Phenanthridine–pyrene conjugates as fluorescent probes for DNA/RNA and an inactive mutant of dipeptidyl peptidase enzyme

• Josipa Matić,
• Tana Tandarić,
• Marijana Radić Stojković,
• Filip Šupljika,
• Zrinka Karačić,
• Ana Tomašić Paić,
• Lucija Horvat,
• Robert Vianello and
• Lidija-Marija Tumir

Beilstein J. Org. Chem. 2023, 19, 550–565, doi:10.3762/bjoc.19.40

• signalize complex formation (interaction with a biomolecule, cyclodextrine, metal cation, etc.) or change of receptor conformation [5][6]. Employment of pyrene as a biosensor is complicated due to its large aromatic surface's hydrophobicity and fluorescence sensitivity to oxygen. Therefore, modifications of

• further promoted by favorable cation–π interactions. In other words, in Phen-Py-1+ and Phen-Py-2+, stacked structures account for around 96% and 98% of population, respectively, while in unionized Phen-Py-1 and Phen-Py-2 these cluster around 84% in both cases (Figure 2). This is further supported by

• that a higher degree of aromatic surfaces overlapping and cation–π interactions also yield excimer fluorescence quenching [30][32][33]. This conclusion is strongly in line with experimental insight reported here and helps in explaining the observed excimer fluorescence quenching with a decrease in the

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• photoexcitation of the photosensitizer 43 to form 44 which can oxidize aniline 36a to give radical cation 46 (Scheme 7). Deprotonation by DBU produces the radical 40. The radical anion photosensitizer 45 can reduce Ni(I) to Ni(0), closing the first catalytic cycle. The Ni(0) complex can undergo oxidative addition

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

Germacrene B – a central intermediate in sesquiterpene biosynthesis

• Houchao Xu and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2023, 19, 186–203, doi:10.3762/bjoc.19.18

• this multistep process is initiated by the abstraction of diphosphate to produce an allyl cation that subsequently undergoes typical cation reactions such as cyclisations by intramolecular attack of an olefin to the cationic centre, Wagner–Meerwein rearrangements, hydride or proton shifts. The process

• cation (B) or a 1,11-cyclisation to the (E,E)-humulyl cation (C) is possible. Reattack of diphosphate at C-3 results in nerolidyl diphosphate (NPP) that can undergo a conformational change by rotation around the C-2/C-3 single bond, which allows reionisation to D. This intermediate can react in a 1,10

• -cyclisation to the (Z,E)-germacradienyl cation (E) or a 1,11-cyclisation to the (Z,E)-humulyl cation (F), the E/Z stereoisomers of B and C. Furthermore, a 1,6-cyclisation to the bisabolyl cation (G) or a 1,7-cyclisation to H may follow, which is not possible from A because of its 2E configuration (a

Total synthesis of insect sex pheromones: recent improvements based on iron-mediated cross-coupling chemistry

• Eric Gayon,
• Guillaume Lefèvre,
• Olivier Guerret,
• Adrien Tintar and
• Pablo Chourreu

Beilstein J. Org. Chem. 2023, 19, 158–166, doi:10.3762/bjoc.19.15

• ]. The exact nature of the interaction between the active ate-ferrous complex and the NMP-ligated magnesium cation is so far unknown. Although often neglected in the mechanistic analysis of a cross-coupling system, the importance of the coordination sphere of the main-group cation brought by the

• nucleophilic partner R[M] in a cross-coupling has been reported in the recent literature. It was indeed shown that some ligands (such as diphosphines) used in Fe-catalyzed Negishi cross-coupling reactions (R[M] = RZnX) were actually involved in the coordination of the ZnII cation in a key on-cycle

1,4-Dithianes: attractive C2-building blocks for the synthesis of complex molecular architectures

• Bram Ryckaert,
• Ellen Demeyere,
• Frederick Degroote,
• Hilde Janssens and
• Johan M. Winne

Beilstein J. Org. Chem. 2023, 19, 115–132, doi:10.3762/bjoc.19.12

• cation in (3 + 2) cycloadditions: 5,6-dihydro-1,4-dithiin-2-methanol as a stabilized allyl cation Allyl cations are versatile electrophiles for the allylation of various nucleophiles, but can also act as C3-π-systems in a range of cycloaddition reactions (Scheme 13) [84][85][86][87][88]. When combined

