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

• benzoguanidine moieties. This explains the ca. 0.2 eV more stabilized LUMO energy level for compound 4BGIPN compared with 4CzIPN. Both 4CzIPN and 4BGIPN exhibit an irreversible oxidation wave observed at +1.25 V for 4BGIPN in THF and +0.94 V for 4CzIPN in MeCN [15]. A higher oxidation potential (Ep) for 4BGIPN

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

• . Route b: the α-C(sp3)–H bonds are activated by a combination of transition metals and radical initiators to give the alkyl radicals, which are coupled with other radical receptors to afford the target product. Cu-catalyzed reactions Copper (common oxidation states are +I, +II and +III) has a

• involved in the activation of DDQ by coordinating the carbonyl oxygen atom which leads to an increase in the oxidation activity of DDQ. Subsequently, Li et al. improved the above method, using a mixture of indium and copper salts as a catalyst, NHPI (N-hydroxyphthalimide) as a co-catalyst to achieve the

• has been proved in many reports, and (3) oxidation of radical B to provide the corresponding alkenyl products 48. In recent years, the CDC reaction of alkyl C(sp3)–H substrates with the C(sp2)–H of an aromatic, which allows the construction of highly diverse compounds, has attracted considerable

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

• development. Outside of bioinorganic chemistry, the concept of radical ligand transfer was investigated in early work by Jay Kochi in purely synthetic systems (Scheme 1) [26][27]. Studies on the oxidation of alkyl radicals with earth abundant cupric salts uncovered the ability of simple Cu(II) chloride to

• (XAT) from the alkyl halide reagent and further oxidation of the transient radical to a carbocation by radical polar crossover (RPC), providing two mechanistic pathways to form the ATRA products [32]. While powerful, this approach is inherently incompatible with introducing alternative functionality

• captured via RLT from an in-situ generated iron–azide complex, resulting in net reduction of iron. The competent RLT species can then be regenerated through oxidation by the iodinane species and coordination of another equivalent of azide. This reaction was particularly notable for the wide alkene scope

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

• artificial photosynthesis. Systems for photocatalytic carbon dioxide reduction are optimized using sacrificial electron donors. One strategy for coupling carbon dioxide reduction and water oxidation to achieve artificial photosynthesis is to use a redox mediator, or recyclable electron donor. This review

• decoupled water splitting research, are introduced as alternative recyclable sacrificial electron donors and their oxidation potentials are compared to the redox potentials of some model photosensitizers. The aim of this review is to act as a reference for researchers developing photocatalytic systems with

• photosynthesis systems species other than water are consumed to provide these electrons and protons [3][4]. Ideally these sacrificial donors would be replaced with redox mediators, regenerated using water, or form stable, commercially valuable oxidation products. However, common sacrificial electron donors, such

Two new lanostanoid glycosides isolated from a Kenyan polypore Fomitopsis carnea

• Winnie Chemutai Sum,
• Sherif S. Ebada,
• Didsanutda Gonkhom,
• Cony Decock,
• Rémy Bertrand Teponno,
• Josphat Clement Matasyoh and
• Marc Stadler

Beilstein J. Org. Chem. 2023, 19, 1161–1169, doi:10.3762/bjoc.19.84

• potency against cancer cells in the presence of a 3-OH group. Notably, hydrolysis of the C3-acetoxy group in pachymic acid to tumulosic acid increased the activity of the compound compared to the positive control (cisplatin), in some instances [36]. Concomitantly, the oxidation of the hydroxy group at C-3

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

• are also low in two-stage synthesis methods. The first of them is based on the three-component condensation of aminopyrazoles, Meldrum's acid, and aromatic aldehydes, followed by the oxidation of the intermediate with DDQ [13][16][19] (method B). The second one includes the reaction of an aromatic

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

• , 9800 Deinze, Belgium 10.3762/bjoc.19.82 Abstract Sustainable oxidation protocols aim to provide an environmentally friendly and cost-effective method for the production of various chemicals and materials. The development of such protocols can lead to reduced energy consumption, fewer harmful

• byproducts, and increased efficiency in industrial processes. As such, this field of research is of great importance and interest to both academia and industry. This work showcases a sustainable and catalyst-free oxidation method for heteroatoms (e.g., S, P, and Se) using only air, water and light. An

