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

• giving esters 3a–c, formation of enoate byproducts 4a and 4b invoke the involvement of an external chemical oxidant species as cinnamaldehyde is added to the cathode chamber after the electrolysis has been stopped. The presence of byproducts 4a and 4b is most likely accounted for by the presence of

Synthesis of odorants in flow and their applications in perfumery

• Merlin Kleoff,
• Paul Kiler and
• Philipp Heretsch

Beilstein J. Org. Chem. 2022, 18, 754–768, doi:10.3762/bjoc.18.76

• oxidant (Scheme 8B) [39]. The process is performed at 120 °C at 10 bar with a residence time of 6 min, and catalyzed homogenously utilizing the established “MC-system” (manganese/cobalt/bromide) in a heated tube reactor. Remarkably, acetophenone is obtained in a good yield of 66% and in 96% purity without

Rapid gas–liquid reaction in flow. Continuous synthesis and production of cyclohexene oxide

• Kyoko Mandai,
• Tetsuya Yamamoto,
• Hiroki Mandai and
• Aiichiro Nagaki

Beilstein J. Org. Chem. 2022, 18, 660–668, doi:10.3762/bjoc.18.67

• Medical Science, Nijigaoka, Kani-city, Gifu Prefecture, 509-0293, Japan 10.3762/bjoc.18.67 Abstract The enhanced reaction rate in the epoxidation of cyclohexene with air as an oxidant was discovered without any added catalyst utilizing a continuous flow reactor constructed with readily available

DDQ in mechanochemical C–N coupling reactions

• Shyamal Kanti Bera,
• Rosalin Bhanja and
• Prasenjit Mal

Beilstein J. Org. Chem. 2022, 18, 639–646, doi:10.3762/bjoc.18.64

• -Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) is a commonly known oxidant. Herein, we report that DDQ can be used to synthesize 1,2-disubstituted benzimidazoles and quinazolin-4(3H)-ones via the intra- and intermolecular C–N coupling reaction under solvent-free mechanochemical (ball milling) conditions. In

• as C–P [17], C–O [18][19][20], and C–S [21] were achieved using DDQ as an oxidant [22][23]. In addition, the utilization of DDQ as a photoredox catalyst [24] and co-catalyst [25][26] have also been documented in organic synthesis [27]. DDQ-mediated oxidative C–N cross-coupling reactions are well

• reagents, but none of them gave better yields (Table 1, entries 4–7). On the other hand, oxone as an oxidant yielded product 2a with up to 43% yield (Table 1, entry 8). Similarly, we have optimized the reaction conditions for the synthesis of 2-phenylquinazolin-4(3H)-one (5a) from anthranilamide and

Substituent effect on TADF properties of 2-modified 4,6-bis(3,6-di-tert-butyl-9-carbazolyl)-5-methylpyrimidines

• Irina Fiodorova,
• Tomas Serevičius,
• Rokas Skaisgiris,
• Saulius Juršėnas and
• Sigitas Tumkevicius

Beilstein J. Org. Chem. 2022, 18, 497–507, doi:10.3762/bjoc.18.52

• methylsulfonyl group was necessary to perform. A suitable oxidant for this purpose appeared to be oxone [40]. Thus, the oxidation of tCbz-mPYR with oxone proceeded in DMF at 80 °C to provide the 2-methylsulfonyl derivative 3 in 92% yield. Then, treatment of compound 3 with NaCN or 4-(tert-butyl)thiophenol led to

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

• studied [63]. Yamazaki reported the use of 10 mol % of chromium(VI) oxide and orthoperiodic acid, as a terminal oxidant, to obtain menadione (10) in 61% yield (Table 1, entry 3) [49]. Alternatives to chromium(VI) compounds to oxidize 2-methylnaphthalene (16) to menadione (10) have also been evaluated and

• yield was only 10%, but after the addition of MTO and acetic anhydride, the yield increased to 46% (Table 1, entry 5) [51]. The authors suggested two simultaneous reaction pathways: a direct oxidation by rhenium bisperoxo complex and an MTO-catalyzed in situ generation of peroxyacetic acid as oxidant

• catalytic activity of selenium mesoporous molecular sieves (SeMCM-41) in the oxidation of 16 (Table 1, entry 10). The approach was performed using H2O2 as oxidant in acetic acid over SeMCM-41 (Si/Se = 30) at 100 °C [56]. In this case, a conversion of 99% was achieved and menadione (10) was obtained with 68

Synthesis of novel [1,2,4]triazolo[1,5-b][1,2,4,5]tetrazines and investigation of their fungistatic activity

• Anna V. Korotina,
• Svetlana G. Tolshchina,
• Rashida I. Ishmetova,
• Natalya P. Evstigneeva,
• Natalya A. Gerasimova,
• Natalya V. Zilberberg,
• Nikolay V. Kungurov,
• Gennady L. Rusinov,
• Oleg N. Chupakhin and
• Valery N. Charushin