• products related to different competing reaction pathways. However, when suitable cation-stabilizing substituents are present, especially on the central carbon atom, very useful transformations can result for the rapid assembly of cycloheptanoid scaffolds [91]. Oxyallyl cations (when Z is an oxygen-based

• reported far less commonly than their use in (4 + 3) cycloadditions [94]. Simple hydrocarbon allyl cations can also undergo (3 + 2) cycloadditions through a purely stepwise cation olefin cyclization-type pathway, but these generally give complex mixtures and low yields and show unpredictable substrate

Revisiting the bromination of 3β-hydroxycholest-5-ene with CBr₄/PPh₃ and the subsequent azidolysis of the resulting bromide, disparity in stereochemical behavior

• Christian Schumacher,
• Jas S. Ward,
• Kari Rissanen,
• Carsten Bolm and
• Mohamed Ramadan El Sayed Aly

Beilstein J. Org. Chem. 2023, 19, 91–99, doi:10.3762/bjoc.19.9

• C3 hydroxy of 1 is activated. Deprotonation of 10 at C2 with bromide as base provides diene 9 as the minor product. Bromide 4 is formed via cyclopropyl cation 11, which is generated from 10 by loss of triphenylphosphine oxide being supported by involvement of the Δ5 π-bond electrons from the α-face

Catalytic aza-Nazarov cyclization reactions to access α-methylene-γ-lactam heterocycles

• Bilge Banu Yagci,
• Selin Ezgi Donmez,
• Onur Şahin and
• Yunus Emre Türkmen

Beilstein J. Org. Chem. 2023, 19, 66–77, doi:10.3762/bjoc.19.6

• (trifluoromethanesulfonic acid), and the N-acyliminium cation was proposed to be protonated with the super acidic TfOH to form a dicationic species, which was shown by computational studies to be crucial for the success of this transformation. In a later study, the same research group showed that benzamides 2 bearing an

Improving the accuracy of ³¹P NMR chemical shift calculations by use of scaling methods

• William H. Hersh and
• Tsz-Yeung Chan

Beilstein J. Org. Chem. 2023, 19, 36–56, doi:10.3762/bjoc.19.4

• to be included in the NMR calculations. Unusual structures such as phosphenium cation 20, having a chemical shift upfield of the trivalent chloride 19, contrary to expectation where the cation is typically 100 ppm downfield of the corresponding chloride [77][84][85][86], were confirmed by each of the

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• the erythrinadienone intermediate 182. On contrary, common scaffold 180 should hydrolyze to sebiferine-type scaffolds in the presence of water. Taking these results into account, the group exploited the ability of HFIP to stabilize the radical cation formed by PIFA and BF3·EtO2 [95][96] to selectively

• further oxidized, and thus producing the respective benzylic cation. Intramolecular cyclization in the cationic position under participation of the methyl ester function provided the core for (+)-grandilodine C (191) and (+)-lapidilectine B (192), while allylation of the benzylic position allowed

• ). Thus, upon irradiation, iridium polypyridyl photocatalyst allowed the oxidation of the phosphate complex 207 to radical cation 206, which can be readily trapped by TEMPO, and hence stabilizing the imine and allowing cyclization with the pendant amine to form the pyrroloindoline core 210 in 81% yield

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• classified according to the catalytically active species or key intermediates: N-oxyl radicals, oxoammonium cations, amine cation radicals, thiyl radicals, quinones, dioxiranes and oxaziridines, hypervalent iodine compounds, etc. However, some examples of organocatalyzed oxidative processes, in which an

• (Scheme 2). In the enamine type of catalysis (Scheme 2A) the key enamine intermediate can undergo one-electron oxidation (route 1), electrophilic radical attack (route 2), or electrophile attack (route 3). The one-electron oxidation leads to the electrophilic cation radical which can further undergo

• addition to the electron-rich C=C bond [58] or proton loss followed by β-functionalization [59][60][61]. The iminium cation catalysis is used in the activation of electrophilic properties of enones for the nucleophilic epoxidation by hydroperoxides (Scheme 2B). N-Heterocyclic carbene (NHC) organocatalysis

