Hypervalent iodine-mediated intramolecular alkene halocyclisation

• Charu Bansal,
• Oliver Ruggles,
• Albert C. Rowett and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 3113–3133, doi:10.3762/bjoc.20.258

• 4 [9][10] (Figure 1). Halogenated cyclised structures have also been found to exhibit medicinal and pharmaceutical properties, including antibacterial [11], antibiotic [12], and enzyme inhibition [13] among others. The general mechanism for the HVI-mediated halocyclisation of alkenes proceeds

• -, stereo-) of the reaction, which is influenced by the type of HVI reagent, the nature of the substrates employed and the proposed mechanism from the authors are all described. The halocyclisation of alkenes to make halogenated carbo or heterocycles is yet to be covered by a review, which is the vacancy

• good yields, demonstrating the scope of the reaction. The authors proposed an alternative reaction mechanism to those already described, in which trans-aminopalladation of the alkene, mediated by Pd(II), occurs with intramolecular attack of the nitrogen on the terminal carbon, generating a 6-membered

Advances in the use of metal-free tetrapyrrolic macrocycles as catalysts

• Mandeep K. Chahal

Beilstein J. Org. Chem. 2024, 20, 3085–3112, doi:10.3762/bjoc.20.257

• active groups for a variety of substrates, making their use as supramolecular organocatalysts based on bifunctional activation mechanism (hydrogen-bonding/Lewis basicity) highly promising. At the same time, additional functional groups that are required for the catalysis can be easily installed on the

• ]pyrrole α,β-isomer 4 was found to be catalytically active providing a 57% conversion to 10, suggesting a concerted cycloaddition mechanism. Calix[4]pyrrole α,α-isomer 3 and dipyrromethane 5 were catalytically inactive. The authors concluded that the catalytic inactivity of 3 is caused by the parallel

• , with TBAI as a co-catalyst, up to 74% yields (Table 1). The inactivity of porphyrin 18 was attributed to the inaccessibility of the inner core imine due to its planar structure. The mechanism of the epoxide ring-opening reaction was elucidated by DFT calculations, which suggested that the macrocycle

Synthesis of the 1,5-disubstituted tetrazole-methanesulfonylindole hybrid system via high-order multicomponent reaction

• Cesia M. Aguilar-Morales,
• América A. Frías-López,
• Nadia V. Emilio-Velázquez,
• Alejandro Islas-Jácome,
• Angelica Judith Granados-López,
• Jorge Gustavo Araujo-Huitrado,
• Yamilé López-Hernández,
• Hiram Hernández-López,
• Luis Chacón-García,
• Jesús Adrián López and
• Carlos J. Cortés-García

Beilstein J. Org. Chem. 2024, 20, 3077–3084, doi:10.3762/bjoc.20.256

• chemistry and optical science. A plausible reaction mechanism for the formation of the target molecules 18a–n via a high-order multicomponent reaction is shown in Scheme 3 and consists of two processes: an Ugi-azide reaction and a Pd/Cu-catalyzed heteroannulation reaction. The Ugi-azide reaction mechanism

• cytotoxic compounds. For example, a cytotoxic effect was found in CAL 27 cells, presumably through a mechanism of TNF-α inhibition in vitro, which could be related to the anti-inflammatory effect identified in several studies of NSAIDs that inhibit cancer cell viability in vitro [37][38]. In another study

• aimed at inhibiting tubulin assembly, N-mesyl-2-(1-phenylvinyl)indoles were active against HCT-116 cells on the order of a GI50 of 10 mM, although the mechanism originally sought was not demonstrated [39]. Therefore, in this work, the cytotoxic activity of methanesulfonylindoles 18a–j was explored

Enantioselective regiospecific addition of propargyltrichlorosilane to aldehydes catalyzed by biisoquinoline N,N’-dioxide

• Noble Brako,
• Sreerag Moorkkannur Narayanan,
• Amber Burns,
• Layla Auter,
• Valentino Cesiliano,
• Rajeev Prabhakar and
• Norito Takenaka

