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

• material is needed to couple the carbon dioxide reduction system to water splitting. That said, to successfully reduce a molecule there must always be a sacrificial electron donor or stoichiometric reductant. In photosynthesis the sacrificial donor is water, and the byproduct is oxygen. Sacrificial

• photocatalyst which re-reduced DcMFc and evolved oxygen. The same reaction scheme was used but in a modified H-cell (Figure 2B) [35]. Both catalysts were confined at the ITIES in two separate chambers and the redox mediator diffused between the two cells via the organic phase. The protons for hydrogen evolution

• to be stored in oxygen-free conditions to prevent re-oxidation. A major advantage of ex-situ or decoupled sacrificial electron donor recycling is that, like decoupled water splitting, the gaseous products can be evolved separately preventing explosive mixtures. However, if the sacrificial donor needs

Exploring the role of halogen bonding in iodonium ylides: insights into unexpected reactivity and reaction control

• Carlee A. Montgomery and
• Graham K. Murphy

Beilstein J. Org. Chem. 2023, 19, 1171–1190, doi:10.3762/bjoc.19.86

• pathway was operative, producing halogen-bonded adducts 28/28’ which could cyclize on the acylium at either carbon or oxygen, to eventually produce 24 and 25 after reductive elimination of iodobenzene (Figure 7, bottom). Based on these initial results and their corresponding mechanistic proposals, iodine

• electron-rich, deactivated arene. Improved results were further realized for 61d, in which the oxygen was one atom removed from the arene, which gave 62d in a 90% RCC and an 82% RCY. These results offered important insight into the hierarchy of fluorination selectivity and pointed directly to secondary

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

• additional oxygen atom compared to compound 1. The 1H, 13C NMR, and HSQC spectral data of compound 2 (Table 1) revealed a close similarity to forpinioside B (1) apart from the presence of an additional aliphatic methine proton at δH 4.02 (ddd, J = 12.3, 4.3, 2.9 Hz; δC 66.5) which exhibited an obvious spin

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

• additional reaction pathway is proposed in which the incorporated oxygen on the heteroatoms originates from water. Furthermore, the addition of certain additives enhances productivity by affecting kinetics. The industrial potential is demonstrated by conveniently transferring the batch protocol to continuous

• 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

• selectivity and safety. Traditional oxidants, such as Oxone, CrO3, NaIO4, or KMnO4, produce significant amounts of toxic waste, exacerbating these issues (Scheme 1A) [1]. As environmental concerns and economic factors increasingly affect chemical processes, hydrogen peroxide and oxygen (or air) are becoming

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

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

• fluorescence under nitrogen atmosphere and a substantial quenching under air or oxygen atmosphere [22], the fluorescence spectra of the dyads containing native PTZ unit under different atmospheres were studied (Figure 3a–d and Figure S32a in Supporting Information File 1). The results show that the

• Supporting Information File 1), the fluorescence intensity is less dependent on the atmosphere. Moreover, we suggest that the reduced luminescence of the oxidized molecules in air may be caused by the quenching effect of oxygen to the S1 state. According to this experimental phenomenon, we preliminarily

• possible relaxation pathway, because the orthogonal geometry of the dyads is beneficial for SOCT-ISC. Previously we have shown that SOCT-ISC occurs for the analogue of NI-PTZ-C5 [39]. In order to study the ISC efficiency of the dyads, we measured the singlet oxygen quantum yield (ΦΔ) of the dyads in

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

• heteroarene and amide oxygen of 45 forcing the heteroarene to approach from the Si-face of the imine moiety predominantly (see transition state 48) achieving high enantiocontrol for both heterocycles (Scheme 13) [38]. The carbocyclic ring in indoles is less reactive than the heterocyclic ring and hence the

• carbonyl oxygen of 69 in the ternary complex, thus bringing more rigidity in the three dimensional transition state (Scheme 18) [46]. In 2021, Chen and co-workers documented a chiral phosphoric acid P17-catalyzed aza-Friedel–Crafts process between racemic 2,3-dihydroisoxazol-3-ol derivatives 76 and

