Recent developments in the engineered biosynthesis of fungal meroterpenoids

• Zhiyang Quan and
• Takayoshi Awakawa

Beilstein J. Org. Chem. 2024, 20, 578–588, doi:10.3762/bjoc.20.50

• the αKG-dependent dioxygenase have been analyzed in detail due to its relatively small molecular weight and the low costs of its cofactors: αKG, ascorbic acid, and iron ions. The αKG reacts with iron and molecular oxygen to form the highly reactive Fe(IV)=O via oxidative decarboxylation. This active

Photoinduced in situ generation of DNA-targeting ligands: DNA-binding and DNA-photodamaging properties of benzo[c]quinolizinium ions

• Julika Schlosser,
• Olga Fedorova,
• Yuri Fedorov and
• Heiko Ihmels

Beilstein J. Org. Chem. 2024, 20, 101–117, doi:10.3762/bjoc.20.11

• species (ROS), such peroxyl, alkoxy and hydroxyl radicals, or carbon-centered radicals, which subsequently induce DNA strand cleavage. In the type-II mechanism, a triplet-excited photosensitizer reacts with molecular oxygen to give highly reactive singlet oxygen, 1O2, as reactive intermediate, which in

Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• , such as organic peroxides, hydrogen peroxide, persulfates undergo homolysis of O–O bonds generating radicals that can break C–H bonds followed by a hydrogen abstraction reaction. Phenolic compounds can be oxidized by molecular oxygen in the presence of laccase, and the resulting phenolic radical reacts

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

• -chain alkyl ethers in the presence of DBU under relatively mild conditions (Scheme 29b) [92]. In 2018, Wang et al. developed the cobalt-catalyzed oxidative CDC reaction of 2-arylimidazo[1,2-a]pyridines with isochroman using molecular oxygen as an oxidant (Scheme 30) [93]. These reactions involved a

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

• , which diminishes the atom economy [2]. To overcome this limitation, the use of molecular oxygen (O2) present in air as an oxidant is one of the ideal solutions [10][11]. The reduction of O2 generates only water as a byproduct, leading to high atom-economy processes. However, the use of O2 as an oxidant

• [15][16]. A compact and closed system improves the process safety of handling molecular oxygen by eliminating unexpected ignition. The safety advantage stimulates the development of various aerobic oxidation processes under continuous-flow conditions accompanied by dedicated devices such as tube-in

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

• oxidized by molecular oxygen to the phthalimide-N-oxyl radical (PINO) at room temperature and atmospheric oxygen pressure. The NHPI/Co(OAc)2 combination [78][79][80], also known as the Ishii catalytic system is one of the most effective in organic synthesis for the room temperature [78][79] aerobic

• were used as redox-active organocatalysts for the oxidative coupling of aryl- and alkenylmagnesium compounds employing molecular oxygen as the terminal oxidant [154] (Scheme 38). Frustrated Lewis pairs (FLP) have gained much attention in the last decade due to unique reactivity, such as metal-free H2

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

• identity can display almost identical biochemical activity. Enzymatic mechanism As monooxygenases, CYPs catalyse the transfer of a single oxygen atom from molecular oxygen to their substrates (Figure 1A). Decades of research on CYPs led to detailed insights into their mechanistic properties based on a

• variety of biochemical, biophysical and computational methods [17][18][19][20][21]. Key for the oxidative chemistry performed by CYPs is a heme prosthetic group that activates molecular oxygen using electrons from an electron donor such as NADPH. A central Fe(III) ion is coordinated by the heme porphyrine

• charge, can then efficiently bind molecular oxygen (step 3), leading to dioxygen adduct D. Transfer of an additional electron from a reducing partner such as cytochrome P450 reductase (step 4) generates peroxo intermediate E, which upon protonation (step 5) gives hydroperoxo intermediate F, also called

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

• hydroperoxide/dicumyl peroxide/phenol from cumene, acetophenone from ethylbenzene, and others. Generally, molecular oxygen has been utilized in the straightforward oxidation of aromatic alkyls. However, since molecular oxygen is highly stable, activation of the molecular oxygen itself is necessary, which

• not residual water in MeCN, but dissolved oxygen. The role of dissolved oxygen was further investigated. As the reaction did not proceed without electricity, it is suggested that the superoxide generated on the cathode is involved in the reaction, rather than dissolved molecular oxygen itself