Synthesis of the biologically important dideuterium-labelled adenosine triphosphate analogue ApppI(d₂)

• Petri A. Turhanen

Beilstein J. Org. Chem. 2022, 18, 1466–1470, doi:10.3762/bjoc.18.153

• disodium salt (269 mg, 0.49 mmol) was converted to the corresponding TBA salt by rapid treatment (5 min of stirring) with Dowex H+ cation exchange resin and the addition of 4 equiv of 40% TBAOH in H2O (1260 µL). The mixture was evaporated to dryness in vacuum and kept several days in vacuum to obtain a dry

Naphthalimide-phenothiazine dyads: effect of conformational flexibility and matching of the energy of the charge-transfer state and the localized triplet excited state on the thermally activated delayed fluorescence

• Kaiyue Ye,
• Liyuan Cao,
• Davita M. E. van Raamsdonk,
• Zhijia Wang,
• Jianzhang Zhao,
• Daniel Escudero and
• Denis Jacquemin

Beilstein J. Org. Chem. 2022, 18, 1435–1453, doi:10.3762/bjoc.18.149

• spectroelectrochemistry of the compounds was studied (Figure 7). For NI-PTZ, when a positive potential of +0.53 V (vs Ag/AgNO3) was applied, the hallmark absorption bands of the PTZ•+ radical cation centered at 516, 794, and 891 nm are observed [20]. These bands are similar to the ones observed for the previously

• the impact of the conformational restriction on the photophysical properties of NI-PhMe2-PTZ. We underline that the absorption of the CT states of the dyads may not be the “simple sum” of the absorption of the radical cation and the radical anion of the dyads, obtained by the spectroelectrochemistry

• (Figure 7). The reason is that, in spectroelectrochemistry, one forms either D•+–A or D–A•−, but not D•+–A•−. When photoexciting the dyads, however, the CT (D•+–A•−) state is formed resulting in a different exciton binding energy related to the interaction between the radical anion and cation; this

1,4,6,10-Tetraazaadamantanes (TAADs) with N-amino groups: synthesis and formation of boron chelates and host–guest complexes

• Artem N. Semakin,
• Ivan S. Golovanov,
• Yulia V. Nelyubina and
• Alexey Yu. Sukhorukov

Beilstein J. Org. Chem. 2022, 18, 1424–1434, doi:10.3762/bjoc.18.148

• ) Host–guest motif in the X-ray structure of 4c·HCl·3.5MeOH (guest molecule is shown in “spacefill” representation). (e) Hirshfeld surface of the TAAD cation in 4a·HCl·H2O·MeOH. (e) Hirshfeld surface of the TAAD cation in 4c·HCl·3.5MeOH. (a) Dynamic processes in TAADs 4 and complexation with ROH. (b

Synthesis and electrochemical properties of 3,4,5-tris(chlorophenyl)-1,2-diphosphaferrocenes

• Almaz A. Zagidullin,
• Farida F. Akhmatkhanova,
• Mikhail N. Khrizanforov,
• Robert R. Fayzullin,
• Tatiana P. Gerasimova,
• Ilya A. Bezkishko and
• Vasili A. Miluykov

Beilstein J. Org. Chem. 2022, 18, 1338–1345, doi:10.3762/bjoc.18.139

• cation. Using this approach, tris(4-chlorophenyl)- and tris(3-chlorophenyl)cyclopropenyl bromides were prepared for the first time. The advantage of this approach is the possibility of synthesis of substituted diarylacetylenes, the corresponding substituted benzal chlorides, and triarylcyclopropenyl

Cytochrome P450 monooxygenase-mediated tailoring of triterpenoids and steroids in plants

• Karan Malhotra and
• Jakob Franke

Beilstein J. Org. Chem. 2022, 18, 1289–1310, doi:10.3762/bjoc.18.135

• compound I (intermediate G), it is now generally accepted as a ferryl (Fe(IV)) oxo species with a radical cation in the porphyrin system [18][23]. In the case of hydroxylations, the oxygen from compound I (intermediate G) can then be transferred by an oxygen rebound mechanism (steps 7 and 8) via the ferryl

Electro-conversion of cumene into acetophenone using boron-doped diamond electrodes

