Kinetically stabilized 1,3-diarylisobenzofurans and the possibility of preparing large, persistent isoacenofurans with unusually small HOMO–LUMO gaps

• Qian Liu and
• Glen P. Miller

Beilstein J. Org. Chem. 2024, 20, 1099–1110, doi:10.3762/bjoc.20.97

• ]. Large acenes are prone to photooxidation, especially when dissolved in solution while exposed to ambient light and air. They sensitize singlet oxygen formation, and the same is expected from large isoacenofurans. Indeed, the endoperoxides observed by Hamura and co-workers [3] confirm this expectation

• reloaded with mesitylene (0.215 g, 1.79 mmol) and an additional 5 mL CH2Cl2. The content of the addition funnel was once again added dropwise into the round bottom flask over 5 minutes with stirring. The light-yellow solution turned to dark brown. After 15 min, 10 mL of a saturated aqueous solution of NaCl

• mmol) and an additional 5 mL CH2Cl2. The content of the addition funnel was once again added dropwise into the round bottom flask over 5 minutes with stirring. The light-yellow solution turned to dark brown. After 30 min, 10 mL of a saturated aqueous solution of NaCl was added to quench the reaction

Light on the sustainable preparation of aryl-cored dibromides

• Fabrizio Roncaglia,
• Alberto Ughetti,
• Nicola Porcelli,
• Biagio Anderlini,
• Andrea Severini and
• Luca Rigamonti

Beilstein J. Org. Chem. 2024, 20, 1076–1087, doi:10.3762/bjoc.20.95

• be employed in two variants modulated by light irradiation. This external switch can be used to selectively trigger side-chain or core halogenation. Keywords: aryl halides; benzyl halides; bromination; sustainability; Introduction Activation through halogens has become a key strategy in achieving

• ] resulting in easier recyclability. Light irradiation often significantly influences the selectivity of halogenation processes. Photolytic cleavage of molecular halogens gives rise to radicals that are known to favour benzylic functionalisation [17]. Conversely, the same molecular halogens exhibit prominent

• functionalisation on the aromatic ring when used in the dark [20]. A classic example is the bromination of toluene with molecular bromine. When the system is exposed to light (right side of Figure 1), a radical mechanism is initiated by Br• coming from Br2 homolysis. Propagation involves the reversible abstraction

Novel route to enhance the thermo-optical performance of bicyclic diene photoswitches for solar thermal batteries

• Akanksha Ashok Sangolkar,
• Rama Krishna Kadiyam and
• Ravinder Pawar

Beilstein J. Org. Chem. 2024, 20, 1053–1068, doi:10.3762/bjoc.20.93

• transformation into a high energy photoisomer [8][9][10][11][12][13]. This photoisomer then can be stored for a certain period and thermal energy can be released when triggered with heat, light, catalyst, etc. The back isomerization of the metastable photoproduct regenerates the parent molecule for continuing

Structure–property relationships in dicyanopyrazinoquinoxalines and their hydrogen-bonding-capable dihydropyrazinoquinoxalinedione derivatives

• Tural N. Akhmedov,
• Ajeet Kumar,
• Daken J. Starkenburg,
• Kyle J. Chesney,
• Khalil A. Abboud,
• Novruz G. Akhmedov,
• Jiangeng Xue and
• Ronald K. Castellano

Beilstein J. Org. Chem. 2024, 20, 1037–1052, doi:10.3762/bjoc.20.92

• . Palladium(II) acetate and anhydrous 1,4-dioxane were purchased from Strem Chemicals or Sigma-Aldrich and used as received. Thin-layer chromatography (TLC) was performed on SiO2-60 F254 aluminum plates with visualization by UV light or staining. Flash column chromatography was performed using Purasil SiO2-60

• (10 mL) and reacted at room temperature for 3 hours. After this time the light orange solution was diluted with water (50 mL) and acidified with 1 N HCl until a white solid precipitated out. The solids were collected via filtration and dried in an oven (120 °C) for 24 hours. An off-white to pale

Auxiliary strategy for the general and practical synthesis of diaryliodonium(III) salts with diverse organocarboxylate counterions

• Naoki Miyamoto,
• Daichi Koseki,
• Kohei Sumida,
• Elghareeb E. Elboray,
• Naoko Takenaga,
• Ravi Kumar and
• Toshifumi Dohi

Beilstein J. Org. Chem. 2024, 20, 1020–1028, doi:10.3762/bjoc.20.90

• benzoate in 70% yield (Scheme 6A). Furthermore, iodonium salt 7aj with an umbelliferone-3-carboxylate counterion displayed extremely weak blue fluorescence emission under 365 nm UV light compared to free carboxylic acid 6j. This unique property was utilized for tracing the counterion exchange process of