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

• molecular oxygen, or electrochemically generated superoxide (cathodic reduction of O2), which oxidize the Breslow intermediate [30][39]. In fact, the presence of some reactive oxygen species in the reaction environment was previously demonstrated by the formation of compound 1b (see Table 1). IL Recycling

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

• ) with molecular oxygen at elevated temperatures providing (+)-nootkatone (8) in 10% yield (Scheme 2). In this setup, neat (+)-valencene (7) is mixed with a stream of oxygen resulting in the formation of a segmented gas–liquid flow. In segmented flow a higher surface-to-volume ratio is achieved and

• state of the decatungstate anion generates carbon-centered radical 48 which is trapped in a segmented flow with molecular oxygen provided by a mass flow controller. Peroxide 49 is formed as intermediate which further reacts to phthalide (50) in 71% yield. This method efficiently utilizes the advantages

• molecules, to macrocyclic musks with higher molar masses and boiling points. In flow, photocatalyzed oxidations with molecular oxygen proceed in higher yields and with shorter reaction times, as it has been used for the synthesis of, e.g., phthalide (50). In contrast, when ethylene is formed in a ring

Structural basis for endoperoxide-forming oxygenases

• Takahiro Mori and
• Ikuro Abe

Beilstein J. Org. Chem. 2022, 18, 707–721, doi:10.3762/bjoc.18.71

• spin density is distributed over C13–C15. The allyl radical at C15 reacts with a second molecular oxygen to afford the C15 peroxyl radical. Finally, the transfer of a hydrogen atom from the catalytic Tyr385 residue quenches the C15 peroxyl radical to yield PGG2 and a tyrosyl radical for the next round

• Tyr224 to form a tyrosyl radical, which abstracts a hydrogen atom from C21 of fumitremorgin B to generate a radical intermediate. The insertion of molecular oxygen at C21 produces a C21 peroxyl radical intermediate, which then reacts with the C26–C27 double bond on another prenyl group to generate the

• tyrosyl radical, first abstracts a hydrogen atom from C21 to form a substrate radical intermediate. The following reaction with molecular oxygen and the formation of an endoperoxide bridge generate the C26 radical intermediate. Finally, HAT from Tyr68 produces verruculogen and a tyrosyl radical at Tyr68

Inductive heating and flow chemistry – a perfect synergy of emerging enabling technologies

• Conrad Kuhwald,
• Sibel Türkhan and
• Andreas Kirschning

Beilstein J. Org. Chem. 2022, 18, 688–706, doi:10.3762/bjoc.18.70

• continuous process could be established by oxidation with molecular oxygen introduced into the reaction stream via a tube-in-tube membrane reactor, a process which should be very attractive for industrial applications, as oxygen or air act as cheap and environmentally friendly oxidants [82]. An interesting

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

• oxidation, a combination of molecular oxygen and aldehydes as a sacrificial agent has been widely studied [9]. However, in general, such a reaction in batch is slow due to the difficulties of performing a gas–liquid reaction in a batch reactor [10]. In addition, even valuable catalysts could not accelerate

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

• -methylnaphthol (17) to menadione (10) are quite similar to those employed for the oxidation of 2-methylnaphthalene (16) using H2O2, molecular oxygen, and tert-butyl hydroperoxide as oxidizing agents. Similar to the oxidation of compound 16, it is possible to oxidize 2-methylnaphthol (17) with H2O2 to produce

• heteropoly acids [71], molecular oxygen [72][73], and organic peroxides [74]. Matveev and co-workers studied phosphomolybdovanadium heteropoly acids of Keggin-type with the general structure H3+nPMo12-nVnO40 (HPA-n) and their acidic salts as reversibly acting oxidants to convert 17 to 10 (Table 2, entry 8

• also reported the oxidation of 2-methylnaphthol (17) using molecular oxygen in the presence of gold nanoparticles as catalyst and the best yield of menadione (10) was obtained using 1.5% Au/TiO2 as catalyst (57%, Table 2, entry 9), while the best conversion of 17 was furnished using 1% Au/C-2 catalyst

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

• 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

• interesting ruthenium-catalyzed oxidative cyanation of tertiary amines using molecular oxygen was reported by Murahashi and co-workers [32]. This RuCl3·nH2O-catalyzed protocol used NaCN in acetic acid as the cyano source, methanol as the solvent under molecular oxygen at 60 °C for 1–2 h (Scheme 7). The

