Photomechanochemistry: harnessing mechanical forces to enhance photochemical reactions

• Francesco Mele,
• Ana M. Constantin,
• Andrea Porcheddu,
• Raimondo Maggi,
• Giovanni Maestri,
• Nicola Della Ca’ and
• Luca Capaldo

Beilstein J. Org. Chem. 2025, 21, 458–472, doi:10.3762/bjoc.21.33

• oxidation of 1,2-diphenylethyne to benzil [71]. Thus, when a 1:2 mixture of 7.1 and 4-chlorothiophenol (7.2) was ground in the presence of eosin Y as the photocatalyst and anhydrous Na2SO4 as a bulking agent, benzil (7.3) was obtained in 43% GC yield under blue light irradiation (LED, 14.5 W). Isolation led

• ). Overall, it was concluded that 7.1 and 7.2 first react to give 7.4 via a dark mechanochemical thiol–yne reaction; the latter is then converted to 7.3 by singlet oxygen generated in situ, by eosin Y. It is important to notice here that the reaction is proposed to proceed according to a different

• (PMMA) jar (Scheme 8) [72]. As far as the irradiation source is concerned, the authors wrapped a LED strip around the jar. A solution-based precedent by the Yan group was used as a benchmark transformation [73]. Under optimized conditions, a mixture of diazonium salt 8.1, B2Pin2 (1.5 equiv) and eosin Y

Red light excitation: illuminating photocatalysis in a new spectrum

• Lucas Fortier,
• Corentin Lefebvre and
• Norbert Hoffmann

Beilstein J. Org. Chem. 2025, 21, 296–326, doi:10.3762/bjoc.21.22

• have been extensively studied in the literature such as bridged Eosin Y 37 [44], BODIPY 38 [45], and dibenzothiazole 39 (Figure 5) [46]. Indeed, organic dyes, with their inherent advantages of low toxicity, environmental friendliness, and tunable optical properties, represent a promising alternative

Advances in radical peroxidation with hydroperoxides

• Oleg V. Bityukov,
• Pavel Yu. Serdyuchenko,
• Andrey S. Kirillov,
• Gennady I. Nikishin,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2024, 20, 2959–3006, doi:10.3762/bjoc.20.249

Recent advances in transition-metal-free arylation reactions involving hypervalent iodine salts

• Ritu Mamgain,
• Kokila Sakthivel and
• Fateh V. Singh

Beilstein J. Org. Chem. 2024, 20, 2891–2920, doi:10.3762/bjoc.20.243

• their essential roles in product formation. Optimized conditions comprised the reaction of the quinoline N-oxides 25 (1 equiv) with diaryliodonium tetrafluoroborates 26 (2 equiv) as the arylating agent, 1,4-benzoquinone (BQ) as an additive (2 equiv), the photocatalyst eosin Y (10 mol %), and Cs2CO3 (1

• mechanism by adding 2 equivalents of TEMPO to the reaction mixture. The absence of the desired product indicated the involvement of a radical pathway in the process. The proposed reaction mechanism begins with the activation of eosin Y by visible light from 5 W blue LEDs, transitioning it to its excited

• state, eosin Y*. This excited state further undergoes oxidation via a single-electron-transfer (SET) reaction with Ar2IBF4 26, producing eosin Y+ and a phenyl radical 30 (Scheme 10). The radical intermediate 30 selectively binds to the C2 position of either quinoline or pyridine N-oxide, forming

Factors influencing the performance of organocatalysts immobilised on solid supports: A review

• Zsuzsanna Fehér,
• Dóra Richter,
• Gyula Dargó and
• József Kupai

Beilstein J. Org. Chem. 2024, 20, 2129–2142, doi:10.3762/bjoc.20.183

• reactions in a less protic and less polar solvent. Attaching catalysts to solid supports also offers the potential for enhancing catalyst stability. Boyer and co-workers reported the use of silica nanoparticle-supported eosin Y 21 as a photocatalyst in reversible addition fragmentation chain transfer (RAFT

