydrogen atoms attached to the nitrogen. The nitrogen atom is the negative end. B) The acidity of the carboxylic group depends on the relative orientation of the substituent dipole with respect to the charged carboxylate. Only
When metal-catalyzed C–H functionalization meets visible-light photocatalysis
Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147
- alkane products could be controlled by adjusting the acidity of the reaction media. As in the previously described examples, molecular oxygen plays a key role in the mechanism of the C–H functionalization (Figure 10). Indeed, both the photoexcited Ir-based catalyst and the superoxide radicals formed in
One-pot synthesis of isosorbide from cellulose or lignocellulosic biomass: a challenge?
Beilstein J. Org. Chem. 2020, 16, 1713–1721, doi:10.3762/bjoc.16.143
- )cellulose such as the acidity, the crystallinity and the particle size of cellulose as well as the nature of the feedstocks. This review highlights all these parameters and all the strategies employed to produce isosorbide from (ligno)cellulose in a one-pot process. Keywords: catalysis; cellulose
- acid or a metal on an acid support. Here, we will report all these strategies to perform the one-pot conversion of (ligno)cellulose to isosorbide and the key parameters of this reaction (acidity, nature of the feedstocks, poisoning of the catalyst). Review Combination of an acidic homogeneous catalyst
- conversion of cellulose. If the Ru/C catalyst was associated with H2SO4 only 14% of isosorbide was produced under similar conditions. This study showed that the nature of the mineral acid and thus the acidity is of importance to produce isosorbide from cellulose. The most active metal catalyst is Ru/C among
Pauson–Khand reaction of fluorinated compounds
Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138
- strategic positions in a drug candidate may result in not only an increase in its potency, but also, perhaps more importantly, bring about an enhanced pharmacokinetic profile resulting in a more “drug-like” molecule [4]. Subtle changes in physicochemical properties such as acidity/basicity, lipophilicity
Fluorohydration of alkynes via I(I)/I(III) catalysis
Beilstein J. Org. Chem. 2020, 16, 1627–1635, doi:10.3762/bjoc.16.135
- using ethyl fluoroacetate as the internal standard. Initially, the effect of Brønsted acidity was explored by varying the amine/HF ratio with mixtures of commercially available NEt3/HF 1:3 and Olah’s reagent (pyr/HF 1:9.23). Lower amine/HF ratios (1:4.5) resulted in poor conversion (9% yield, Table 1
- , entry 1), whereas increasing the Brønsted acidity to 1:7.5 furnished the desired α-fluoroketone 2 in 64% yield (Table 1, entry 2). However, employing Olah’s reagent (1:9.23) had a negative impact on the efficiency (45% yield, Table 1, entry 3) thereby allowing a plateau to be established (vide infra
- ). Having established that an amine/HF ratio of 1:7.5 provides the optimal Brønsted acidity for catalysis, a solvent screen was conducted to assess the effect of the reaction medium. Chlorinated solvents proved to be most effective, with reactions performed in CHCl3 slightly outperforming those in CH2Cl2
Recent synthesis of thietanes
Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116
- 143. A proton transfer generated hydroxyalkanethiolates 144 because the acidity of the thiols is higher than that of alcohols, the newly generated thiolates 144 underwent an intramolecularly nucleophilic displacement to give thietane-3-ols 145 [56] (Scheme 28). In a similar approach
Highly selective Diels–Alder and Heck arylation reactions in a divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles from 2-formylpyrrole
Beilstein J. Org. Chem. 2020, 16, 1320–1334, doi:10.3762/bjoc.16.113
- similar chemoselectivity has been previously observed, being explained as a consequence of the acidity of the C–H bond being cleaved [6][44]. Additional intramolecular cross-coupling reactions were carried out by utilizing dimethyl malonates 8k and 8l, which were prepared through the N-benzylation of 16c
The charge-assisted hydrogen-bonded organic framework (CAHOF) self-assembled from the conjugated acid of tetrakis(4-aminophenyl)methane and 2,6-naphthalenedisulfonate as a new class of recyclable Brønsted acid catalysts
Beilstein J. Org. Chem. 2020, 16, 1124–1134, doi:10.3762/bjoc.16.99
- Supporting Information File 1) to be 4.94, 4.46, 4.04, and 3.79. Thus, the difference in the acidity of the NDS and TAPM components was large enough to ensure a complete salt formation. Solid F-1 was practically insoluble in organic solvents with the exception of DMSO. The analytical data supported its