Beilstein J. Org. Chem. 2022, 18, 243–250, doi:10.3762/bjoc.18.29

• can also be used as an oxidant for the oxidation of benzamidine derivatives 2b,c in acetonitrile under microwave irradiation. Along with the cyclization reaction, bromination of the pyrazole ring proved to occur at position C(4) to give the products 3j,k, as evidenced by disappearance of the

Multi-faceted reactivity of N-fluorobenzenesulfonimide (NFSI) under mechanochemical conditions: fluorination, fluorodemethylation, sulfonylation, and amidation reactions

• José G. Hernández,
• Karen J. Ardila-Fierro,
• Dajana Barišić and
• Hervé Geneste

Beilstein J. Org. Chem. 2022, 18, 182–189, doi:10.3762/bjoc.18.20

• -milling conditions. NFSI is a colorless crystalline powder (mp 114–116 °C), bench-stable, and an easy-to-handle reagent, which, due to its commercial availability, has been extensively used as a fluorinating agent in solution [7][8][9]. Additionally, NFSI has also been explored as an oxidant, amidation

Recent advances and perspectives in ruthenium-catalyzed cyanation reactions

• Thaipparambil Aneeja,
• Cheriya Mukkolakkal Abdulla Afsina,
• Padinjare Veetil Saranya and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 37–52, doi:10.3762/bjoc.18.4

• cyanoformate as the cyanide source. They carried out the optimization studies using N,N-dimethylaniline (1.0 mmol) and ethyl cyanoformate (2.0 mmol) as the model substrates and the optimized conditions include 5 wt % Ru/C (20 mg) as catalyst and 2.5 equiv of TBHP (in decane) as oxidant in methanol at 60 °C for

• the cyanation reaction. This strategy utilized eco-friendly hydrogen peroxide and molecular oxygen as the oxidant system. This method was found highly favorable to tertiary amines with electron-donating substituents. The first report on an MCM-41-immobilized N-alkylethylenediamine Ru(III) complex (MCM

• group reported a novel synthetic pathway for the oxidative cyanation of tertiary amines using sodium cyanide [33]. The optimized conditions for this reaction included the use of 0.05 mmol of RuCl3 as the catalyst, 1.2 mmol of NaCN in acetic acid as the cyanide source and 2.5 mmol of H2O2 as the oxidant

DABCO-promoted photocatalytic C–H functionalization of aldehydes

• Bruno Maia da Silva Santos,
• Mariana dos Santos Dupim,
• Cauê Paula de Souza,
• Thiago Messias Cardozo and
• Fernanda Gadini Finelli

Beilstein J. Org. Chem. 2021, 17, 2959–2967, doi:10.3762/bjoc.17.205

• accessibility, it is still underused, and has only recently started to gain attention from the synthetic community. Murphy and co-workers reported the use of the DABCO radical cation, generated by a stoichiometric oxidant (TPTA-PF6), as a hydrogen abstractor for alpha-nitrogen C–H functionalization [21] (Figure

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• ) [94]. Interestingly, the protocol used air as the oxidant, avoiding the use of stoichiometric oxidants like previous radical cyclization cascades. Generally, substrates with an electron-withdrawing group afforded the product in greater yield. The reaction proceeds through the formation of a sulfonyl

• 106 (Scheme 21) [104]. The use of Ag2CO3 as a SET oxidant was shown to be key for the success of the reaction, as typical organic oxidants, like peroxides, displayed low activity. No clear trend was observed for the difference in efficiency between the Fe catalysts used. It was noted the use of the Fe

The PIFA-initiated oxidative cyclization of 2-(3-butenyl)quinazolin-4(3H)-ones – an efficient approach to 1-(hydroxymethyl)-2,3-dihydropyrrolo[1,2-a]quinazolin-5(1H)-ones

• Alla I. Vaskevych,
• Nataliia O. Savinchuk,
• Ruslan I. Vaskevych,
• Eduard B. Rusanov,
• Oleksandr O. Grygorenko and
• Mykhailo V. Vovk

Beilstein J. Org. Chem. 2021, 17, 2787–2794, doi:10.3762/bjoc.17.189

• oxidant and 24 h reaction time were necessary (Table 2, entry 10). The optimized conditions were applied to all quinazolones 7a–l, and target 1-(hydroxymethyl)-2,3-dihydropyrrolo[1,2-a]quinazolin-5(1H)-ones 6a–l were obtained in 75–83% yield (see Table 3). Their structural analysis showed that the

• of them (pathway a) includes the formation of the nitrene cation 11 [41][42][44][45][53] under action of PIFA as an oxidant. A subsequent electrophilic attack at the double bond provides aziridinium cation 12 that undergoes selective ring opening with the trifluoroacetate anion to give intermediate