• a hydroxyquinoline-substituted aza-quaternary stereocenter in the 3 position. Most of the examples in this report involved 6-hydroxyquinoline as nucleophile whereas two examples each were presented with 5- and 7-hydroxyquinolines, respectively. Both the imine nitrogen and the carbonyl oxygen of the

Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• the ability of MgI2 etherate to act as a Lewis acid activator. The iodine counterion is coordinated to the Lewis basic oxygen atom of the acetal group to give the more Lewis acidic cataonic Mg-coordinated intermediate A. Intermediate A upon nucleophilic reaction with amines 20 yields B, which upon

First synthesis of acylated nitrocyclopropanes

• Kento Iwai,
• Rikiya Kamidate,
• Khimiya Wada,
• Haruyasu Asahara and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2023, 19, 892–900, doi:10.3762/bjoc.19.67

• , but a dihydrofuran, so the cyclopropane 1b’ reported in the literature [12][13][19] is presumably incorrect [22]. In the cases of donor–acceptor cyclopropanes possessing an electron-donating group such as an alkoxy or amino group, ring expansion caused by an intramolecular attack of nitro oxygen

• proceeded, to produce furan 13 with a 46% yield (Scheme 6). The coordination of two carbonyl groups to the tin species facilitated the ring opening of the cyclopropane ring to afford betaine [7], then the oxygen atom of the enolate attacked the benzyl cation to construct a five-membered ring. The subsequent

Light-responsive rotaxane-based materials: inducing motion in the solid state

• Adrian Saura-Sanmartin

Beilstein J. Org. Chem. 2023, 19, 873–880, doi:10.3762/bjoc.19.64

• -crystal X-ray structure of rotaxane 1a (R1 = Me, R2 = R3 = H) showing two interlocked molecules of the crystalline array [44]. Colour key of the solid structure: light blue = carbon atoms; purple = nitrogen atoms; red = oxygen atoms; and orange = iron atoms. Hydrogen atoms are omitted for clarity. (a

• the solid structure of UMUMOF-(E)-3 showing a rhombohedral metallogrid; and (c) cartoon representation of the operation mode of UMUMOF-(E)-3 as a molecular nanodispenser [62]. Colour key of the solid structure: light blue = carbon atoms; purple = nitrogen atoms; red = oxygen atoms; and grey = copper

• array [63]. Colour key of the solid structure: light blue = carbon atoms; purple = nitrogen atoms; red = oxygen atoms; and magenta = uranium atoms. Acknowledgements All figures included in this article are original and have been redrawn based on the content of the referenced research articles by using

A fluorescent probe for detection of Hg²⁺ ions constructed by tetramethyl cucurbit[6]uril and 1,2-bis(4-pyridyl)ethene

• Xiaoqian Chen,
• Naqin Yang,
• Yue Ma,
• Xinan Yang and
• Peihua Ma

Beilstein J. Org. Chem. 2023, 19, 864–872, doi:10.3762/bjoc.19.63

• outside the cavity, forming a 1:1 inclusion complex with TMeQ[6]. Figure 4b shows that the hydrogen atoms on the G molecule form C–H30···O1, C–H30···O2 and C–H31···O4 hydrogen bonds with the carbonyl oxygen and carbon atoms on TMeQ[6], and the bond distances are 2.163, 2.707 and 2.228 Å, respectively. In

• Figure 4c, the hydrogen atoms of G and the carbonyl oxygen of TMeQ[6] form C–H22···O1, C–H26···O1, C–H25···O4 and C–H27···O4 hydrogen bonds with bond distances of 2.370, 2.474, 2.564 and 2.685 Å, respectively. These interactions contribute to the formation of stable inclusion complexes. Figure 4d is a

• one-dimensional supramolecular chain of G@TMeQ[6], which is composed of hydrogen bonds C24–H···O6 and N13–H···O6 formed by the protons on the pyridyl group outside the cavity and the carbonyl oxygen of the adjacent TMeQ[6] port. The G molecule acts as a medium for connecting two adjacent TMeQ[6]. The