Beilstein J. Org. Chem. 2024, 20, 3069–3076, doi:10.3762/bjoc.20.255

• ][34]. In sharp contrast, propargyltrichlorosilane is configurationally stable and only reacts through the SE2’ mechanism under Lewis base-catalyzed conditions [43][44][45], although it was reported that distillation of propargyltrichlorosilane substantially isomerizes it to the thermodynamically more

• structure–enantioselectivity relationship is exactly opposite to that for the analogous allylation reaction reported by Nakajima [47], thus it raises a possibility that the asymmetric induction mechanism could be fundamentally different between the present allenylation with propargyltrichlorosilane and the

• study, Hoveyda and co-workers proposed a similar mechanism for the isomerization of alkynes to allenes catalyzed by 1,8-diazabicyclo[5.4.0]undec-7-ene [61]. Conclusion In this study, we prepared distilled propargyltrichlorosilane with >99% isomeric purity for the first time, developed its asymmetric

Chemical structure metagenomics of microbial natural products: surveying nonribosomal peptides and beyond

• Thomas Ma and
• John Chu

Beilstein J. Org. Chem. 2024, 20, 3050–3060, doi:10.3762/bjoc.20.253

• molecules were screened for various bioactivities and led to the discovery of new antibiotics, antifungals, as well as anticancer compounds (Figure 4). Importantly, the underlying mechanism of bacterial growth suppression has been identified for several Syn-BNP antibiotics, which includes both general mode

• herein are hits from various bioactivity screens. For each Syn-BNP, its name is in bold, the microorganism that harbors the corresponding BGC is italicized, followed by its bioactivity and the target/mechanism of action (if known). a) “Offloading” is the final step of NRP biosynthesis, wherein the mature

Cyclodextrin-based rotaxanes for polymer materials: challenge on simultaneous realization of inexpensive production and defined structures

• Yosuke Akae

Beilstein J. Org. Chem. 2024, 20, 3026–3049, doi:10.3762/bjoc.20.252

Advances in radical peroxidation with hydroperoxides

• Oleg V. Bityukov,
• Pavel Yu. Serdyuchenko,
• Andrey S. Kirillov,
• Gennady I. Nikishin,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2024, 20, 2959–3006, doi:10.3762/bjoc.20.249

• colleagues firstly demonstrated that the decomposition of tert-butyl hydroperoxide (TBHP) by Co(II) naphthenate proceeds via a chain mechanism, leading to the formation of tert-butoxy and tert-butylperoxy radicals (Scheme 4) [24]. When cyclohexene (1) and oct-1-ene (3) were added, the corresponding products

• -t-Bu)2. Allylic peroxidation of 3-substituted prop-1-ene-1,3-diyldibenzenes 8 was performed with TBHP as the oxidant/peroxidation agent and with Cu2O as the catalyst [42] (Scheme 6). The proposed mechanism of peroxides 9 formation does not include peroxo–copper complexes and begins with the

• peroxidation of 31 with the formation of products 32 can be achieved as both using Cu-catalysis and in metal-free conditions (Scheme 13). The metal-free peroxidation with TBHP was also demonstrated using 3,4-dihydro-1,4-benzoxazin-2-ones 33 as substrates (Scheme 13) [54]. The assumed mechanism of the target

Structure and thermal stability of phosphorus-iodonium ylids

• Andrew Greener,
• Stephen P. Argent,
• Coby J. Clarke and
• Miriam L. O’Duill

Beilstein J. Org. Chem. 2024, 20, 2931–2939, doi:10.3762/bjoc.20.245

• correspond to a geometric rearrangement, e.g., Berry pseudorotation, which occurs prior to decomposition [31]. A large dihedral angle φ is thought to facilitate this rearrangement, thus accelerating decomposition [38][39]. Decomposition mechanism Further analysis was carried out to gain a better

• understanding of the decomposition mechanism. Despite large differences in Tonset, most samples showed relatively consistent second decomposition steps at ca. 225 °C (Figure 3b), which is indicative of a common decomposition intermediate for all compounds. To investigate this common intermediate, ex-situ mass

• heated to temperature T2 (136–205 °C, see Supporting Information File 1) until 20–40% mass loss of original weight. Based on this data, the following decomposition mechanism is proposed (Figure 4a): MS, 1H and 31P NMR analysis after heating to T1 showed the presence of (methyloxycarbonylmethyl

