Synthesis of 5-arylidenerhodanines in L-proline-based deep eutectic solvent

• Stéphanie Hesse

Beilstein J. Org. Chem. 2023, 19, 1537–1544, doi:10.3762/bjoc.19.110

•  2, entry 5). This observation demonstrates the positive role of proline on the reaction mechanism but clearly indicates that it is not sufficient. In fact, the exact role of DES in this reaction is still not clear as ʟ-proline may act as a catalyst via an iminium pathway as previously described [21

Synthesis and biological evaluation of Argemone mexicana-inspired antimicrobials

• Jessica Villegas,
• Bryce C. Ball,
• Katelyn M. Shouse,
• Caleb W. VanArragon,
• Ashley N. Wasserman,
• Hannah E. Bhakta,
• Allen G. Oliver,
• Danielle A. Orozco-Nunnelly and
• Jeffrey M. Pruet

Beilstein J. Org. Chem. 2023, 19, 1511–1524, doi:10.3762/bjoc.19.108

• ]. Similar to berberine, results have demonstrated that the antibacterial activity of chelerythrine can be tied to DNA intercalation and disruption to cell membrane permeability [11][24]. One particular mechanism of action noted for chelerythrine’s antitumor bioactivity is through the inhibition of protein

• noteworthy structure–activity relationship was one mentioned earlier, with the complete obliteration of activity seen with the 13-hydroxy-substituted berberine variants; though no analogous feature exists within the chelerythrine series. Identifying the primary mechanism of action for these variants is

Unraveling the role of prenyl side-chain interactions in stabilizing the secondary carbocation in the biosynthesis of variexenol B

• Moe Nakano,
• Rintaro Gemma and
• Hajime Sato

Beilstein J. Org. Chem. 2023, 19, 1503–1510, doi:10.3762/bjoc.19.107

• offer many valuable insights from a fundamental organic chemistry perspective. The terpene cyclization cascade generally involves a multistep domino-type reaction. Therefore, it is challenging to reveal the detailed reaction mechanism solely by an experimental method. To address this issue

• as the C–H–π interaction between the carbocation intermediate and the Phe residue of terpene cyclase in the biosynthesis of sesterfisherol [21], and the intricated rearrangement reaction mechanism promoted by the equilibrium state of the homoallyl cation and the cyclopropylcarbinyl cation in the

• aspects. First, this cyclization cascade involves a prenyl side chain that do not participate in the cyclization cascade. This type of terpene compounds has already been reported, such as santalene, bergamotene, mangicol, etc. The idea that the reaction mechanism changes due to differences in the prenyl

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• (PIDA) and meta-chloroperbenzoic acid (m-CPBA) toward 3-sulfinylated and 3-sulfonylated product, respectively, were performed in this work. A plausible mechanism involves the treatment of 1 with BF3·Et2O toward cation I, which reacted with the C–C triple bond in 12 to give sulfonium intermediate II

• efficient Lewis acid catalyst (Scheme 10) [50]. In the procedure, oxidative cleavage of one S–N bond and 1,2-sulfur migration afforded π-conjugated 6-substituted 2,3-diarylbenzo[b]thiophenes 16. A plausible mechanism is shown in Scheme 11. The coordination of AlCl3 with the phthalimide/succinimide unit of 1

• and acetic acid (AcOH) as a Brønsted acid, whereas i(a)midation was achieved by using Pd(OAc)2 as catalyst and Cu(OAc)2 as a Lewis acid. A possible mechanism for this chemodivergent C–H activation is depicted in Scheme 16. First, Pd catalyzed the formation of palladacycle I. Oxidative addition of AcOH

α-(Aminomethyl)acrylates as acceptors in radical–polar crossover 1,4-additions of dialkylzincs: insights into enolate formation and trapping

• Angel Palillero-Cisneros,
• Paola G. Gordillo-Guerra,
• Fernando García-Alvarez,
• Olivier Jackowski,
• Franck Ferreira,
• Fabrice Chemla,
• Joel L. Terán and
• Alejandro Perez-Luna

