Mechanistic investigations of polyaza[7]helicene in photoredox and energy transfer catalysis

• Johannes Rocker,
• Till J. B. Zähringer,
• Matthias Schmitz,
• Till Opatz and
• Christoph Kerzig

Beilstein J. Org. Chem. 2024, 20, 1236–1245, doi:10.3762/bjoc.20.106

• catalyst in the sulfonylation/arylation of styrenes and as a triplet sensitizer in energy transfer catalysis. The singlet lifetime is sufficiently long to exploit the exceptional excited state reduction potential for the activation of 4-cyanopyridine. Photoinduced electron transfer generating the radical

• /H2O (9:1). The low reduction potential of singlet-excited Aza-H (PC•+/PC* = –1.87 V vs SCE) led us to propose that the singlet-excited photocatalyst is oxidized by 4-cyanopyridine (4CP) (4CP/4CP•− = −1.81 V vs SCE) as the first step in this multicomponent reaction (Scheme 1, left). The oxidized

• -excited state lifetime), the quenching rate constant is roughly four orders of magnitude lower than singlet quenching (kq ≈ 105 M−1 s−1). This is in good agreement with the reported high triplet energy of 4CP [75] at 3.08 eV compared to 2.32 eV of 3Aza-H and the lower reduction potential provided by the

Competing electrophilic substitution and oxidative polymerization of arylamines with selenium dioxide

• Vishnu Selladurai and
• Selvakumar Karuthapandi

Beilstein J. Org. Chem. 2024, 20, 1221–1235, doi:10.3762/bjoc.20.105

• [30][31][32]. Due to the oxidative nature, the use as selenium source in the synthesis of arylchalcogen compounds, in particular diorganyl selenides, can be a challenging process that involves sequential formation of two C–Se bonds and reduction of a Se=O bond in a single-pot reaction. Further

• ]. This reaction comprises four main steps: (i) iodide-mediated aryl transfer from boronic acid to selenium dioxide, (ii) reduction of arylseleninic acid to diaryl diselenide, (iii) oxidation of diaryl diselenide to aryl selenenyl iodide with iodine, and (iv) electrophilic substitution of aniline

Two-fold addition reaction of silylene to C₆₀: structural and electronic properties of a bis-adduct

• Masahiro Kako,
• Masato Kai,
• Masanori Yasui,
• Michio Yamada,
• Yutaka Maeda and
• Takeshi Akasaka

Beilstein J. Org. Chem. 2024, 20, 1179–1188, doi:10.3762/bjoc.20.100

• irreversible, probably because of the removal of silylene addends, whereas the electrochemically reversible behavior was observed for the reduction waves. Table 2 presents the redox potentials of 3 obtained by DPV with those of C60 and 2, as reference compounds. Both the reduction (Ered) and the oxidation (Eox

• ) potentials of 3 were found to be shifted cathodically compared respectively to those of C60 and 2, indicating the electron-donating effects of the two Dip2Si groups. It is noteworthy that the first reduction potential of 3 (Ered1 = −1.52 V) is the most negative among those of the silylated empty fullerenes

Bismuth(III) triflate: an economical and environmentally friendly catalyst for the Nazarov reaction

• Manoel T. Rodrigues Jr.,
• Aline S. B. de Oliveira,
• Ralph C. Gomes,
• Amanda Soares Hirata,
• Lucas A. Zeoly,
• Hugo Santos,
• João Arantes,
• Catarina Sofia Mateus Reis-Silva,
• João Agostinho Machado-Neto,
• Leticia Veras Costa-Lotufo and
• Fernando Coelho

Beilstein J. Org. Chem. 2024, 20, 1167–1178, doi:10.3762/bjoc.20.99

• ], Reformatsky reaction [65], azalactone synthesis [66], nitro reduction [67][68], epoxide rearrangement, thiourea guanylation, and others [69][70]. In this article, we describe a simple and direct protocol for the preparation of indanones through a classical Nazarov reaction catalyzed by bismuth(III) triflate

