Synthesis of new representatives of A₃B-type carboranylporphyrins based on meso-tetra(pentafluorophenyl)porphyrin transformations

• Victoria M. Alpatova,
• Evgeny G. Rys,
• Elena G. Kononova and
• Valentina A. Ol'shevskaya

Beilstein J. Org. Chem. 2024, 20, 767–776, doi:10.3762/bjoc.20.70

• the p-fluorine atom in the pentafluorophenyl substituent with an azide functionality which upon reduction with SnCl2 resulted in the formation of the corresponding porphyrin with an amino group. Pentafluorophenyl-substituted A3B-porphyrins were studied and transformed to thiol and amino-substituted

• temperature for 4 h. Under these reaction conditions, monoazide derivative 2 was obtained in 40% yield along with a mixture of porphyrin 1, di- and triazido-substituted derivatives. The reaction mixture was separated by column chromatography on SiO2 using CH2Cl2/hexane 2:8 as an eluent. The reduction of the

• fluorophenylporphyrin substituents via the boron atom. At the same time the SNAr substitution reaction for the azido-substituted porphyrin 2 with mercaptocarborane 4 also afforded the amino-substituted porphyrin 5 in 32% yield (Scheme 2). During the reaction the reduction of the azide group under the action of

Substrate specificity of a ketosynthase domain involved in bacillaene biosynthesis

• Zhiyong Yin and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2024, 20, 734–740, doi:10.3762/bjoc.20.67

• of a ketoreductase (KR) domain in module 1, the starter unit was initially suggested to be α-hydroxyisocaproate [14], but later it was shown that the KR of module 3 acts twice, in the reduction of the β-ketoacyl intermediate of the elongation step of module 3 and in the reduction of the α

• -ketoisocaproate starter unit with introduction of an S configured stereocentre (highlighted in red in Scheme 1) [15]. The domain organisation of module 3 containing no enoylreductase (ER) domain furthermore suggests the formation of an α,β-unsaturated intermediate, and not a full reduction at this stage, in

Chemoenzymatic synthesis of macrocyclic peptides and polyketides via thioesterase-catalyzed macrocyclization

• Senze Qiao,
• Zhongyu Cheng and
• Fuzhuo Li

Beilstein J. Org. Chem. 2024, 20, 721–733, doi:10.3762/bjoc.20.66

• TE-catalyzed marcolactonization [69]. The synthesis of linear peptide 34 commenced with the lactone opening of 26 to afford Weinreb amide 27. Following primary alcohol protection and amide reduction, the aldehyde 28 was coupled with iodide 29 to afford 30 via Nozaki–Hiyama–Kishi coupling, which was

SOMOphilic alkyne vs radical-polar crossover approaches: The full story of the azido-alkynylation of alkenes

• Julien Borrel and
• Jerome Waser

Beilstein J. Org. Chem. 2024, 20, 701–713, doi:10.3762/bjoc.20.64

• building blocks bearing two of the most versatile functional groups, allowing a rich panel of functionalization. They have been used as intermediates in numerous syntheses to access bioactive compounds [1][2][3][4] or materials [5][6][7]. In addition, azide reduction affords homopropargylic amines, which

• since it is known to be reduced by photocatalysts such as Cu(dap)2Cl [17]. This perfectly fits a catalytic cycle involving the reduction of Ts-ABZ (3) followed by oxidation of the carbon radical to form a carbocation and regenerate the ground state catalyst. Styrene (1a) was used as model substrate

• formation of 6 (Table 2, entry 4). In contrast, Ru(bpz)3(PF6)2 did not form the desired product probably due to its too high reduction potential compared to Ts-ABZ (3) (value reported for ABX: E1/2(ABX) = −0.43 V vs SCE) [52] (Table 2, entry 5). In general, organic dyes could not catalyze the transformation