Beilstein J. Org. Chem. 2023, 19, 1443–1451, doi:10.3762/bjoc.19.103

• a radical addition mechanism. This is further supported by the result of an I-atom transfer experiment (Scheme 7, top). In the presence of two equivalents of iPrI, the reaction of 8a with Et2Zn leads to a mixture of product 14a and product 25a, incorporating an iPr moiety, in a 14a/25a 30:70 mixture

• configuration of the major diastereomer of (RS)-14b. Air-promoted tandem 1,4-addition–aldol condensation reactions of Et2Zn with α-(aminomethyl)acrylates. Diagnostic experiments for a radical mechanism and for enolate formation. Diagnostic experiments with N-benzyl enoate 10. Reactivity manifolds for the air

Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• compounds, including diaryl- and dialkyl ketones and prochiral ketones, respectively (Scheme 36) [50]. Riant, Leyssens and co-workers investigated the mechanism of the hydrosilylation reaction of ketones using DFT, in situ FTIR, NMR, and kinetic methods [51][52]. The catalytic characteristics of sterically

• conversion occurred using either Pd–NHC or Cu–NHC alone. 2.9 C(sp2)–H amidation Chang and co-workers [96] reported an NHC–Cu-catalyzed direct amidation of C–H bonds by using N-chlorocarbamates or N-chloro-N-sodiocarbamates as amino source. In this mechanism, a copper–aryl intermediate reacts with the

Functional characterisation of twelve terpene synthases from actinobacteria

• Anuj K. Chhalodia,
• Houchao Xu,
• Georges B. Tabekoueng,
• Binbin Gu,
• Kizerbo A. Taizoumbe,
• Lukas Lauterbach and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2023, 19, 1386–1398, doi:10.3762/bjoc.19.100

• 26 can be well understood from the cyclisation mechanism towards 23 (Scheme 1B). After substrate ionisation to A a 1,10-cyclisation leads to the (E,E)-germacradienyl cation (B) that can either be deprotonated to 24 or captured with water to yield 26. Both compounds are important neutral intermediates

• as plasticisers. A) Cope rearrangement of 24 and 26. B) Cyclisation mechanism from FPP to 23, identifying compound 26 as a biosynthetic intermediate and 24 as a side product. Terpene synthase homologs characterised in this study. Supporting Information Supporting Information File 162: Additional

Visible-light-induced nickel-catalyzed α-hydroxytrifluoroethylation of alkyl carboxylic acids: Access to trifluoromethyl alkyl acyloins

• Feng Chen,
• Xiu-Hua Xu,
• Zeng-Hao Chen,
• Yue Chen and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2023, 19, 1372–1378, doi:10.3762/bjoc.19.98

• -difluoroethoxyphthalimide as the fluoroalkylating reagent failed to afford the desired product. According to our previous work [39] and literature precedent [27][35][38], a possible mechanism is proposed in Figure 2. The interaction between 2 and HE generates an electron donor–acceptor (EDA) complex A, which undergoes a

• column chromatography to give the coupling product 3. Selected natural products and pharmaceuticals bearing acyloins. Proposed reaction mechanism. Strategies for the synthesis of α-trifluoromethyl acyloins. Substrate scope. Standard conditions: a solution of alkyl carboxylic acid 1 (0.4 mmol), 2 (0.6

Synthesis of ether lipids: natural compounds and analogues

• Marco Antônio G. B. Gomes,
• Alicia Bauduin,
• Chloé Le Roux,
• Romain Fouinneteau,
• Wilfried Berthe,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2023, 19, 1299–1369, doi:10.3762/bjoc.19.96

• properties via an original mechanism of action. The increasing interest in studying ether lipids for fundamental and applied researches invited to review the methodologies developed to prepare ether lipids. In this review we focus on the synthetic method used for the preparation of alkyl ether lipids either

• with biomembranes via supramolecular interactions with the lipids and proteins that are embedded in these membranes. We can hypothesis that their mechanism of action occurs via a direct interaction with membrane proteins or by a modification of the biophysical properties of the membranes. It must be

Organic thermally activated delayed fluorescence material with strained benzoguanidine donor

• Alexander C. Brannan,
• Elvie F. P. Beaumont,
• Nguyen Le Phuoc,
• George F. S. Whitehead,
• Mikko Linnolahti and
• Alexander S. Romanov