• ), and Bi(OTf)3 (0.05 mmol) were added to a sealed tube. The reaction mixture was stirred at 100 °C and monitored by TLC. Impact of indanone derivatives on cell viability of tumor cells. Cell viability was determined by MTT assay. Data is expressed as reduction in viability in relation to the vehicle

• , and the dotted line indicates 75% reduction in cell viability. Compounds that reduced cell viability by at least 75% at 5 µg/mL are highlighted in the graph. Previous methods describing decarboxylation reactions of indanones and xanthenones. Optimization of the reaction conditions. Evaluation of the

Manganese-catalyzed C–C and C–N bond formation with alcohols via borrowing hydrogen or hydrogen auto-transfer

• Mohd Farhan Ansari,
• Atul Kumar Maurya,
• Abhishek Kumar and
• Saravanakumar Elangovan

Beilstein J. Org. Chem. 2024, 20, 1111–1166, doi:10.3762/bjoc.20.98

• , hydroaminomethylation, reduction of nitriles and nitro compounds or through reductive amination of carbonyl derivatives [26][27][28][29][30]. However, for example, cross-coupling reactions with alkyl or aryl halides generate considerable amounts of waste (Scheme 2A). Even though many different approaches exist for

• condenses with hydrazine followed by reduction and condensation with another aldehyde to afford the N-substituted hydrazones (Scheme 8). Balaraman and co-workers established a phosphine-free manganese catalyst generated in situ from a manganese precursor and a ligand for the N-alkylation of anilines with

• step, reduction of unsaturated compounds with manganese hydride complexes giving the desired C-alkylated products. In 2016, Beller and co-workers introduced the first air-stable manganese(I)-PNP-pincer pre-catalyst for the α-alkylation of ketones with primary alcohols [57]. The reaction conditions were

Synthesis of 1,4-azaphosphinine nucleosides and evaluation as inhibitors of human cytidine deaminase and APOBEC3A

• Maksim V. Kvach,
• Stefan Harjes,
• Harikrishnan M. Kurup,
• Geoffrey B. Jameson,
• Elena Harjes and
• Vyacheslav V. Filichev

Beilstein J. Org. Chem. 2024, 20, 1088–1098, doi:10.3762/bjoc.20.96

• racemisation, and nucleoside 14 with the same α/β ratio of 3:2 formed from either anomerically pure 17 or from a mixture of the anomers. Catalytic hydrogenation is usually used for the removal of benzyl protecting groups. However, standard hydrogenation conditions using 10% Pd/C led to reduction of the C=C

Light on the sustainable preparation of aryl-cored dibromides

• Fabrizio Roncaglia,
• Alberto Ughetti,
• Nicola Porcelli,
• Biagio Anderlini,
• Andrea Severini and
• Luca Rigamonti

Beilstein J. Org. Chem. 2024, 20, 1076–1087, doi:10.3762/bjoc.20.95

• favour of the monohalide 3am (entry 1, Table 1). The reduction of the volume of the aqueous phase (Table 1, entry 2) resulted in a small shift towards the desired product 3a but also in the predominant overreaction towards tribromide 3at. Formation of 3at was substantially controlled by reducing the

• plateau around 60%. Data available in the literature suggested a beneficial effect coming from the reduction of the water amount [62]. As all the existing water originates from the employed reagents like aqueous HBr and H2O2, the combination of NaBr and H2SO4 was explored as a potential source of

Structure–property relationships in dicyanopyrazinoquinoxalines and their hydrogen-bonding-capable dihydropyrazinoquinoxalinedione derivatives

• Tural N. Akhmedov,
• Ajeet Kumar,
• Daken J. Starkenburg,
• Kyle J. Chesney,
• Khalil A. Abboud,
• Novruz G. Akhmedov,
• Jiangeng Xue and
• Ronald K. Castellano

