Competitive cyclization of ethyl trifluoroacetoacetate and methyl ketones with 1,3-diamino-2-propanol into hydrogenated oxazolo- and pyrimido-condensed pyridones

• Svetlana O. Kushch,
• Marina V. Goryaeva,
• Yanina V. Burgart,
• Marina A. Ezhikova,
• Mikhail I. Kodess,
• Pavel A. Slepukhin,
• Alexandrina S. Volobueva,
• Vladimir V. Zarubaev and
• Victor I. Saloutin

Beilstein J. Org. Chem. 2025, 21, 2716–2729, doi:10.3762/bjoc.21.209

• octahydropyrido[1,2-a]pyrimidinones 4a–d and hexahydrooxazolo[3,2-a]pyridones 5a–c was determined by IR, 1H, 19F, 13C NMR spectroscopy, two-dimensional NMR experiments, and X-ray diffraction analysis (XRD). The IR spectra of octahydropyrido[1,2-a]pyrimidinones 4a–d are characterized by reduced vibrational

• frequencies of the carbonyl function (ν 1633–1593 cm−1) and N–H, O–H groups (ν 3435–3126 cm−1), which indicates their participation in the hydrogen bond formation [67]. On the other hand, the IR spectra of hexahydrooxazolo[3,2-a]pyridones 5a–c contain intense absorption bands of the C=O function at ν 1652

• . Supporting Information Supporting Information File 16: General synthetic procedures, characterization data, XRD analysis data and copies of 1H, 19F, 13C NMR spectra, IR spectra, HRMS spectra of all synthesized compounds. Acknowledgements Analytical studies were carried out using the equipment of the Center

Tandem hydrothiocyanation/cyclization of CF₃-iminopropargyl alcohols with NaSCN in the presence of AcOH

• Ruslan S. Shulgin,
• Ol’ga G. Volostnykh,
• Anton V. Stepanov,
• Igor’ A. Ushakov,
• Alexander V. Vashchenko and
• Olesya A. Shemyakina

Beilstein J. Org. Chem. 2025, 21, 2694–2702, doi:10.3762/bjoc.21.207

• . Results and Discussion We commenced our investigation using CF3-subsituted iminopropargyl alcohol 1a and NaSCN as model substrates. The completion of the reaction was monitored using IR spectroscopy to observe the disappearance of the band at 2219 cm−1 (–C≡C–). It was found that CF3-iminopropargyl alcohol

• internal reference at 20–25 °C. IR spectra were measured on a Bruker Vertex-70 instrument in thin layer, films or KВr pellets. Microanalyses were performed on a Flash 2000 elemental analyzer. Melting points were determined using a Kofler micro hot stage. Mass spectra were recorded on a GCMSQP5050A

• available starting materials were used without further purification. CF3/n-C3F7-substituted iminopropargyl alcohols 1 were prepared according to published methods [31][32]. The structures of synthesized products have been proven by 1H, 13C and 2D (1Н,13С HMBC) NMR, 19F NMR techniques, as well as IR spectra

Recent advancements in the synthesis of Veratrum alkaloids

• Morwenna Mögel,
• David Berger and
• Philipp Heretsch

Beilstein J. Org. Chem. 2025, 21, 2657–2693, doi:10.3762/bjoc.21.206

Synthesis of new tetra- and pentacyclic, methylenedioxy- and ethylenedioxy-substituted derivatives of the dibenzo[c,f][1,2]thiazepine ring system

• Gábor Berecz,
• András Dancsó,
• Mária Tóthné Lauritz,
• Loránd Kiss,
• Gyula Simig and
• Balázs Volk

Beilstein J. Org. Chem. 2025, 21, 2645–2656, doi:10.3762/bjoc.21.205

• standard open 40 μL aluminum pan under 50 mL/min nitrogen atmosphere. IR spectra were obtained on a Bruker ALPHA FT-IR spectrometer in KBr pellets or in neat. NMR spectra were recorded at 295 K on a Bruker Avance III HD 600 (600 and 150 MHz for 1H and 13C NMR spectra, respectively) spectrometer equipped

• (thickness of the stationary phase: 30 mm, eluent: DCM). After evaporation of the solvent, the residue was triturated with Et2O (50 mL) to give pure 7 (25.30 g, 84%) as colorless crystals. Mp 223‒225 °C (CH3CN/EtOH 1:1 (v/v)); IR (KBr): 1638, 1604, 1574, 1501, 1354, 1300, 1175, 1063, 854 cm−1; 1H NMR (600