• flow using the HANU flow reactor, indicating scalability and improving safety. Keywords: catalyst-free; flow chemistry; oxygen; photochemistry; sustainable oxidation; Introduction Oxidation reactions are widely used in the chemical industry, but are often problematic due to challenges with

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

• generation of super-reductants [15] and by Wagenknecht in 2018 for the generation of super-oxidants [16]. Herein, initial excitation of the photocatalyst by a single photon is followed by reduction or oxidation by a sacrificial SET donor (e.g., Et3N [15]) or acceptor (e.g., SF6 [16]) to yield the catalyst

• doublet states which are photoexcited to yield super-oxidants or super-reductants while recycling e-PRC involves the turnover of a ‘standard’ (typically closed-shell) photoredox catalyst (PC) by means of anodic oxidation or cathodic reduction [28][29]. Furthermore, a series of new protocols using

• SCE (1c) were readily reduced and dehalogenated products obtained in excellent yields (70–92%) (Figure 11A). Sodium formate was found to be a more efficient terminal reductant than trialkylamines which the authors attributed to the formation of a carbon dioxide radical anion (CO2•−) upon oxidation 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

• capability of the PTZ and NI moieties, respectively, by oxidation of the PTZ unit, or by using different aryl substituents attached to the NI unit. This tuning effect was manifested in the UV–vis absorption and fluorescence emission spectra, e.g., in the change of the charge transfer absorption bands. TADF

• transient absorption spectra showed that the charge separation takes ca. 0.6 ps, and admixtures of locally excited (3LE) state and charge separated (1CS/3CS) states formed (in n-hexane). The subsequent charge recombination from the 1CS state takes ca. 7.92 ns. Upon oxidation of the PTZ unit, the beginning

• the energy ordering of the transient species involved in the TADF photophysical process, the electron-donating strength of the PTZ moiety is lowered by oxidation of the sulfur atom to the corresponding sulfoxide. Conversely, the electron-accepting capability of the NI unit is varied by introducing

Copper-catalyzed N-arylation of amines with aryliodonium ylides in water

• Kasturi U. Nabar,
• Bhalchandra M. Bhanage and
• Sudam G. Dawande

Beilstein J. Org. Chem. 2023, 19, 1008–1014, doi:10.3762/bjoc.19.76

• in oxidation, C–C, C–X bond formation, rearrangements, and halogenation reactions [23][24][25]. Due to the nontoxic nature, easier preparation, and handling of the hypervalent iodine reagents, many researchers are attracted to unravel the chemistry and reactivity of these reagents. Amongst different

Aromatic C–H bond functionalization through organocatalyzed asymmetric intermolecular aza-Friedel–Crafts reaction: a recent update

• Anup Biswas

Beilstein J. Org. Chem. 2023, 19, 956–981, doi:10.3762/bjoc.19.72

• reaction between α-naphthol (17) and methyl 2-acetamidoacrylate (18) but promising selectivity was not achieved. The highest enantiomeric excess of 64% was obtained in the presence of P7 as the catalyst (Scheme 6) [30]. In 2018, Reddy and co-workers developed a one pot protocol comprising oxidation and an

• enantioselective aza-Friedel–Crafts addition. In the first step, the DDQ-promoted oxidation of 3-indolinonecarboxylate 22 generated indolenines that performed as the potential electrophiles towards indoles 4. The chiral catalyst effectively assembled the reacting partners in a chiral transition state through H

• ketimines 52 proceeding through C2 functionlization and follow up oxidation to provide 2-substitued indoles 56 which are typically difficult to obtain directly from unsubstituted indoles through electrophilic substitution. The process was catalyzed by the chiral phosphoric acid P17 to install a quaternary

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

• manner due to their intrinsic mildness and broad substrate compatibility [16][17][18][19][20]. This transformative synthetic tool often utilizes direct single-electron transfer (SET) between an electronically excited photoredox catalyst and an organic substrate, resulting in oxidation or reduction, to

• their ability to participate in either redox step of the catalytic cycle [42][43][44][45]. For example, the main use of α-amino acids in syntheses via photoredox catalysis is as readily available precursors of regioselective α-amino radicals by decarboxylative transformations, by oxidation of the

• selectively targeted by photoredox catalysis to enable unprecedented modification of the amino acid. In this context, it is worth mentioning that the single-electron oxidation of the indole moiety in tryptophan provides the radical cation, which enables selective C-radical generation at the weaker benzylic

