Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• electronically excited substrate (*S) through an energy transfer (EnT) mechanism (path c). In addition to these mechanistic blueprints, the formation of charge-transfer complexes involving NHPI esters, as well as examples of photoinduced transition metal-catalyzed activation will be discussed. Depending on the

• type addition reactions (Scheme 4A). In 1991, Okada and co-workers reported the addition of alkyl radicals to α,β-unsaturated ketones, by subjecting NHPI esters to visible-light irradiation in the presence of the photocatalyst [Ru(bpy)3]Cl2 and the reductant 1-benzyl-1,4-dihydronicotinamide (BNAH) [37

• esters for the construction of quaternary carbons via conjugate addition of 3° radicals [39][40]. In general, this transformation operates under a reductive quenching photocatalytic cycle, requiring a stoichiometric reductant (Scheme 4A). Both TM complexes, and organic dyes such as eosin Y [41][42][43

Facile approach to N,O,S-heteropentacycles via condensation of sterically crowded 3H-phenoxazin-3-one with ortho-substituted anilines

• Eugeny Ivakhnenko,
• Vasily Malay,
• Pavel Knyazev,
• Nikita Merezhko,
• Nadezhda Makarova,
• Oleg Demidov,
• Gennady Borodkin,
• Andrey Starikov and
• Vladimir Minkin

Beilstein J. Org. Chem. 2024, 20, 336–345, doi:10.3762/bjoc.20.34

• ][12]. At the first stage, this reaction follows one of three possible reaction pathways, including Schiff base formation (attack at the C(3) center), Michael addition at C(1), or nucleophilic substitution (SNH) at the C(2) center [13][14][15]. Most readily used is the pathway involving carbonyl–amine

Discovery of unguisin J, a new cyclic peptide from Aspergillus heteromorphus CBS 117.55, and phylogeny-based bioinformatic analysis of UngA NRPS domains

• Sharmila Neupane,
• Marcelo Rodrigues de Amorim and
• Elizabeth Skellam

Beilstein J. Org. Chem. 2024, 20, 321–330, doi:10.3762/bjoc.20.32

• γ-aminobutyric acid (GABA) (1 equiv). In addition to the COSY and HMBC correlations, the NOESY experiment showed important interactions between the NH signals corroborating with the peptide sequence defined to be Ala-1, Val-2, Leu-3, Phe-4, Ala-5, Trp-6, and GABA-7 (Figure 3). Analysis of the NMR

Elucidating the glycan-binding specificity and structure of Cucumis melo agglutinin, a new R-type lectin

• Jon Lundstrøm,
• Emilie Gillon,
• Valérie Chazalet,
• Nicole Kerekes,
• Antonio Di Maio,
• Ten Feizi,
• Yan Liu,
• Annabelle Varrot and
• Daniel Bojar

Beilstein J. Org. Chem. 2024, 20, 306–320, doi:10.3762/bjoc.20.31

• overnight. Then, 1 L LB medium supplemented with 25 µg/mL kanamycin was inoculated with 25 mL of the pre-culture and incubated at 37 °C, 180 rpm. When OD600nm reached 0.4, the temperature was lowered to 16 °C, and when OD600nm reached 0.8, protein expression was induced by the addition of 0.1 mM isopropyl β

• -ᴅ-thiogalactoside (IPTG) [Euromedex, #EU0008-C]. After 20 h, the cells were harvested by centrifugation at 5,000g for 10 min at 4 °C. For purification of bacterial recombinant CMA1, each gram of cell pellet was resuspended with 5 mL of buffer A (20 mM Tris-HCl pH 7.5, 500 mM NaCl). After addition of

• zinc acetate), or 5 mM CdCl2, and in the presence or not of 5 mM GalNAc. Cocrystals of CMA1-Nter in complex with LacNAc (Galβ1-4GlcNAc, Elicityl, #GLY008) were obtained by the addition of 5 mM LacNAc to the protein solution and incubation at room temperature for 30 min prior to crystallization. For

Synthesis of π-conjugated polycyclic compounds by late-stage extrusion of chalcogen fragments