• chromatography (short aluminum oxide column, eluent: heptane/DCM 1:1, DCM) and isomer 8 (0.62 g, 2%) was isolated as pale yellow crystals. Mp 254‒256 °C (CH3CN); IR (KBr): 1665, 1485, 1344, 1111, 1061, 859 cm−1; 1H NMR (500 MHz, CDCl3): 7.96 (d, 4J = 2.0 Hz, 1H), 7.94 (d, 3J = 8.6 Hz, 1H), 7.63 (dd, 4J = 2.1 Hz

Thiazolidinones: novel insights from microwave synthesis, computational studies, and potentially bioactive hybrids

• Luan A. Martinho,
• Victor H. J. G. Praciano,
• Guilherme D. R. Matos,
• Claudia C. Gatto and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2025, 21, 2618–2636, doi:10.3762/bjoc.21.203

• inconsistency made it challenging to rely on NMR as the primary method for confirming the structure of the expected products. To overcome this limitation, other analytical techniques, such as mass spectrometry and infrared (IR) spectroscopy, were employed. These methods successfully corroborated the formation

Visible-light-driven NHC and organophotoredox dual catalysis for the synthesis of carbonyl compounds

• Vasudevan Dhayalan

Beilstein J. Org. Chem. 2025, 21, 2584–2603, doi:10.3762/bjoc.21.200

• presence of NHC (20 mol %), 4CzIPN (2 mol %) under mild conditions, producing corresponding unsymmetrical ketone derivatives 8 in up to 95% yield. An Ir-based photocatalyst was initially selected because its excited state is a strong oxidant (E1/2[Ir*III/II] = +1.21 V). Although 4-ethylanisole exhibits a

• higher oxidation potential (E1/2 = +1.52 V). This reaction was examined using different solvents, and it was found that toluene and 1,4-dioxane gave low yields (4–5% yield). Under blue LED irradiation, Ir-based PC is photoexcited, and its excited state is reductively quenched by the electron-rich arene

• substrate 7, generating the aryl radical cation C along with the formation of corresponding radical anion of the photocatalyst (PC•–). The reduction potentials are (E1/2(P/P•–) = –1.37V vs SCE for [Ir(dF(CF₃)ppy)₂(dtbbpy)]PF₆ and –1.21V vs SCE for 4CzIPN as an organophotocatalyst. This method permits the C

Synthesis of the tetracyclic skeleton of Aspidosperma alkaloids via PET-initiated cationic radical-derived interrupted [2 + 2]/retro-Mannich reaction

• Ru-Dong Liu,
• Jian-Yu Long,
• Zhi-Lin Song,
• Zhen Yang and
• Zhong-Chao Zhang

Beilstein J. Org. Chem. 2025, 21, 2470–2478, doi:10.3762/bjoc.21.189

• formation of unique radical intermediates [9][10]. We previously demonstrated the Ir-catalyzed [2 + 2] cyclization/retro-Mannich reaction of a tryptamine-substituted cyclopentenone F, which led to the formation of indoline J (Figure 1b) [15]. Unlike other reported methods [16][17][18], the PET reaction of F

• construction of the tetracyclic core of Aspidosperma alkaloids. Our method involves an Ir-catalyzed PET reaction of K for the stereoselective formation of the cis-configured BC bicyclic core with an all-carbon quaternary center [25][26]. Computational studies suggest that the observed tandem PET reaction of K

The high potential of methyl laurate as a recyclable competitor to conventional toxic solvents in [3 + 2] cycloaddition reactions

• Ayhan Yıldırım and
• Mustafa Göker

Beilstein J. Org. Chem. 2025, 21, 2389–2415, doi:10.3762/bjoc.21.184

• performed using silica gel (60 F254, Merck, Darmstadt, Germany) plates. Melting points were recorded using a Büchi melting point B-540 apparatus (Büchi Labortechnik AG in Flawil, Switzerland). The IR spectra were measured by Spectrum Two FT-IR spectrometer (PerkinElmer, Massachusetts, USA). The NMR spectra