- . However, the framework F-1 underwent “breathing” in organic solvent solutions (see below), which allowed catalytic sites to become available without the need for a pore structure in the desolvated material. The calculated acidity of the components of F-1 (see above) indicated possible catalytic
- incorporating multitopic tectons with a greater number of negatively charged sulfonate groups mutually rigidly fixed in space. Such arrangement should produce large pores within the framework and further reduce the framework’s solubility in water and organic solvents. Additionally, the acidity of these
Fluorinated phenylalanines: synthesis and pharmaceutical applications
Beilstein J. Org. Chem. 2020, 16, 1022–1050, doi:10.3762/bjoc.16.91
- size of fluorine, the next in size to hydrogen. However, the high electronegativity of the fluorine leads to low polarizability and a strong covalent bond to carbon [1][2][3][4]. Therefore, the introduction of fluorine into phenylalanine (Phe) can modulate the acidity, basicity, hydrophobicity
- the properties of peptides and proteins [5][6][7], influencing aspects such as protein folding, protein–protein interactions, ribosomal translation, lipophilicity, acidity/basicity, optimal pH, stability, thermal stability, and therapeutic properties [8][9][10]. This extends to metabolic properties of
Efficient synthesis of piperazinyl amides of 18β-glycyrrhetinic acid
Beilstein J. Org. Chem. 2020, 16, 798–808, doi:10.3762/bjoc.16.73
- factor is that the acidity of chloroacetic acid (pKa = 2.87) was stronger than that of acetic acid (pKa = 4.76). The procedure for the generation of byproduct 11 was similar to N-Boc-deprotection using trifluoroacetic acid. The effective synthesis of compound 10 was then explored (Table 3). In our
Asymmetric synthesis of CF2-functionalized aziridines by combined strong Brønsted acid catalysis
Beilstein J. Org. Chem. 2020, 16, 638–644, doi:10.3762/bjoc.16.60
- no enantioselectivity at all. As arylboronic acids have been harnessed to enhance the Brønsted acidity in asymmetric organocatalysis in combination with chiral diols or chiral aminoalcohols [40][41][42][43][44], we envisioned that the simultaneous use of arylboronic acids and chiral Brønsted acids
- limited Brønsted acidity of chiral phosphoric acids. Bearing this in mind, we then turned our attention to chiral disulfonimides developed by List, which have been established as a unique type of stronger Brønsted acids [45]. Putting it into practice, a range of BINOL-derived disulfonimides was used as
- attributed to the increased Brønsted acidity when the strong electron-withdrawing trifluoromethyl group was placed on the benzene ring of the arylboronic acid. Removing the boronic acid from the reaction system leads to a dramatic decrease in both yield and enantiocontrol (Table 1, entry 16). The challenge
Architecture and synthesis of P,N-heterocyclic phosphine ligands
Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35
- , Scheme 23) which could only be obtained by using a strong base such as n-BuLi for proton abstraction, probably due to a reduced acidity induced by the positive inductive effect of the substituents. The use of a weaker base such as triethylamine did not result in the targeted compounds and the authors
Why do thioureas and squaramides slow down the Ireland–Claisen rearrangement?
Beilstein J. Org. Chem. 2019, 15, 2948–2957, doi:10.3762/bjoc.15.290
- demanding ones, e.g., C6, C9 or C11. In addition, the acidity of the hydrogen-bond-donating moiety also ranges over a rather large area from pKa (H2O) 1 for phosphoric acid C10 to pKa (DMSO) 28 of diols C7 and C8. However, neither steric factors, nor the acidity of the H-bond-donor moiety seemed to play a
Small anion-assisted electrochemical potential splitting in a new series of bistriarylamine derivatives: organic mixed valency across a urea bridge and zwitterionization
Beilstein J. Org. Chem. 2019, 15, 2277–2286, doi:10.3762/bjoc.15.220
- used for anion recognition [27][28][29]. In the oxidized state, the enhanced acidity of NH protons can increase the strength of H-bonds and give them more dynamic properties, which can be useful for refined designs of supramolecular systems [30] and proton-coupled electron-transfer systems [31][32][33
- oxidation from 1 to 1+ (Supporting Information File 1, Figure S5). The enhanced acidity of the NH protons in 1b+, compared to that in 1b, was well predicted by electrostatic potential maps. The positive regions (blue) were found around the two hydrogen atoms of the urea bridge in the electrostatic potential
- 2.75 Å), primarily reflecting the absence of packing in the former. In the optimized structure of 1a+–PF6−, the N–H···F hydrogen-bonding was comparable to that in 1b+–PF6− with regard to the atomic geometry and the N···F distances. The increased acidity of 1 upon one-electron-oxidation enhances the
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