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

• nitrogen and carbonyl oxygen, generating both nucleophilic and electrophilic centers, i.e., a free amino group and protonated carbonyl group, which is much more prone to nucleophilic attack than a carbonyl group itself. Quantum calculations (see the left side of Figure 2) show that the relative stabilities

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

• has safety risks due to its potential for explosions when employed on a manufacturing scale [12]. These risks are due to the presence of two out of the three elements of combustion, namely combustibles, oxygen supply and an ignition source [13], and unexpected ignition caused by static electricity

• [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

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

• the NG precursor 39 by heating dialkyne 38 and tetracyclone 2, which led to two hexarylbenzene units connected by an oxygen linker. Upon treatment of 39 under Scholl reaction conditions (DDQ, TfOH), an oxa-[7]helicene containing chiral NG 40 was obtained in high yield [43]. Meanwhile, they enlarged

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

• an oxygen in the heterocyclic ring as opposed to nitrogen in azepines, are known from natural sources (compounds 13–18 as examples) [17][18][19][20][21][22][23][24][25], the application thereof in a clinical setting is limited (Figure 5). Novartis CGP 3466 (19), a propargylamine derivative, showed

• 10,11-dihydrodibenzo[b,f]heteropines (2). The following section will briefly touch on functionalisation of the scaffold. While some reports are limited to the introduction of a single heteroatom, e.g., nitrogen in the case of azepines 1a or oxygen in the case of oxepines 1b, some approaches allow for

• transition metal (Ni, Fe, V) porphyrin catalysts and oxygen. Catalytic reduction (H2, Pd/C) affords 2,2'-diaminobibenzyl (20) in the subsequent step [28]. 1.2 Ring-closing via amine condensation The initial synthesis of 10,11-dihydro-5H-dibenzo[b,f]azepine (2a) was reported in 1899 by Thiele and Holzinger

Synthesis of medium and large phostams, phostones, and phostines

• Jiaxi Xu

Beilstein J. Org. Chem. 2023, 19, 687–699, doi:10.3762/bjoc.19.50

• of the etheric oxygen atom and the antibonding orbital of the P=O bond (the stereoelectronic effect), leading to the more stable anti-diastereomer 74 (Scheme 16) [38]. In the phostone 74 was installed a linker 2-(5-aminopentoxy) group via transesterification with benzyl N-(5-hydroxypentyl)carbamate

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

• singlet oxygen production have been identified in porphyrin-based butadiynes [7][8][9], 1,3-butadiyne-linked oligoporphycenes [10], and 1,3-butadiyne-linked amines [13]. A wide variety of applications was proposed for graphdiynes (2D allotropes of graphene), including electrocatalysts and energy devices

• 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

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

• boron complex (B2pin2), and using an expensive metal-based photocatalyst [fac-Ir(ppy)3] under inert atmosphere. We have recently demonstrated that aerial oxygen could be captured by alkyl radicals to install a keto-functionality onto alkenes in an organophotocatalytic way [23]. We aimed to extend this

• using air as the sole oxygen source. Keeping in mind the progress in photochemical relay catalysis [24] and the attention paid to photocatalytic carbon-bond functionalization in the past several years [25], here we developed an organophotoredox-catalyzed C–H functionalization of imidazo[1,2-a]pyridines

• degassed conditions with or without water only delivered a trace amount (<5%) of the desired products, indicating that aerial oxygen plays a crucial role in the second catalytic cycle for the conversion of 5 to 3a or 4a (Scheme 3C). To determine the role of zinc acetate, a standard reaction of 1a and 2a in

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

Access to cyclopropanes with geminal trifluoromethyl and difluoromethylphosphonate groups

• Ita Hajdin,
• Romana Pajkert,
• Mira Keßler,
• Jianlin Han,
• Haibo Mei and
• Gerd-Volker Röschenthaler

