Generation of multimillion chemical space based on the parallel Groebke–Blackburn–Bienaymé reaction

• Evgen V. Govor,
• Vasyl Naumchyk,
• Ihor Nestorak,
• Dmytro S. Radchenko,
• Dmytro Dudenko,
• Yurii S. Moroz,
• Olexiy D. Kachkovsky and
• Oleksandr O. Grygorenko

Beilstein J. Org. Chem. 2024, 20, 1604–1613, doi:10.3762/bjoc.20.143

• yellow. Distribution of maximal values among pairwise-calculated Tanimoto similarities T (MFP2 fingerprints [46]) of extended Bemis–Murcko scaffolds for the generated chemical space members (5.60 Mln. scaffolds) to the extended Bemis–Murcko scaffolds of A) ChEMBL compounds (v. 33); B) PubChem compounds

• ) comparative analysis of 50,000 randomly selected molecules picked from the generated chemical space and A) ChEMBL compounds; B) PubChem compounds; C) ZINC15 compounds; and D) enamine’s stock screening collection. Some biologically active representatives of the generated GBB chemical space found in the ChEMBL

• database. Groebke–Blackburn–Bienaymé (GBB) reaction. A) Parallel GBB reaction and B) examples of library members 4 obtained (relative configurations are shown). Supporting Information The Supporting Information for this article contains structures of reactants 1–3, experimental details on the parallel

Supramolecular assemblies of amphiphilic donor–acceptor Stenhouse adducts as macroscopic soft scaffolds

• Ka-Lung Hung,
• Leong-Hung Cheung,
• Yikun Ren,
• Ming-Hin Chau,
• Yan-Yi Lam,
• Takashi Kajitani and
• Franco King-Chi Leung

Beilstein J. Org. Chem. 2024, 20, 1590–1603, doi:10.3762/bjoc.20.142

• solution (20 μM). (a) DA11, (c) DA7, (e) DA6 solutions in the beginning (black line), upon 625-nm irradiation over the course of 1 min (orange lines), and after irradiation to reach the PSS (red line). (b) DA11, (d) DA7, (f) DA6 upon thermal back reaction over the course of 60 min at 20 °C (cyan lines) and

• 400–480 nm area), (b) DA7 (inset: enlarged 275–290 nm area), (c) DA6 (inset: enlarged 430–490 nm area) in the beginning (black line), upon white-light irradiation over the course of 60 min (orange lines), and after 60 min (red line). Irradiation was carried out at 20 °C using a light-guide-equipped

• BBZM-I xenon light source (380–800 nm, 300 W) positioned at a distance of 1 cm from the sample. TEM images of freshly prepared aqueous solutions before irradiation of (a) DA11 (0.25 wt %, 4.1 mM), (c) DA7 (0.25 wt %, 4.5 mM), and (e) DA6 (0.25 wt %, 4.6 mM). The solutions of (b) DA11, (d) DA7, and (f

Regio- and stereochemical stability induced by anomeric and gauche effects in difluorinated pyrrolidines

• Ana Flávia Candida Silva,
• Francisco A. Martins and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2024, 20, 1572–1579, doi:10.3762/bjoc.20.140

• Gaussian 16 package of software [24]. a) Pseudoequatorial and pseudoaxial conformations of pyrrolidine. b) Cis- and trans-isomers of 3-fluoropyrrolidine. Flat representations of 2,3-, 3,4-, and 2,4-difluoropyrrolidines. The potential effects resulting from the addition of a second 1,2- or 1,3-fluorine atom

• the CCSD structure is 20.3316. “a” denotes DGTZVP and “b” denotes 6-311++G**. Exhaustive illustration of all conformational, configurational, and constitutional isomers of difluorinated pyrrolidine, illustrating the relative orientation of the C–F and N–H bonds used to build the input geometry for the

Electrocatalytic hydrogenation of cyanoarenes, nitroarenes, quinolines, and pyridines under mild conditions with a proton-exchange membrane reactor