Comparative analysis of complanadine A total syntheses

• Reem Al-Ahmad and
• Mingji Dai

Beilstein J. Org. Chem. 2025, 21, 2334–2344, doi:10.3762/bjoc.21.178

• with an Ir-catalyzed regioselective C–H borylation developed simultaneously by Ishiyama, Miyaura, Hartwig, and co-workers and Smith and co-workers [26][27]. First, the triflate group of 33 was removed by a Pd-catalyzed reduction with ammonium formate as the reducing reagent. The resulting Boc-protected

• lycodine 34 underwent Ir-catalyzed C3–H borylation mainly guided by steric factors to provide boronic ester 35 in 75% yield. With the boronic ester handle at the C3 position, the subsequent Suzuki–Miyaura cross coupling between 35 and 33 occurred smoothly to deliver pseudo-dimer 36, which upon acidic

• . With optically active 51 in hand, its extra ketone functionality was reduced via thioacetalization (51 → 52) and radical reduction (52 → 53) to provide 53, a diverging point to access C–H arylation partners 54 and 55. mCPBA oxidation of 53 afforded pyridine N-oxide 54. The Ir-catalyzed C–H borylation

Recent advances in Norrish–Yang cyclization and dicarbonyl photoredox reactions for natural product synthesis

• Peng-Xi Luo,
• Jin-Xuan Yang,
• Shao-Min Fu and
• Bo Liu

Beilstein J. Org. Chem. 2025, 21, 2315–2333, doi:10.3762/bjoc.21.177

• 82, followed by dehydrogenation, delivered compound 83 in 49% yield over three steps. Pyridone 83 could be funneled into pyridine 85 through O-triflation followed by Pd-catalyzed reductive detriflation. Ir-catalyzed meta-selective C–H borylation of 85, followed by bromodeborylation of the pyridine

Insoluble methylene-bridged glycoluril dimers as sequestrants for dyes

• Suvenika Perera,
• Peter Y. Zavalij and
• Lyle Isaacs

Beilstein J. Org. Chem. 2025, 21, 2302–2314, doi:10.3762/bjoc.21.176

• but insoluble in CHCl3, CH2Cl2, methanol, acetone, acetonitrile, and hexane; G2W4: soluble in CHCl3, CH2Cl2, acetonitrile, DMSO, and TFA but insoluble in methanol, acetone, and hexane). The new hosts G2W1–G2W4 were fully characterized spectroscopically (1H and 13C NMR, IR, MS) and the data is in

• -insoluble acyclic CB[n]-type receptors that possess benzene (G2W4), naphthalene (G2W3), and triphenylene (G2W1 and G2W2) walls bearing methoxy substituents. The new hosts were fully characterized by 1H NMR, 13C NMR, IR, mass spectrometry, and X-ray crystallography (G2W1 and G2W3). We studied the efficiency

• locking or in deuterated dimethyl sulfoxide (DMSO-d6) or in deuterated chloroform (CDCl3). Melting points were measured on a Meltemp apparatus in open capillary tubes and are not corrected. IR spectra were recorded on a Thermo Nicolet NEXUS 670 FT/IR spectrometer by attenuated total reflectance (ATR) and

Enantioselective radical chemistry: a bright future ahead

• Anna C. Renner,
• Sagar S. Thorat,
• Hariharaputhiran Subramanian and
• Mukund P. Sibi

Beilstein J. Org. Chem. 2025, 21, 2283–2296, doi:10.3762/bjoc.21.174

• enantioselectivities. A radical chaperone methodology is based on a multicatalytic system in which a chiral Cu(I) catalyst, Brønsted acid (camphoric acid) and Ir photocatalyst work synergistically. An asymmetric synthetic method based on radical C–H functionalization was reported by Nagib and co-workers for the

• quenching, in some cases involving radical–polar crossover processes. The photoredox catalysts used in most of the synergistic catalysis are Ir and Ru-based systems that are expensive and less readily available. This limitation can be overcome by developing green and sustainable organophotoredox systems

Thiadiazino-indole, thiadiazino-carbazole and benzothiadiazino-carbazole dioxides: synthesis, physicochemical and early ADME characterization of representatives of new tri-, tetra- and pentacyclic ring systems and their intermediates

• Gyöngyvér Pusztai,
• László Poszávácz,
• Anna Vincze,
• András Marton,
• Ahmed Qasim Abdulhussein,
• Judit Halász,
• András Dancsó,
• Gyula Simig,
• György Tibor Balogh and
• Balázs Volk

