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Search for "activation" in Full Text gives 1165 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Research progress on calixarene/pillararene-based controlled drug release systems
Beilstein J. Org. Chem. 2025, 21, 1757–1785, doi:10.3762/bjoc.21.139
Approaches to stereoselective 1,1'-glycosylation
Beilstein J. Org. Chem. 2025, 21, 1700–1718, doi:10.3762/bjoc.21.133
- (Scheme 2). Switching from “disarming” ester to “arming” benzyl protecting groups, as in the donor 21, enhanced the activation of the glycosidic center, resulting in the formation of a substantial amount of the methyl glycoside by-product and a reduced yield of the 1,1'-disaccharide 22. Securing the
- coordination of the boron center with the remaining C2-OH group increases its acidity, thereby generating in situ an acidic catalyst for the activation of the glycosyl donor [62][63]. In this approach, the use of glycosyl phosphites of gluco- (35) and galacto- (38) configuration as donors, in combination with
- '-Disaccharides were also synthesized using glycosyl organoboron catalysis and employing 1,2-diols as acceptors, while activation of the glycosyl donor was facilitated by the "acidic" C2–OH group of the borinic acid-complexed acceptor moiety [63]. For instance, the phosphite donor 35 was coupled with a Man
Continuous-flow-enabled intensification in nitration processes: a review of technological developments and practical applications over the past decade
Beilstein J. Org. Chem. 2025, 21, 1678–1699, doi:10.3762/bjoc.21.132
- generated during the dilution process. While many nitration processes usually exhibit rapid kinetics, specific transformations like partial dinitration reactions demonstrate notably slower reaction rates, substantially compromising process throughput. Although thermal activation via temperature elevation
- equals . Next, the observed rate constant based on SM and HNO3, kobs, can be calculated from the slope. Then, the apparent activation energy Ea for the nitration between HNO3 with SM molecules and the pre-exponential factor A can be obtained according to the Arrhenius equation. For example, Zhang et al
- . Using the Arrhenius equation, the activation energy Ea for NO2+ attack on SM molecules and the pre-exponential factor A can be determined from the values of k* obtained at multiple temperatures. The researches for the mixed acid nitration in homogeneous systems usually conducted the kinetics study to
Structural analysis of stereoselective galactose pyruvylation toward the synthesis of bacterial capsular polysaccharides
Beilstein J. Org. Chem. 2025, 21, 1671–1677, doi:10.3762/bjoc.21.131
- 10 was formed, giving 71% yield (α/β = 1:6). According to the RRV/Aka platform [44], compound 9 is a robust nucleophile, with an Aka value of 12 [45]. This high nucleophilicity favors a SN2-like mechanism, promoting β-selectivity [46]. Using the difference in acceptor reactivity and activation method
- same reaction mixture, in situ activation of disaccharide donor 8 and acceptor 9 using TolSCl/AgOTf reagent combination was introduced. This two-step, one-pot glycosylation gave a 42% yield of disaccharide 10, maintaining good β-stereoselectivity at the galactosyl linkage (α/β = 1:5.8). The 2
- position of the galactoside using 1.3 equivalents of bis(trimethylsilyl)amine (HMDS), concurrently leaving the 3-OH group at the non-reducing end available for glycosylation with the ᴅ-Galf donor 12 [47]. After the in situ activation with TolSCl/AgOTf, product 13 was obtained with a 76% yield and exclusive
Catalytic asymmetric reactions of isocyanides for constructing non-central chirality
Beilstein J. Org. Chem. 2025, 21, 1648–1660, doi:10.3762/bjoc.21.129
- iodides (Scheme 1a) [27]. This transformation proceeded via two key steps, isocyanide insertion and desymmetric C(sp2)–H bond activation. By using phosphoramidite L1 as the chiral ligand, planar chiral pyridoferrocenes 2 were obtained in 61–99% yield with 72–99% ee. In addition, this catalytic system
- 34f could be used as the starting material to prepare the axially chiral olefin-oxazole 37, which might be a potentially useful ligand in asymmetric catalysis. A possible stereochemical model was proposed as well, involving synergistic activation of both the alkynyl ketone and isocyanoacetate by the