Beilstein J. Org. Chem. 2023, 19, 1289–1298, doi:10.3762/bjoc.19.95

• : guanidine; organic; photoluminescence; TADF; yellow; Introduction Thermally activated delayed fluorescence (TADF) is a photoluminescence mechanism where excitons undergo thermally-assisted reverse-intersystem crossing from an excited triplet state to a higher-lying in energy singlet state to emit delayed

• aerated MCH solution. The reduction in quantum yield on exposure to oxygen is due to quenching of the triplet excited states indicating a TADF luminescence mechanism. PLQY in Zeonex films is 39% in air, which is lower than the PLQY of 87% reported for 4CzIPN [17]. The two-component excited state lifetime

• 4CzIPN, vide supra. We collected steady state luminescence and PL after long time delays for 4BGIPN at 77 K to further support the assignment of the TADF mechanism and attempt to characterize LE and CT triplet states. The emission profiles experienced minor narrowing upon cooling to 77 K, while the PL

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

• bonds The possible mechanism of the CDC reaction involving ether α-C(sp3)–H bonds mainly follows the two pathways outlined in Scheme 2. Route a: First, the C(sp3)–H bond at the α-position of the oxygen atom undergoes a single-electron transfer under the combined action of the transition metal and an

• benzylic ethers occurs at room temperature in the presence of Cu(OTf)2/InCl3 as catalysts and DDQ as oxidant (Scheme 3) [51]. By this route, a series of 2-alkoxymalonate diester derivatives was synthesized through direct CDC reaction. The mechanism study showed that the first step of the catalytic cycle

• , tetrahydrofuran or tetrahydropyran can smoothly react with many methyl aryl ketones to obtain the desired coupling products (Scheme 6a) [54]. The mechanism of the dehydrogenation cross-coupling reaction may undergo a radical pathway. Initially, the tert-butoxy radical produced by the dissociation of t-BuOOH may

Metal catalyst-free N-allylation/alkylation of imidazole and benzimidazole with Morita–Baylis–Hillman (MBH) alcohols and acetates

• Olfa Mhasni,
• Jalloul Bouajila and
• Farhat Rezgui

Beilstein J. Org. Chem. 2023, 19, 1251–1258, doi:10.3762/bjoc.19.93

• elimination of imidazole (2a) finally providing the allylated derivative 6a (Scheme 2) [24][25][26][31]. It is notable, that such reaction mechanism involving the intermediate I was previously explored by Smith [32] and supported by studies of Tamura [33]. Next, in order to explore the scope of the above

• -substituted imidazole derivatives from MBH adducts. Proposed mechanism for the allylation of imidazole with alcohol 4a. Allylation of imidazole derivatives 2a,b with cyclic MBH adducts 4 and 5. Optimization of the reaction conditions of imidazole (2a) with acyclic MBH 1a. Michael addition of imidazole (2a

Selective construction of dispiro[indoline-3,2'-quinoline-3',3''-indoline] and dispiro[indoline-3,2'-pyrrole-3',3''-indoline] via three-component reaction

• Ziying Xiao,
• Fengshun Xu,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2023, 19, 1234–1242, doi:10.3762/bjoc.19.91

• substituent. A plausible reaction mechanism is proposed to explain the formation of the different spirooxindoles. Keywords: cascade reaction; dimedone; isatin; 3-methyleneoxindole; multicomponent reaction; spirooxindole; Introduction Spirooxindole is one important privileged structural skeleton and is found

• to explain the formation of different cyclic compounds, a plausible reaction mechanism was proposed in Scheme 2 on the basis of the present experiments and the previous works [51][52][53]. Firstly, 3-isatyl-1,4-dicarbonyl compound 1 was converted to a carbanion in the presence of base. In the

• . This reaction provided efficient synthetic protocols for the synthesis of dispiro[indoline-3,2'-quinoline-3',3''-indoline] and dispiro[indoline-3,2'-pyrrole-3',3''-indoline] derivatives. A plausible reaction mechanism was proposed to explain the selective formation of the different polycyclic compounds