• the diaryliodonium(III) salt by irradiating with 365 nm UV light. The counterion exchange in umbelliferone carboxylate salt 7aj with trifluoroacetic acid was rapid, and after 30 s, the completion of the reaction was confirmed by the emergence of strong blue fluorescence emission due to the liberation

Carbonylative synthesis and functionalization of indoles

• Alex De Salvo,
• Raffaella Mancuso and
• Xiao-Feng Wu

Beilstein J. Org. Chem. 2024, 20, 973–1000, doi:10.3762/bjoc.20.87

• process was catalyzed by visible light in the presence of Mo(CO)6 (1 equiv) as CO source, I2 (2 equiv), and K2CO3 (3 equiv) at 120 °C in an inert reaction environment (N2) and in DMSO as solvent (Scheme 38). Functionalization through direct C–H carbonylations The direct functionalization of indoles via C

• that kind of chemicals [74]. The reaction was cheap because it took place by irradiation with green light (5 W) in the presence of eosin Y as photocatalyst, under 70 bar of CO, in CH3CN at room temperature (Scheme 41). In 2018, Wu et al. published two papers about the functionalization of indoles. In

Three-component N-alkenylation of azoles with alkynes and iodine(III) electrophile: synthesis of multisubstituted N-vinylazoles

• Jun Kikuchi,
• Roi Nakajima and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2024, 20, 891–897, doi:10.3762/bjoc.20.79

• ], and sulfonic acids [31]. On the other hand, nitrogen-based nucleophiles amenable to this reaction manifold have thus far been limited to nitriles in the context of Ritter-type iodo(III)amidation [29]. In light of the significance of vinylated azoles, our attention was attracted to the feasibility of

Advancements in hydrochlorination of alkenes

• Daniel S. Müller

Beilstein J. Org. Chem. 2024, 20, 787–814, doi:10.3762/bjoc.20.72

• reaction. In light of the numerous research articles on polar hydrochlorination reactions, we have categorized the reports based on the source of HCl (Scheme 2). The first section covers reactions involving HCl gas, typically supplied from an HCl gas cylinder. The second section explores reactions

• functional group tolerance. Yang reported a hydrochlorination promoted by visible light over platinum, gold, and palladium supported on zirconia [74]. The reaction demonstrated moderate efficiency, yielding an 85:15 mixture of products 100 and 126 with low conversion (Scheme 20). The use of hydrochloric acid

• . Formation of chlorophosphonium complex 104 and the reaction thereof with H2O. Snyder’s hydrochlorination with stoichiometric amounts of complex 104 or 108. In situ generation of HCl by mixing of MsOH with CaCl2. First hydrochlorination of alkenes using hydrochloric acid. Visible-light-promoted

Synthesis and characterization of water-soluble C₆₀–peptide conjugates

• Yue Ma,
• Lorenzo Persi and
• Yoko Yamakoshi

Beilstein J. Org. Chem. 2024, 20, 777–786, doi:10.3762/bjoc.20.71

• most other solvents. C60–oligo-Lys and C60–oligo-Glu were characterized by 1H and 13C NMR. Photoinduced 1O2 generation was observed in the most soluble C60–oligo-Lys conjugate under visible light irradiation (527 nm) to show the potential of this highly water-soluble molecule in biological systems, for

• aggregations in aqueous solution, as observed by dynamic light scattering (DLS), cryoTEM, and concentration-dependent surface tension measurements [40]. Despite the small size (≈10 nm in hydrodynamic diameter), the aggregation of these fullerene moieties was not ideal for biological applications as

• the HRESIMS results (Figure S2, Supporting Information File 1), it was confirmed that the highly water-soluble compound 5a was successfully synthesized. 1O2 generation under visible light irradiation To preliminarily evaluate the synthesized C60–oligo-Lys (5a) as a PS, generation of singlet oxygen was

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

• biosensors, bioimaging probes, and especially as photosensitizers (PSs) in photodynamic therapy (PDT) [2]. PDT is a treatment modality that uses the combination of a non-toxic PS, oxygen, and light to treat diseases ranging from cancer to age-related macular degeneration and antibiotic-resistant infections

Methodology for awakening the potential secondary metabolic capacity in actinomycetes

• Shun Saito and
• Midori A. Arai

Beilstein J. Org. Chem. 2024, 20, 753–766, doi:10.3762/bjoc.20.69

• carbonate and terminal olefin functionalities [50]. Thus, artificial methods of genetic engineering and chemistry also play an important role in the identification of novel secondary metabolites. Culture conditions Medium composition, pH, oxygen supply, light Simply modifying the culture conditions is an

• Zeeck and co-workers in the early 2000s, is a method in which the target bacteria are cultured under various conditions (medium composition, temperature, pH, oxygen supply, light quality and quantity, addition of precursors and enzyme inhibitors, etc.) and all metabolites obtained from them are analyzed