Beilstein J. Org. Chem. 2024, 20, 1037–1052, doi:10.3762/bjoc.20.92

• secured due to the favorable hydrogen bonding (O–H∙∙∙N) between the oxime units; this idea is supported by 1H NMR spectroscopy which shows the presence of two distinct hydroxyl proton signals. The reduction of 7d in the presence of Pd/C and hydrazine monohydrate afforded 1,10-phenanthroline-5,6-diamine

• efficient electron transport. However, compounds with LUMO levels ≈−4.0 eV are prone to undergo oxidation with O2 or reduction with H2O [35]. This could be the reason why electron transport properties in the OFETs previously reported by Yamashita are not very good [25]. Therefore, in the case of DPQD

Spin and charge interactions between nanographene host and ferrocene

• Akira Suzuki,
• Yuya Miyake,
• Ryoga Shibata and
• Kazuyuki Takai

Beilstein J. Org. Chem. 2024, 20, 1011–1019, doi:10.3762/bjoc.20.89

• . The reduction in the absolute value of χconst suggests the upshift of the Fermi energy from the Dirac point in the electronic band of nanographene in ACFs, being consistent with charge transfer from FeCp2 observed in XPS. The decrease in the absolute value of the Weiss temperature Θ from −6.4 K for

• cation spins are less than those for edge-state spins. The apparent reduction in Θ for FeCp2-ACFs-150 is attributed to the contribution of FeCp2+ spins having less exchange interaction in the observed magnetic susceptibility. So, the spin magnetism of the guest molecule is induced by host–guest

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

• the presence of K2CO3 (3 equiv) as base, an isonitrile (1.2 equiv), and Pd(OAc)2 (10 mol %) which in situ undergoes a reduction to Pd(0) (Scheme 2). Another example was published by Wu's group, who carried out the synthesis of 1-(1H-indol-1-yl)-2-arylethan-1-one derivatives by promoting the formation

• reaction mechanism proceeds with an initial reduction of Pd(II) to Pd(0) followed by oxidative addition on the ArCH2–Cl bond to form the ArCH2–PdII–Cl complex. Then, insertion of CO, from TFBen, takes place followed by nucleophilic displacement and reductive elimination. The obtained compound undergoes

• the catalyst undergoes reduction, therefore, rather using only CO, a mixture of CO–air (12:48 bar) was used with the aim of oxidizing the Pd(0) species in order to restore the catalyst able to catalyze the process again. The reaction mechanism proceeds with an initial interaction between the Pd(II

Direct synthesis of acyl fluorides from carboxylic acids using benzothiazolium reagents

• Lilian M. Maas,
• Alex Haswell,
• Rory Hughes and
• Matthew N. Hopkinson

Beilstein J. Org. Chem. 2024, 20, 921–930, doi:10.3762/bjoc.20.82

• 2.0 equiv of diisopropylethylamine (DIPEA), 2a could be obtained in quantitative 19F NMR yield although a reduction to 1.5 equiv led to a significant drop in efficiency, delivering the acyl fluoride in only 30% 19F NMR yield together with 45% of thioester 3a (Table 1, entries 4 and 5). At this stage

• the efficiency of the reaction, whereas a 19F NMR yield of only 11% was achieved in DMF (Table 1, entries 10–12). Increasing the reaction concentration to 0.2 M in DCM led to a reduction in the 19F NMR yield of 2a to 74% (Table 1, entry 13). Finally, optimisation of the reaction time revealed the

• the acyl fluoride with addition/elimination of fluoride to a thioester intermediate and independent deoxyfluorination of a second equivalent of the acid substrate by the released −SCF3 anion both operating under the reaction conditions. This allows for the reduction in the loading of BT-SCF3 to sub

Synthesis and properties of 6-alkynyl-5-aryluracils

• Ruben Manuel Figueira de Abreu,
• Till Brockmann,
• Alexander Villinger,
• Peter Ehlers and
• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 898–911, doi:10.3762/bjoc.20.80

• appears to have the opposite effect, as 5m demonstrates. Although it was expected that this would result in a higher absorption intensity, a drastic reduction in the intensity was observed. The extinction coefficient of 5m (8766 M−1 cm−1) was rather low compared to 5d. Furthermore, the substitution of a π