Radical ligand transfer: a general strategy for radical functionalization

• David T. Nemoto Jr,
• Kang-Jie Bian,
• Shih-Chieh Kao and
• Julian G. West

Beilstein J. Org. Chem. 2023, 19, 1225–1233, doi:10.3762/bjoc.19.90

• body’s own cytochrome P450 enzymes. These catalysts exhibit unique “radical rebound” reactivity at their heme active sites (Scheme 1) [12], a mechanism proposed by Groves and co-workers and heavily explored beginning in the 1970s [13][14]. This two-step functionalization sequence begins with HAT from an

• indicative of a carbocationic pathway are not observed, suggesting that RPC does not occur. Further, the inability of ATRA products to undergo SN2 with the added nucleophiles under our reaction conditions is inconsistent with a tandem ARTA/nucleophilic displacement alternative mechanism. Finally, a

• . Further, we demonstrated that diazidation could be rendered catalytic using Fe(III) nitrate hydrate III as the iron source and performing the reaction under continuous flow conditions. Interestingly, this mechanism bears some similarity to Lin’s electrocatalytic diazidation, where azido radical generation

Unravelling a trichloroacetic acid-catalyzed cascade access to benzo[f]chromeno[2,3-h]quinoxalinoporphyrins

• Chandra Sekhar Tekuri,
• Pargat Singh and
• Mahendra Nath

Beilstein J. Org. Chem. 2023, 19, 1216–1224, doi:10.3762/bjoc.19.89

• afford copper(II) benzo[f]chromeno[2,3-h]quinoxalinoporphyrin 3 in 65% yield (Scheme 2). The successful isolation of intermediate 17 and its conversion to copper(II) benzo[f]chromeno[2,3-h]quinoxalinoporphyrin 3 as shown in Scheme 2 clearly support the proposed mechanism for the formation of the desired

• afford porphyrin 17 in 67% yield. Plausible mechanism for the formation of copper(II) benzo[f]chromeno[2,3-h]quinoxalinoporphyrins. Electronic absorption spectra of copper(II) benzo[f]chromeno[2,3-h]quinoxalinoporphyrins 3–8 in CHCl3 (1.5 × 10−6 M) at 298 K. (Inset shows Q-bands). Electronic absorption

Enabling artificial photosynthesis systems with molecular recycling: A review of photo- and electrochemical methods for regenerating organic sacrificial electron donors

• Grace A. Lowe

Beilstein J. Org. Chem. 2023, 19, 1198–1215, doi:10.3762/bjoc.19.88

• electrochemically irreversible oxidation or an EC mechanism where the oxidized donor undergoes a chemical step that prevents recombination but forms a stable, recyclable byproduct. The dimerization of thiolates to disulfides is a good example because unlike dimers of NADH analogues that form carbon–carbon bonds the

Exploring the role of halogen bonding in iodonium ylides: insights into unexpected reactivity and reaction control

• Carlee A. Montgomery and
• Graham K. Murphy

Beilstein J. Org. Chem. 2023, 19, 1171–1190, doi:10.3762/bjoc.19.86

• numerous similar attributes, halogen bonding has also proven to be a viable alternative in methodologies that rely on hydrogen bond initiation. For example, both halogen- and hydrogen bonding can be used in supramolecular chemistry as the binding mechanism in photoresponsive receptors [73][74][75][76][77

• previously proposed for hypervalent iodine compounds [9][117][118][119], Moriarty proposed a carbene-free mechanism for the formation of 11 [113]. In this, the nucleophilic olefin first attacked the electrophilic iodine center to form zwitterion 15, which closed to produce iodocycle 16 and then underwent

• ). In the earlier study, Koser recovered 24 and 27, and they proposed an ionic mechanism wherein the ylide acted as a nucleophile, giving 26 as the initial intermediate (Figure 7, top). To account for the differing products observed, Hadjiarapoglou instead suggested that an electrophilic addition

New one-pot synthesis of 4-arylpyrazolo[3,4-b]pyridin-6-ones based on 5-aminopyrazoles and azlactones

• Vladislav Yu. Shuvalov,
• Ekaterina Yu. Vlasova,
• Tatyana Yu. Zheleznova and
• Alexander S. Fisyuk

