Synthesis of spiroindolenines through a one-pot multistep process mediated by visible light

• Francesco Gambuti,
• Jacopo Pizzorno,
• Chiara Lambruschini,
• Renata Riva and
• Lisa Moni

Beilstein J. Org. Chem. 2024, 20, 2722–2731, doi:10.3762/bjoc.20.230

• indole alkaloids. Here, we develop a novel approach for the one-pot multistep synthesis of different spiro[indole-isoquinolines]. The protocol proposed involves the visible light mediated oxidation of N-aryl tertiary amines using bromochloroform with the generation of a reactive iminium species, which

• reacts with an isocyanide and an electron-rich aniline in a three-component Ugi-type reaction to give an α-aminoamidine. This compound might undergo an additional visible light-mediated oxidation to furnish a second iminium intermediate, which acts as electrophile in an intramolecular electrophilic

• : isocyanide; multicomponent reactions; one-pot reaction; oxidation; spiroindolenine; Ugi reaction; visible light; Introduction Diversity-oriented synthesis (DOS) is a successful approach to biologically active scaffolds directed to create an enormous exploratory space in pharmaceutical hit discovery [1][2

Photoluminescence color-tuning with polymer-dispersed fluorescent films containing two fluorinated diphenylacetylene-type fluorophores

• Kazuki Kobayashi,
• Shigeyuki Yamada,
• Motohiro Yasui and
• Tsutomu Konno

Beilstein J. Org. Chem. 2024, 20, 2682–2690, doi:10.3762/bjoc.20.225

• especially indispensable for our affluent life, is more difficult than the development of the blue-, yellow-, and red-light-emitting molecules mentioned above [24][25][26]. Therefore, to achieve white luminescence covering the entire spectral range of the visible light region, two or more colors of

Anion-dependent ion-pairing assemblies of triazatriangulenium cation that interferes with stacking structures

• Yohei Haketa,
• Takuma Matsuda and
• Hiromitsu Maeda

Beilstein J. Org. Chem. 2024, 20, 2567–2576, doi:10.3762/bjoc.20.215

• +) cations, used as visible light fluorescent dyes, have been synthesized via a nucleophilic aromatic substitution (SNAr) reaction with primary alkylamines (e.g., 1a+; Figure 1) [15][16]. The highly planar geometry of the TATA+ core unit induces π–π stacking structures in single-crystal and film states, as

Visible-light-mediated flow protocol for Achmatowicz rearrangement

• Joachyutharayalu Oja,
• Sanjeev Kumar and
• Srihari Pabbaraja

Beilstein J. Org. Chem. 2024, 20, 2493–2499, doi:10.3762/bjoc.20.213

• and development of a visible light-assisted modular photo-flow reactor with a seamlessly integrated post-synthetic work-up procedure enabling the efficient synthesis of dihydropyranones from furfuryl alcohols. The reaction uses sun light as green energy source, and the novel photo-flow reactor

• a result, developing an alternative strategy would be an attractive solution to address the limitations described above. Flow chemistry was chosen as the most attractive alternative for the photo-induced (visible light) Achmatowicz rearrangement to convert furfuryl alcohol scaffolds into

• product synthesis. Scope of the integrated continuous photo-flow (visible light)-induced Achmatowicz rearrangement reaction. Reaction conditions: Stock solution (A) comprise of 2/K2S2O8/Ru(bpy)3Cl·6H2O/ACN/DMSO/H2O in a molar ratio of 1:1:0.005:70:54:408; yields are based on isolated yields. Proposed

O,S,Se-containing Biginelli products based on cyclic β-ketosulfone and their postfunctionalization

• Kateryna V. Dil and
• Vitalii A. Palchykov

Beilstein J. Org. Chem. 2024, 20, 2143–2151, doi:10.3762/bjoc.20.184

• ][4][9] or even visible light-driven methods [25][26][27][28]. We started our study from the optimization of the reaction conditions using β-ketosulfone 1, benzaldehyde and thiourea as model reaction. According to the literature, the reaction has been shown to work best and most efficiently under

Efficacy of radical reactions of isocyanides with heteroatom radicals in organic synthesis