• -donor group by a π-acceptor group led to a reduction of the absorption intensity until it almost disappeared. This behavior can be observed in the spectra of 5l. As the spectra of 5k and 5l indicate, the spectral influence of a p-substituted alkyne-linked phenyl group appears to be negligible. However

(Bio)isosteres of ortho- and meta-substituted benzenes

• H. Erik Diepers and
• Johannes C. L. Walker

Beilstein J. Org. Chem. 2024, 20, 859–890, doi:10.3762/bjoc.20.78

• fluorothalidomide [8]. Similarly, the reduction in the number of aromatic groups and increase in the level of saturation have risen to prominence as a way of improving low aqueous solubility, metabolic instability, or low lipophilicity in drug candidates that contain a high number of these functionalities [9][10

• (±)-30. In a related strategy, Procter and co-workers prepared 1,2-BCHs (±)-33a–e from BCBs 32 via a SmI2-catalysed radical relay alkene insertion (Scheme 3C) [35]. This approach relied on single-electron reduction of the ketone moiety and ring-expansion from the ketyl radical anion. Electron-deficient

• alkenes including acrylates, vinyl sulfones, and acrylamides could all be incorporated and the number of accessible bifunctional 1,2-BCHs was increased further by chemical transformation (Scheme 3D) [35]. Among the reported transformations were reduction of the ketone (to (±)-34), hydrolysis of the

Activity assays of NnlA homologs suggest the natural product N-nitroglycine is degraded by diverse bacteria

• Kara A. Strickland,
• Brenda Martinez Rodriguez,
• Ashley A. Holland,
• Shelby Wagner,
• Michelle Luna-Alva,
• David E. Graham and
• Jonathan D. Caranto

Beilstein J. Org. Chem. 2024, 20, 830–840, doi:10.3762/bjoc.20.75

• characterized. Each isolated homolog exhibited similar oligomerization and heme occupancy as Vs NnlA. Reduction of this heme was shown to be required for NnlA activity in each homolog, and each homolog degraded NNG to glyoxylate, NO2− and NH4+ in accordance with observations of Vs NnlA. It was also shown that

• reduction of which is required for NNG degradation activity. In addition, we show that NnlA cannot degrade 2-NAE. Combined with previous substrate scope studies, this result strongly suggests that NnlA is specific for NNG. The implications of our results in understanding the environmental abundance and

• stoichiometric heme occupancy (Table 1). All homologs degrade NNG to glyoxylate, NH4+, and NO2− Previous work showed that reduction of the Vs NnlA heme was required to activate NNG degradation. To test this requirement for the homologs, reduced samples of 5 μM of each NnlA homolog containing 350 μM NNG in

Skeletal rearrangement of 6,8-dioxabicyclo[3.2.1]octan-4-ols promoted by thionyl chloride or Appel conditions

• Martyn Jevric,
• Julian Klepp,
• Johannes Puschnig,
• Oscar Lamb,
• Christopher J. Sumby and
• Ben W. Greatrex

Beilstein J. Org. Chem. 2024, 20, 823–829, doi:10.3762/bjoc.20.74

• ) is produced selectively when cellulose-containing materials, including lignocellulosic biomass, are acidified and pyrolysed [1][2]. Lab scale synthesis of this chiral material can be accomplished in a single step without special glassware [3], while large scale production of the reduction product

• reduction using NaBH4 as per our previously published approach (Scheme 1) [9]. When α-alkylations are performed using 2, the second alkylation step is faster than the first, meaning that only the dialkylated products are formed [16], and the reduction is highly selective with approach of the reductant from

• stereoisomer 10f in 91% yield. The selectivity of the NaBH4 reduction was confirmed for both 10d (see discussion in Supporting Information File 1) and 10e by X-ray crystallography (Figure 2 and Scheme 1, respectively). The oxygen-migration reaction giving 11a was initially observed using the readily available