• Aissam Okba,
• Pablo Simón Marqués,
• Kyohei Matsuo,
• Naoki Aratani,
• Hiroko Yamada,
• Gwénaël Rapenne and
• Claire Kammerer

Beilstein J. Org. Chem. 2024, 20, 287–305, doi:10.3762/bjoc.20.30

• compounds, thus limiting their final purity, and restricts the processing techniques to physical vapor deposition. In addition, some π-CPCs appear to be sensitive to oxidative and/or photolytic degradation, which hinders their use in devices under ambient conditions. The case of acenes is representative of

• small volatile molecules. Importantly, this ultimate synthetic step, performed in situ, should be quantitative and should not require the addition of chemical reagents, since any non-volatile byproduct would be trapped in the material and thus impact its performances. The “precursor approach” was

• precursors of π-CPCs bearing non linearly-fused benzene rings. In addition, the non-planar geometry of such heteropines appears as an asset towards increased solubility, and the existence of several oxidation states for these heteroatoms expands the panel of reaction conditions applicable to trigger the

Unveiling the regioselectivity of rhodium(I)-catalyzed [2 + 2 + 2] cycloaddition reactions for open-cage C₇₀ production

• Cristina Castanyer,
• Anna Pla-Quintana,
• Anna Roglans,
• Albert Artigas and
• Miquel Solà

Beilstein J. Org. Chem. 2024, 20, 272–279, doi:10.3762/bjoc.20.28

• (fulleroid) derivatives. The aim is to shed light on the regioselectivity of the process through both experimental and computational approaches. In addition, the photooxidation of one of the C–C double bonds in the synthesized bis(fulleroids) affords open-cage C70 derivatives having a 12-membered ring

• we analyzed by UV–vis spectroscopy. This peak was assigned as a bis(fulleroid) compound by comparing the spectra with the UV–vis absorption pattern exhibited by previously characterized C70 bis(fulleroids) reported by Murata et al. [43][48]. In addition, a minor peak at a retention time of 20 minutes

Additive-controlled chemoselective inter-/intramolecular hydroamination via electrochemical PCET process

• Kazuhiro Okamoto,
• Naoki Shida and
• Mahito Atobe

Beilstein J. Org. Chem. 2024, 20, 264–271, doi:10.3762/bjoc.20.27

• , entry 3); thus, the phosphate base plays a crucial role in N-alkylation, while its basicity is insufficient to promote aza-Michael addition (pKa of the conjugate acid of the phosphate base is 1.72 in H2O) [12]. Furthermore, N-alkylation proceeded in a divided cell (anodic chamber); thus, the possibility

• of conjugate addition of a cathodically generated carbamate anion was ruled out, prompting us to consider that N-alkylation proceeded via a radical mechanism. On the other hand, the addition of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) led to the predominant formation of cyclized dimer 4 without N

• wave was observed at approximately +1.4 V (Figure 2A). The oxidation current of this wave decreased significantly in the presence of a phosphate base and the subsequent addition of HFIP enhanced this phenomenon (Figure 2B, grey line). In contrast, using AcOH instead of HFIP did not affect the oxidation

Nucleophilic functionalization of thianthrenium salts under basic conditions

• Xinting Fan,
• Duo Zhang,
• Xiangchuan Xiu,
• Bin Xu,
• Yu Yuan,
• Feng Chen and
• Pan Gao

Beilstein J. Org. Chem. 2024, 20, 257–263, doi:10.3762/bjoc.20.26

• ][20]. On the other hand, sulfonium salts have emerged as appealing sources of aryl radicals for a wide range of transformations aimed at creating novel chemical bonds driven by their distinctive structural attributes and chemical tendencies (Scheme 1a) [9][21][22][23][24][25][26]. In addition to late

Catalytic multi-step domino and one-pot reactions

• Svetlana B. Tsogoeva

Beilstein J. Org. Chem. 2024, 20, 254–256, doi:10.3762/bjoc.20.25

• mixed in one flask, in which all reaction steps take place autonomously without the addition of further reactants [1]. The domino process contrasts the conventional "stop-and-go" synthetic approach in the way that multiple reactions proceed in a direct sequence. In such a reaction sequence, one step