• Akiya Ogawa and
• Yuki Yamamoto

Beilstein J. Org. Chem. 2024, 20, 2114–2128, doi:10.3762/bjoc.20.182

• , when using sunlight, which is an inexhaustible natural energy, it is expected to be the most environmentally friendly method. The homolysis of E–E upon visible light irradiation is induced by exciting one electron of the isolated electron pair on E to the anti-bonding orbital of the E–E-bond (σ

• %). Since it is known that the carbon radical capturing ability of (PhTe)2 is even four times higher than that of (PhSe)2 [31], we investigated the radical addition to isocyanides using a disulfide–ditelluride binary system under photoirradiation. The visible-light-irradiated thiotelluration reaction did

• not proceed at all for normal isocyanides, but for aromatic isocyanides with electron-withdrawing groups (EWG) such as p-NO2, p-CF3, p-CN, p-Cl, and m-MeO, the desired thiotelluration reaction proceeded under visible light irradiation to successfully afford the corresponding thiotelluration products 4

Understanding X-ray-induced isomerisation in photoswitchable surfactant assemblies

• Beatrice E. Jones,
• Camille Blayo,
• Jake L. Greenfield,
• Matthew J. Fuchter,
• Nathan Cowieson and
• Rachel C. Evans

Beilstein J. Org. Chem. 2024, 20, 2005–2015, doi:10.3762/bjoc.20.176

• ]. In addition to this, AAPTAB has a high thermal half-life at room temperature (5.7 years [19]), meaning there is no significant contribution from thermal Z–E isomerisation over the course of these experiments. Using in-situ UV- and visible-light irradiation with SAXS, here we measure the intermediate

• that Z–E isomerisation cannot be easily induced using gentle heating or visible light, as shown by the stability of the UV–vis absorbance spectra and SAXS patterns under these conditions (Figures S1 and S3, Supporting Information File 1). In contrast, irradiation with X-rays leads to significant

A facile three-component route to powerful 5-aryldeazaalloxazine photocatalysts

• Ivana Weisheitelová,
• Radek Cibulka,
• Marek Sikorski and
• Tetiana Pavlovska

Beilstein J. Org. Chem. 2024, 20, 1831–1838, doi:10.3762/bjoc.20.161

• /alloxazine photoredox catalysis [9][14][15][16][17][18][19], 7-methoxyderivatives should also be considered due to their absorption closer to the visible light region. This allows longer wavelength LEDs with lower energy photons to be applied, potentially contributing to avoiding undesired reactions [14][15

• potent, biologically active compounds. Interestingly, the introduction of a strong methoxy group at position 7 of the 5-aryldeazaalloxazine core led to a bathochromic shift in the absorption spectra of the synthesised molecules, making them more suitable for visible light photocatalysis. Experimental

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

• moiety. The excellent photoswitchability in organic medium and the photoresponsiveness in aqueous medium, driven by visible light, were investigated by UV–vis absorption spectroscopy. The assembled supramolecular nanostructures were confirmed by electron microscopy, while the supramolecular packing was

• revealed by X-ray diffraction analysis. Upon visible-light irradiation, significant transformations of the DA geometry enabled transformations of the supramolecular assemblies on a microscopic scale, subsequently disassembling macroscopic soft scaffolds of DAs. The current work shows promising use for the

• fabrication of visible-light-controlled macroscopic scaffolds, offering the next generation of biomedical materials with visible-light-controlled microenvironments and future soft-robotic systems. Keywords: donor–acceptor Stenhouse adduct; photoresponsive molecular amphiphile; supramolecular transformation

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

• pioneering report in 2013 that used photocatalyst 9-fluorenone under visible-light irradiation to generate a photoexcited aryl ketone, capable of HAT to promote benzylic fluorination with Selectfluor (Figure 23) [69]. The reaction tolerated an exceptional range of functional groups and enabled the

• disclosed the use of catalytic amounts of the organic dye Acr+-Mes under visible-light irradiation in combination with stoichiometric amounts of Selectfluor to achieve benzylic fluorination (Figure 29) [74]. It was proposed that a SET between Selectfluor and the photoexcited catalyst liberated fluoride and