New variochelins from soil-isolated Variovorax sp. H002

• Jabal Rahmat Haedar,
• Aya Yoshimura and
• Toshiyuki Wakimoto

Beilstein J. Org. Chem. 2024, 20, 692–700, doi:10.3762/bjoc.20.63

• transporters to form the siderophore Fe(III) complex extracellularly [2][3]. Subsequently, the stable and water soluble siderophore Fe(III) complex is transported across the cell membrane into the cytoplasm, where the iron is released from the complex by reduction, generating free Fe(II) ions that are

Regioselective quinazoline C2 modifications through the azide–tetrazole tautomeric equilibrium

• Dāgs Dāvis Līpiņš,
• Andris Jeminejs,
• Una Ušacka,
• Anatoly Mishnev,
• Māris Turks and
• Irina Novosjolova

Beilstein J. Org. Chem. 2024, 20, 675–683, doi:10.3762/bjoc.20.61

• , which is present in pharmaceutically active substances. The methodology application is showcased by transforming the obtained 4-azido-6,7-dimethoxy-2-sulfonylquinazolines into the α1-adrenoceptor blockers terazosin and prazosin by further C2-selective SNAr reaction and azide reduction. Keywords

• form can be in either the azide (17e, 17f) or tetrazole form (17a–d). With derivatives 17e,f in hand, the reduction of the azido group in the C4 position was carried out by bubbling hydrogen through the solution in the presence of palladium on charcoal. In the last step, the product was acidified with

Palladium-catalyzed three-component radical-polar crossover carboamination of 1,3-dienes or allenes with diazo esters and amines

• Geng-Xin Liu,
• Xiao-Ting Jie,
• Ge-Jun Niu,
• Li-Sheng Yang,
• Xing-Lin Li,
• Jian Luo and
• Wen-Hao Hu

Beilstein J. Org. Chem. 2024, 20, 661–671, doi:10.3762/bjoc.20.59

• % yield. Compound 4a could be hydrogenated to the corresponding reduction product 12 using Pd/C and ammonium formate conditions (Scheme 6a). Notably, as shown in Scheme 6b, treatment of the unsaturated γ-AA derivative 6a with Pd/C and ammonium formate led to a cyclization reaction, furnishing γ-lactam 13

Enhanced reactivity of Li⁺@C₆₀ toward thermal [2 + 2] cycloaddition by encapsulated Li⁺ Lewis acid

• Hiroshi Ueno,
• Yu Yamazaki,
• Hiroshi Okada,
• Fuminori Misaizu,
• Ken Kokubo and
• Hidehiro Sakurai

Beilstein J. Org. Chem. 2024, 20, 653–660, doi:10.3762/bjoc.20.58

• redox waves, with subsequent reduction resulting in an irreversible electrochemical response. The first reduction potentials of 5a and 5b were measured at −0.51 V and −0.52 V (vs Fc/Fc+), respectively, which were more negative than that of pristine Li+@C60 (E1/2red1 = −0.39 V). While the detailed

• reasons for the irreversible redox properties after the second reduction process have not been thoroughly investigated, the observed phenomena could potentially be attributed to ring opening or simple decomposition under the conditions. From these results, the LUMO levels of the compounds were estimated

• − with substrates 1–4. a100 equiv for the reaction screening, 20 equiv for the synthesis of 5a, and 40 equiv for the synthesis of 5b. bRoom temperature for the reaction screening, 50 °C for the synthesis. cIsolated yield. dHPLC yield. First reduction potential and estimated LUMO level of 5a and 5b. The

Production of non-natural 5-methylorsellinate-derived meroterpenoids in Aspergillus oryzae

• Jia Tang,
• Yixiang Zhang and
• Yudai Matsuda

Beilstein J. Org. Chem. 2024, 20, 638–644, doi:10.3762/bjoc.20.56

• instead of the C-4′ carbonyl group (Figure 2C). It is unlikely that 8 is the direct product of InsA7; thus, we hypothesized that an endogenous enzyme in A. oryzae is responsible for the reduction, with an enoylreductase first reducing the C-2′/C-3′ double bond of 7 and the resulting product undergoing