• , molecular oxygen as the oxidant, and TiO2-immobilized ruthenium(II) polyazine complex as the heterogeneous photoredox catalyst in methanol at room temperature (Table 1). The substrate scope studies revealed a better reactivity of aromatic tertiary amines substituted with electron-donating groups compared to

α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

• Scott Benz and
• Andrew S. Murkin

Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172

• 64 (Figure 14b) [20][21]. The other enzyme believed to catalyze an α-ketol rearrangement is AuaG, which is a monooxygenase that uses FAD and molecular oxygen to convert aurachin C (66) to 69 (Figure 14c) [22]. Subsequent reduction and dehydration by AuaH produces aurachin B (71). While the above are

Visible-light-mediated copper photocatalysis for organic syntheses

• Yajing Zhang,
• Qian Wang,
• Zongsheng Yan,
• Donglai Ma and
• Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

• cation I and a CuI species. This process regenerated CuII in the presence of molecular oxygen. The deprotonation of the nitrogen radical cation produces an α–amino radical II, which was further oxidized to the iminium ion III to which the copper alkynylide added forming the desired product (Scheme 17

• to generate the CuII hydroperoxo complex C and the corresponding aldehyde. Complex C can undergo a reductive elimination to recover 64a. The liberated aminobenzamide 64a and the aldehyde undergo a condensation reaction to produce quinazolinone 66′, followed by oxidation with molecular oxygen to

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

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

• [7][8][9][10][11][12][13][14][15][16][17]. In order to overcome the limitations, various homogeneous and heterogeneous catalytic oxidation systems have been reported. Aerobic oxidation is particularly attractive as it allows the transformations under mild reaction conditions with molecular oxygen

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

A new and efficient methodology for olefin epoxidation catalyzed by supported cobalt nanoparticles

• Lucía Rossi-Fernández,
• Viviana Dorn and
• Gabriel Radivoy

Beilstein J. Org. Chem. 2021, 17, 519–526, doi:10.3762/bjoc.17.46

• greener oxidizing agents as molecular oxygen, hydrogen peroxide or tert-butyl hydroperoxide (TBHP) [14][15][16][17]. However, using any of these oxidants alone results in considerable low reactivity and selectivity in olefin epoxidation reactions. Thus, several transition-metal-based catalytic methods

• the other hand, the use of supported cobalt nanoparticles as efficient catalysts for the epoxidation of olefins has received increasing attention in the last years. In most cases, a crucial influence of the support (TiO2, HAP, CNTs, SBA, SiO2), the oxidant agent (molecular oxygen or TBHP) and the

• solvent (DMF, MeCN, ethyl acetate, DMSO, solvent free) on the activity and selectivity of the nanocatalysts has been noted [27][41][42][43][44]. Furthermore, all the reported methodologies use either molecular oxygen together with an aldehyde as a co-reductant, or only a “green” peroxide (H2O2, TBHP) as

Biochemistry of fluoroprolines: the prospect of making fluorine a bioelement

• Vladimir Kubyshkin,
• Rebecca Davis and
• Nediljko Budisa

Beilstein J. Org. Chem. 2021, 17, 439–460, doi:10.3762/bjoc.17.40

• modifications of proline residues are sparse. The most common among them is hydroxylation at position 4 by molecular oxygen, which is mediated by prolyl-4-hydroxylase [34]. This process has a remarkable relevance in the stabilization of collagen in higher organisms [35]. The experimental expression of the

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• corresponding trimethylsumanene 28 by means of nucleophilic oxidation using NaHMDS in the presence of molecular oxygen in DMF as the solvent (Scheme 8). It has been noticed from the literature that the directly linked π-conjugated systems act as promising electron-accepting materials because of their high LUMO

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• selecting judiciously a PC with adequate redox potentials, the ground state of the latter could be regenerated by means of a mild and abundant oxidant such as molecular oxygen. The overall process thus allowed the replacement of stoichiometric amounts of external oxidants with a suitable PC. Following this

• photoredox catalysis (Figure 5) [73]. The coupling products were generally isolated in good yields, although this procedure required high temperature (120 °C). Remarkably, molecular oxygen was used as the terminal oxidizing agent of the overall C–H functionalization reaction. The mechanistic studies revealed

• of the photocatalyst in the absence of oxygen, suggesting that a direct electron transfer from the photosensitizer allowed the reoxidation of the active catalyst. However, the participation of molecular oxygen cannot be excluded. Rueping further demonstrated the capacity of the dual catalytic systems

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125