• Koichi Mitsudo,
• Atsushi Osaki,
• Haruka Inoue,
• Eisuke Sato,
• Naoki Shida,
• Mahito Atobe and
• Seiji Suga

Beilstein J. Org. Chem. 2024, 20, 1560–1571, doi:10.3762/bjoc.20.139

• ) a PEM reactor and (b) MEA. Hypothesis of the trap of quinoline on membrane and tetrahydroquinoline and the effect of adding an acid. Recycled use of MEA for the electroreduction of 6a in the presence of PTSA (0.10 equiv). Reaction conditions: anode catalyst, Pt/C; cathode catalyst, Pt/C; 6a, 1.5

• standard. b0.125 M. c0.25 M. d1,4-dioxane/H2O (7:1, 0.25 M). a) Large scale synthesis of 7a and b) electoreduction of 6a using H2SO4 as a proton source. Scope of the electroreduction of 6 in the presence of PTSA (1 equiv). Reaction conditions: anode catalyst, Pt/C; cathode catalyst, Pt/C; 8, 1.5 mmol

Mining raw plant transcriptomic data for new cyclopeptide alkaloids

• Draco Kriger,
• Michael A. Pasquale,
• Brigitte G. Ampolini and
• Jonathan R. Chekan

Beilstein J. Org. Chem. 2024, 20, 1548–1559, doi:10.3762/bjoc.20.138

• alkaloids, containing both Ziziphus and Ceanothus genera. In addition to the subclass defining Tyr-phenol-O to carbon linkage, the cyclopeptide alkaloids of this family are typically oxidatively decarboxylated and N-methylated (Figure 1, adouetine X and Figure 3, ceanothine B) [19][20][21]. Our

• (Figure 3 and Supporting Information File 2). Malvaceae family The Malvaceae family contains Hibiscus syriacus (Rose of Sharon), the only known producer of hibispeptin-type burpitides (Figure 3, hibispeptin B) [24][25]. These molecules contain a C–C linkage between the phenol derived from tyrosine and the

• γ-carbon of isoleucine. As expected from previous genomic analysis [7], the transcriptome of H. syriacus contained precursor peptides corresponding to both hibispeptin A and B (Figure 3 and Supporting Information File 2). The closely related Hibiscus cannabinus possessed similar transcripts, while

Benzylic C(sp³)–H fluorination

• Alexander P. Atkins,
• Alice C. Dean and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 1527–1547, doi:10.3762/bjoc.20.137

• for the heterobenzylic position, as shown by compound 4. In 2018, a subsequent publication by the same group detailed the use of increased lithium carbonate and NFSI loadings (conditions [B]) to access the difluorinated products [37]. This report also demonstrated a single example of 18F

• the loadings of K2S2O8 and Selectfluor, selectivity for the mono- (conditions A) or difluorination (conditions B) products could be achieved. Building on their previous iron-catalysed work, Figure 11, Lectka and co-workers reported in 2014 the use of triethylborane as a radical chain initiator for C

• in the concerted transfer of an electron and a proton from the benzylic substrate resulting in the benzylic radical II – pathway [A] [67]. This radical can also be accessed via sequential oxidative single-electron-transfer (SET) and proton-transfer (PT) steps (pathway [B]), or concerted proton

Tetrabutylammonium iodide-catalyzed oxidative α-azidation of β-ketocarbonyl compounds using sodium azide

• Christopher Mairhofer,
• David Naderer and
• Mario Waser

Beilstein J. Org. Chem. 2024, 20, 1510–1517, doi:10.3762/bjoc.20.135

• , heptanes/EtOAc = 7:3, 298 K, Rf 0.47; mp: 75.9–78.4 °C. General illustration of the oxidative α-azidation of carbonyl derivatives using quaternary ammonium iodides (A), Ishihara’s protocol using NaN3 (B), and the herein reported combination of Bu4NI (TBAI), NaN3 and DBPO ((PhCOO)2) (C). Proposed