Recent advances in transition-metal-free arylation reactions involving hypervalent iodine salts

• Ritu Mamgain,
• Kokila Sakthivel and
• Fateh V. Singh

Beilstein J. Org. Chem. 2024, 20, 2891–2920, doi:10.3762/bjoc.20.243

• presence of fluorine and a newly installed electron-deficient aryl group on α-carbon which increases electrophilicity of the α-carbon center [55]. The proposed reaction mechanism (Scheme 2) begins with the formation of one of two potential iodine intermediates, labeled as I or II. These intermediates arise

• absence of a base. Additionally, the presence of 40 equivalents of water proved to be crucial for the reaction, as altering the amount of water significantly impacted the product yield, indicating the importance of water in the reaction mechanism. A diverse range of functionalized diaryliodonium salts

• mechanism by adding 2 equivalents of TEMPO to the reaction mixture. The absence of the desired product indicated the involvement of a radical pathway in the process. The proposed reaction mechanism begins with the activation of eosin Y by visible light from 5 W blue LEDs, transitioning it to its excited

Synthesis of pyrrole-fused dibenzoxazepine/dibenzothiazepine/triazolobenzodiazepine derivatives via isocyanide-based multicomponent reactions

• Marzieh Norouzi,
• Mohammad Taghi Nazeri,
• Ahmad Shaabani and
• Behrouz Notash

Beilstein J. Org. Chem. 2024, 20, 2870–2882, doi:10.3762/bjoc.20.241

• analysis, mass spectrum, and IR are consistent with the structure (for details see Supporting Information File 1). Finally, a single crystal X-ray analysis of compound 6a was performed, confirming the structure (Figure 4). The proposed mechanism for an isocyanide-based multicomponent domino reaction for

• mmol) under solvent-free conditions, stirring in an oil bath at 80 °C for 2 h (monitored by TLC). A suggested mechanism for compounds 4. Synthesis of pyrrole-fused dibenzoxazepine/triazolobenzodiazepine through a 4-CR. Gram-scale synthesis of pyrrole-fused dibenzoxazepine/triazolobenzodiazepine 4a and

N-Glycosides of indigo, indirubin, and isoindigo: blue, red, and yellow sugars and their cancerostatic activity

• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 2840–2869, doi:10.3762/bjoc.20.240

Synthesis of tricarbonylated propargylamine and conversion to 2,5-disubstituted oxazole-4-carboxylates

• Kento Iwai,
• Akari Hikasa,
• Kotaro Yoshioka,
• Shinki Tani,
• Kazuto Umezu and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2024, 20, 2827–2833, doi:10.3762/bjoc.20.238

• results, a plausible mechanism was proposed, as shown in Scheme 3a. The 5-exo-dig ring closure is induced by O-attack of the amide moiety on the ethynyl group to form 6, during which a stoichiometric proton source (water in the solvent) is necessary. Subsequently, one of the ethoxycarbonyl groups at the 4

• mechanism, as illustrated in Scheme 3b [13][14], we cannot negate this mechanism because the reaction media and bases were different. PCPA 4a was heated in the presence of methanesulfonic acid to undergo 6-endo-dig cyclization. However, hydration predominantly occurred, converting the ethynyl group to a

Investigation of a bimetallic terbium(III)/copper(II) chemosensor for the detection of aqueous hydrogen sulfide

• Parvathy Mini,
• Michael R. Grace,
• Genevieve H. Dennison and
• Kellie L. Tuck

Beilstein J. Org. Chem. 2024, 20, 2818–2826, doi:10.3762/bjoc.20.237

• for the detection of both gaseous and/or aqueous H2S are shown in Figure 1 [12][16][17]. These sensors all function via the copper sequestration mechanism, where upon addition of hydrogen sulfide to the quenched bimetallic species, luminescence modulation occurs. In our quest for highly selective

Synthesis and antimycotic activity of new derivatives of imidazo[1,2-a]pyrimidines

• Dmitriy Yu. Vandyshev,
• Daria A. Mangusheva,
• Khidmet S. Shikhaliev,
• Kirill A. Scherbakov,
• Oleg N. Burov,
• Alexander D. Zagrebaev,
• Tatiana N. Khmelevskaya,
• Alexey S. Trenin and
• Fedor I. Zubkov