Advancements in hydrochlorination of alkenes

• Daniel S. Müller

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

• more efficient reactions with alkene 88 (Table 6). In 2022, Oestreich reported the in situ formation of HCl by Lewis acid-induced Grob fragmentation of acid chloride 92 (Scheme 15B) [68]. The inconvenience of this method is that 92 has to be prepared in two steps, including a Birch reduction (Scheme

• state thereof, denoted with an asterisk, possessing a reduction potential of 2.0 V versus SCE (saturated calomel electrode). Subsequently, this excited state undergoes quenching through photoinduced electron transfer (PET) with styrene 5. The resulting vinyl radical cation exhibits electrophilicity at

Synthesis of new representatives of A₃B-type carboranylporphyrins based on meso-tetra(pentafluorophenyl)porphyrin transformations

• Victoria M. Alpatova,
• Evgeny G. Rys,
• Elena G. Kononova and
• Valentina A. Ol'shevskaya

Beilstein J. Org. Chem. 2024, 20, 767–776, doi:10.3762/bjoc.20.70

• the p-fluorine atom in the pentafluorophenyl substituent with an azide functionality which upon reduction with SnCl2 resulted in the formation of the corresponding porphyrin with an amino group. Pentafluorophenyl-substituted A3B-porphyrins were studied and transformed to thiol and amino-substituted

• temperature for 4 h. Under these reaction conditions, monoazide derivative 2 was obtained in 40% yield along with a mixture of porphyrin 1, di- and triazido-substituted derivatives. The reaction mixture was separated by column chromatography on SiO2 using CH2Cl2/hexane 2:8 as an eluent. The reduction of the

• fluorophenylporphyrin substituents via the boron atom. At the same time the SNAr substitution reaction for the azido-substituted porphyrin 2 with mercaptocarborane 4 also afforded the amino-substituted porphyrin 5 in 32% yield (Scheme 2). During the reaction the reduction of the azide group under the action of

Substrate specificity of a ketosynthase domain involved in bacillaene biosynthesis

• Zhiyong Yin and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2024, 20, 734–740, doi:10.3762/bjoc.20.67

• of a ketoreductase (KR) domain in module 1, the starter unit was initially suggested to be α-hydroxyisocaproate [14], but later it was shown that the KR of module 3 acts twice, in the reduction of the β-ketoacyl intermediate of the elongation step of module 3 and in the reduction of the α

• -ketoisocaproate starter unit with introduction of an S configured stereocentre (highlighted in red in Scheme 1) [15]. The domain organisation of module 3 containing no enoylreductase (ER) domain furthermore suggests the formation of an α,β-unsaturated intermediate, and not a full reduction at this stage, in

Chemoenzymatic synthesis of macrocyclic peptides and polyketides via thioesterase-catalyzed macrocyclization

• Senze Qiao,
• Zhongyu Cheng and
• Fuzhuo Li

Beilstein J. Org. Chem. 2024, 20, 721–733, doi:10.3762/bjoc.20.66

• TE-catalyzed marcolactonization [69]. The synthesis of linear peptide 34 commenced with the lactone opening of 26 to afford Weinreb amide 27. Following primary alcohol protection and amide reduction, the aldehyde 28 was coupled with iodide 29 to afford 30 via Nozaki–Hiyama–Kishi coupling, which was

SOMOphilic alkyne vs radical-polar crossover approaches: The full story of the azido-alkynylation of alkenes

• Julien Borrel and
• Jerome Waser

Beilstein J. Org. Chem. 2024, 20, 701–713, doi:10.3762/bjoc.20.64

• building blocks bearing two of the most versatile functional groups, allowing a rich panel of functionalization. They have been used as intermediates in numerous syntheses to access bioactive compounds [1][2][3][4] or materials [5][6][7]. In addition, azide reduction affords homopropargylic amines, which

• since it is known to be reduced by photocatalysts such as Cu(dap)2Cl [17]. This perfectly fits a catalytic cycle involving the reduction of Ts-ABZ (3) followed by oxidation of the carbon radical to form a carbocation and regenerate the ground state catalyst. Styrene (1a) was used as model substrate