• pH of the culture medium from becoming too acidic [17]. In addition, Mehmood et al. reported that the oxygen supply controls the production of pristinamycins 27 in Streptomyces pristinaespiralis (Figure 3e) [68]. Takano et al. discovered the light-induced production of carotenoid pigments, including

Research progress on the pharmacological activity, biosynthetic pathways, and biosynthesis of crocins

• Zhongwei Hua,
• Nan Liu and
• Xiaohui Yan

Beilstein J. Org. Chem. 2024, 20, 741–752, doi:10.3762/bjoc.20.68

• derivatives in microorganisms has been achieved by various teams. This article comprehensively reviews the research progress on the extraction, separation, pharmacological activity, biosynthesis, and synthetic biology of crocins. The biosynthesis of crocins is depicted in detail to shed light on the efficient

• are highly soluble in hot water but slightly soluble in anhydrous ethanol and ether. The presence of multiple conjugated double bonds in crocins makes them susceptible to degradation when exposed to certain conditions, such as high temperature, the presence of metal ions or light, certain pH values

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

• exhibits a cyclization activity against a peptide methyl ester that is feeble but readily detectable [61]. This finding indicates that SurE has a high tolerance for leaving groups. In the light of this property, Wakimoto, Matsuda, and co-workers discovered that ethylene glycol (EG) can act as a linker on

• hydroxylation and epoxidation using three P450s (TylI, JuvD and MycCI) involved in the biosynthesis of several different macrolides, eight additional macrolides were achieved from 50, including juvenimicin B1, M-4365 G2, and juvenimicin A3. In the light of this approach, the following bioactive assay

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

• source. Upon light irradiation, it can release an azide radical by homolysis of the I−N3 bond [46]. We were pleased to see that irradiation of a mixture of styrene (1a), Ph-EBX (2) and Ts-ABZ (3) afforded 17% isolated yield of the desired homopropargylic azide 4a (Table 1, entry 1). Heating the reaction

• to 80 °C instead of using light to form the radical only afforded traces of the product (Table 1, entry 2). Changing the solvent to DCE slightly increased the yield (Table 1, entry 3). Blue light with an emission spectrum centered around 467 nm was initially selected since Ph-EBX is known to absorb

• light of lower wavelength, which is expected to cause degradation [47]. Indeed, when the reaction was carried out using 440 nm blue light a lower yield of 10% was obtained and full conversion of the EBX reagent was observed (Table 1, entry 4). Next, we wanted to test different additives in the

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

• accessible for the cell [2][3]. In addition to the siderophores forming the stable Fe(III) complexes described above, certain siderophores create Fe(III) complexes with the ability to release Fe(II) ions in a light-responsive manner within the extracellular environment. The released Fe(II) ions in the ocean

Organic electron transport materials

• Joseph Cameron and
• Peter J. Skabara

Beilstein J. Org. Chem. 2024, 20, 672–674, doi:10.3762/bjoc.20.60

• transport materials for organic semiconductor devices due to their potential to be applied in various technologies. For example, such materials can be used to improve charge balance in the emissive layer of an organic light-emitting diode, charge extraction in perovskite solar cells or used as the

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

• -light-mediated palladium-catalyzed three-component radical-polar crossover carboamination of 1,3-dienes or allenes with diazo esters and amines, affording unsaturated γ- and ε-amino acid derivatives with diverse structures. In this methodology, the diazo compound readily transforms into a hybrid α-ester

• reaction of diazo compounds mediated by visible light has been reported by the group of Gevorgyan, which achieves the monofunctionalization of alkenes [52]. Inspired by these collective studies, we considered diazo compounds could be a competent activated alkyl halide equivalent to overcome the synthetic

• started our studies with the palladium-catalyzed MCR of ethyl diazoacetate (1a), 1,3-butadiene (2a), and 1-phenylpiperazine (3a) in the presence of 5 mol % Pd(OAc)2 and 10 mol % Xantphos as ligand. To our delight, after irradiation with blue LED light in dimethylformamide (DMF) for 12 h at room

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

• , compound 7, corresponding to the major peak in our optimized fermentation (Figure 1), was obtained at the gram level. Compound 1 (shentonin A) was obtained as a light green solid with a chemical formula of C20H26N2O3, as determined by HRMS m/z 365.1828 [M + Na]+ (calcd for C20H26N2O3Na+, 365.1835) and HRMS

• calculated spectrum of 2R,3R,16R-1 matched better with the experimental one, so the absolute configuration of 1 was tentatively determined to be 2R,3R,16R, namely shentonin A. Compound 2 (shentonin B) was isolated as a light green solid. Its chemical formula, C19H24N2O2, was confirmed by HRMS with m/z