• mesoporous material. Photoinduced RAFT polymerisation of n-butyl acrylate (19) catalysed by silica nanoparticle-supported eosin Y 21, which could be recycled over five reaction cycles. Pressure and temperature dependence of the 1,4-addition of propanal to trans-β-nitrostyrene under continuous flow conditions

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

• 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

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

• 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

• , the aminodecarboxylation reaction proved unsuccessful when employing alternative photocatalysts such as Ru(bpy)3Cl2 or eosin Y, underscoring the distinctive ability of q-OAc to activate TCNHPI esters via EDA complex formation. Photoinduced transition metal-catalyzed mechanisms The in situ formation of

Copper-promoted C5-selective bromination of 8-aminoquinoline amides with alkyl bromides

• Changdong Shao,
• Chen Ma,
• Li Li,
• Jingyi Liu,
• Yanan Shen,
• Chen Chen,
• Qionglin Yang,
• Tianyi Xu,
• Zhengsong Hu,
• Yuhe Kan and
• Tingting Zhang

Beilstein J. Org. Chem. 2024, 20, 155–161, doi:10.3762/bjoc.20.14

• selective C5-bromination of 8-aminoquinoline amides using carbon tetrabromide and dibromomethane under photo- and electrocatalysis conditions [27][28]. In 2017, Xia and co-workers reported a novel, mild, metal-free, and regioselective bromination of amides, wherein the organic dye eosin Y acted as the

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp³)–H to construct C–C bonds

• Hui Yu and
• Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

• this type of CDC reaction (Scheme 43b–e). Efficient CDC reactions could be achieved with 1 mol % of eosin Y in the absence of additional base or oxidizing agents. In this transformation, eosin Y may act as a direct hydrogen atom transfer photocatalyst (Scheme 43b) [124]. The CDC reaction between

Tetraphenylethylene-embedded pillar[5]arene-based orthogonal self-assembly for efficient photocatalysis in water

• Zhihang Bai,
• Krishnasamy Velmurugan,
• Xueqi Tian,
• Minzan Zuo,
• Kaiya Wang and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2022, 18, 429–437, doi:10.3762/bjoc.18.45

• intramolecular phenyl-ring rotations and functioned as an ideal donor. After the loading of eosin Y (EsY) as acceptor on the surface of the assembly of m-TPEWP5 and G, the worm-like nanostructures changed into nanorods, which facilitates a Förster resonance energy transfer (FRET) from the m-TPEWP5 and G

• supramolecular assembly with a two-step FRET process by the utilization of a metallacycle-tetraphenylethylene (TPE) donor and eosin Y (EsY) and sulforhodamine (SR101) as first and second acceptors, respectively. The resulting supramolecular energy transfer system was applied to the alkylation of C–H bonds via a

Visible-light-mediated copper photocatalysis for organic syntheses

• Yajing Zhang,
• Qian Wang,
• Zongsheng Yan,
• Donglai Ma and
• Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

• -catalyzed trifluoromethylchlorosulfonylation of unactivated alkenes 4 under photochemical conditions. When used in place of [Cu(dap)2]Cl, ruthenium-based, iridium-based, and eosin Y catalysts promoted the trifluoromethylchlorination of alkenes with the extrusion of SO2 (e.g., product 6). Studies were

• chlorosulfonylated products 8 and 9, whereas replacing the copper catalyst by ruthenium-based, iridium-based, and eosin Y catalysts afforded the desired products only in trace amount. Unexpectedly, the corresponding CuII complex, Cu(dap)Cl2, also produced the desired product with good yield. Based on the literature

• . Reiser and co-workers [52][53] unexpectedly observed the iodoperfluoroalkylation of alkenes and perfluoroalkyl iodides 10 in the presence of [Cu(dap)2]Cl. Consistent with the previous report, the desired products 11 were not obtained with ruthenium-based, iridium-based, and eosin Y catalysts (Scheme 9