- catalysis, particularly with palladium and silver, has proven to be highly effective, expanding the scope as well as the activation mode of chiral catalysts could greatly enrich reaction types and accessible structural diversity. Third, further investigation into the potential applications of the resulting
Transition-state aromaticity and its relationship with reactivity in pericyclic reactions
Beilstein J. Org. Chem. 2025, 21, 1613–1626, doi:10.3762/bjoc.21.125
- aromatic character in their transition states, this increased aromaticity does not necessarily correlate with lower activation barriers. State-of-the-art computational methods on reactivity, such as the combined activation strain model (ASM)–energy decomposition analysis (EDA) method, reveal that factors
- other than aromaticity govern the barrier heights of these pericyclic reactions. Keywords: activation barrier; activation strain model; aromaticity; computational chemistry; transition state; Introduction Aromaticity is arguably one of the most fundamental and extensively studied concepts in chemistry
- conclusion by Evans in 1939 [18] indicating that “...the lowering of the activation energy arises from the increased mobility which the π electrons of such reactions possess in the TS.” Indeed, it was found, both experimentally and computationally, that the concerted pathway (i.e., involving an aromatic TS
Chemical synthesis of glycan motifs from the antitumor agent PI-88 through an orthogonal one-pot glycosylation strategy
Beilstein J. Org. Chem. 2025, 21, 1587–1594, doi:10.3762/bjoc.21.122
- in mannosyl PVB 8 (1.0 equiv) in the presence of TMSOTf as catalyst proceeded smoothly at 0 °C to room temperature, affording the α-Man-(1→3)-Man PVB disaccharide. The further coupling of the above PVB disaccharide with the poorly reactive 2-OH in mannoside 9 (0.9 equiv) under activation with NIS and
pH-Controlled isomerization kinetics of ortho-disubstituted benzamidines: E/Z isomerism and axial chirality
Beilstein J. Org. Chem. 2025, 21, 1568–1576, doi:10.3762/bjoc.21.120
- rotational barrier as in the parent chalcogen amides, regardless of whether it is in the molecular form or protonated state, and the protonation of the nitrogen atom increases the activation energy by 33–43 kJ·mol−1. To investigate how protonation affects the double-bond nature of the amidine moiety, we
- at 313 K (1.17 and 0.95 ppm), and they gradually fused as the temperature increased. The activation energy of E/Z isomerization was calculated to be 77 kJ·mol−1 from the observed coalescence temperature (Tc = 378 K). On the other hand, the two methyl signals of amidine 1 trifluoroacetate salt were
- double-bond nature of the C–N bond in the transition state of the C–N/C–C concerted rotation was decreased due to the twisted structure, and the activation energy varies depending on whether the amidine was protonated or in its molecular form (Figure 2). To investigate the effect of protonation on the
General method for the synthesis of enaminones via photocatalysis
Beilstein J. Org. Chem. 2025, 21, 1535–1543, doi:10.3762/bjoc.21.116
- indicate that the key to the success of this process is the formation of an unexplored ternary Ni-complex with 3-bromochromone and a pyridinium salt, which is crucial for the effective activation of the α,β-unsaturated system towards the nucleophilic addition. Keywords: chromones; dehalogenation
- enaminones. This transformation is simple, straightforward, and proceeds under mild conditions. Results and Discussion The initial challenge in achieving the desired reactivity was the activation of the unsaturated system towards the nucleophilic addition of the amine. The most common strategy to increase
Photoredox-catalyzed arylation of isonitriles by diaryliodonium salts towards benzamides
Beilstein J. Org. Chem. 2025, 21, 1480–1488, doi:10.3762/bjoc.21.110
- . Finally, control experiments without irradiation gave only traces of the benzamide 2aa showing no activation by the Ru complex at room temperature (Table 1, entry 24). An experiment conducted under an air atmosphere yielded only 9% of 2aa (Table 1, entry 25) indicating that the presence of atmospheric