Beilstein J. Org. Chem. 2025, 21, 2220–2233, doi:10.3762/bjoc.21.169

• characterized in detail either below (5a, 5b, 7e, (E)-7h, (Z)-7h, 3e, 3h) or in Supporting Information File 1 ((E)-7a, 7b, (E)-7c, (Z)-7c, 7d, (E)-7f, 7g, 7i, 7j, (E)-9a, (E)-9b, 3a–d, 3f, 3g, 3i, 3j, 10a, 10b). Melting points were determined using a Büchi B-540 melting point apparatus. IR spectra were obtained

• on a Bruker ALPHA FT-IR spectrometer in KBr pellets, ν̃ was reported in cm−1. NMR spectra were recorded at 295 K on a Bruker Avance III HD 600 (600 and 150 MHz for 1H and 13C NMR spectra, respectively) spectrometer equipped with a Prodigy cryo-probe head. Full 1H and 13C assignments were achieved

• , 20.5; IR (KBr) ν̃: 3407, 3360, 1477, 1302, 1151, 1106 cm−1; HREIMS (m/z): [M•]+ calcd for C9H12N4O2S, 240.0675; found, 240.0677. 8-Hydrazino-2-methyl-4-phenyl-2H-1,2,3-benzothiadiazine 1,1-dioxide (5b). To a mixture of 4b (4.00 g, 13.0 mmol) and pyridine (36 mL), hydrazine monohydrate (6.30 mL, 6.50 g

A m-quaterphenyl probe for absolute configurational assignments of primary and secondary amines

• Yuka Takeuchi,
• Mutsumi Kobayashi,
• Yuuka Gotoh,
• Mari Ikeda,
• Yoichi Habata,
• Tomohiko Shirai and
• Shunsuke Kuwahara

Beilstein J. Org. Chem. 2025, 21, 2211–2219, doi:10.3762/bjoc.21.168

• used without further purification. Melting points were obtained with a Mel-Temp capillary apparatus and were not corrected. IR spectra were obtained as KBr disks on a JASCO FT/IR-410 spectrophotometer. The FAB mass spectra were recorded using a JEOL 600H mass spectrometer. 1H and 13C{1H} NMR spectra

• ), 7.00 (dt, J1 = 8.7 Hz, J2 = 3.6 Hz, 4H), 3.86 (s, 6H), 3.68–3.46 (m, 6H), 3.20–3.12 (m, 2H), 1.12 (d, J = 6.6 Hz); 13C NMR (100 MHz, CDCl3) δ 159.3, 141.4, 140.7, 134.0, 133.2, 130.3, 128.2, 126.3, 126.0, 114.3, 63.4, 60.7, 55.4, 51.3, 13.3; IR (KBr) νmax: 3407, 2959, 1732, 1607, 1517, 1489, 1249, 1178

C2 to C6 biobased carbonyl platforms for fine chemistry

• Jingjing Jiang,
• Muhammad Noman Haider Tariq,
• Florence Popowycz,
• Yanlong Gu and
• Yves Queneau

Beilstein J. Org. Chem. 2025, 21, 2103–2172, doi:10.3762/bjoc.21.165

The application of desymmetric enantioselective reduction of cyclic 1,3-dicarbonyl compounds in the total synthesis of terpenoid and alkaloid natural products

• Dong-Xing Tan and
• Fu-She Han

Beilstein J. Org. Chem. 2025, 21, 2085–2102, doi:10.3762/bjoc.21.164

• 69 and lactone 70 at 456 nm with fac-Ir(ppy)3 as the photocatalyst furnished a mixture of isomeric olefins. Finally, DBU-promoted the isomeric olefins conjugation and removal of the two silyl ether completed the first total synthesis of (+)-randainin D (13). Total synthesis of (−)-hunterine A and

Bioinspired total syntheses of natural products: a personal adventure

• Zhengyi Qin,
• Yuting Yang,
• Nuran Yan,
• Xinyu Liang,
• Zhiyu Zhang,
• Yaxuan Duan,
• Huilin Li and
• Xuegong She

Beilstein J. Org. Chem. 2025, 21, 2048–2061, doi:10.3762/bjoc.21.160

• subsp. brachystachys, and discovered a series of complex natural products named sargalmides A–E [43] (Scheme 7a). To clearly elucidate the complex structures, Yue and co-workers used multiple methods including extensive spectroscopic analysis (NMR, IR and MS), X-ray crystallography, quantum-chemical