A visible-light-induced, metal-free bis-arylation of 2,5-dichlorobenzoquinone

• Pieterjan Winant and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 2315–2320, doi:10.3762/bjoc.17.149

• eosin Y and green light as a reducing agent an array of substrates were functionalized. Common among reports on the radical CH-arylation of benzoquinones is the use of multiple equivalents of starting material to prevent bis-arylation. The latter inherently relies on the use of an excess of radical

• functionalizing 2,5-dichlorobenzoquinone (1), using conditions similar to those reported by König et al. [28], differing only in the use of an excess of radical precursor. As expected, exposing a mixture of 1, aryldiazonium salt 2a and eosin Y in DMSO to green light resulted in a complex reaction mixture

• investigating the influence of the catalyst, we discovered that the reaction proceeded smoothly in the absence of eosin Y, implying an autocatalytic or self-promoting system. A similar process has recently been described by Wu et al. [40], in the arylation of BODIPYs [41][42][43], where radicals are formed

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• ) [121]. Notably, the organic photocatalyst eosin Y was employed, and the cyclizations proceeded with excellent diastereoselectivity, usually higher than 19:1. When 1,3-ketocarbonyl substrates 100 were employed, the use of a weak Lewis acid (LiBr) was required to accomplish the cyclizations, and no

Heterogeneous photocatalytic cyanomethylarylation of alkenes with acetonitrile: synthesis of diverse nitrogenous heterocyclic compounds

• Guanglong Pan,
• Qian Yang,
• Wentao Wang,
• Yurong Tang and
• Yunfei Cai

Beilstein J. Org. Chem. 2021, 17, 1171–1180, doi:10.3762/bjoc.17.89

• ). Traditional g-C3N4 exhibited a low catalytic activity for this transformation (Table 1, entry 6). Switching from CN-K to a homogeneous organo photocatalyst such as eosin Y and 4CzIPN, led to lower yields of the desired product (Table 1, entries 7 and 8). The expensive Ru/Ir-based metal complexes gave similar

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• , Lakhdar and colleagues [10] obtained the target product 3 with LED (5 W) irradiation of a solution containing arylphosphine oxide 2, alkynes 1, eosin Y (EY, 4 mol %), N-ethoxy-2-methylpyridinium (4), and sodium bicarbonate in DMF (Scheme 2). As a distinct example of EDA complexes, the process efficiency

• depends on the association of eosin Y and oxidant 4 to a donor–acceptor EY–4 ground-system complex (high reactivity). Due to the ability of aryl groups to stabilize the formed alkenyl radical, this protocol could control regioselectivity efficiently with unsymmetrical alkynes. In addition, EPR

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

• Minzan Zuo,
• Krishnasamy Velmurugan,
• Kaiya Wang,
• Xueqi Tian and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• evolution ability in the presence of eosin Y (EY) dye (9.9 ± 0.2 mmol H2 in 60 min) in a neutral aqueous solution compared to that of a mixed α-,β-CD:CoPyS complex and free CoPyS (8.5 ± 0.3 mmol H2 in 60 min). This significant H2 evolution might be due to the fact that the electrostatic repulsion between

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• elimination, producing a Co(I) species. Finally, the photoexcited eosin Y reoxidizes Co(I) to Co(II), while the photosensitizer is reoxidized by molecular oxygen, thus completing the overall catalytic process. In addition, a complementary strategy towards photocatalytic C–H annulation was disclosed by Rueping

• similar arylation was disclosed by Balaraman et al. using eosin Y as a photoredox catalyst (Figure 24) [86]. This methodology operated under mild conditions, was efficient using a low loading of both catalysts and could be scaled-up to a gram-scale. The procedure featured a good functional tolerance and