• facile stereoselective tandem reaction based on the asymmetric conjugate addition of dialkylzinc reagents to unsaturated acylimidazoles, followed by trapping of the intermediate zinc enolate with carbocations [12]. A practical one-pot synthesis of fluorescent pyrazolo[3,4-b]pyridin-6-ones by reacting 5

Substitution reactions in the acenaphthene analog of quino[7,8-h]quinoline and an unusual synthesis of the corresponding acenaphthylenes by tele-elimination

• Ekaterina V. Kolupaeva,
• Narek A. Dzhangiryan,
• Alexander F. Pozharskii,
• Oleg P. Demidov and
• Valery A. Ozeryanskii

Beilstein J. Org. Chem. 2024, 20, 243–253, doi:10.3762/bjoc.20.24

• studied for the first time. In addition to the pronounced tendency of the title compound to form associates with an intramolecular hydrogen bond of the NHN type (new examples with the participation of pyridine rings, including self-associates are shown) and its inertness to amination reactions of the

• ), the basicity of which must obviously be higher than that of the starting heterocycle 5. To this end, we conducted a series of experiments on its oxidative amination by varying the reaction conditions (time, temperature, addition of n-butyllithium to increase the nucleophilicity of amines), and

• (Scheme 8). In addition to the spectral data confirming the composition and asymmetric structure of compound 16, a clear sign of the emerging acenaphthylene system is its yellow-orange color, which distinguishes the UV-active (yellow-green luminescence) acenaphthylene 16 from the light-beige UV-inactive

Photochromic derivatives of indigo: historical overview of development, challenges and applications

• Gökhan Kaplan,
• Zeynel Seferoğlu and
• Daria V. Berdnikova

Beilstein J. Org. Chem. 2024, 20, 228–242, doi:10.3762/bjoc.20.23

• benzene (Figure 3). This indicates that in addition to structure I, which is traditionally used to depict indigo, intraionic resonance structures II and III with single C–O bonds and double C=N bonds make a pronounced contribution in the ground state of indigo (Figure 3) [13][14]. In the excited state

• causes a hypsochromic shift of the absorption band, while the presence of the EA substituents at these positions leads to a bathochromic shift (Figure 5). In addition, electron-donating substituents on the nitrogen atom produce bathochromic shifts, while electron-withdrawing groups at this position give

• particular, the lifetime of Z-11a in CCl4 was found to be only 3.1 s versus 18 h measured previously. Nevertheless, it was obvious that N,N'-dialkylindigos were prone to the reversible photochemical isomerization. In addition, it was also found that the thermal backward Z–E conversion of 11a and 12

Copper-catalyzed multicomponent reaction of β-trifluoromethyl β-diazo esters enabling the synthesis of β-trifluoromethyl N,N-diacyl-β-amino esters

• Youlong Du,
• Haibo Mei,
• Ata Makarem,
• Ramin Javahershenas,
• Vadim A. Soloshonok and
• Jianlin Han

Beilstein J. Org. Chem. 2024, 20, 212–219, doi:10.3762/bjoc.20.21

• system to produce the expected product (4p). In addition, the β-trifluoromethyl β-amino benzyl ester substrates 1 with different ester groups were tried to react with benzoic acid (3a) to further extend the substrate range. To our delight, both the amines with electron-donating groups (4q and 4r) and

• reaction, several control experiments were performed. First, the reaction was conducted under the optimized conditions without the addition of CuI. The conversion of the starting substrates to the desired product 4a was decreased and only 14% yield of 4a was obtained (Scheme 3a). However, as shown in entry

• 1 of Table 1, 54% yield product 4a was produced by this reaction in the presence of 10 mol % CuI. These results demonstrate that copper catalysis plays a crucial role in the generation of the desired product 4a. Moreover, we performed this reaction without the addition of tert-butyl nitrite (Scheme

Chiral phosphoric acid-catalyzed transfer hydrogenation of 3,3-difluoro-3H-indoles