Towards an asymmetric β-selective addition of azlactones to allenoates

• Behzad Nasiri,
• Ghaffar Pasdar,
• Paul Zebrowski,
• Katharina Röser,
• David Naderer and
• Mario Waser

Beilstein J. Org. Chem. 2024, 20, 1504–1509, doi:10.3762/bjoc.20.134

• using Maruoka’s spirocyclic binaphthyl-based quaternary ammonium salts B as catalysts this transformation can be achieved with enantioselectivities up to 83:17 er. Furthermore, the herein accessed cyclic products 5 could be successfully engaged in ring-opening reactions with different amines, thus

• ammonium salt-catalyzed β-selective addition of compounds 2 to allenoates 3 (B), and the herein investigated β-selective addition of azlactones 1 to allenoates 3 (C). Application scope (conditions as detailed in Table 1, entry 13). Azlactone opening reactions. Optimization of the addition of azlactone 1a

Photoswitchable glycoligands targeting Pseudomonas aeruginosa LecA

• Yu Fan,
• Ahmed El Rhaz,
• Stéphane Maisonneuve,
• Emilie Gillon,
• Maha Fatthalla,
• Franck Le Bideau,
• Guillaume Laurent,
• Samir Messaoudi,
• Anne Imberty and
• Juan Xie

Beilstein J. Org. Chem. 2024, 20, 1486–1496, doi:10.3762/bjoc.20.132

• was stirred at room temperature until total deprotection. The solution was neutralized using Amberlite IR-120 (H), filtered, concentrated and the crude material used without further purification to give the desired product in quantitative yield. (A) Selected monovalent inhibitors for PA LecA and (B

• represents a ΔG value of −30 kJ/mol, corresponding to a Kd of approx 5 μM in the experimental conditions. (B) Manual docking of scaffold for compound 3 with selected low energy conformations of the E-isomer (yellow sticks) and Z-isomer (cyan sticks) superimposed on conserved position of galactose in all LecA

Bioinformatic prediction of the stereoselectivity of modular polyketide synthase: an update of the sequence motifs in ketoreductase domain

• Changjun Xiang,
• Shunyu Yao,
• Ruoyu Wang and
• Lihan Zhang

Beilstein J. Org. Chem. 2024, 20, 1476–1485, doi:10.3762/bjoc.20.131

• -positions of a polyketide chain [5][6][7]. KRs are classified into three types: A-type and B-type denote KRs that form ʟ- and ᴅ-configured β-hydroxy products, respectively, while C-type denotes KRs incapable of reducing the β-keto group [8][9]. KRs are further classified into subtypes 1 and 2 when the

• identified through bioinformatic and structural analyses (Figure 1c) [8][9][10][11]. A pioneering work by Caffrey identified that A-type KRs possess the conserved “W” motif but lack the “LDD” motif, whereas B-type KRs possess the “LDD” motif but lack the “W” motif, based on the sequence alignment of 68 KRs

• adopted, the prediction accuracy and the applicable range of these conserved motifs remain elusive, and not a few exceptions to these prediction rules have been reported (Figure 1c). For instance, the stereoselectivity of KR7 of ibomycin [12], KR15 of neaumycin B [14], and KR7 and KR10 of rifamycin [18

Synthesis of 4-functionalized pyrazoles via oxidative thio- or selenocyanation mediated by PhICl₂ and NH₄SCN/KSeCN

• Jialiang Wu,
• Haofeng Shi,
• Xuemin Li,
• Jiaxin He,
• Chen Zhang,
• Fengxia Sun and
• Yunfei Du

Beilstein J. Org. Chem. 2024, 20, 1453–1461, doi:10.3762/bjoc.20.128

• -ranging biological activities. Specifically, representative examples include fasicularin (IV, Figure 1), which possesses cytotoxic properties [21] and psammaplin B (V, Figure 1), which shows antimicrobial and mild tyrosine kinase inhibition activities [22]. In addition, Se-aspirin (VI, Figure 1) has been