Intermediates and shunt products of massiliachelin biosynthesis in Massilia sp. NR 4-1

• Till Steinmetz,
• Blaise Kimbadi Lombe and
• Markus Nett

Beilstein J. Org. Chem. 2023, 19, 909–917, doi:10.3762/bjoc.19.69

• reactions (e.g., hydrolysis, esterification, oxidation) might be due to the isolation conditions or they could be attributed to unspecific enzymatic biotransformations. For compound 1, no spontaneous conversion to the ester 2 was observed, even after storage in methanol for two months. In contrast, the

Pyridine C(sp²)–H bond functionalization under transition-metal and rare earth metal catalysis

• Haritha Sindhe,
• Malladi Mounika Reddy,
• Karthikeyan Rajkumar,
• Akshay Kamble,
• Amardeep Singh,
• Anand Kumar and
• Satyasheel Sharma

Beilstein J. Org. Chem. 2023, 19, 820–863, doi:10.3762/bjoc.19.62

• intact under the reaction conditions without any further oxidation. Different oxidants resulted in different products such as the monoarylated product 118 formed in the presence of TBHP as oxidant and the benzylated product 119 was obtained when potassium persulfate was used. Interestingly, aza-fluorene

Eschenmoser coupling reactions starting from primary thioamides. When do they work and when not?

• Lukáš Marek,
• Jiří Váňa,
• Jan Svoboda and
• Jiří Hanusek

Beilstein J. Org. Chem. 2023, 19, 808–819, doi:10.3762/bjoc.19.61

• ) as a polar aprotic solvent that can be easily distilled-off after the ECR under reduced pressure. The last complication with aromatic primary thioamides concerns their easy oxidation with electron-poor α-haloesters (acetoacetates and α-cyanoacetates). As early as in 1976 Potts and Marshall noticed

• File 1. Only oxidation of thiobenzamide to 3,5-diphenyl-1,2,4-thiadiazole was never observed. Triethylamine (pKa = 10.67 in water, 9.25 in DMF, and 18.5 in MeCN) [22] causes the decomposition of imidothioates 6a,b''' in both polar aprotic solvents (DMF and MeCN) through the elimination route. For

Sulfate radical anion-induced benzylic oxidation of N-(arylsulfonyl)benzylamines to N-arylsulfonylimines

• Joydev K. Laha,
• Pankaj Gupta and
• Amitava Hazra

Beilstein J. Org. Chem. 2023, 19, 771–777, doi:10.3762/bjoc.19.57

• with ortho-substituted anilines is also reported. The key features of the protocol include the use of a green oxidant, a short reaction time (30 min), chromatography-free isolation, scalability, and economical, delivering N-arylsulfonylimines in excellent yields of up to 96%. While the oxidation of N

• -aryl(benzyl)amines to N-arylimines using K2S2O8 is reported to be problematic, the oxidation of N-(arylsulfonyl)benzylamines to N-arylsulfonylimines using K2S2O8 has been achieved for the first time. The dual role of the sulfate radical anion (SO4·−), including hydrogen atom abstraction (HAT) and

• single electron transfer (SET), is proposed to be involved in the plausible reaction mechanism. Keywords: arylsulfonylimine; benzylic oxidation; benzyl sulfonamide; K2S2O8; sulfate radical anion; Introduction Among various imine compounds [1], N-arylsulfonylimines are perhaps the most prominent due to

Honeycomb reactor: a promising device for streamlining aerobic oxidation under continuous-flow conditions

• Masahiro Hosoya,
• Yusuke Saito and
• Yousuke Horiuchi

Beilstein J. Org. Chem. 2023, 19, 752–763, doi:10.3762/bjoc.19.55

• 10.3762/bjoc.19.55 Abstract We report on the high potential of a honeycomb reactor for the use in aerobic oxidation under continuous-flow conditions. The honeycomb reactor is made of porous material with narrow channels separated by porous walls allowing for high density accumulation in the reactor. This

• structure raised the mixing efficiency of a gas–liquid reaction system, and it effectively accelerated the aerobic oxidation of benzyl alcohols to benzaldehydes under continuous-flow conditions. This reactor is a promising device for streamlining aerobic oxidation with high process safety because it is a

