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

• Grace A. Lowe van ’t Hoff Institute for Molecular Sciences (HIMS), Universiteit van Amsterdam (UvA), Science Park 904, Amsterdam, 1098 XH, The Netherlands 10.3762/bjoc.19.88 Abstract This review surveys advances in the literature that impact organic sacrificial electron donor recycling in

• 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

• sacrificial electron donors, and for researchers interested in designing new redox mediator and recyclable electron donor species. Keywords: artificial photosynthesis; photocatalysis; redox couple; sacrificial electron donor; solar fuels; Introduction Artificial photosynthesis research has resulted in the

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

• include nucleophile σ-hole selectivity, and how ylide structural modifications and intramolecular halogen bonding (e.g., the ortho-effect) can improve ylide stability or solubility, and alter reaction outcomes. Keywords: electron donor–acceptor complex; halogen bonding; σ-holes; iodonium ylides; ortho

• pattern shown in Figure 1, where R is the host atom or functional group to which the halogen is covalently bound, where X is the halogen atom possessing the σ-hole (halogen bond donor), and where Y is the Lewis base (halogen bond acceptor) [31]. σ-Holes arise from anisotropic covalent bonds between the

• –180° [39][49][50], and with halogen bond lengths that are typically less than or equal to the sum of the atomic Van der Waals radii of the engaged atoms [33]. The strength of a subsequent halogen bond is influenced by the magnitudes of the positive electrostatic potential (VS,max) of the donor and the

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

• retardants [14]. Sulfoxides are prominent pharmaceutical ingredients, while phosphine oxides improve solubility of corresponding compounds [15] and have applications in catalysis and materials science [16]. Selenoxides find use as oxygen transfer agents and donor ligands in metal catalysis and organic

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

• SET with an electron acceptor (A), leading to PC•+ and A•−. The ground state photocatalyst is then regenerated by an SET reaction with an electron donor (D), affording also D•+. Both species described can be further involved in various organic transformations to form the target products (or byproducts

• 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

• late-stage functionalization (17i and 17j) (Figure 12A). Interestingly, sodium oxalate could be used as the electron donor provided a catalytic loading of 4-cyanopyridine was added. Although the role of the latter species was not proposed by authors, it is more facile to reduce than an aryl chloride so

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

• University, Beijing 100875, P. R. China Key Laboratory of Hainan Trauma and Disaster Rescue, The First Affiliated Hospital of Hainan Medical University, Hainan Medical University, Haikou 571199, P. R. China 10.3762/bjoc.19.79 Abstract A series of 1,8-naphthalimide (NI)-phenothiazine (PTZ) electron donor

• intersystem crossing (rISC) is slow, without coupling with an approximate 3LE state. These studies are useful for an in-depth understanding of the photophysical mechanisms of the TADF emitters, as well as for molecular structure design of new electron donor–acceptor TADF emitters. Keywords: charge-transfer

• ; electron donor; intersystem crossing; TADF; triplet state; Introduction Thermally activated delayed fluorescence (TADF) compounds are promising emitters to be used in organic light-emitting diodes (OLED) [1][2][3][4][5][6][7][8][9][10][11][12]. These emitters have the advantage of low cost and high

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

• performs as an H-bond donor towards the imidazoline nitrogen and the electrophile acts as H-bond acceptor from the OH group of the catalyst. These interactions rearrange the three molecules in a chiral pocket as shown by transition state 7, favoring stereoinduction in the products through C3

• as H-bond donor to the catalyst (see transition state 97, Scheme 22a) [51]. Recently, the same research group documented another aza-Friedel–Crafts reaction between indoles 4 and 95 that frames aza-quaternary stereocenter at the α-carbon of unnatural amino acid derivatives 96. Enantiocontrol was

• rationalized by dual H-bonding interactions between both the reagents and the catalyst. The indole’s NH performed as the H-bond donor whereas the imine nitrogen of 95 was the H-bond acceptor towards the catalyst enabling a face-selective attack by the π-nucleophile to the electrophile C=N plane (see transition

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

• bond donating groups were investigated. Among these, the DES prepared by mixing quaternary ammonium salts choline chloride (ChCl) and the hydrogen-bond donor L-(+)-tartaric acid gives the best result. Moreover, L-(+)-tartaric acid–ChCl acts as both solvent and catalyst for pyrrole synthesis. This

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

Synthesis of substituted 8H-benzo[h]pyrano[2,3-f]quinazolin-8-ones via photochemical 6π-electrocyclization of pyrimidines containing an allomaltol fragment

• Constantine V. Milyutin,
• Andrey N. Komogortsev,
• Boris V. Lichitsky,
• Mikhail E. Minyaev and
• Valeriya G. Melekhina

Beilstein J. Org. Chem. 2023, 19, 778–788, doi:10.3762/bjoc.19.58

• photoreaction can be carried out for starting compounds with both donor and acceptor substituents in the aryl fragment. However, it is interesting to note that the UV irradiation of thiophene containing pyrimidines 9g and 10g leads to a complicated mixture of unidentified products. Probably, this is due to