• to give (SeCN)2 [60]. Then, one selenium atom of (SeCN)2 nucleophilically attacks the iodine center in PhICl2 to generate intermediate A, which was further transformed into intermediate B by release of one molecule of iodobenzene. Next, the nucleophilic attack of chloride anion to the bivalent

• selenium center of intermediate B resulted in the formation of two molecules of Cl–SeCN. Subsequently, Cl–SeCN undergoes an electrophilic addition reaction with pyrazole 1 to give intermediate C, which, after deprotonative rearomatization affords the 4-selenocyanated pyrazole 3. Conclusion In conclusion

Predicting bond dissociation energies of cyclic hypervalent halogen reagents using DFT calculations and graph attention network model

• Yingbo Shao,
• Zhiyuan Ren,
• Zhihui Han,
• Li Chen,
• Yao Li and
• Xiao-Song Xue

Beilstein J. Org. Chem. 2024, 20, 1444–1452, doi:10.3762/bjoc.20.127

• halogen skeletons and transfer groups. a) Linear dependence between the homolytic BDEs of cyclic hypervalent halogen reagents; b) linear dependence between the heterolytic BDEs of cyclic hypervalent halogen reagents. a) Composition and distribution of homolytic BDE dataset; b) graph attention network (GAT

Rapid construction of tricyclic tetrahydrocyclopenta[4,5]pyrrolo[2,3-b]pyridine via isocyanide-based multicomponent reaction

• Xiu-Yu Chen,
• Ying Han,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2024, 20, 1436–1443, doi:10.3762/bjoc.20.126

• Xiu-Yu Chen Ying Han Jing Sun Chao-Guo Yan College of Chemistry & Chemical Engineering, Yangzhou University, Jiangsu, Yangzhou 225002, China 10.3762/bjoc.20.126 Abstract An efficient protocol for the synthesis of polyfunctionalized tetrahydrocyclopenta[4,5]pyrrolo[2,3-b]pyridine-3,4b,5,6,7(1H

• )-pentacarboxylates was developed by a three-component reaction. In the absence of any catalyst, the three-component reaction of alkyl isocyanides, dialkyl but-2-ynedioates and 5,6-unsubstituted 1,4-dihydropyridines in refluxing acetonitrile afforded polyfunctionalized tetrahydrocyclopenta[4,5]pyrrolo[2,3-b]pyridine

• reaction with 5,6-unsubstituted 1,4-dihydropyridine. Keywords: [3 + 2] cycloaddition; cyclopenta-1,3-diene; cyclopenta[4,5]pyrrolo[2,3-b]pyridine; 1,4-dihydropyridine; electron-deficient alkyne; isocyanide; Introduction Isocyanide is a unique and attractive functional group in organic chemistry. The

Synthesis of cyclic β-1,6-oligosaccharides from glucosamine monomers by electrochemical polyglycosylation

• Md Azadur Rahman,
• Hirofumi Endo,
• Takashi Yamamoto,
• Shoma Okushiba,
• Norihiko Sasaki and
• Toshiki Nokami

Beilstein J. Org. Chem. 2024, 20, 1421–1427, doi:10.3762/bjoc.20.124

• rate: 7.5 mL/min, recycle numbers: 3) to obtain pure cyclic oligosaccharide 16 (0.125 mmol, 79.7 mg, 62%). Preparation of cyclic oligoglucosamines a) via intramolecular glycosylation and b) via polyglycosylation and intramolecular glycosylation. Proposed reaction mechanism of the formation of 1,6

Challenge N- versus O-six-membered annulation: FeCl₃-catalyzed synthesis of heterocyclic N,O-aminals

• Giacomo Mari,
• Lucia De Crescentini,
• Gianfranco Favi,
• Fabio Mantellini,
• Diego Olivieri and
• Stefania Santeusanio