• formation of 6 (Table 2, entry 4). In contrast, Ru(bpz)3(PF6)2 did not form the desired product probably due to its too high reduction potential compared to Ts-ABZ (3) (value reported for ABX: E1/2(ABX) = −0.43 V vs SCE) [52] (Table 2, entry 5). In general, organic dyes could not catalyze the transformation

New variochelins from soil-isolated Variovorax sp. H002

• Jabal Rahmat Haedar,
• Aya Yoshimura and
• Toshiyuki Wakimoto

Beilstein J. Org. Chem. 2024, 20, 692–700, doi:10.3762/bjoc.20.63

• transporters to form the siderophore Fe(III) complex extracellularly [2][3]. Subsequently, the stable and water soluble siderophore Fe(III) complex is transported across the cell membrane into the cytoplasm, where the iron is released from the complex by reduction, generating free Fe(II) ions that are

Regioselective quinazoline C2 modifications through the azide–tetrazole tautomeric equilibrium

• Dāgs Dāvis Līpiņš,
• Andris Jeminejs,
• Una Ušacka,
• Anatoly Mishnev,
• Māris Turks and
• Irina Novosjolova

Beilstein J. Org. Chem. 2024, 20, 675–683, doi:10.3762/bjoc.20.61

• , which is present in pharmaceutically active substances. The methodology application is showcased by transforming the obtained 4-azido-6,7-dimethoxy-2-sulfonylquinazolines into the α1-adrenoceptor blockers terazosin and prazosin by further C2-selective SNAr reaction and azide reduction. Keywords

• form can be in either the azide (17e, 17f) or tetrazole form (17a–d). With derivatives 17e,f in hand, the reduction of the azido group in the C4 position was carried out by bubbling hydrogen through the solution in the presence of palladium on charcoal. In the last step, the product was acidified with

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

• % yield. Compound 4a could be hydrogenated to the corresponding reduction product 12 using Pd/C and ammonium formate conditions (Scheme 6a). Notably, as shown in Scheme 6b, treatment of the unsaturated γ-AA derivative 6a with Pd/C and ammonium formate led to a cyclization reaction, furnishing γ-lactam 13

Enhanced reactivity of Li⁺@C₆₀ toward thermal [2 + 2] cycloaddition by encapsulated Li⁺ Lewis acid

• Hiroshi Ueno,
• Yu Yamazaki,
• Hiroshi Okada,
• Fuminori Misaizu,
• Ken Kokubo and
• Hidehiro Sakurai

Beilstein J. Org. Chem. 2024, 20, 653–660, doi:10.3762/bjoc.20.58

• redox waves, with subsequent reduction resulting in an irreversible electrochemical response. The first reduction potentials of 5a and 5b were measured at −0.51 V and −0.52 V (vs Fc/Fc+), respectively, which were more negative than that of pristine Li+@C60 (E1/2red1 = −0.39 V). While the detailed

• reasons for the irreversible redox properties after the second reduction process have not been thoroughly investigated, the observed phenomena could potentially be attributed to ring opening or simple decomposition under the conditions. From these results, the LUMO levels of the compounds were estimated

• − with substrates 1–4. a100 equiv for the reaction screening, 20 equiv for the synthesis of 5a, and 40 equiv for the synthesis of 5b. bRoom temperature for the reaction screening, 50 °C for the synthesis. cIsolated yield. dHPLC yield. First reduction potential and estimated LUMO level of 5a and 5b. The

Production of non-natural 5-methylorsellinate-derived meroterpenoids in Aspergillus oryzae

• Jia Tang,
• Yixiang Zhang and
• Yudai Matsuda

Beilstein J. Org. Chem. 2024, 20, 638–644, doi:10.3762/bjoc.20.56

• instead of the C-4′ carbonyl group (Figure 2C). It is unlikely that 8 is the direct product of InsA7; thus, we hypothesized that an endogenous enzyme in A. oryzae is responsible for the reduction, with an enoylreductase first reducing the C-2′/C-3′ double bond of 7 and the resulting product undergoing