• closed system. Keywords: aerobic oxidation; benzaldehydes; benzyl alcohols; homogeneous catalyst; honeycomb reactor; Introduction Oxidation plays a key role in synthesizing highly functionalized molecules [1][2]. While Jones oxidation [3] and oxidation using KMnO4 [4] are classical and powerful methods

Construction of hexabenzocoronene-based chiral nanographenes

• Ranran Li,
• Di Wang,
• Shengtao Li and
• Peng An

Beilstein J. Org. Chem. 2023, 19, 736–751, doi:10.3762/bjoc.19.54

• dibenzocyclooctyne 8 and tetracyclone 2 in a 91% yield. After a subsequent sequence of deprotection and oxidation, ketone 10 was obtained. Through the oxidative cyclodehydrogenation reaction of 10 in the presence of DDQ and trifluoromethanesulfonic acid (TfOH), a saddle-helix hybrid nanographene 11, bearing an

• . And the derivative 16 was also synthesized by allylic oxidation of compound 15 using selenium dioxide. As helical chiral NGs, helicene 14 and its derivatives 15 and 16 showed highly distorted helical conformation and also exhibited a relatively high isomerization barrier (over 28.9 kcal/mol determined

• nanographenes 96 and 100 using helicene or oxa-helicene as the linkers, respectively [56]. The first π-extension started from the borylated penta-tert-butyl HBC 92. The chemical selective Suzuki−Miyaura cross-coupling reaction between 92 and 93 followed by Scholl oxidation produced compound 94 in an overall 50

Strategies in the synthesis of dibenzo[b,f]heteropines

• David I. H. Maier,
• Barend C. B. Bezuidenhoudt and
• Charlene Marais

Beilstein J. Org. Chem. 2023, 19, 700–718, doi:10.3762/bjoc.19.51

• nitrotoluene (22) under alkaline conditions (e.g., O2, KOt-Bu; O2, KOH, MeOH, ethylenediamine, etc.), as reported by Stansbury and Proops [33]. Aerobic oxidation of 22 in alkaline methanol with added ethylenediamine, gave 21 in 36% yield (Scheme 2), which is poor compared to that reported for the p-nitro

• 24 was reported by Cong et al. [45] as a method for the synthesis of substituted dibenzo[b,f]oxepines 25 (Scheme 6). Treatment of the malonate derivative 24 with Mn(OAc)3 in 90% acetic acid gave C-10 carboxylate derivatives of dibenzo[b,f]oxepine 25. The authors proposed a one-electron oxidation of

• Sargent [18] synthesised pacharin (13) using a novel method through oxidation of a bisphosphonium diphenyl ether prepared in situ from dibromide 130 (Scheme 28). On treatment with base and exposure to oxygen, the diylide intermediate underwent oxidative coupling to give the isopropyl-protected dibenzo[b,f

Synthesis, structure, and properties of switchable cross-conjugated 1,4-diaryl-1,3-butadiynes based on 1,8-bis(dimethylamino)naphthalene

• Semyon V. Tsybulin,
• Ekaterina A. Filatova,
• Alexander F. Pozharskii,
• Valery A. Ozeryanskii and
• Anna V. Gulevskaya

Beilstein J. Org. Chem. 2023, 19, 674–686, doi:10.3762/bjoc.19.49

• oxidation of chloroform with atmospheric oxygen. We also succeeded in growing crystals of the salt 11c in the MeCN/EtOH system (Figure 5). Unfortunately, good crystals of other salts have not been obtained. From Figure 3 and Figure 4 it is easy to see that all molecules 5b, 5d, and 5e are rather distorted

• electrode, and reference electrode Ag/Ag+ 0.01 M AgNO3 (Figure 11, Table 4). Compounds 5a–d displayed two waves of irreversible oxidation in the potentials range of 0.0–1.1 V and one reduction wave (−1.5 to −1.6 V) with the little variation of the potentials induced by the substituent R. The CV curve of

• nitro derivative 5e demonstrated the minimum peak current. Considering that the current is a quantitative expression of how fast an electrochemical process is happening, compound 5e shows the lowest oxidation rate. In this case, two quasi-reversible reduction waves with lower E1/2ox compared to the

Photocatalytic sequential C–H functionalization expediting acetoxymalonylation of imidazo heterocycles