Microwave-enhanced additive-free C–H amination of benzoxazoles catalysed by supported copper
Beilstein J. Org. Chem. 2025, 21, 1462–1476, doi:10.3762/bjoc.21.108
- ][44] and sulfamoyl chlorides [32] can perform the coupling under basic conditions, the need for the activation of the amine as an electrophilic agent generates additional waste. This reduces atom economy and indicates lower reaction efficiency. Acid-catalysed protocols have also been specifically
- temperatures were generally required for the heterogeneous catalytic reactions due to them having higher activation barriers than the homogeneous procedures. As reported in Table 3 (entry 3), excellent results were observed with the silica-supported catalyst when the reaction was performed at 80 °C for 6 hours
Wittig reaction of cyclobisbiphenylenecarbonyl
Beilstein J. Org. Chem. 2025, 21, 1454–1461, doi:10.3762/bjoc.21.107
- slightly preferred at room temperature with approximately a 3:2 ratio of figure-eight and bathtub conformations. We have also estimated the activation barriers of the interconversion of 3 and 5 between the figure-eight and bathtub conformations by measuring VT 1H NMR spectra in toluene-d8 because the
- signals due to the exo-methylene groups overlapped with the solvent signal in CD2Cl2. The thus obtained activation barriers of 3 and 5 were 11 and 12 kcal mol–1 at 263 and 253 K, respectively (Figure S27 in Supporting Information File 1). Previous DFT calculations at the B3LYP/6-31G(d) level of theory
- conformation (Sa,Sa)-A is feasible with a small activation barrier of 9.9 kcal mol−1. The figure-eight conformer (M,M)-B untwists to adopt an achiral conformation C with the exo-alkene units rotated inwards in opposite directions. These conformational changes are almost identical to those of CBBC 1. However
High-pressure activation for the solvent- and catalyst-free syntheses of heterocycles, pharmaceuticals and esters
Beilstein J. Org. Chem. 2025, 21, 1374–1387, doi:10.3762/bjoc.21.102
- hydrostatic pressure (HHP) was found to be an efficient activation method in several catalyst- and solvent-free reactions and has found application for the syntheses of heterocycles and the preparation of active pharmaceutical ingredients (APIs) via acylation and acid- and solvent-free esterification. The
- -products. A computational study accompanies the experimental data to interpret the outcome of the reactions. Keywords: acetaminophen; acetylsalicylic acid; benzimidazoles; catalyst-free synthesis; cyclization; esters; high hydrostatic pressure; pyrazoles; Introduction Non-traditional activation methods
- are one of the major driving forces in green synthesis [1][2]. High hydrostatic pressure (HHP) activation, one of such methods, is based on mechanical compression force. The typical pressure range is 2–20 kbar that is orders of magnitude greater than the conditions traditionally employed in chemistry
Oxetanes: formation, reactivity and total syntheses of natural products
Beilstein J. Org. Chem. 2025, 21, 1324–1373, doi:10.3762/bjoc.21.101
- (176, X = NHBoc or NHCbz) is allowed to cyclise into a lactam. 3 Reactions of oxetanes 3.1 Ring-opening reactions The inherent ring strain of oxetanes and its polarised C–O bonds allow for relatively facile ring-opening reactions, typically upon a Lewis-acid activation. This type of reactivity has been
Recent advances in amidyl radical-mediated photocatalytic direct intermolecular hydrogen atom transfer
Beilstein J. Org. Chem. 2025, 21, 1306–1323, doi:10.3762/bjoc.21.100
- activation energy modulation during transition state formation. Specifically, donor/acceptor electronic configurations in the substrate could either stabilize or destabilize the transient hybrid state, thereby thermodynamically governing the energy barrier for intermolecular HAT progression. When the partial
- demonstrated the homolytic cleavage of the N–O bond using N-(tert-butyl)-O-(1-phenylvinyl)-phenylhydroxyamide as a HAT reagent [78][79]. This compound was capable of initiating the formation of amidyl radicals through visible light activation. Although their controlled experiments showed that this method was