Beilstein J. Org. Chem. 2024, 20, 1412–1420, doi:10.3762/bjoc.20.123

• . Based on our previous findings [17][18][19], the initial nucleophilic addition of α-aminoacetals 2a,b as nitrogen source to the activated heterodiene system of 4-methoxycarbonyl-DDs 1a–f in dichloromethane (DCM) or ethanol (EtOH) at room temperature affords N-aminohydrazone derivatives I (Scheme 2

• providing intermediate A. The latter, by loss of a trichloro(alkoxy)ferrate(III) anion, generates a strong electrophile such as the oxocarbenium cation intermediate B. The released trichloro(alkoxy)ferrate(III) splits into FeCl3, which enters the catalytic cycle, and a free alkoxide, which acts as a base

• line with the values found for the slower reactions previously described (compounds 6b,d,g,i,n–p). By adding 500 μL of water to the medium the cyclization did not proceed, and the starting material 4j was recovered unchanged (experiment B, Scheme 5). This observation seems to suggest that the presence

Hypervalent iodine-catalyzed amide and alkene coupling enabled by lithium salt activation

• Akanksha Chhikara,
• Fan Wu,
• Navdeep Kaur,
• Prabagar Baskaran,
• Alex M. Nguyen,
• Zhichang Yin,
• Anthony H. Pham and
• Wei Li

Beilstein J. Org. Chem. 2024, 20, 1405–1411, doi:10.3762/bjoc.20.122

• difluorinated iodotoluene B. Then, LiBF4 can perform a salt metathesis with B to produce LiF along with the active hypervalent iodoarene catalyst C. The activated hypervalent iodine catalyst C can coordinate to the alkene to form complex D. The nucleophilic oxygen of the amide will attack in the internal

• reaction designs. Time studies of the amide and alkene coupling. a) Iodoarene time studies: styrene (1), para-substituted iodoarenes, LiBF4, and benzamide (2). b) Li salt time studies: styrene (1), iodoanisole, Li salts, and benzamide (2). c) Alkene time studies: para-substituted styrenes, iodotoluene A

• , 16 h. b) Iodoanisole (20 mol %). Alkene substrate scope studies. a) Standard conditions: alkene (0.25 mmol), iodotoluene (20 mol %), LiBF4 (100 mol %), Selectfluor (150 mol %), 3,4-dimethylbenzamide (400 mol %), MeNO2 (0.25 M), rt, 16 h. b) Iodoanisole (20 mol %), MeCN (0.25 M). Proposed catalytic

Synthesis of substituted triazole–pyrazole hybrids using triazenylpyrazole precursors

• Simone Gräßle,
• Laura Holzhauer,
• Nicolai Wippert,
• Olaf Fuhr,
• Martin Nieger,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2024, 20, 1396–1404, doi:10.3762/bjoc.20.121

• , THF/pyridine (9:1), −20 °C to 21 °C, 12 h, b) Cs2CO3, DMSO, 120 °C, 2–3 d, c) TFA, TMS-N3, DCM, 25 °C, 12 h, d) 1. TFA, TMS-N3, DCM, 0–50 °C, 12 h; 2. alkyne, THF/H2O, CuSO4, sodium ascorbate, 16 h, 50 °C. Synthesis of triazenylpyrazoles 15a–d and functionalization to N-substituted triazenylpyrazoles

Synthetic applications of the Cannizzaro reaction

• Bhaskar Chatterjee,
• Dhananjoy Mondal and
• Smritilekha Bera

Beilstein J. Org. Chem. 2024, 20, 1376–1395, doi:10.3762/bjoc.20.120

• of a hydride ion from a tetracoordinated intermediate (B), which is formed upon hydroxide addition to the aldehyde (A). The primary pathway of the reaction entails the rate-determining step of hydride ion transfer via either a linear or bent transition state (C) to a second molecule of aldehyde