Beilstein J. Org. Chem. 2023, 19, 1155–1160, doi:10.3762/bjoc.19.83

• domino reaction of enamines with azlactones [22][23][24][25][26][27][28][29][30]. We have previously reported a plausible mechanism of such reactions [22][25]. 1H-Pyrazol-5-amines also enter into similar transformations with azlactones in various solvents. The yields of tetrahydro-1H-pyrazolo[3,4-b

Selective and scalable oxygenation of heteroatoms using the elements of nature: air, water, and light

• Damiano Diprima,
• Hannes Gemoets,
• Stefano Bonciolini and
• Koen Van Aken

Beilstein J. Org. Chem. 2023, 19, 1146–1154, doi:10.3762/bjoc.19.82

• a study was conducted to explore possible additives that can further enhance the reaction rate (Figure 1) thus increasing the overall productivity. Also, analyzing the effect of the additives on the kinetics might give further clues for the extensive elucidation of the reaction mechanism. For a

• 3.5 minutes (air). In order to determine the robustness and overall safety of the flow process, a two-hours run was performed without facing any operational problem. Proposed alternative reaction pathway In 2017, Bonesi et al. described in detail the oxidation mechanism of sulfides via direct

• originates from water. In this tentative mechanism, the sulfide I forms with water and oxygen a photoactive complex II which is excited at 365 nm towards III. Via single-electron transfer both a radical cation IV and the superoxide V are generated. Subsequently, the sulfide radical cation IV undergoes a

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

• methods for SET chemistry. In the context of synthetic molecular photoelectrochemistry, there are various sub-fields classified depending on how the electrochemical and photochemical steps interplay in the mechanism. This Review’s main focus is on electrochemically mediated photoredox catalysis (e-PRC

• electron transfer (conPET) mechanism (Figure 4C), PDI is photoexcited and reductively quenched by Et3N to form its stable, colored radical anion PDI•− that can be photoexcited again to generate an even stronger reductant; *PDI•− (*E1/2 = −1.87 V vs SCE) [34]. A SET process to the aryl halide regenerates

• cyclized product 5a was obtained – albeit only in 28% yield – corroborating a radical mechanism. PDI catalysts have since found applications in other chemical transformations, their photophysical properties have been investigated further [40], and new variants [41] including heterogeneous versions have

Synthesis of imidazo[4,5-e][1,3]thiazino[2,3-c][1,2,4]triazines via a base-induced rearrangement of functionalized imidazo[4,5-e]thiazolo[2,3-c][1,2,4]triazines

• Dmitry B. Vinogradov,
• Alexei N. Izmest’ev,
• Angelina N. Kravchenko,
• Yuri A. Strelenko and
• Galina A. Gazieva

Beilstein J. Org. Chem. 2023, 19, 1047–1054, doi:10.3762/bjoc.19.80

• transformations of the heterocyclic system proceeding by an ANRORC mechanism under the action of KOH in methanol. Thus, 6-oxindolylideneimidazo[4,5-e]thiazolo[3,2-b]-1,2,4-triazines are transformed into substituted 2-oxoquinoline-4-carboxylates in the presence of excess KOH [20] while their 6-arylmethylidene

• . however, acid 5l underwent partial transformations even under these conditions and was not isolated as individual substance. We assumed the following mechanism for the formation of products 9 (Scheme 8). Redistribution of the electron density in the acid molecule 5 after protonation of the carbonyl group

• mechanism of imidazo[4,5-e]thiazolo[2,3-c][1,2,4]triazine 1d into imidazo[4,5-e][1,3]thiazino[2,3-c][1,2,4]triazine 3d. Synthetic approaches to imidazo[4,5-e][1,3]thiazino[2,3-c][1,2,4]triazines 3a–d,j. Synthesis of imidazo[4,5-e][1,3]thiazino[2,3-c][1,2,4]triazine-7-carboxylic acids 5a–j. Synthesis of

The effect of dark states on the intersystem crossing and thermally activated delayed fluorescence of naphthalimide-phenothiazine dyads