Electrophotochemical metal-catalyzed synthesis of alkylnitriles from simple aliphatic carboxylic acids

• Yukang Wang,
• Yan Yao and
• Niankai Fu

Beilstein J. Org. Chem. 2024, 20, 1497–1503, doi:10.3762/bjoc.20.133

• esters, the so called "Barton esters", for decarboxylative cyanation of aliphatic acids with tosyl cyanide as the nitrile source under visible light irradiation at room temperature [21][22]. Although two synthetic steps are required, this is the first practical decarboxylative cyanation protocol because

• by anodic oxidation and visible light irradiation of the Ce species in a sequential fashion [38][39][40][41][42][43][44][45]. Therefore, the anodic electrode potential for this process could be substantially reduced. In doing so, a low working potential at the anode offers the opportunity for

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

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

• ][53]. Furthermore, odd-numbered [n]cumulenes have proven to be effective redox mediators for electroreductive radical borylation of unactivated aryl chlorides without visible-light irradiation by the group of Milner [54]. Herein, we report transition-metal-catalyst-free electroreductive alkene

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

Advancements in hydrochlorination of alkenes

• Daniel S. Müller

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

• 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

• 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

• measured by the ESR spin trapping method under irradiation of visible light (527 nm green LED). 4-Oxo-TEMP was used as a spin trapping reagent to form an adduct with 1O2, i.e., 4-oxo-TEMPO, which was observed by ESR (Figure 7b). As shown in Figure 7a, upon visible light irradiation, three peaks

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

• 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

• in a moderate yield. Conclusion In summary, we have developed a visible-light-mediated palladium-catalyzed carboamination reaction of 1,3-dienes or allenes with diazo esters and amines, providing a broad array of synthetically valuable unsaturated γ- and ε-AA derivatives. This methodology represents

• Geng-Xin Liu Xiao-Ting Jie Ge-Jun Niu Li-Sheng Yang Xing-Lin Li Jian Luo Wen-Hao Hu Guangdong Key Laboratory of Chiral Molecule and Drug Discovery, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, Guangdong 510006, China 10.3762/bjoc.20.59 Abstract Herein, we report a visible

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

• 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

• -Acylated compounds 2a–c in solutions exhibited fluorescence in the region of 465–468 nm, and the excitation emission spectra agreed well with the absorption spectra (Figure 1). Compounds 2a–c in solutions demonstrated a typical negative photochromism [1][16] when irradiated with visible light of 436 nm

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

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

• 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

• 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

• ], have been employed as suitable photocatalysts (Scheme 4B). Under visible light irradiation the photocatalyst (PC) is excited into its corresponding excited state (*PC), where it can be reduced by a suitable electron donor such as DIPEA or Hantzsch ester to generate the reduced form of the photocatalyst

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

• , which have been shown to be particularly sensitive to light [70]. Upon exposure to UV or visible light, thiarubrine A (36) undergoes a desulfurization process to give rise to the corresponding thiophene 37, exhibiting enhanced antibiotic activity (Scheme 10, bottom). This naturally-occurring S-extrusion

• sulfur and regenerate the initial 5-membered carbocycle, the thiopyran scaffold in (H2)n@52 was first oxidized with m-CPBA to yield the corresponding sulfoxide (H2)n@53. As a key step, the latter was next subjected to photoinduced SO-extrusion under visible light, leading to a ring contraction in 86

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

• Abstract In recent years, S-(alkyl)thianthrenium salts have become an important means of functionalizing alcohol compounds. However, additional transition metal catalysts and/or visible light are required. Herein, a direct thioetherification/amination reaction of thianthrenium salts is realized under metal

• ]. Recently, Ritter and co-workers reported that alkylthianthrenium salts can be employed to undergo reactions with N/O-nucleophiles under photocatalytic conditions [46]. Nevertheless, additional transition metal catalysts, visible light, or electrochemical devices are required for the reported works

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

• new level of complexity and promise. The photochromic indigos represent a relatively rare type of visible-light-responsive T-type photoswitches demonstrating negative photochromism. The absorption of the photoswitchable indigos covers the spectral range from green to NIR light (≈550–700 nm) making