Photochemical reduction of acylimidazolium salts

• Michael Jakob,
• Nick Bechler,
• Hassan Abdelwahab,
• Fabian Weber,
• Janos Wasternack,
• Leonardo Kleebauer,
• Jan P. Götze and
• Matthew N. Hopkinson

Beilstein J. Org. Chem. 2025, 21, 1973–1983, doi:10.3762/bjoc.21.153

• representative substrate in two steps from benzoyl chloride, imidazole and methyl trifluoromethanesulfonate. In an initial reaction, this species was reacted under photoredox conditions in the presence of [Ir(dF(CF3)ppy)2(dtbpy)]PF6 (2 mol %, dF(CF3)ppy = 3,5-difluoro-2-[5-(trifluoromethyl)-2-pyridine, dtbpy

• to the photocatalyzed process, testing a selection of photocatalysts in the presence of 1 equivalent of DIPEA under blue light irradiation (λmax = 440 nm). Notably, under these modified conditions, the photocatalyzed reaction with the originally test photocatalyst, [Ir(dF(CF3)ppy)2(dtbpy)]PF6

• , resulted in clean formation of the fully reduced product 2 in 48% 1H NMR yield with no intermediate species 3 being detected (Table 1, entry 17). The related iridium complex [Ir(ppy)2(dtbpy)]PF6 (ppy = 2-phenylpyridine) delivered 2 in a similar yield of 46% (Table 1, entry 18) while the organic species

Synthesis, biological and electrochemical evaluation of glycidyl esters of phosphorus acids as potential anticancer drugs

• Almaz A. Zagidullin,
• Emil R. Bulatov,
• Mikhail N. Khrizanforov,
• Damir R. Davletshin,
• Elvina M. Gilyazova,
• Ivan A. Strelkov and
• Vasily A. Miluykov

Beilstein J. Org. Chem. 2025, 21, 1909–1916, doi:10.3762/bjoc.21.148

• as thick liquids with good yields (44–67%) and purity. The structures of glycidyl esters of phosphorus acids 1–3 were confirmed by 31P, 1H NMR, IR spectroscopy, and elemental analysis (see Experimental part for additional information). The 31P{1H} NMR spectrum of diglycidyl methylphosphonate (1

• , 13C 100.6 MHz). 1H and 13C NMR data are reported with reference to solvent resonances, and 31P NMR spectra were reported with respect to external 85% H3PO4 (0 ppm). All experiments were carried out using standard Bruker pulse programs. Infrared (IR) spectra were recorded on a Bruker Vector-22

• –3.69 (m, 2H, OCH2), 4.07–4.09 (m, 2H, OCH2); 31P{1H} NMR (CDCl3, δ, ppm, J, Hz) 32.04 (s); IR (liquid, cm−1): 762 (m, oxirane), 858 (m,oxirane), 927 (m, oxirane), 1019 (m), 1139 (w), 1166 (w, P=O), 1240 (m, oxirane), 1316 (m, R-P(O)OR), 1349 (s, P=O), 1425 (w), 1455 (m), 1647 (m), 2932 (m), 3004 (m

Preparation of spirocyclic oxindoles by cyclisation of an oxime to a nitrone and dipolar cycloaddition

• Beth L. Ritchie,
• Alexandra Longcake and
• Iain Coldham

Beilstein J. Org. Chem. 2025, 21, 1890–1896, doi:10.3762/bjoc.21.146

• silica gel 60F254 plates and visualised by UV irradiation at 254 nm or by staining with an alkaline KMnO4 dip. Flash column chromatography was performed using silica gel (40–63 micron mesh). Infrared spectra were recorded on a Perkin Elmer Spectrum RX Fourier Transform–IR System and only selected peaks

• EtOAc/petrol 1:4, to give the tosylate 3 (1.30 g, 79%) as an amorphous solid; Rf 0.57 (EtOAc/petrol 1:1); IR (film, cm−1) νmax: 2943, 1708, 1647, 1611, 1599, 1494, 1468, 1455, 1425, 1359, 1314, 1292, 1258, 1178, 1119, 1023, 976, 936, 885, 831, 816, 776, 752; 1H NMR (400 MHz, CDCl3) δ 7.66–7.59 (m, 2H