• transformation of the aryl glyoxals is outlined below (Scheme 4), which depicts the coordination of the hemiacetal B with the metal catalyst to give C, followed by hydride transfer to form the metal-coordinated Cannizzaro product D. Another intramolecular asymmetric Cannizzaro reaction was reported by Wu et al

• intramolecular Cannizzaro reaction was demonstrated by the group of Schmalz in the total synthesis of the marine antibiotic pestalone [86]. They observed a facile isomerization of the pestalone derivatives 55/57 into the intramolecular lactone derivatives rac-56a,b which features a Cannizzaro–Tishchenko-type

Generation of alkyl and acyl radicals by visible-light photoredox catalysis: direct activation of C–O bonds in organic transformations

• Mithu Roy,
• Bitan Sardar,
• Itu Mallick and
• Dipankar Srimani

Beilstein J. Org. Chem. 2024, 20, 1348–1375, doi:10.3762/bjoc.20.119

• subsequently undergoes addition to B2cat2 (19) to produce the boryl radical 41. Here, the choice of solvent is also important. The interaction between DMF and the boryl radical 41 assists B–B bond scission to furnish the target borylated products and an intermediate 43, which is oxidized by [Ir(IV

Rhodium-catalyzed homo-coupling reaction of aryl Grignard reagents and its application for the synthesis of an integrin inhibitor

• Kazuyuki Sato,
• Satoki Teranishi,
• Atsushi Sakaue,
• Yukiko Karuo,
• Atsushi Tarui,
• Kentaro Kawai,
• Hiroyuki Takeda,
• Tatsuo Kinashi and
• Masaaki Omote

Beilstein J. Org. Chem. 2024, 20, 1341–1347, doi:10.3762/bjoc.20.118

• . Conditions: a) The reaction was carried out at rt for 1–3 h without Mg. b) The side product 6h by SNAr reaction onto 3h was obtained in 8%. Tentative reaction mechanism. Ullmann and Ullmann-type homo-coupling reactions. Rh-catalyzed homo-coupling reactions. Rh-catalyzed homo-coupling reaction by using

Synthesis of 1,2,3-triazoles containing an allomaltol moiety from substituted pyrano[2,3-d]isoxazolones via base-promoted Boulton–Katritzky rearrangement

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

Beilstein J. Org. Chem. 2024, 20, 1334–1340, doi:10.3762/bjoc.20.117

• , intramolecular recyclization accompanied by opening of the isoxazole ring and formation of the N–N bond leads to intermediate B. Finally, target 1,2,3-triazole 4 is produced via acidification of anion B. Next, we tried to expand the presented rearrangement to hydrazones derived from aliphatic hydrazines (MeNHNH2

• recyclization is depicted at Scheme 8. Initially, hydrazine molecule is added to double bond of the pyranone ring leading to zwitter-ion A. Further, cleavage of dihydropyranone fragment results in intermediate B. Next, enehydrazine C is formed from compound B through migration of a proton. Then, intramolecular

Transition-metal-catalyst-free electroreductive alkene hydroarylation with aryl halides under visible-light irradiation

• Kosuke Yamamoto,
• Kazuhisa Arita,
• Masami Kuriyama and
• Osamu Onomura

Beilstein J. Org. Chem. 2024, 20, 1327–1333, doi:10.3762/bjoc.20.116

• . Recently, the groups of Lin and Lambert [48] and Wickens [49] independently demonstrated that aryl chlorides with highly negative reduction potentials engaged in C–X (X = P, Sn, B) and C–C bond formation reactions involving aryl radical species by integrating photochemistry and electrochemistry [50][51][52

• alkene 2 to provide alkyl radical species B. Further single-electron reduction by 1,3-DCB•− or at the cathode followed by protonation of B provides hydroarylation product 3. Meanwhile, the sacrificial anode is oxidized to form Al cations. Although the exact role of visible-light irradiation in the