Chemical and biosynthetic potential of Penicillium shentong XL-F41

• Ran Zou,
• Xin Li,
• Xiaochen Chen,
• Yue-Wei Guo and
• Baofu Xu

Beilstein J. Org. Chem. 2024, 20, 597–606, doi:10.3762/bjoc.20.52

• enzymatic ring-expansion process in their respective fungi. Both shentonins A (1) and B (2) also feature a reduction of a carbonyl to a hydroxy group within the succinimide ring. All isolated compounds were subjected to antimicrobial evaluations, and compound 12 was found to have moderate inhibitory

Synthesis and biological profile of 2,3-dihydro[1,3]thiazolo[4,5-b]pyridines, a novel class of acyl-ACP thioesterase inhibitors

• Jens Frackenpohl,
• David M. Barber,
• Guido Bojack,
• Birgit Bollenbach-Wahl,
• Ralf Braun,
• Rahel Getachew,
• Sabine Hohmann,
• Kwang-Yoon Ko,
• Karoline Kurowski,
• Bernd Laber,
• Rebecca L. Mattison,
• Thomas Müller,
• Anna M. Reingruber,
• Dirk Schmutzler and
• Andrea Svejda

Beilstein J. Org. Chem. 2024, 20, 540–551, doi:10.3762/bjoc.20.46

• show good acyl-ACP thioesterase inhibition in line with strong herbicidal activity against commercially important weeds in broadacre crops, e.g., wheat and corn. The desired substituted 2,3-dihydro[1,3]thiazolo[4,5-b]pyridines were prepared via an optimized BH3-mediated reduction involving tris

• to afford thiazolopyridines 12a–c in good yield. This allowed us to circumvent the previously employed alkylation–oxidation–reduction sequences (Scheme 2) [12]. Thereupon, we recognized that we could introduce two halogen atoms in the halogenation step and carry one through to the end of the

• conditions to prepare 2,3-dihydro[1,3]thiazolo[4,5-b]pyridines 7a–c and 13a–c via a late-stage reduction (Scheme 2 and Table 1). Whilst several synthetic approaches towards 2,3-dihydro-1,3-benzothiazoles involving the hydrogenation of 1,3-benzothiazoles have been described [20], the corresponding preparation

Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

• achieved by chemical (hydroxide/proton) or electrochemical (reduction/oxidation) stimuli allowing the enrichment of perylene from a mixture of polycyclic aromatic hydrocarbons (PAHs) in phase-transfer experiments into a perfluorocarbon phase. Metal cation responsive tweezers In the early 2000s, Lehn and co

• electronic or geometrical properties upon oxidation or reduction. TTF and derivatives tweezers One of the most widely used electroactive moieties is tetrathiafulvalene (TTF). Its electron-donor π-system can form non-covalent interactions with various electron-poor π-systems, and those interactions can be

Pseudallenes A and B, new sulfur-containing ovalicin sesquiterpenoid derivatives with antimicrobial activity from the deep-sea cold seep sediment-derived fungus Pseudallescheria boydii CS-793

• Zhen Ying,
• Xiao-Ming Li,
• Sui-Qun Yang,
• Hong-Lei Li,
• Xin Li,
• Bin-Gui Wang and
• Ling-Hong Meng

Beilstein J. Org. Chem. 2024, 20, 470–478, doi:10.3762/bjoc.20.42

• -rich fluid emissions and unique sulfur oxidation–reduction reactions [1]. Due to the unique habitat, microorganisms surviving in the deep-sea cold seeps may serve as promising sources of secondary metabolites with functional and structural diversity [2]. In particular, two indole diketopiperazine

Enhanced host–guest interaction between [10]cycloparaphenylene ([10]CPP) and [5]CPP by cationic charges

• Eiichi Kayahara,
• Yoshiyuki Mizuhata and
• Shigeru Yamago

Beilstein J. Org. Chem. 2024, 20, 436–444, doi:10.3762/bjoc.20.38

• neutral, free [10]CPP. Upon scanning into the negative direction, two pseudo reversible reduction waves of [5]CPP2+ were observed at 0.22 and 0.17 V vs Fc/Fc+ (Figure 3b), which were negatively shifted by 0.11 and 0.10 V from that of free [5]CPP2+[B(C6F5)4−]2. These results suggest the electron density of