Beilstein J. Org. Chem. 2024, 20, 2806–2817, doi:10.3762/bjoc.20.236

• maleimides or N-arylitaconimides. The mechanism of the studied processes was postulated basing on experimental data, HPLC–MS analysis of reaction mixtures, and quantum chemical calculations. Molecular docking results of the obtained imidazo[1,2-a]pyrimidines, when compared with voriconazole, a drug already

• -spectrum antifungal agents. Among the many drugs and hits, the azole-based systems (including triazoles and imidazoles) are of particular importance in this context. Their mechanism of action is the inhibition of the activity of the enzyme lanosterol 14α-demethylase (CYP51), which is encoded by the CYP51

• method of controlling fungal infections. The mechanism of inhibition of azoles and their derivatives is based on the formation of a coordination bond between their heterocyclic nitrogen atom, which carries an unshared electron pair, and the haem iron atom. The formation of this bond leads to inhibition

Mechanochemical difluoromethylations of ketones

• Jinbo Ke,
• Pit van Bonn and
• Carsten Bolm

Beilstein J. Org. Chem. 2024, 20, 2799–2805, doi:10.3762/bjoc.20.235

• , proceeding through a five-membered transition state. To clarify the mechanism, two experiments were conducted. In the first one, 2-acetonaphthone with a trideuteromethyl group (1i-d3) was subjected to the standard reaction conditions. Two products were obtained: First, 3i-d2 containing a CF2H group, and

• yields were determined by 1H NMR spectroscopy using 1,2-dichloroethane as the internal standard. In parentheses: yields after column chromatography (with product purities of ca. 90%). aWith CsCl. bWith KCl. Proposed mechanism (A) and mechanistic investigations (B and C). The yields were determined by 1H

Access to optically active tetrafluoroethylenated amines based on [1,3]-proton shift reaction

• Yuta Kabumoto,
• Eiichiro Yoshimoto,
• Bing Xiaohuan,
• Masato Morita,
• Motohiro Yasui,
• Shigeyuki Yamada and
• Tsutomu Konno

Beilstein J. Org. Chem. 2024, 20, 2776–2783, doi:10.3762/bjoc.20.233

• ]-proton shift reaction in this study is expected to proceed via the reaction mechanism reported by Soloshonok [25][26][27][28][29][30][31][32], as shown in Scheme 6. First, DBU interacts with the benzylic hydrogen of the imine (R)-16, and this hydrogen is about to be abstracted as a proton. This hydrogen

• reaction mechanism. Investigation of the reaction conditions. Supporting Information Supporting Information File 3: Full experimental details, 1H, 13C, 19F NMR spectra of 16a–g and 23a–g, and HPLC charts of racemic as well as chiral compounds 23a–g. Supporting Information File 4: Crystallographic

Copper-catalyzed yne-allylic substitutions: concept and recent developments

• Shuang Yang and
• Xinqiang Fang

Beilstein J. Org. Chem. 2024, 20, 2739–2775, doi:10.3762/bjoc.20.232

• mechanism and relatively harsh reaction conditions such as anhydrous, anaerobic, and low temperatures are usually required (Scheme 1a). Therefore, using stabilized nucleophiles in Cu-catalyzed allylic substitutions is a tremendous challenge. On the other hand, since the pioneering work of van Maarseveen [52

• ] and Nishibayashi [53] groups in 2008, Cu-catalyzed asymmetric propargylic substitutions have made significant progress [54][55][56][57][58][59][60]. The protocol allows the use of stabilized nucleophiles via the outer-sphere mechanism, and the copper allenylidene intermediate formed by copper and

• chelation interaction between the enolate derived from acyclic 1,3-dicarbonyl compounds and copper (Scheme 5, 8a–j). Detailed control experiments indicate that the terminal alkyne moiety is critical and the reaction proceeds through an SN1 mechanism. An outer-sphere nucleophilic attack through copper

Synthesis of spiroindolenines through a one-pot multistep process mediated by visible light

• Francesco Gambuti,
• Jacopo Pizzorno,
• Chiara Lambruschini,
• Renata Riva and
• Lisa Moni