• aldehyde 4 (562 mg, 41%) as needles; mp 94–96 °C; Rf 0.35 (EtOAc/petrol 1:1); IR (film, cm−1) νmax: 2942, 1712, 1614, 1581, 1495, 1472, 1260, 1190, 1177, 1122, 1096, 1064, 1019, 815, 785, 755; 1H NMR (400 MHz, CDCl3) δ 9.44 (t, J = 1.0 Hz, 1H), 7.69–7.62 (m, 2H), 7.36–7.28 (m, 3H), 7.20 (dd, J = 7.5, 1.0

Photoswitches beyond azobenzene: a beginner’s guide

• Michela Marcon,
• Christoph Haag and
• Burkhard König

Beilstein J. Org. Chem. 2025, 21, 1808–1853, doi:10.3762/bjoc.21.143

• -linear optical properties, switching with two-photon absorption of near-IR wavelengths [3][27]. This could open the way to laser-storage devices and to application in biological systems, where longer wavelengths are preferred due to improved tissue penetration [28]. When the push–pull character is not so

General method for the synthesis of enaminones via photocatalysis

• Paula Pérez-Ramos,
• Raquel G. Soengas and
• Humberto Rodríguez-Solla

Beilstein J. Org. Chem. 2025, 21, 1535–1543, doi:10.3762/bjoc.21.116

• by DME, DMSO or acetone diminished the product yields (Table 1, entries 7–9). The reactivity of acridinium PC1 was superior to that of other photocatalysts, including 4-CzlPN (PC2) and [Ir(dF(CF3)ppy)2(dtbbpy)]PF6 (PC3) (Table 1, entries 10 and 11). Attempts to increase the temperature of the process

Highly distinguishable isomeric states of a tripodal arylazopyrazole derivative on graphite through electron/hole-induced switching at ambient conditions

• Himani Malik,
• Sudha Devi,
• Debapriya Gupta,
• Ankit Kumar Gaur,
• Sugumar Venkataramani and
• Thiruvancheril G. Gopakumar

Beilstein J. Org. Chem. 2025, 21, 1496–1507, doi:10.3762/bjoc.21.112

• tapping mode and an ATM300 from RHK Technology, respectively. Aluminum-coated silicon cantilevers from Nanosensors (PPP-NCHR) were used as AFM probes. The force constant and resonance frequency of the cantilevers during the imaging were 30–34 N/m and ≈300 kHz, respectively. A Pt/Ir (80:20) tip was

Photoredox-catalyzed arylation of isonitriles by diaryliodonium salts towards benzamides

• Nadezhda M. Metalnikova,
• Nikita S. Antonkin,
• Tuan K. Nguyen,
• Natalia S. Soldatova,
• Alexander V. Nyuchev,
• Mikhail A. Kinzhalov and
• Pavel S. Postnikov

Beilstein J. Org. Chem. 2025, 21, 1480–1488, doi:10.3762/bjoc.21.110

• spectrum of the crude mixture (Supporting Information File 1, Figure S4). Despite its higher reductive potential, fac-Ir(ppy)3 gave a lower yield of 26% for 2aa compared to [Ru(bpy)3](PF6)2 (Table 1, entry 3). Inspired by the first positive results, we tested various cyanoarene-based catalytic systems

Oxetanes: formation, reactivity and total syntheses of natural products

• Peter Gabko,
• Martin Kalník and
• Maroš Bella

Beilstein J. Org. Chem. 2025, 21, 1324–1373, doi:10.3762/bjoc.21.101

• by the same research group [65][66], the Ir catalyst initially interacts through hydrogen bonds with the quinolone substrate 84, and then upon irradiation, energy transfer occurs to the unbound ketone which enantioselectively reacts with the bound quinolone. Unfortunately, investigations of the

• reduction of the Ni(II) pre-catalyst) via oxidative addition, radical coupling and reductive elimination. The last step is a single-electron transfer between the resulting Ir(II) and Ni(I) complexes, regenerating the active catalysts and closing the two cycles. In 2021, Romanov-Michailidis and Knowles et al

• from the photoexcited Ir complex, Giese-type addition of the resulting triplet diradical 164 to the electron-deficient alkene, intersystem crossing generating a singlet diradical 166 and intramolecular radical recombination. In 2022, Bull and colleagues disclosed an unprecedented synthesis of 3-aryl-3