• Mana Kitano,
• Tsuyoshi Saitoh,
• Shigeru Nishiyama,
• Yasuaki Einaga and
• Takashi Yamamoto

Beilstein J. Org. Chem. 2022, 18, 1154–1158, doi:10.3762/bjoc.18.119

• 10.3762/bjoc.18.119 Abstract A straightforward electro-conversion of cumene into acetophenone has been reported using boron-doped diamond (BDD) electrodes. This particular conversion is driven by the addition reaction of a cathodically generated hydroperoxide anion to an anodically generated cumyl cation

• , where the BDD’s wide potential window enables the direct anodic oxidation of cumene into the cumyl cation. Since electricity is directly employed as the oxidizing and reducing reagents, the present protocol is easy to use, suitable for scale-up, and inherently safe. Keywords: aromatic alkyl; boron

• anode. The role of electrode materials was investigated with electrochemical measurements. Only the BDD anode with a wide potential window can oxidize cumene directly to afford a cumyl cation as the reaction intermediate. Furthermore, acetophenone is produced via cumene hydroperoxide, and this molecular

A Streptomyces P450 enzyme dimerizes isoflavones from plants

• Run-Zhou Liu,
• Shanchong Chen and
• Lihan Zhang

Beilstein J. Org. Chem. 2022, 18, 1107–1115, doi:10.3762/bjoc.18.113

• addition, radical cation addition, and electrophilic aromatic addition, have also been proposed [1][10][29]. A proposed mechanism is depicted in Scheme 2: First, the hydroxy group on the A- or B-ring is converted into a radical by a P450-induced single-electron transformation. The resulting radical then

Radical cation Diels–Alder reactions of arylidene cycloalkanes

• Kaii Nakayama,
• Hidehiro Kamiya and
• Yohei Okada

Beilstein J. Org. Chem. 2022, 18, 1100–1106, doi:10.3762/bjoc.18.112

• 183-8509, Japan 10.3762/bjoc.18.112 Abstract TiO2 photoelectrochemical and electrochemical radical cation Diels–Alder reactions of arylidene cycloalkanes are described, leading to the construction of spiro ring systems. Although the mechanism remains an open question, arylidene cyclobutanes are found

• to be much more effective in the reaction than other cycloalkanes. Since the reaction is completed with a substoichiometric amount of electricity, a radical cation chain pathway is likely to be involved. Keywords: arylidene cycloalkane; Diels–Alder reaction; radical cation; single-electron transfer

• ; spiro ring system; Introduction Single-electron transfer is one of the simplest modes for small molecule activation, employing a polarity inversion to generate radical ions which have proven to be unique reactive intermediates in the field of synthetic organic chemistry. A radical cation Diels–Alder

Electrochemical Friedel–Crafts-type amidomethylation of arenes by a novel electrochemical oxidation system using a quasi-divided cell and trialkylammonium tetrafluoroborate

• Hisanori Senboku,
• Mizuki Hayama and
• Hidetoshi Matsuno

Beilstein J. Org. Chem. 2022, 18, 1040–1046, doi:10.3762/bjoc.18.105

• solvent and a divided cell with a low temperature (−78 °C) and a relatively high concentration of the supporting electrolyte are necessary, the cation pool method [21] developed by Yoshida and Suga was effective for electrochemical oxidation-induced Friedel–Crafts-type amidomethylation (path d in Scheme 1

• amidoalkylation, the desired products were not obtained/detected by 1H NMR. In contrast, it was reported that anisole [9][11][23] and 1,3,5-trimethylbenzene [23] could react with acyliminium ions generated by the chemical [9][11] or cation pool method [23] to produce amidomethylated products. These results

• indicate that the present electrochemical amidomethylation seems to be relatively less reactive than other chemical methods and the cation pool method. On the other hand, similar electrolysis of 1,3-dimethoxybenzene gave a mixture of products including regioisomeric mono-amidomethylation products together

Electrochemical vicinal oxyazidation of α-arylvinyl acetates

• Yi-Lun Li,
• Zhaojiang Shi,
• Tao Shen and
• Ke-Yin Ye

Beilstein J. Org. Chem. 2022, 18, 1026–1031, doi:10.3762/bjoc.18.103

• ). The enol acetate A first undergoes anodic oxidation to form a radical cation intermediate B, which is then intercepted by azidotrimethylsilane to afford the benzyl radical C. Subsequently, this radical is further anodically oxidized to its oxocarbenium ion intermediate D, which finally reacts with