- across diverse bond activation challenges, particularly in C(sp³)–H, C(sp²)–H, S–H, Ge–H, and B–H bond transformations. The proposed system architecture emphasizes synergistic reagent cooperation rather than isolated component performance, representing a paradigm shift in photoredox catalysis design
Recent advances and future challenges in the bottom-up synthesis of azulene-embedded nanographenes
Beilstein J. Org. Chem. 2025, 21, 1272–1305, doi:10.3762/bjoc.21.99
- ]. Interestingly, initial attempts to convert 65 into 66 using various procedures for the palladium-catalysed C–H activation were unsuccessful, even when conducted at elevated temperatures. However, treatment of 65 with KOH in refluxing quinoline successfully yielded the desired PAH 66, albeit in a modest 15
Recent advances in oxidative radical difunctionalization of N-arylacrylamides enabled by carbon radical reagents
Beilstein J. Org. Chem. 2025, 21, 1207–1271, doi:10.3762/bjoc.21.98
- -coupling, using Cp2Fe-catalyzed electrochemical oxidation. This method leveraged the selective activation of the acidic α-C–H bond within the 1,3-dicarbonyl moiety to generate a carbon-centered radical, which was crucial for the subsequent cyclization. The reaction was carried out under reflux conditions
- quinolinone products. Beyond electrochemical protocols, photochemical activation – particularly visible-light photoredox catalysis – has become a powerful and sustainable strategy for generating carbon radicals under mild conditions. In 2023, Fan’s group discovered a radical cyclization of N-arylacrylamides
- with α-aminoalkyl radicals generated from tertiary arylamines using photoredox catalysis (Scheme 13) [9]. In this system, Ir[dF(CF3)ppy]2(dtbbpy)PF6 was used as a photosensitizer to trigger the α-C–H activation of N,N-dimethylaniline, generating an alkyl radical under 30 W blue LED (454 nm) irradiation
Enhancing chemical synthesis planning: automated quantum mechanics-based regioselectivity prediction for C–H activation with directing groups
Beilstein J. Org. Chem. 2025, 21, 1171–1182, doi:10.3762/bjoc.21.94
- molecular architectures in pharmaceuticals, polymers, and agrochemicals. Despite advancements in directing group (DG) methodologies and computational approaches, predicting accurate regioselectivity in C–H activation poses significant difficulties due to the diversity and complexity of organic compounds
- . This study introduces a novel quantum mechanics-based computational workflow tailored for the regioselective prediction of C–H activation in the presence of DGs. Utilizing (semi-empirical) quantum calculations hierarchically, the workflow efficiently predicts outcomes by considering concerted
- metallation deprotonation mechanisms mediated by common catalysts like Pd(OAc)2. Our methodology not only identifies potential activation sites but also addresses the limitations of existing models by including a broader range of directing groups and reaction conditions while maintaining moderate
Recent advances in synthetic approaches for bioactive cinnamic acid derivatives
Beilstein J. Org. Chem. 2025, 21, 1031–1086, doi:10.3762/bjoc.21.85
- ) reported a carboxyl group activation of cinnamic acid (7) by applying pivalic anhydride in a single step to afford the corresponding amide 8 in excellent yield (Scheme 3B) [35]. Moreover, pivalic anhydride is easier to handle than its chloride counterpart. Wang and co-workers (2022) utilized 5-nitro-4,6
- could be recycled by adding POCl3 and KSCN, thus promoting the reagent’s sustainability by reducing waste. Carboxyl group activation can also be achieved by using triazine-based reagents. For example, Saberi and Salimiyan (2019) applied 2,4,6-trichloro-1,3,5-triazine (TCT) to perform amidation of
- cinnamic acid (7) and N,N’-dimethylformamide (DMF)-mediated by POCl3 via acid chloride 36 formation (Scheme 20) [52]. On top of the carboxyl activation approaches demonstrated above, O/N-acylation could also be achieved by employing an electrophilic alkylating agent by exploiting the nucleophilicity of the
Pd-Catalyzed asymmetric allylic amination with isatin using a P,olefin-type chiral ligand with C–N bond axial chirality
Beilstein J. Org. Chem. 2025, 21, 1018–1023, doi:10.3762/bjoc.21.83
- Education, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan Molecular Chirality Research Center, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan Soft Molecular Activation Research Center, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan Institute for