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

• -conjugation of 1,8-bis(dimethylamino)naphthalene (DMAN) fragments through a butadiyne linker and a donor–acceptor aryl–C≡C–DMAN conjugation path. The conjugation path can be “switched” simply by protonation of DMAN fragments. X-ray diffraction, UV–vis spectroscopy and cyclic voltammetry are applied to analyze

• the extent of π-conjugation and the efficiency of particular donor–acceptor conjugation path in these new compounds. X-ray structures and absorption spectra of doubly protonated tetrafluoroborate salts of the oligomers are also discussed. Keywords: 1,8-bis(dimethylamino)naphthalene; cross-conjugated

• systems; 1,4-diaryl-1,3-butadiynes; donor–acceptor systems; Glaser–Hay reaction; Introduction π-Conjugated oligomers and polymers attracted considerable attention from the very start as a promising class of semiconductors, chemosensors, and various electronic devices [1][2]. Although silicon and

Nucleophile-induced ring contraction in pyrrolo[2,1-c][1,4]benzothiazines: access to pyrrolo[2,1-b][1,3]benzothiazoles

• Ekaterina A. Lystsova,
• Maksim V. Dmitriev,
• Andrey N. Maslivets and
• Ekaterina E. Khramtsova

Beilstein J. Org. Chem. 2023, 19, 646–657, doi:10.3762/bjoc.19.46

• -aminothiophenol with donor–acceptor cyclopropanes (Scheme 2, entry 10) [27], condensations of o-aminothiophenol with 4-oxo acids or their derivatives (Scheme 2, entry 11) [2][28][29][30][31] and cascade reactions of o-aminothiophenol, furfural and anhydrides of 2,3-unsaturated carboxylic acids (Scheme 2, entry 12

Direct C2–H alkylation of indoles driven by the photochemical activity of halogen-bonded complexes

• Martina Mamone,
• Giuseppe Gentile,
• Jacopo Dosso,
• Maurizio Prato and
• Giacomo Filippini

Beilstein J. Org. Chem. 2023, 19, 575–581, doi:10.3762/bjoc.19.42

• , the process is driven by the photochemical activity of halogen-bonded complexes formed upon complexation of a sacrificial donor, namely 1,4-diazabicyclo[2.2.2]octane (DABCO), with α-iodosulfones. The reaction provides a variety of densely functionalized products in good yields (up to 96% yield

• tool to guide the development of greener and more convenient synthetic protocols [7][8][9][10][11][12]. In this context, photochemical approaches based on electron donor–acceptor (EDA) complexes have been successfully exploited to drive the direct C–H functionalization of a large number of organic

• substrates [13][14][15][16][17][18]. In this approach, an electron acceptor substrate (“A”) and a donor molecule (“D”) interact to form a new aggregate defined as EDA complex (Figure 1a). Although the two molecular entities might not directly absorb visible light, the newly formed complex usually presents a

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

• obtained by the deoxofluorination of the corresponding dicarboxylic acids with sulfur tetrafluoride, thiophilic ring-opening reactions with nucleophiles or reactions of donor-substituted furans with bis(trifluoromethyl)-substituted ethylenes (Scheme 1D) [41][42][43]. The lack of application of highly

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

Mechanochemical solid state synthesis of copper(I)/NHC complexes with K₃PO₄

• Ina Remy-Speckmann,
• Birte M. Zimmermann,
• Mahadeb Gorai,
• Martin Lerch and
• Johannes F. Teichert

Beilstein J. Org. Chem. 2023, 19, 440–447, doi:10.3762/bjoc.19.34

• inactive complexes (see Supporting Information File 1 for details). This also supports the notion that during catalytic ester hydrogenation, the guanidinium moiety acts as a hydrogen bond donor to the esters [48]. The formation of a CO2 adduct hinders the ability to form hydrogen bonds. Furthermore

Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities

• Jorge de Lima Neto and
• Paulo Henrique Menezes

Beilstein J. Org. Chem. 2023, 19, 399–427, doi:10.3762/bjoc.19.31

• for synthesis. In general, the synthesis of these macrocyclic compounds can be accomplished by using two distinct disconnections (Scheme 3): one concerns the formation of the macrocycle through macrolactonization reaction from the former seco-acid formed from the Ar–O–Ar coupling from the aryl donor

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

• -porphyrin and copper-corrole moieties upon photoexcitation. Moreover, the theoretical calculations suggested that the porphyrin moiety acted as a donor while the corrole unit acted as an acceptor in dimer 60. Recently S. Y. Yap and co-workers [38] used “click chemistry” to link a water-soluble porphyrin

• BODIPY 163 containing an azide moiety (Scheme 35). Photophysical studies confirmed that a good spectral overlap was found between the energy donor (BODIPY) and the energy acceptor (porphyrin subunits). Also, complex 164 exhibited a highly efficient photoinduced energy transfer process with an energy

Catalytic aza-Nazarov cyclization reactions to access α-methylene-γ-lactam heterocycles