• observations also agree well with the change in oxidation and reduction potentials upon complex formation observed in the electrochemical analysis. The double-layered structure of the complex was unambiguously determined by single-crystal X-ray analysis (Figure 7), which was performed on a crystal obtained by

Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

• Periklis X. Kolagkis,
• Eirini M. Galathri and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36

• number of inflammatory processes, which can lead to inflammatory bowel disease or Alzheimer’s disease. Therefore, GPR84 agonists are used as medicine for the treatment of various inflammatory diseases, but they have been also linked to the reduction of leukemia cells, since the continuous expression of

• reduction in the concentration of these cytokines, as well as, increased intestinal permeability and improved expression of tight junction proteins that control the polarity of cells when using DIM in Caco-2 human cells [3]. BIMs have also been linked with the therapy of various cancers with one of their

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

• many applications as radical precursors. Mechanistically, NHPI esters undergo a reductive decarboxylative fragmentation to provide a substrate radical capable of engaging in diverse transformations. Their reduction via single-electron transfer (SET) can occur under thermal, photochemical, or

• electrochemical conditions [30][31]. Due to their propensity towards single-electron reduction, NHPI esters, and similar derivatives such as N-hydroxytetrachlorophthalimide (TCNHPI) esters, are collectively referred to as "redox-active esters" (RAEs). The versatility of RAEs stems, in part, to the sensitivity of

• their reduction half peak potentials (Ep/2) to their environment. For instance, a recent study by Cornella and co-workers, showed that RAEs derived from phenylacetic acid exhibited varying reduction half peak potentials (Ep/2) ranging from −2.0 V for the NHPI ester 4 to −1.2 V for the corresponding

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

• , Supporting Information File 1), 2-(arylamino)-3H-phenoxazin-3-ones 4a–h manifest two reduction waves at Е1/2RED1 = −1.36 ± 1.69 V and Е1/2RED2 = −1.85 ± 2.12 V. Oxidation of 4a–f,h occurs as an irreversible process at Е1/2OX = 0.81–1.07 V. For 4g bearing an amino group, the oxidation potential is shifted to

• Е1/2OX = 0.25 V. The irreversible two-wave reduction (Е1/2RED1 = −1.40 ± 1.60 V and Е1/2RED2 = −1.92 ± 2.45 V) is also characteristic of 14H-quinoxaline[2,3-b]phenoxazines 5a–c and 6a,b. In contrast to 5a–c and 6a,b, benzo[5,6][1,4]oxazino[2,3-b]phenothiazine 10c is reversibly reduced at Е1/2RED1

• = −1.39 V to a radical anion and then undergoes irreversible reduction at Е1/2RED2 = −1.91 V and irreversible oxidation at Е1/2OX = 0.48 V. These CV parameters are close to those recorded for triphenodioxazines [23]. The energy of the HOMO and LUMO orbitals assessed on the basis of the CV and electronic

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

• voltammetry studies revealed that reduction of dinaphthooxepine 33 proceeds irreversibly, giving rise to a new chemical species (Figure 2), and this was further confirmed by chemical reduction in the presence of decamethylcobaltocene CoCp*2 at room temperature. Using two equivalents of this 1-electron

• , since previously reported bare and aryl-substituted dinaphthooxepines exhibited reversible reduction [67]. In summary, owing to the heteroatom-dependent behavior of heteropines, it is possible to control the structure of the target compound: on the one hand, thermally stable chalcogen-doped π-CPCs with

• 2020 American Chemical Society. This content is not subject to CC BY 4.0. Cyclic voltammogram of dinaphthooxepine 33, evidencing the irreversibility of the reduction process during the first cycle, leading to the formation of PBI 6f upon redox-triggered O-extrusion. Reprinted with permission from [66