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• density functional theory calculations [46]. Recently, Shi, Lin and co-workers reported the atroposelective synthesis of axially chiral biaryls by Pd(II)-catalyzed free amine-directed atroposelective C–H olefination using chiral spirophosphoric acid CPA 5 as an efficient ligand and Ag2CO3 as the oxidant

Synthesis of highly substituted fluorenones via metal-free TBHP-promoted oxidative cyclization of 2-(aminomethyl)biphenyls. Application to the total synthesis of nobilone

• Ilya A. P. Jourjine,
• Lukas Zeisel,
• Jürgen Krauß and
• Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2668–2679, doi:10.3762/bjoc.17.181

• backbone. Expected 9-aminofluorene intermediates 5 were envisaged to undergo subsequent oxidation by the same oxidant to hopefully provide the fluorenones 3 in a domino reaction. Results and Discussion After comprehensive literature search for successful oxidations of benzylic C–N bonds we tested a variety

• cyclization. From aldehyde 2l an acyl radical should subsequently be formed, for which cyclization reactions with heteroarenes and benzenoids are well documented [67][68]. Aldehyde 2l may also be further oxidized to give carboxylic acid B instead. With the oxidant of choice, aqueous TBHP, however, aldehyde 2l

A novel methodology for the efficient synthesis of 3-monohalooxindoles by acidolysis of 3-phosphate-substituted oxindoles with haloid acids

• Li Liu,
• Yue Li,
• Tiao Huang,
• Dulin Kong and
• Mingshu Wu

Beilstein J. Org. Chem. 2021, 17, 2321–2328, doi:10.3762/bjoc.17.150

• Prathima group established an expedient approach for the direct oxidative chlorination of indole-3-carboxaldehyde to 3-monochlorooxindoles using a combination of NaCl and oxone as the chlorine source and oxidant in a CH3CN/H2O 1:1 system (Scheme 1, reaction 2) [22]. Nearly at the same time, Yu and co

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

• Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

• benzene which resulted in low yields of the products 134 (Scheme 18a) [44]. Using different N-protected substituted indoles 135, Naidu observed improved yields of 136 when catalytic oxidant I2 was added in 1,4-dioxane as solvent (Scheme 18b) [96]. Using aerial oxygen as the oxidant, Yang used Se0 in the

• 10% yield when chloranil was used as the oxidant (Scheme 25) [115]. The high electrophilicity of 178 at the C7 position resulted in this product formation. The reaction proceeds through the radical intermediate 181. Sulfides Reddy synthesized the di(indol-5-yl)sulfide (183) via a cascade strategy

Towards new NIR dyes for free radical photopolymerization processes

• Haifaa Mokbel,
• Guillaume Noirbent,
• Didier Gigmes,
• Frédéric Dumur and
• Jacques Lalevée

Beilstein J. Org. Chem. 2021, 17, 2067–2076, doi:10.3762/bjoc.17.133

• ][9]. NIR dyes, and more especially cyanine dyes, have been studied in NIR photosensitive systems [5][6][7][9][10][11][12][13][14][15]. The cyanine acts as a photosensitizer: it absorbs the light emitted in the NIR range and then acts with a combination of additives (oxidant agents and reducing agents

• other works when other NIR dyes were used in three-component PISs comprising an oxidant agent and an amine [8]. In all cases, NIR dyes proposed showed excellent reactivity using different amines and an iodonium salt. This suggests that an NIR approach is an elegant way for fast curing processes upon

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• monofunctionalized naphthyl substrates. These authors demonstrated that the rhodium-catalyzed oxidative 1:2 coupling reactions of arylboronic acids 7 with alkyne 8 occurred in the presence of a copper–air oxidant, to give the corresponding 1,2,3,4-tetrasubtituted anthracene derivatives 9a and 9b (Scheme 1) [34

• and asymmetric alkynes with heterocyclic compounds and obtained reasonable to satisfactory results (examples 12h–k) [35]. Cu(OAc)2 proved to be an essential oxidant for the success of both the Miura and the Bao methodologies [34][35]. In 2013, Ye and co-workers reported a concise method to synthesize

• -workers reported a one-pot synthesis of substituted anthracenes 37 from o-tolualdehyde 34 and aryl iodides 35 via a palladium-catalyzed C–H arylation with a silver oxidant (Scheme 8) [42]. During optimization studies, the authors noted that steric and electronic effects strongly affected the cyclization