• Liyuan Cao,
• Xi Liu,
• Xue Zhang,
• Jianzhang Zhao,
• Fabiao Yu and
• Yan Wan

Beilstein J. Org. Chem. 2023, 19, 1028–1046, doi:10.3762/bjoc.19.79

• may also enhance the rISC in OLED devices, in which the electron–hole recombination produces mainly the triplet state (the theoretical probability is 75%, by following the spin statistic rule) [1]. Compared to the application studies, the investigation of the photophysical mechanism of TADF emitters

• [38][39][40][41][42][43][44] and, more recently, time-resolved electron paramagnetic resonance (TREPR) spectroscopy [33][39][44][45][46] were also applied to study TADF mechanisms, but the examples are limited. Therefore, much room is left for studies of the photophysical mechanism of the TADF

• insights into the TADF mechanism. For the dyads with the oxidized PTZ units, however, the CS state energy is increased by up to 0.8 eV, yet the 3LE state energy does not change. Thus the spin–vibronic coupling between the 3LE and 3CS is weak and no TADF was observed for this dyad only a long-lived 3LE

The unique reactivity of 5,6-unsubstituted 1,4-dihydropyridine in the Huisgen 1,4-diploar cycloaddition and formal [2 + 2] cycloaddition

• Xiu-Yu Chen,
• Hui Zheng,
• Ying Han,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2023, 19, 982–990, doi:10.3762/bjoc.19.73

• -configured. For explaining the formation of the various cyclic compounds, a plausible reaction mechanism was proposed on the base of the previously reported works [41][42][43][44] and the present experiments (Scheme 2). Initially, the nucleophilic addition of isoquinoline to dimethyl acetylenedicarboxylate

• -dihydropyridines. Plausible reaction mechanism for the various products 4, 5, and 6. Optimizing the reaction conditions.a Synthesis of isoquinolino[1,2-f][1,6]naphthyridines 4a–o.a Synthesis of the bicyclic compounds 5a–o and 6a–o.a Supporting Information The crystallographic data of compounds 4k (CCDC 2260340

Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• -assisted reactions in water, solvent-free conditions and in other organic solvents. Clauson–Kaas reaction and its mechanism The Clauson–Kaas reaction refers to the synthesis of various N-substituted pyrroles via an acid-catalyzed reaction between aromatic or aliphatic primary amines and 2,5

• nanoorganocatalysts. Various solvent systems, such as aqueous conditions, different organic solvents, solvent-free conditions, ionic liquids, and DESs, have been reported in modified Clauson–Kaas reactions at room temperature, under thermal and microwave-assisted conditions. In the Clauson–Kaas reaction mechanism

• reactivity of the aromatic amine depends on the electron density of the amino compounds. In addition, the authors also performed the reaction of aliphatic amines with 2,5-DMTHF (2), and found that aliphatic amines are inert in the presence of MgI2 etherate. The proposed mechanism shown in Scheme 9b suggests

Photoredox catalysis enabling decarboxylative radical cyclization of γ,γ-dimethylallyltryptophan (DMAT) derivatives: formal synthesis of 6,7-secoagroclavine

• Alessio Regni,
• Francesca Bartoccini and
• Giovanni Piersanti

Beilstein J. Org. Chem. 2023, 19, 918–927, doi:10.3762/bjoc.19.70

• : 1) it functions as the central intermediate in the biosynthetic pathways leading to numerous prenylated indole alkaloids, such as ergot alkaloids in normal biosynthesis and clavicipitic acid in derailment biosynthesis [68][69][70][71]; and 2) the mechanism of the fundamental central C-ring formation

• of all ergot alkaloids, specifically the decarboxylative cyclization of DMAT, is still a puzzle even though a radical mechanism has been proposed (Figure 1a) [72][73]. Results and Discussion Herein, we propose that visible light irradiation of the cationic iridium photocatalyst Ir[dF(CF3)ppy]2(dtbbpy

• a tentative mechanism (Figure 2). First, the radical cation I was generated via the oxidation of indole 5 by the excited Ir-based photocatalyst, followed by sequential regioselective proton transfer on the benzylic dimethylallyl unit C–H bond of the C4 side-chain, thereby generating II. Here, the