First example of organocatalysis by cathodic N-heterocyclic carbene generation and accumulation using a divided electrochemical flow cell

• Daniele Rocco,
• Ana A. Folgueiras-Amador,
• Richard C. D. Brown and
• Marta Feroci

Beilstein J. Org. Chem. 2022, 18, 979–990, doi:10.3762/bjoc.18.98

• reactions and usually the product separation is easy [4][5]. Among ILs, imidazolium derivatives are the most studied, in part due to their ease of synthesis, low cost and diverse applications from solvents and reagents in synthesis, to supporting electrolytes in electrochemistry [6]. The imidazolium cation

• reduction of an imidazolium cation to NHC, in an undivided cell under flow conditions, coupled with the anodic generation of Cu(I) from a sacrificial anode to yield the corresponding N-heterocyclic carbene complex [34][35]. In this case, irreversible capture of the NHC by the metallic cation prevented NHC

• (Table 1, entry 4). However, using a silver electrode the corresponding thione was not observed (Table 1, entry 3) [37]. In view of the acidic character of the perfluorosulfonic acid Nafion® membrane, and possible NHC protonation to form the imidazolium cation, the Nafion® membrane was pretreated with an

Understanding the competing pathways leading to hydropyrene and isoelisabethatriene

• Shani Zev,
• Marion Ringel,
• Ronja Driller,
• Bernhard Loll,
• Thomas Brück and
• Dan T. Major

Beilstein J. Org. Chem. 2022, 18, 972–978, doi:10.3762/bjoc.18.97

• -phase calculations commenced with geranylgeranyl cation (A and A’) in a fully extended form. HP pathway The HP gas-phase pathway commences with a C1–C10 cyclization, which yields cation B, which is more stable than A by −11.4 kcal/mol. A subsequent 1,3-hydride transfer results in an allyl cation (C

• yields cation B’, which is more stable than A’ by −15.7 kcal/mol. A subsequent 1,3-hydride transfer results in an allyl cation (C’, −32.1 kcal/mol relative to A’), with a barrier of 5.4 kcal/mol. Cation C’ collapses into D’ via a barrierless 1,6-ring closure (ΔGr of −35.9 kcal/mol relative to A’). D’ can

• be deprotonated to yield IE B or conversely may undergo a 1,2-hydride transfer, forming carbocation E’ (ΔGr of −34.4 kcal/mol relative to A’). This transformation has a ΔG‡ of 6.6 kcal/mol. Cation E’ may then be deprotonated to form IE A. Overall, the exergonicity for the formation of IEs A/B from

Electrochemical and spectroscopic properties of twisted dibenzo[g,p]chrysene derivatives

• Tomoya Imai,
• Ryuhei Akasaka,
• Naruhiro Yoshida,
• Toru Amaya and
• Tetsuo Iwasawa

Beilstein J. Org. Chem. 2022, 18, 963–971, doi:10.3762/bjoc.18.96

• groups are introduced in place of the isopropyl groups, which has a 0.06 V higher oxidation potential than that of MeO-DBC-1. This indicates that alkyl substituents in the X position are effective in stabilizing the radical cation, thus making it more susceptible to oxidation. Unlike DBC-H, an

Introducing a new 7-ring fused diindenone-dithieno[3,2-b:2',3'-d]thiophene unit as a promising component for organic semiconductor materials

• Valentin H. K. Fell,
• Joseph Cameron,
• Alexander L. Kanibolotsky,
• Eman J. Hussien and
• Peter J. Skabara

Beilstein J. Org. Chem. 2022, 18, 944–955, doi:10.3762/bjoc.18.94

• Figure 9, for the generation of a radical cation and dication at half-wave potential values of +0.65 V (ΔEp = 0.05 V) and +0.87 V (ΔEp = 0.06 V), respectively. Two reduction waves, corresponding to the radical anion and dianion, can be seen at the half-wave potentials of −1.51 V (ΔEp = 0.06 V) and −1.64