• Yumei Wang,
• Guangzhu Wang,
• Yanping Zhu and
• Kaiwu Dong

Beilstein J. Org. Chem. 2024, 20, 205–211, doi:10.3762/bjoc.20.20

• relatively strict reaction conditions (up to 150 bar H2). In 2022, Liu’s group reported an asymmetric hydrogenation of 3H-indoles catalyzed by a chiral Mn complex, which showed good yield and enantioselectivity [25]. In addition to metal catalysis for the enantioselective reduction, asymmetric

Metal-catalyzed coupling/carbonylative cyclizations for accessing dibenzodiazepinones: an expedient route to clozapine and other drugs

• Amina Moutayakine and
• Anthony J. Burke

Beilstein J. Org. Chem. 2024, 20, 193–204, doi:10.3762/bjoc.20.19

• careful review of the product structure it was revealed that the purported dibenzodiazepine products were, in fact, diarylimines, which resulted from a nucleophilic addition of the aniline reagents to the aldimine substrates, followed by elimination of an tosylamine product. This was one of the principle

• (1a), followed by the oxygen-promoted insertion of the phenylboronic acid coupling partner 7 to deliver intermediate II that undergoes reductive elimination to give diarylamine 3a along with regeneration of the copper catalyst (Scheme 5). Then, a palladium-promoted oxidative addition of the C–Br bond

• ) was added to a Radleys reaction tube (a Radleys® 12 position carousel reactor station was used) under N2 and dissolved in dry dioxane (5 mL). Next, (0.055 mL, 0.46 mmol) of 1,2-dibromobenzene (2) was added to the reaction mixture, followed by the addition of Pd(OAc)2 (0.01 g, 0.046 mmol), XPhos (0.032

Comparison of glycosyl donors: a supramer approach

• Anna V. Orlova,
• Nelly N. Malysheva,
• Maria V. Panova,
• Nikita M. Podvalnyy,
• Michael G. Medvedev and
• Leonid O. Kononov

Beilstein J. Org. Chem. 2024, 20, 181–192, doi:10.3762/bjoc.20.18

• a reaction solvent might not be as relevant when the reaction solution contains also glycosyl acceptor, promoter, suspended molecular sieves, etc., in addition to the glycosyl donor, and the presence of these components may also affect [31][32][33] solution structure and hence the glycosylation

• this reason, it makes sense to include this concentration in the experimental design to enable a direct comparison with data already published in the field. In addition, it is the highest concentration that belongs to the low concentration range found for compound 2 (Figure 1b). The concentration 0.15

• overnight, then quenched by addition of dry ice (solid CO2) and concentrated under reduced pressure. The residue was co-concentrated with toluene (3 mL), dried in vacuo, dissolved in anhydrous pyridine (3 mL per 0.1 mmol of sialyl donor), and acetic anhydride (3 mL per 0.1 mmol of sialyl donor) was added

Synthesis of the 3’-O-sulfated TF antigen with a TEG-N₃ linker for glycodendrimersomes preparation to study lectin binding

• Mark Reihill,
• Hanyue Ma,
• Dennis Bengtsson and
• Stefan Oscarson

Beilstein J. Org. Chem. 2024, 20, 173–180, doi:10.3762/bjoc.20.17

• treated with 1 M Bu4NF/THF and after 2 hours, full consumption of the starting material was observed by TLC. However, MALDI–TOF mass spectrometry (super-DHB matrix) revealed that only the Troc group had been removed, with the DTBS substituent proving to be stable under these conditions. Addition of a

• removed from the reaction mixture in vacuo. Sulfation was then performed through addition of SO3·NMe3 to the DMF solution. Consumption of 1 was observed by TLC after 72 hours and stirring with Dowex® 50WX4 (Na+ form) resin resulted in formation of target 2. Purification by flash chromatography, however

Correction: Synthesis of highly substituted fluorenones via metal-free TBHP-promoted oxidative cyclization of 2-(aminomethyl)biphenyls. Application to the total synthesis of nobilone

• Ilya A. P. Jourjine,
• Lukas Zeisel,
• Jürgen Krauß and
• Franz Bracher

Beilstein J. Org. Chem. 2024, 20, 170–172, doi:10.3762/bjoc.20.16

• ; total synthesis; We noticed a number of minor errors in our original publication, including in Supporting Information File 1, that mostly concern the percent yield given for some of the precursors. In addition, there was a larger error related to the yield for the key step of the total synthesis of the