Recent total synthesis of natural products leveraging a strategy of enamide cyclization
Beilstein J. Org. Chem. 2025, 21, 999–1009, doi:10.3762/bjoc.21.81
- first report by Stork in the 1950s [1][2][3]. Compared with enols, enamines benefit from the lone pair of electrons on the nitrogen atom, which enhances the nucleophilicity of the alkene, enabling it to react with a broad range of electrophiles. This activation mode of carbonyl compounds has been so
On the photoluminescence in triarylmethyl-centered mono-, di-, and multiradicals
Beilstein J. Org. Chem. 2025, 21, 964–998, doi:10.3762/bjoc.21.80
- , hinting at the type of non-radiative decay pathways in these molecules [63]. For medium strong donors the Gibbs energy of activation ΔGCT‡ for crossing over into the CT state is low, and emission can occur from here with high ϕ (see point 2 in Figure 9). For strong donors, ΔGCT‡ is close to 0 allowing
Silver(I) triflate-catalyzed post-Ugi synthesis of pyrazolodiazepines
Beilstein J. Org. Chem. 2025, 21, 915–925, doi:10.3762/bjoc.21.74
- ) [46]. In 2019, Li, Yang, Van der Eycken and co-workers reported a modification of this strategy relying on thermal activation instead of cationic gold catalysis [47]. The approach worked particularly well with substrates featuring terminal alkynes. Inspired by these developments and taking into
- heteroannulation leading to the pyrazolo[1,5-a][1,4]diazepine scaffold. Our initial choice was to investigate the use of silver(I) triflate (AgOTf) as a catalyst in toluene, given its previously demonstrated efficiency in various transformations involving the activation of triple bonds towards nucleophilic attack
- . The first step, the Ugi-4CR, introduces molecular diversity, while the second step, an efficient silver(I)-catalyzed heteroannulation, facilitates the formation of the pyrazolodiazepine core via alkyne activation towards the nucleophilic attack by the pyrazole nitrogen. This strategy expands the array
Recent advances in controllable/divergent synthesis
Beilstein J. Org. Chem. 2025, 21, 890–914, doi:10.3762/bjoc.21.73
- pathway bifurcated based on the steric demands of Si–C-bond activation. The methyl-substituted ligand (S)-8H-binaphthyl phosphoramidite L4, featuring a spacious cavity, favored sterically encumbered Si–C(sp3)-bond activation, selectively delivering axially chiral (S)-1-silacyclohexenyl arenes 17 with high
- enantiocontrol. Conversely, the bulky tert-butyl-decorated (R)-spirophosphoramidite L5 imposed a confined cavity, steering selectivity toward Si–C(sp2)-bond activation and predominantly afforded the regioisomeric (S)-2-silacyclohexenylarenes 18. In 2025, Gong and co-workers reported a visible-light-mediated
- species Int-44. This reactive intermediate then engages with a Ti(IV)-enolate complex through radical recombination, ultimately delivering 2-aza-bicyclo[3.1.1]heptene (BCHepe) while regenerating the Ti(III) catalyst to complete the catalytic cycle. (2) Scandium-catalyzed pathway: Activation of the donor
Light-enabled intramolecular [2 + 2] cycloaddition via photoactivation of simple alkenylboronic esters
Beilstein J. Org. Chem. 2025, 21, 854–863, doi:10.3762/bjoc.21.69
- facilitated landmark organic transformations, such as the venerable Paternò–Büchi [6][7][8], Norrish–Yang [9][10][11], and enone–alkene cycloadditions [12][13][14], that proceed via the generation of a singlet or triplet diradical through the activation of an unsaturated bond [2][14]. While these seminal
- contributions have enabled the efficient activation of carbonyl and alkene moieties, the inability of most organic molecules to efficiently absorb photons at longer wavelengths often preclude their use in direct excitation strategies, requiring unique experimental set ups and light sources that are
- activation of polyboronated alkenes [51] and β-borylstyrenes [43][48], was ineffective and no reactivity was observed. Implementing a higher energy iridium sensitizer (≈60 kcal/mol) was also unsuccessful (Table 1, entry 2), however, employing thioxanthone (65 kcal/mol) demonstrated efficient activation of
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