• combining palladium-catalyzed C–H activation and photoredox catalysis (Figure 27) [89]. Interestingly, the transformation occurred smoothly in the presence of eosin Y, an inexpensive (in comparison with Ir- or Ru-based photoredox catalysts), and easily accessible organic photocatalyst. The reaction, carried

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

Photocatalyzed syntheses of phenanthrenes and their aza-analogues. A review

• Alessandra Del Tito,
• Havall Othman Abdulla,
• Davide Ravelli,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 1476–1488, doi:10.3762/bjoc.16.123

• method was applied to the two-step synthesis of the alkaloid trisphaeridine (15.3) on a gram-scale quantity (Scheme 15) [78]. O-2,4-Dinitrophenyloximes were competent substrates for the photocatalyzed generation of iminyl radicals. In this case, the reaction was photoorganocatalyzed by eosin Y and took

• desired products 18.3a–d in good yields [91]. Notably, a metal-free version of this strategy, based on the use of the 1-chloroanthraquinone photoorganocatalyst, was likewise reported [92]. A dual-catalytic system, comprising of eosin Y sodium salt (1 mol %) as photoredox catalyst and the thermal catalyst

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• reported a visible light-promoted photochemical reductive decarboxylation/alkylation of carboxylic acid analogs (Scheme 4) [45]. In this protocol, the carboxylic acids are converted into the corresponding RAE 4.1 by a condensation with N-hydroxyphthalimide. The organic dye eosin Y (OD13, E(PC/PC−) ≈ −1.1 V

• combination of eosin Y (OD13) with a sacrificial electron donor can trigger the reductive debromination of several α-carbonyl halides [53]. Riboflavin (OD11) [54] and thiaporphyrin [55] have been applied as well as organic photocatalysts for similar reductive dehalogenations. Hydrogen atom transfer

• successfully employed for the generation of C(sp3) radicals via HAT [58]. Interestingly, Wu and co-workers demonstrated that eosin Y (OD13) can also act as a direct HAT catalyst under visible-light irradiation [59]. Organic photoredox catalysis can also drive indirect HAT processes. In these reactions, the

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• (bpy)3)]2+, [Ir(ppy)3], eosin Y, and 4CzTPN [12] (Figure 3). However, some porphyrin and metalloporphyrin derivatives possess adequate potentials to be applied as photoredox catalysts in C–C and C-heteroatom bond formations [10][22]. Furthermore, supramolecular porphyrin-containing molecules, such as

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• upon optimization, 4-anisaldehyde (52) proved to be a better photocatalyst under UV-A irradiation than the initially used eosin Y. Compound 182, the all-trans-isomer, was the major product. The optimized conditions are presented in Scheme 43a. Conducting several control experiments and noticing that

Photocatalytic deaminative benzylation and alkylation of tetrahydroisoquinolines with N-alkylpyrydinium salts

• David Schönbauer,
• Carlo Sambiagio,
• Timothy Noël and
• Michael Schnürch

Beilstein J. Org. Chem. 2020, 16, 809–817, doi:10.3762/bjoc.16.74

• borylations [41][42], heteroarylations [43], and thioesterifications [44]. Additionally, several methods using photoredox chemistry were also published. For instance, the alkylation of isoquinolines under iridium catalysis and alkynylation with eosin Y as the catalyst [45][46]. In this contribution, we

• obtained with [Ru(bpy)3]Cl2, albeit the reaction was still low-yielding (29%, Table 1, entry 1) and was accompanied with substantial decomposition of the starting material. Eosin Y, fluorescein, and [Ir(dtbbpy)(ppy)2]PF6 gave lower yields in comparison (Table 1, entries 2, 3 and 4). Applying strictly inert

• ). Eosin Y was inefficient under these conditions (Table 1, entry 20). Since [Ru(bpy)3]Cl2 is significantly cheaper than the iridium catalyst, the former was used in further reactions. Regarding the addition of different bases, the yield remained unchanged, when lutidine was added. Potassium carbonate and