Beilstein J. Org. Chem. 2024, 20, 2722–2731, doi:10.3762/bjoc.20.230

• . Repeating the reaction on 500 mg for a longer reaction time a notable 68% isolated yield of 3d was obtained (Table 3, entry 2). These slightly different conditions were applied to the gram scale synthesis of 3a obtaining good results (Table 3, entry 3). To obtain some information of the reaction mechanism

• and highly reactive BrCCl3 radical anion. Anyway, the N-Ph-THIQ can undergo numerous pathways towards the iminium ion 1a (see reference [28] for details). The oxidation of compound 2d may occur according to the same mechanism. However, alternative mechanisms, such as the direct hydride transfer from

• mechanism. Initial investigation of the GO-promoted oxidation/3C-Ugi reaction process. Investigation of the one-pot four-step synthesis of spiro[indole-THIQ] 3a. Gram scale reaction for the synthesis of spiro[indole-THIQs] 3. Supporting Information Supporting Information File 22: Additional optimization

Synthesis of benzo[f]quinazoline-1,3(2H,4H)-diones

• Ruben Manuel Figueira de Abreu,
• Peter Ehlers and
• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 2708–2719, doi:10.3762/bjoc.20.228

• -dioxane/water 5:1, 100 °C, 1 h. Scope and isolated yields of the synthesis of 5. Reaction conditions: 4 (1 equiv), p-TsOH·H2O (20 equiv), toluene, 100 °C, 4 h. Proposed reaction mechanism of the cyclisation with N,N-dimethylanilino functional groups. Optimization of the synthesis of 5a. Photophysical data

Computational design for enantioselective CO₂ capture: asymmetric frustrated Lewis pairs in epoxide transformations

• Maxime Ferrer,
• Iñigo Iribarren,
• Tim Renningholtz,
• Ibon Alkorta and
• Cristina Trujillo

Beilstein J. Org. Chem. 2024, 20, 2668–2681, doi:10.3762/bjoc.20.224

• noted previously [51][52], the reaction depicted in Scheme 1 can proceed via two distinct mechanisms. In the first mechanism, the catalyst initiates epoxide opening, followed by CO2 insertion. The second mechanism suggests that CO2 activation by the catalyst precedes its transfer to the epoxide. To

• determine the more feasible mechanism, a comprehensive investigation of both possibilities was conducted. To determine the most probable mechanism within our system, the capture of CO2 and a symmetric epoxide (E) using the FLP proposed by Stephan et al. [37] was evaluated (Scheme 2). A symmetric epoxide was

• initial study, it can be concluded that the mechanism for our system proceeds according to mechanism two. The following simulations were performed on this conclusion. Regioselectivity PO exhibits two distinct electrophilic sites, which can be subject to nucleophilic attack (Figure 2B). Thus, the

Transition-metal-free decarbonylation–oxidation of 3-arylbenzofuran-2(3H)-ones: access to 2-hydroxybenzophenones

• Bhaskar B. Dhotare,
• Seema V. Kanojia,
• Chahna K. Sakhiya,
• Amey Wadawale and
• Dibakar Goswami

Beilstein J. Org. Chem. 2024, 20, 2655–2667, doi:10.3762/bjoc.20.223

• temperature proved to be advantageous compared to the reported Ni-catalyzed decarbonylation–oxidation method of benzofuranones [2]. Next, to elucidate the mechanism of the decarbonylation–oxidation reaction of 3-arylbenzofuran-2(3H)-ones 3aa–ka, control experiments were performed. The fact that the reaction

• proceeded well only in solvents which can produce hydroperoxides in situ, we hypothesized that hydroperoxides have a pivotal role in the reaction mechanism. In order to confirm that the reaction proceeds through a radical mechanism, the decarbonylation–oxidation reaction of 3ba was performed in the presence

• insertion of the hydroperoxide into the substrate leading to the decrease in the –O–OH peak. An increase in the peak at δ 9.6 ppm indicated the formation of a phenolic moiety over time. Based on these observations, a plausible reaction mechanism is proposed (Figure 5). Proton abstraction followed by

Deciphering the mechanism of γ-cyclodextrin’s hydrophobic cavity hydration: an integrated experimental and theoretical study

