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

• presented a method for the C–H thiocyanation of pyrazoles by using a sustainable catalyst of graphite-phase carbon nitride (g-C3N4) under visible light irradiation (Scheme 1c) [2]. Furthermore, Yao harnessed an electrochemical approach to form the electrophilic SCN+ intermediate, which reacted with

A comparison of structure, bonding and non-covalent interactions of aryl halide and diarylhalonium halogen-bond donors

• Nicole Javaly,
• Theresa M. McCormick and
• David R. Stuart

Beilstein J. Org. Chem. 2024, 20, 1428–1435, doi:10.3762/bjoc.20.125

• interaction in a wide range of applications that include crystal engineering, drug discovery and light-emitting materials [1][2][3][4]. Although, halogen bonding was first “observed” over 200 years ago [5][6] and the structural characteristics were elucidated in the latter half of the nineteenth century [7

• points, in which XB donors with larger Vs,max values also had more exergonic associations, we actually observed two almost parallel clusters of data (Scheme 6c). In this case, neutral XB donors 26–28, and 30–36 had Vs,max values ≈5–50 kcal/mol and a slope of −0.24 (Scheme 6c, light grey dots), whereas

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

• radicals by activation of C–O bonds using visible-light photoredox catalysis offers a mild and environmentally benign approach to useful chemical transformations. Alcohols, carboxylic acids, anhydrides, xanthates, oxalates, N-phthalimides, and thiocarbonates are some examples of alkyl and acyl precursors

• photocatalysts, transition-metal photoredox catalysts, and metallaphotocatalysts to produce acyl and alkyl radicals driven by visible light. Keywords: acyl radical; alkyl radical; sustainable catalysis; visible light; Introduction The growing awareness of the necessity for sustainable developments has been

• synthesis [4][5][6][7][8][9]. In the context of sustainable catalysis, visible-light-mediated chemistry is becoming a prominent viable option for radical transformations in the synthesis of biologically useful compounds due to the energy efficiency and environmental friendliness [10][11]. Recently, the

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

• conditions. The key to success is the use of 1,3-dicyanobenzene as a redox mediator and visible-light irradiation, which effectively suppresses the formation of simple reduction, i.e., hydrodehalogenation, products to afford the desired products in good to high yields. Mechanistic investigations proposed

• that a reductive radical-polar crossover pathway is likely to be involved in this transformation. Keywords: aryl halides; C–C bond formation; electroreduction; radicals; visible light; Introduction Alkene hydroarylation is an attractive method for the construction of alkylarenes, which serve as

• -light-mediated alkene hydroarylation commonly requires external reductants and/or hydrogen atom sources to complete the catalytic cycle [21][22][23][24][25]. Over the past few decades, electrochemistry has proven to be an environmentally benign and convenient approach for accessing open-shell

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

• moieties absorbing ≈465 nm light (Figure 1b) should be excited at the resonance Raman spectroscopy using a 488 nm laser. This is supported by the observation that the excitation at 633 and 785 nm where 1b did not show any absorption (Figure 1b) did not give any Raman signals [20]. Extraction of SWNTs with

• breathing vibration, resulting in higher frequency shift as shown in Figure 4 [11][26]. With normalization in G-band at 1570 cm−1, the relative intensity decreases in the RBM region of e- and i-SWNTs may be due to light absorption and/or peak broadening caused by the interlocking Cu-nanobrackets 1b

Mechanistic investigations of polyaza[7]helicene in photoredox and energy transfer catalysis

• Johannes Rocker,
• Till J. B. Zähringer,
• Matthias Schmitz,
• Till Opatz and
• Christoph Kerzig

Beilstein J. Org. Chem. 2024, 20, 1236–1245, doi:10.3762/bjoc.20.106

• thorough photochemical characterization is essential for efficient light-driven applications. In this article, the mode of action of a polyazahelicene catalyst (Aza-H) was investigated using laser flash photolysis (LFP). The study revealed that the chromophore can function as a singlet-state photoredox

• (distance 6 cm) was used as the excitation light source. D) Irradiation experiments of (E)-stilbene (blue) and (Z)-stilbene (red) with 2 mol % Aza-H employing a 427 nm LED as light source. E) Schematic energy diagram of triplet sensitized E/Z isomerization of stilbene. F) Reaction scheme of the cyclization

Competing electrophilic substitution and oxidative polymerization of arylamines with selenium dioxide

• Vishnu Selladurai and
• Selvakumar Karuthapandi

Beilstein J. Org. Chem. 2024, 20, 1221–1235, doi:10.3762/bjoc.20.105

• sample vials and monitored the apparent color change (Figure S34, Supporting Information File 1). Instantaneous color change from colorless to blackish dark was observed for an o-anisidine solution after addition of SeO2. For an aniline solution, the color became light pink immediately upon addition of

Cofactor-independent C–C bond cleavage reactions catalyzed by the AlpJ family of oxygenases in atypical angucycline biosynthesis

• Jinmin Gao,
• Liyuan Li,
• Shijie Shen,
• Guomin Ai,
• Bin Wang,
• Fang Guo,
• Tongjian Yang,
• Hui Han,
• Zhengren Xu,
• Guohui Pan and
• Keqiang Fan

Beilstein J. Org. Chem. 2024, 20, 1198–1206, doi:10.3762/bjoc.20.102

• anion O2•−. This discovery sheds more light on the biosynthesis of atypical angucyclines and extends the repertoire of cofactor-independent oxygenases. Results and Discussion Cofactor-independent oxidative ring cleavage and rearrangement reactions catalyzed by AlpJ with CR1 (8) as substrate Given the

• analysis of the alp gene cluster from Streptomyces ambofaciens revealed AlpG as the homolog of JadH. The N-terminal His6-tagged construct of AlpG was expressed and purified to homogeneity in E. coli (Figure S2, Supporting Information File 1). The purified AlpG displayed a light yellow color, and the

Stability trends in carbocation intermediates stemming from germacrene A and hedycaryol

• Naziha Tarannam,
• Prashant Kumar Gupta,
• Shani Zev and
• Dan Thomas Major

Beilstein J. Org. Chem. 2024, 20, 1189–1197, doi:10.3762/bjoc.20.101

• several significant processes, terpenoids play an indispensable role in cell-wall and membrane biosynthesis, sensing, plant defense, electron transport, or conversion of light into chemical energy [1][2]. Based on the number of hydrocarbon units, terpenes are classified into various families like

• . 6-6 and 5-7 bicyclic carbocations formed by protonation and cyclization of germacrene A and hedycaryol. Bar plot for the relative free energies of germacrene A and hedycaryol carbocations relative to carbocation A. Germacrene A carbocations are shown in light color shades and hedycaryol carbocations

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