Asymmetric organocatalyzed synthesis of coumarin derivatives

• Natália M. Moreira,
• Lorena S. R. Martelli and
• Arlene G. Corrêa

Beilstein J. Org. Chem. 2021, 17, 1952–1980, doi:10.3762/bjoc.17.128

• yields and enantioselectivities when subjected to four sequential reactions mediated by a cooperative catalysis of a NHC organocatalyst with LiCl in the presence of DPQ as an oxidant, as shown in Scheme 17. Recently, Chen et al. used a NHC catalyst 59 in γ,δ-difunctionalization of coumarins 56 through an

• together with tetraphenylphosphonium monoperoxysulfate (TPPP) as the stoichiometric oxidant [76]. The authors mentioned that this epoxidation had been previously reported using Jacoben’s (S,S)-(+)-salen-Mn(III) catalyst with 78–83% yield and 95% ee, and via organocatalysis they obtained 98% yield and ≥99

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

• derivatives. Using H2O2 as an oxidant agent, ketones and aldehydes were obtained from hydrocarbons with high yields (85–99%, Scheme 9B and 9C). Although the authors did not explore the biological effects of the obtained products, this class of molecules resembles the basic structure of several important

• -methoxybenzaldehyde imine derivatives with phenyl Grignard reagents as coupling partners. As the catalyst CrCl2 is used and either 2,3-dichlorobutane (DCB) or 1,2-dichloropropane (DCP) are used as oxidant to give 2,5-diarylbenzaldehyde after imine hydrolysis (Scheme 16B). Although benzaldehyde is a basic structure

• reaction was kept at room temperature to avoid the difunctionalization, and the oxidant was added only in the second step. Following this route, six examples were obtained with moderate yields (56–70%, Scheme 16C). Although the use of chromium catalysis is still considered challenging due to the high

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

Sustainable manganese catalysis for late-stage C–H functionalization of bioactive structural motifs

• Jongwoo Son

Beilstein J. Org. Chem. 2021, 17, 1733–1751, doi:10.3762/bjoc.17.122

• molecules bearing unactivated Csp3–H bonds facilitated by electricity (Scheme 5) [43]. Several pharmaceutically active molecules were committed to the external oxidant-free reaction conditions and were shown to undergo chemoselective azidation. Azidation of ibuprofen methyl ester (14a) was selective for the

Cerium-photocatalyzed aerobic oxidation of benzylic alcohols to aldehydes and ketones

• Girish Suresh Yedase,
• Sumit Kumar,
• Jessica Stahl,
• Burkhard König and
• Veera Reddy Yatham

Beilstein J. Org. Chem. 2021, 17, 1727–1732, doi:10.3762/bjoc.17.121

• , Universitätstraße 31, D-93053 Regensburg, Germany 10.3762/bjoc.17.121 Abstract We have developed a cerium-photocatalyzed aerobic oxidation of primary and secondary benzylic alcohols to aldehydes and ketones using inexpensive CeCl3·7H2O as photocatalyst and air oxygen as the terminal oxidant. Keywords: alcohol

• acting as the terminal oxidant [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. Most aerobic oxidation reactions utilize either metal complexes and nanoparticles or persistent radical reagents as catalysts [21]. In the past ten years, visible light-induced

• air as the oxidant (Table 1). The best results were found using 10 mol % CeCl3·7H2O as a photocatalyst and 10 mol % of NaHCO3 as a base in CH3CN under blue LED irradiation at 50 °C for 35 h giving compound 2a in 65% isolated yield (Table 1, entry 1). The product formation was reduced upon employing

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• products instead of reductive ones. Their formation also leads to the generation of Pd(0) species that require the presence of an external oxidant to regenerate the active Pd(II) complex, as well as an additional hydrogenation step, if the hydrofunctionalized product is desired [18]. This particularity

• -substituted β-diketones 2a and 2b (61 and 70% yield, respectively). Notably, the unsaturated carbocycles expected from palladium β-hydride elimination were not observed, indicating that an oxidant was not required in the reaction medium to regenerate the Pd(II) species. Later, deuterium-labeling experiments

• oxidant (Scheme 30) [99]. Bicycle units 82 founded in natural products could be synthetized under Co(II) salen complex 80 catalysis at room temperature with excellent stereoselectivity. Only trans-decalins 82 were observed in the presence of secondary OTBS groups in the substrate backbone; this was not

Cascade intramolecular Prins/Friedel–Crafts cyclization for the synthesis of 4-aryltetralin-2-ols and 5-aryltetrahydro-5H-benzo[7]annulen-7-ols

• Jie Zheng,
• Shuyu Meng and
• Quanrui Wang

Beilstein J. Org. Chem. 2021, 17, 1481–1489, doi:10.3762/bjoc.17.104

• + antagonist, and exhibits promising anti-oxidant properties. 4-Phenyl-2-propionamidotetralin (4-P-PDOT, 3, Figure 1) [5] is a melatonin MT2 selective antagonist that can be used to map melatonin receptor subtypes in tissue and serves as a chemical biology tool to identify sub-type selective analogues with