Computation-guided scaffold exploration of 2E,6E-1,10-trans/cis-eunicellanes

• Zining Li,
• Sana Jindani,
• Volga Kojasoy,
• Teresa Ortega,
• Erin M. Marshall,
• Khalil A. Abboud,
• Sandra Loesgen,
• Dean J. Tantillo and
• Jeffrey D. Rudolf

Beilstein J. Org. Chem. 2024, 20, 1320–1326, doi:10.3762/bjoc.20.115

• Ring fusion configuration does not affect protonation-induced cyclization Our initial observation that albireticulene (2) was unstable in chloroform, resulting in two tricyclic isomers gersemienes A (5) and B (6) [7], while benditerpetriene (1) was stable [5], led us to investigate the protonation

• diterpenoids and their biosyntheses. (A) The 6/10-bicyclic hydrocarbon framework is conserved in eunicellane diterpenoids. Selected natural products consisting of cis- (red) and trans-eunicellane skeletons (blue) are shown. (B) Four types of diterpene synthases are known to form the eunicellane skeleton, each

• epoxide 9, but the similar reaction with 2 yields gersemienol 8. Isolation yields are provided. (B and C) Results of DFT calculations on the protonation-induced cyclizations of 1 and 2. The energies of the cationic intermediates (italicized values) are not on the same energy scale as for the substrates

Sustainable tandem acylation/Diels–Alder reaction toward versatile tricyclic epoxyisoindole-7-carboxylic acids in renewable green solvents

• Ayhan Yıldırım

Beilstein J. Org. Chem. 2024, 20, 1308–1319, doi:10.3762/bjoc.20.114

• study indicates that the retro-IMDAF reaction does not occur under the reaction conditions developed. As seen in Figure 4b, the different sigma bond lengths formed in the exo transition state (calculations which were performed in Gaussian 16 Rev B.01 (Gaussian, Inc., Wallingford, CT, USA)) [135

• . Louis, MO), or Acros Organics (Thermo Fisher Scientific, Geel, Belgium) and used without further purification. Thin-layer chromatography was performed using silica gel (60 F254, Merck, Darmstadt, Germany) plates. Melting points were recorded by Büchi melting point B-540 apparatus (Büchi Labortechnik AG

• IMDAF reaction. IRC calculations of a) endo-, b) exo-transition structures and products for compound 2a (semi-empirical method, PM6) [136]. Synthesis of epoxyisoindole-7-carboxylic acids 2a–m and 2n–p. Possible side reactions of unsaturated fatty acids with maleic anhydride. Equilibrium of 2n–p with

Diameter-selective extraction of single-walled carbon nanotubes by interlocking with Cu-tethered square nanobrackets

• Guoqing Cheng and
• Naoki Komatsu

Beilstein J. Org. Chem. 2024, 20, 1298–1307, doi:10.3762/bjoc.20.113

• Cu-nanobrackets@SWNTs complexes were computed with the GFN2-xTB method by using the xtb software [16][17]. (a) MALDI-TOF mass spectrum of Cu-nanobrackets 1b, where the inset shows the isotope peaks of [1b]+ comparing with the simulated ones; (b) absorption spectra of the nanobracket 4b and Cu

• -nanobrackets 1b. DFT-optimized structure of Cu-nanobrackets (a) 1a and (b) 1b. The yellow regions indicate their spherical cavities. (c) Experimental and calculated results of Raman spectra of 1b (λex = 488 nm). For calculation, Raman activity was transferred to Raman intensity (298.15 K, the full width at

• half maximum (FWHM) is 10 cm−1) and the frequency scale factor 0.952 was used for correction [21]. (a) Absorption spectra of Cu-nanobrackets 1b and SWNT extract; (b) Raman spectra of Cu-nanobrackets 1b, HiPco SWNTs, extracted, interlocked, and pristine SWNTs, corresponding to e-, i- and p-SWNTs