• Deepak Singh,
• Shyamal Pramanik and
• Soumitra Maity

Beilstein J. Org. Chem. 2023, 19, 666–673, doi:10.3762/bjoc.19.48

• conversion into ZnBr2 (confirmed by HRMS). These in situ-generated free acetate ions function as a base, deprotonating carbocation III to produce the intermediate IV and AcOH. The first step of cycle-2 involves the oxidation of the excited photocatalyst by aerial oxygen to generate superoxide anion and PC

• ∙+. The superoxide anion (O2·−) then captures the proton from the active methylene center of intermediate IV to generate the malonyl anion V, which undergoes single electron oxidation by PC∙+ generating the malonyl radical VI [30][31]. Meanwhile, the hydroperoxy radical (∙OOH) formed, reacts with AcOH

Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• enantiomeric purity. Further transformations of the products were demonstrated in several examples, including reduction, acidic deprotection and subsequent base-mediated cyclization, or Baeyer–Villiger oxidation. At about the same time, Huang and co-workers have developed similar asymmetric tandem sequences

• formylation products. The methodology was later exploited in the expedient synthesis of the Taxol core (Scheme 34) [71]. Tandem conjugate borylations and silylations Chiral organoboron compounds are well-known synthetic building blocks with diverse possibilities for subsequent derivatization (e.g., oxidation

• -workers explored the copper-catalyzed asymmetric conjugate borylation of β-substituted cyclic enones using chiral bisphosphine ligand L21 [77]. Other than the oxidation and hydrolysis of the produced enantiomerically enriched tertiary boronates, in one example, they have demonstrated the utilization of

A new oxidatively stable ligand for the chiral functionalization of amino acids in Ni(II)–Schiff base complexes

• Alena V. Dmitrieva,
• Oleg A. Levitskiy,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2023, 19, 566–574, doi:10.3762/bjoc.19.41

• and the reaction scope, making possible new types of transformations [32][33][34][35]. On the other hand, it puts additional requirements on the design of the chiral ligand. Another important structurally tunable parameter comprises the oxidation or reduction potential of the complex. Additionally, as

• dimerization of the Schiff base complex and the radical cation formed under one-electron electrochemical oxidation will be sufficiently stable, opening a route to further oxidative modification of the amino acid side chain under appropriate conditions. Additionally, this bulky group may significantly alter the

• chemical transformations. The oxidation potential value of the deprotonated glycine complex correlates with the reactivity of the α-carbanionic species towards electrophiles [37]. Therefore, the electrochemical approach is very convenient and informative for the estimation of the relative reactivity of 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

• 5.0 equivalents of Cs2CO3 provided the naphthalene core via sequential dehydration. Based on preliminary mechanistic experiments, the authors proposed the reaction begins with the oxidation of Co(II) to Co(III) by O2. MHP-directed C–H activation of the ortho-C–H position generates 90 which can

• allylic alcohol isomerization in 137 resulting in the aldehyde 138. This aldehyde, in close proximity to the tertiary alcohol, leads to the production of the hemiacetal 139 which can finally undergo an oxidation producing the final bicyclo[2.2.2]lactone product 136. In 2011, the Radhakrishnan laboratory

Transition-metal-catalyzed C–H bond activation as a sustainable strategy for the synthesis of fluorinated molecules: an overview

• Louis Monsigny,
• Floriane Doche and
• Tatiana Besset

Beilstein J. Org. Chem. 2023, 19, 448–473, doi:10.3762/bjoc.19.35

• the presence of an electrophilic source or an oxidation/ligand exchange in the presence of a nucleophilic source (i.e., AgSCF3) and an oxidant (B in Scheme 4). Finally, after a reductive elimination step, the expected functionalized product 6 is obtained and the palladium catalyst is regenerated. In

• with AgSCF3 occurs before the oxidation step, generating the palladium(II) complex F. After an oxidative addition in the presence of Selectfluor®, the palladium(IV) intermediate E is generated. Finally, after reductive elimination step, the desired product 12 is released and the catalyst regenerated

• methyl, methoxy or methylthio groups (17b–d) or by halogen (17e) was achieved (Scheme 8, up to 77% yield). Note that in case of disubstituted 2-(4-ethoxy-3-fluorophenyl)pyridine (17h), the expected product 18h was isolated in 31% yield. Moreover, selective oxidation of the SCF3 residue into the