• Stiliyana Pereva,
• Stefan Dobrev,
• Tsveta Sarafska,
• Valya Nikolova,
• Silvia Angelova,
• Tony Spassov and
• Todor Dudev

Beilstein J. Org. Chem. 2024, 20, 2635–2643, doi:10.3762/bjoc.20.221

• light on the mechanism of the γ-CD hydration and to address some unanswered questions: (i) what are the preferable locations for water molecules in the macrocyclic cavity (“hot spots”); (ii) what are the major factors contributing to the stability of the water cluster in the CD interior; (iii) what type

• of interactions (i.e., water–water and/or water–CD walls) contribute to the stability of the water assemble; (iv) how does the mechanism of the γ-CD hydration compare with those of its α-CD and β-CD counterparts. Keywords: cyclodextrin; DFT calculation; DSC/TG; hydration; thermodynamic

• the mechanism of its hydration is still a matter of controversial discussion. Too much of a surprise for the scientific community, it has been reported that γ-CD, having the largest cavity (≈9–10 Å in inner diameter) compared to α-CD and β-CD (≈5–6 and ≈7–8 Å in inner diameter, respectively [1][15][16

Applications of microscopy and small angle scattering techniques for the characterisation of supramolecular gels

• Connor R. M. MacDonald and
• Emily R. Draper

Beilstein J. Org. Chem. 2024, 20, 2608–2634, doi:10.3762/bjoc.20.220

• the mechanism of aggregation is further exemplified by Jones et al. [44]. It was shown that SEM could directly observe structural defects, resulting in the collapse of helically braided structures into their constituent fibrils which can interact with other fibres (Figure 10). The branching density

• , a potential mechanism could be identified which allows for the directed design of compounds which form mechanoresponsive aggregates, by indicating that a focus on increased fibre length is required. Information at longer length scales may be lost due to the limited q range provided by SANS

Efficient modification of peroxydisulfate oxidation reactions of nitrogen-containing heterocycles 6-methyluracil and pyridine

• Alfiya R. Gimadieva,
• Yuliya Z. Khazimullina,
• Aigiza A. Gilimkhanova and
• Akhat G. Mustafin

Beilstein J. Org. Chem. 2024, 20, 2599–2607, doi:10.3762/bjoc.20.219

• not increase the yield of pyridine 11 further (Table 2). Despite the numerous works in the field of peroxydisulfate oxidation, there is still no unified view of the reaction mechanism. Consequently, in [31], the assumption of an electrophilic substitution mechanism for the Elbs and Boyland–Sims

• the amino group is involved in the formation of an intermediate hydroxylamine derivative. Scheme 3 demonstrates a possible reaction mechanism using the example of the peroxydisulfate oxidation of MU and TMU catalyzed by PcM. It is proposed that PcM provides the necessary polarization of peroxydi(mono

• , 24% NaOH, 45 °C, PcM; b) (NH4)2S2O8, 24% NaOH, 45 °C, H2O2; c) HCl, 85–95 °C. Potential mechanism of peroxydisulfate oxidation of 6-methyluracil and 1,3,6-trimethyluracil. Yield dependence of 1,3,6-trimethyluracil-5-ammonium sulfate (5) on the amount and type of catalyst.a Yield dependence of

Base-promoted cascade recyclization of allomaltol derivatives containing an amide fragment into substituted 3-(1-hydroxyethylidene)tetronic acids

• Andrey N. Komogortsev,
• Constantine V. Milyutin and
• Boris V. Lichitsky

Beilstein J. Org. Chem. 2024, 20, 2585–2591, doi:10.3762/bjoc.20.217

• additional nitrogen atoms in compounds 4 leads to the fact that the other tautomeric form becomes more favorable. A proposed mechanism of the investigated recyclization is presented in Scheme 4. Initially, imidazolide A is formed via condensation of the starting amide 3 with CDI. Then, intermediate A

• : 3a (1 mmol), CDI (0.49 g, 3 mmol), DBU (0.17 g, 1.1 mmol), MeCN (7 mL). Proposed reaction mechanism for the formation of products 4. Synthesis of derivatization products 7 and 9. Optimization of the reaction conditionsa. Supporting Information Supporting Information File 141: General information