• Bilge Banu Yagci,
• Selin Ezgi Donmez,
• Onur Şahin and
• Yunus Emre Türkmen

Beilstein J. Org. Chem. 2023, 19, 66–77, doi:10.3762/bjoc.19.6

• ). Finally, we investigated the activity of the achiral thiophosphoric triamide 13 as a triple hydrogen-bond donor [67]. With the use of 1.2 equiv of 13 at 23 °C, product 7b was isolated in 25% yield (Table 1, entry 16). Overall, while AgOTf still appeared to be the best reagent to be used in catalytic

NaI/PPh₃-catalyzed visible-light-mediated decarboxylative radical cascade cyclization of N-arylacrylamides for the efficient synthesis of quaternary oxindoles

• Dan Liu,
• Yue Zhao and
• Frederic W. Patureau

Beilstein J. Org. Chem. 2023, 19, 57–65, doi:10.3762/bjoc.19.5

• ethers and N-heteroarenes by using a novel catalytic system based on sodium iodide (NaI) and triphenylphosphine (PPh3), suggested to function as an electron donor–acceptor (EDA) complex [55][56][57][58][59][60]. Compared to previously reported radical reactions, this novel catalytic system has the key

Inline purification in continuous flow synthesis – opportunities and challenges

• Jorge García-Lacuna and
• Marcus Baumann

Beilstein J. Org. Chem. 2022, 18, 1720–1740, doi:10.3762/bjoc.18.182

• of the ethyl acetate solvent (used as acetyl donor) whereas the recovered aqueous phase contains the unreacted amine that can be recirculated in the system (Scheme 3) [54]. Amongst the commonly cited challenges of implementing these membranes are their high cost and the perceived difficulties

• system consists of a membrane reactor for the enzyme-mediated synthesis, a saturator vessel for the continuous supply of the amine donor, and a crystallizer where the desired product precipitates. Flow reactions can be performed as neat reactions in certain circumstances allowing for the precipitation of

Total synthesis of grayanane natural products

• Nicolas Fay,
• Rémi Blieck,
• Cyrille Kouklovsky and
• Aurélien de la Torre

Beilstein J. Org. Chem. 2022, 18, 1707–1719, doi:10.3762/bjoc.18.181

• optimization showed that chiral squaramide 47 developed by Jacobsen’s group significantly accelerated the Mukaiyama reaction compared to TMSOTf or TiCl4 thanks to chiral hydrogen bond-donor effect [35]. After Sakurai cyclization promoted by EtAlCl2, the desired product 48 was obtained with the required

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

• of a hydroperoxide (terminal oxidant) on a ketone or imine, respectively, is followed by intramolecular cyclization with O–O bond cleavage and the formation of a strained 3-membered ring, an electrophilic oxygen atom donor for oxidative processes (Scheme 30). It should be noted that in the ketone

• oxaziridinium organocatalysis was developed recently [138]. The advantage of this method is the compatibility with secondary alcohol groups, which are not oxidized and can be used as a directing moiety. The use of HFIP as a strong hydrogen bond donor solvent protecting alcohols from oxidation was considered as

Functionalization of imidazole N-oxide: a recent discovery in organic transformations

• Koustav Singha,
• Imran Habib and
• Mossaraf Hossain

Beilstein J. Org. Chem. 2022, 18, 1575–1588, doi:10.3762/bjoc.18.168

• %). Nucleophilic halogenation reactions In 2015, Evgeny I. Adiulin and co-workers reported a methodology for the deoxygenative nucleophilic halogenation of 2-unsubstituted imidazole N-oxides at the C-2 position using tosyl halogenides (TsHal) as halogen donor in THF as the solvent [18]. In this procedure, the

One-pot synthesis of 2-arylated and 2-alkylated benzoxazoles and benzimidazoles based on triphenylbismuth dichloride-promoted desulfurization of thioamides

• Arisu Koyanagi,
• Yuki Murata,
• Shiori Hayakawa,
• Mio Matsumura and
• Shuji Yasuike

Beilstein J. Org. Chem. 2022, 18, 1479–1487, doi:10.3762/bjoc.18.155

• desired product 8a in an excellent yield, whereas the N,N-disubstituted thioamide 5 did not react (Table 1, entries 1, 20–22). These results show that N-phenylbenzothioamide (2a) is superior as a C1 unit donor at the 2-position of benzoxazole. Consequently, the best result was obtained when 1a and 2a were

Design, synthesis, and evaluation of chiral thiophosphorus acids as organocatalysts

• Karen R. Winters and
• Jean-Luc Montchamp

Beilstein J. Org. Chem. 2022, 18, 1471–1478, doi:10.3762/bjoc.18.154

• dual donor–acceptor role, such as P-stereogenic triflamide CPAs P(O)NHSO2CF3, is currently under investigation since BINOL-derived triflamides have been successful [48][49]. Another possibility would be to look at reactions in which the catalyst would not require a Brønsted basic site. Both directions