Perspectives on push–pull chromophores derived from click-type [2 + 2] cycloaddition–retroelectrocyclization reactions of electron-rich alkynes and electron-deficient alkenes

• Michio Yamada

Beilstein J. Org. Chem. 2024, 20, 125–154, doi:10.3762/bjoc.20.13

• ]. In addition to anilino groups, a myriad of donor entities, including urea-substituted phenyl groups [18][19], carbazoles [20], phenothiazines [21][22], thiophenes [23][24][25][26], tetrathiafulvalenes (TTFs) [27], extended TTFs [28], ferrocenes [27][29][30][31][32][33][34][35][36][37][38][39][40][41

• , exhibiting enhanced electron-accepting capabilities, reacts with 1, it displays a more intricate reaction profile compared with that of 4 (Scheme 5). In addition to pentacyano-1,3-5-hexatriene (PCHT) compound 7, compounds 8 and 9 are generated [102]. This reaction is notably influenced by the different

• + 2] cycloaddition reaction with the anthracene moiety, yielding the DA cycloadduct 17. To achieve the conversion of the alkyne moiety of 16 into TCBD, the addition of five equivalents of TCNE to 16 or one equivalent of TCNE to 17 is required. This results in the formation of TCBD compound 18 bearing

Visible-light-induced radical cascade cyclization: a catalyst-free synthetic approach to trifluoromethylated heterocycles

• Chuan Yang,
• Wei Shi,
• Jian Tian,
• Lin Guo,
• Yating Zhao and
• Wujiong Xia

Beilstein J. Org. Chem. 2024, 20, 118–124, doi:10.3762/bjoc.20.12

• . The addition of a typical radical scavenger – TEMPO (2,2,6,6-tetramethylpiperidin-1-yloxyl) significantly inhibited the reaction (as shown in Scheme 3), suggesting the involvement of radical species during the reaction process. Moreover, the radical trapping product was detected and confirmed via 19F

Photoinduced in situ generation of DNA-targeting ligands: DNA-binding and DNA-photodamaging properties of benzo[c]quinolizinium ions

• Julika Schlosser,
• Olga Fedorova,
• Yuri Fedorov and
• Heiko Ihmels

Beilstein J. Org. Chem. 2024, 20, 101–117, doi:10.3762/bjoc.20.11

• irradiation of the styrylpyridines and formation of the intercalator directly in the presence of DNA. In addition to the DNA-binding properties, the tested benzo[c]quinolizinium derivatives also operate as photosensitizers, which induce DNA damage at relative low concentrations and short irradiation times

• [19]. As a result, several photoactive compounds have been developed, whose DNA-binding properties can be efficiently switched on and off by light [14][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. In addition to their DNA-binding properties some annelated quinolizinium derivatives have

• DNA. In contrast, upon addition of DNA to compounds 3c,e–g, the absorption maxima at 398 nm, 393 nm, 386 nm and 394 nm were red-shifted with a hypochromic effect, and isosbestic points developed during all titrations (Figure 4, Table 1). Furthermore, the addition of DNA to substrates 3c,e–g led to

Optimizing reaction conditions for the light-driven hydrogen evolution in a loop photoreactor

• Pengcheng Li,
• Daniel Kowalczyk,
• Johannes Liessem,
• Mohamed M. Elnagar,
• Dariusz Mitoraj,
• Radim Beranek and
• Dirk Ziegenbalg

Beilstein J. Org. Chem. 2024, 20, 74–91, doi:10.3762/bjoc.20.9

• due to extended ion transport distances. These effects cause significant potential losses, eventually reducing the efficiency of the reactors. The addition of large amounts of supporting electrolyte and vigorous circulation of the electrolyte solution also complicates the scale-up process [17][18]. On

• probability value larger than 0.10 renders the parameter generally as insignificant [35]. It is evident from Table 2 that light intensity and inert gas flow can be regarded as significant, while the photocatalyst amount and the stirring speed are insignificant. In addition to this analysis, it is necessary to