• isolation of compound 3 (2.19 mg). Physical and spectroscopic data of compounds 1–3 Shentonin A (1): light green solid; [α]D20 +40.0 (c 0.17, CH3OH); UV (CH3OH) λmax, nm (log ε): 400 (3.45), 240 (4.24) nm; IR (KBr) νmax: 3347, 2960, 2926, 1688, 1654, 1612, 1260, 1078, 1021, 797 cm−1; for 1H NMR (CDCl3, 600

A myo-inositol dehydrogenase involved in aminocyclitol biosynthesis of hygromycin A

• Michael O. Akintubosun and
• Melanie A. Higgins

Beilstein J. Org. Chem. 2024, 20, 589–596, doi:10.3762/bjoc.20.51

• containing 3.7 mL p-anisaldehyde, 135 mL ethanol, 5 mL sulfuric acid, and 1.5 mL glacial acetic acid. Light pink spots were observed following heating at 105 °C. Kinetics assays were carried out by varying concentrations of substrate (myo-inositol or scyllo-inositol) from 1 mM to 60 mM with 1 μM Hyg17 and 10

Possible bi-stable structures of pyrenebutanoic acid-linked protein molecules adsorbed on graphene: theoretical study

• Yasuhiro Oishi,
• Motoharu Kitatani and
• Koichi Kusakabe

Beilstein J. Org. Chem. 2024, 20, 570–577, doi:10.3762/bjoc.20.49

• their responses are observed. The elastic wave is excited by a pump light, and the response of the substrate is observed via the probe light. The refractive index of metallic substrates such as graphene may change due to the arrival of elastic waves, and this change can be observed by detecting the

• reflected light of the probe light. For such laser-based biosensors, graphene's conductivity can provide a unique advantage. In fact, the conductivity of multilayered graphene is highly anisotropic. Therefore, the use of multilayer graphene avoids the burning of biomaterials by lasers irradiated from the

Synthesis of photo- and ionochromic N-acylated 2-(aminomethylene)benzo[b]thiophene-3(2Н)-ones with a terminal phenanthroline group

• Vladimir P. Rybalkin,
• Sofiya Yu. Zmeeva,
• Lidiya L. Popova,
• Irina V. Dubonosova,
• Olga Yu. Karlutova,
• Oleg P. Demidov,
• Alexander D. Dubonosov and
• Vladimir A. Bren

Beilstein J. Org. Chem. 2024, 20, 552–560, doi:10.3762/bjoc.20.47

• a terminal phenanthroline receptor substituent was synthesized. Upon irradiation in acetonitrile or DMSO with light of 436 nm, they underwent Z–E isomerization of the C=C bond, followed by very fast N→O migration of the acyl group and the formation of nonemissive O-acylated isomers. These isomers

• light and H+ or sequential addition of Fe2+ and AcO− ions. Keywords: fluorescence; molecular switches; N→O acyl rearrangement; naked eye effect; photochromism; Introduction Photochromism is defined as the reversible transformation of a molecular entity between different forms, having different

• change depending on the intensity of sunlight), photochromic tags for biological research and optical sensors [15][16][17][18][19][20][21]. To develop new dual-mode molecular switches capable of efficient modulation of optical and fluorescent properties, both upon irradiation with visible light and upon

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

• other hand, photochemical stimuli offer cleaner alternatives, relying solely on a light source that can be focused on specific areas. However, they may be limited by photostationary states and penetration depth in absorbing media that might prevent full conversion and potential side photochemical

Development of a chemical scaffold for inhibiting nonribosomal peptide synthetases in live bacterial cells

• Fumihiro Ishikawa,
• Sho Konno,
• Hideaki Kakeya and
• Genzoh Tanabe

Beilstein J. Org. Chem. 2024, 20, 445–451, doi:10.3762/bjoc.20.39

• competitively inhibit the labeling of recombinant GrsA using the ABP ʟ-Phe-AMS-BPyne (3). GrsA (1 µM) was incubated with probe 3 (1 µM) in the absence or presence of either inhibitor 1, 2, or 4–9 (100 µM). The mixtures were exposed to ultraviolet light at 365 nm to form a covalent bond between GrsA and the

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

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

• radicals were successfully generated by subjecting NHPI esters to light irradiation in the presence of the photoreductant 1,6-bis(dimethylamino)pyrene (BDMAP). Following their initial discovery, multiple studies have shown their versatility as radical progenitors under thermal, photochemical, and

• readers to recently published review articles for additional discussion [30][31]. Discussion Mechanism under photochemical conditions In this section we provide a summary of the various conditions and activation modes employed in radical reactions of NHPI esters using visible-light irradiation. Upon

• absorption of light, an excited photocatalyst (*PC) engages in single-electron transfer (SET) with either donor (D) or acceptor (A) molecules (Scheme 3) [8][36]. Accordingly, a reductive quenching mechanism (path a) will operate when an excited photocatalyst effects the one-electron oxidation of a