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

• affect the oxidation current. In cathodic events, the reduction of CH2Cl2 primally occurred under standard conditions because the reduction wave of the blank solution appeared at approximately −1.0 V (Figure 2D, blue line). The resulting cathodically generated chloride ion (Cl−) has a lower oxidation

• under standard conditions gave the corresponding N−Cl species (C) as an unstable compound. We considered that this result as direct evidence for the plausibility of the existence of N−Cl species which driving the minor reaction pathway. Further single-electron reduction affords the amidyl radical [17

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

• , synthesized in situ from a chiral boron phosphate complex with water, for asymmetric indole reduction (Scheme 1b) [30]. The mild reaction conditions, low catalyst loading, and high enantioselectivity rendered this transformation an attractive approach to synthesize optically active indolines. However, these

• asymmetric reduction studies focused on alkyl or aryl-substituted 3H-indoles whereas the synthesis of chiral difluorinated indole derivatives could have potential applications in pharmaceutical chemistry. Herein, an organocatalyzed transfer hydrogenation of 3,3-difluoro-3H-indoles to obtain fluorinated 3H

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

• catalyst, in the presence of Et3N both in dioxane and DMF. These conditions resulted in the obtainment of the desired compound 3a in 59% and 35% yield, respectively (entries 4 and 5, Table 4). Increasing the reaction temperature to 100 °C resulted in a reduction of the reaction yield due to purported

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

• exemplified by the emergence of a maximum absorption peak at 1,024 nm, indicating the one-electron reduced form of C60. Although the observation of the oxidation process of the ferrocene unit was obstructed by the more substantial absorption changes associated with fullerene reduction, the lifetimes of the

• guaranteeing long-lived CS states. Guldi et al. synthesized 16 distinct donor–acceptor conjugated molecules, denoted as 89–104 (Figure 11). These molecules comprised ZnP as an electron donor and push–pull chromophores with varying reduction potentials as electron acceptors interconnected by various rigid

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

• of 3,4-dimethoxybenzaldehyde with 5-substituted 2-picoline derivatives in low to moderate yields ranging from 13% (2f) to 65% (2a) (Scheme 2). The amino-substituted derivative 2b was synthesized by reduction of the nitrostyrylpyridine 2a with Pd/C and hydrazine in 83% yield. Subsequent acylation of

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

• , Germany 10.3762/bjoc.20.9 Abstract Photocatalytic hydrogen production from water is a promising way to fulfill energy demands and attain carbon emission reduction goals effectively. In this study, a loop photoreactor with a total volume of around 500 mL is presented for the photocatalytic hydrogen

• ) processes, and photocatalysis. Upon upscaling, both PV-E and PEC reactors exhibit pH gradients at electrodes and elevated solution electrical resistivity. These challenges arise from the substantial separation between reduction and oxidation sites, alongside mass transport restrictions in the liquid phase

Multi-redox indenofluorene chromophores incorporating dithiafulvene donor and ene/enediyne acceptor units

• Christina Schøttler,
• Kasper Lund-Rasmussen,
• Line Broløs,
• Philip Vinterberg,
• Ema Bazikova,
• Viktor B. R. Pedersen and
• Mogens Brøndsted Nielsen

Beilstein J. Org. Chem. 2024, 20, 59–73, doi:10.3762/bjoc.20.8

• indenofluorene (IF) or fluorene cores and containing various dithiafulvene (DTF) donor units that gain aromaticity upon oxidation and a variety of acceptor units, such as vinylic diesters, enediynes, and cross-conjugated radiaannulenes (RAs) that gain aromaticity upon reduction. In some cases, the DTF units are

• with one of the exocyclic enediyne units removed) [17][18] is a particularly good electron acceptor as it gains 14π-aromaticity upon reduction. In this work, we also want to further explore pyrrolo-annelated IF-DTFs with different substituents on the nitrogen atom, and the functionalization at the

• therefore it was not possible to determine the purity of the product by this method. In an initial attempt to investigate other synthetic pathways to extended IF compounds, the reduced IF 29 was synthesized from IF dione 1 by a Wolff–Kishner reduction of the two ketones as shown in Scheme 6. Compound 29