Preparing a liquid crystalline dispersion of carbon nanotubes with high aspect ratio

• Keiko Kojima,
• Nodoka Kosugi,
• Hirokuni Jintoku,
• Kazufumi Kobashi and
• Toshiya Okazaki

Beilstein J. Org. Chem. 2024, 20, 52–58, doi:10.3762/bjoc.20.7

• addition, the shapes of the spindle-shaped nematic LC, or so-called tactoids, in the biphasic state were examined. The transition from homogeneous tactoids to bipolar tactoids occurred at a larger tactoid volume than that previously observed [23]. This can be ascribed to the higher L/D of the DWCNTs in

Using the phospha-Michael reaction for making phosphonium phenolate zwitterions

• Matthias R. Steiner,
• Max Schmallegger,
• Larissa Donner,
• Johann A. Hlina,
• Christoph Marschner,
• Judith Baumgartner and
• Christian Slugovc

Beilstein J. Org. Chem. 2024, 20, 41–51, doi:10.3762/bjoc.20.6

• the mentioned reactions, the first step of the catalytic cycle is the nucleophilic attack of the phosphine on the electrophile, in many cases an electron-deficient olefin. The zwitterion formed from this conjugate addition can subsequently act as a nucleophile or as a base [3][4][5]. The efficiency of

• this zwitterion formation is of great importance since it is the initiation step for the catalytic cycle in Michael reactions [8]. Generally, the conjugate addition is favored for strong nucleophiles, which is why electron-rich trialkylphosphines were among the first catalysts used in this type of

• alkylphosphine, an aldehyde and an alkyne [32]. Another example resulting from phosphine addition to α,β-unsaturated aldehydes was published shortly afterwards [33]. Phosphonium carboxylate zwitterions have been obtained by the reaction of phosphines with acrylic acid [8] and ortho-carboxylated arylphosphines

Facile access to pyridinium-based bent aromatic amphiphiles: nonionic surface modification of nanocarbons in water

• Lorenzo Catti,
• Shinji Aoyama and
• Michito Yoshizawa

Beilstein J. Org. Chem. 2024, 20, 32–40, doi:10.3762/bjoc.20.5

• , and graphene nanoplatelets) are achieved through noncovalent encircling with the bent amphiphiles. The resultant imidazole-modified nanocarbons display a pH-responsive surface charge, as evidenced by NMR and zeta-potential measurements. In addition, solubilization of a nitrogen-doped nanocarbon (i.e

• could be efficiently solubilized in water via noncovalent encircling by newly synthesized amphiphiles PA-R [22]. A mixture of solid PA-OCH3 (1.7 mg, 2.7 μmol) and water-insoluble C60 (1.4 mg, 1.9 μmol) was manually ground for 3 min using an agate mortar and pestle (Figure 4a) [23]. Following addition of

• protons upon addition of HCl (40 equiv based on PA-Im; Figure 5a,b). These properties enabled a pH-responsive surface charge of its host–guest composite (Table 2). Accordingly, (PA-Im)n·(C60)m displayed a ZP of 60.3 mV at pH 2.8 contrary to 52.8 mV at pH 6.8 (ΔZP = +7.5 mV) [26]. Control experiments using

NMRium: Teaching nuclear magnetic resonance spectra interpretation in an online platform

• Luc Patiny,
• Hamed Musallam,
• Alejandro Bolaños,
• Michaël Zasso,
• Julien Wist,
• Metin Karayilan,
• Eva Ziegler,
• Johannes C. Liermann and
• Nils E. Schlörer

Beilstein J. Org. Chem. 2024, 20, 25–31, doi:10.3762/bjoc.20.4

• common approach in academic laboratories, the ability of chemists to conduct the interpretation of experimental results becomes crucial. In addition, NMR spectroscopy is one of the methods that has been delivering digital experimental raw data for a long time. However, the way the spectra are interpreted

• project website (as well as in the supplementary information) and is continuously extended. In addition, NMRium features online assistance with short movies. For teaching, the web-based nature makes the software an outstanding tool for live instruction: Steps demonstrated by the instructor may be