Beilstein J. Org. Chem. 2023, 19, 541–549, doi:10.3762/bjoc.19.39

• . Phosphonates containing CF2 groups can sterically and electronically mimic oxygen, enabling the second dissociation constant, pKa2, to closer mirror those of the phosphates due to the electron-withdrawing effect of fluorine [39]. As a result, improved lipophilicity, metabolic stability or bioavailability of

• the case of TS2_1 and TS2_2 to the intermediates Int3_1 and Int3_2. Afterwards, the Cu–C bond is broken, and a Cu–O bond is formed. CuI is transferred to the oxygen atom from the phosphonate group, yielding Int4_1 and Int4_2. In the case of TS2_3 and TS2_4, the addition proceeds smoothly towards

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

• undergoing reductive elimination to afford to [2 + 2] adduct, β-oxygen elimination followed by E/Z isomerization and intramolecular lactonization generates the annulated coumarin scaffold. In 2003, the Cheng lab extended on this Ni-catalyzed ring-opening strategy [31]. It was noted the addition of 1.5

• the bicyclic alkene followed by migratory insertion affords intermediate 12 which undergoes β-oxygen elimination to form 13. Rearrangement of 13 via β-hydride elimination and enolization generates a 1-naphthol species which undergoes intramolecular cyclization with the ester to form the final product

• the coordination of the alkyne 17 and alkene 1 to the Ni(0) center, followed by oxidative cyclometallation, yields the following nickelocycle 24. Unlike Cheng’s 2003 report, which proposes subsequent β-oxygen elimination (Scheme 1) [31], alkoholysis by MeOH affords an alkyl(methoxy)nickel intermediate

CuAAC-inspired synthesis of 1,2,3-triazole-bridged porphyrin conjugates: an overview

• Dileep Kumar Singh

Beilstein J. Org. Chem. 2023, 19, 349–379, doi:10.3762/bjoc.19.29

• albumin and LDL. Furthermore, the Zn and Pd porphyrin complexes revealed a good capability to yield singlet oxygen (quantum yield >70%) and exhibited significant photoinduced cytotoxicity. In another report, Prakash Rao et al. [65] highlighted the click protocol to accomplish the synthesis of hydrogenated

Synthesis and reactivity of azole-based iodazinium salts

• Thomas J. Kuczmera,
• Annalena Dietz,
• Andreas Boelke and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2023, 19, 317–324, doi:10.3762/bjoc.19.27

• reactivity and utility in XB catalysis. We also established one-pot methods for generating six-membered carbon-, oxygen-, and nitrogen-bridged iodonium salts, such as the iodazinium triflate 3 [32][33]. Based on these promising findings, we further wanted to elaborate this chemistry and herein we present the

• the dicationic salts is a reactive site for oxidative transformations [44][45]. The reaction of the iodine-protected benzimidazolium salts 5ax–az and 12 with different oxygen sources revealed K2CO3 and NCS as the optimal system to form the benzimidazole-2-ones 13a–d in 18–48% yield, with the best

Synthesis, α-mannosidase inhibition studies and molecular modeling of 1,4-imino-ᴅ-lyxitols and their C-5-altered N-arylalkyl derivatives

• Martin Kalník,
• Sergej Šesták,
• Juraj Kóňa,
• Maroš Bella and
• Monika Poláková

Beilstein J. Org. Chem. 2023, 19, 282–293, doi:10.3762/bjoc.19.24

• inhibitor:enzyme complexes were analyzed by molecular modeling. Keywords: glycosidase inhibitor; Golgi mannosidase II; iminosugar; inhibition; molecular modeling; Introduction Iminosugars are analogs of monosaccharides in which the endocyclic oxygen atom is replaced with a nitrogen atom [1][2][3][4][5]. These

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

• combined computational and experimental approach that in this enzyme the main chain carbonyl oxygen of Gly182 near the helix G kink and an active site water are involved in the deprotonation–reprotonation sequence in the biosynthesis of 10 (Scheme 8B) [69]. γ-Selinene (10) has been synthesised from ketone