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

• diazonium salts produces highly reactive aryl radicals (Scheme 18) [153]. The chemical conversion can be initiated by electrochemical reduction [154], a reducing agent [155][156][157], a base [158], heating [159], or photochemically [160]. Aryl radicals may act as a halogen abstractor for alkyl halides and

Complexes of resorcin[4]arene with secondary amines: synthesis, solvent influence on “in-out” structure, and theoretical calculations of non-covalent interactions

• Waldemar Iwanek

Beilstein J. Org. Chem. 2023, 19, 1525–1536, doi:10.3762/bjoc.19.109

• , finally, the structure with the lowest energy, with the functional PBE0-D4/mTZVPP/CPCM. The Hartree–Fock plus London dispersion (HFLD) method was used for the study of non-covalent interactions (NCI). The calculations lead to the conclusion that a reduction in electrostatic interactions and an increase in

• the non-covalent interactions stabilizing the formation of 1:1 stoichiometry complexes was noted for the charge-transfer interactions. They are only slightly higher in CHCl3 than in DMSO, ranging from 1.4 to 2.9%. In general, it can be concluded from these calculations that the reduction of

• -covalent interactions in the appropriate solvent was assessed using the HFLD method. The calculations show that the reduction of electrostatic interactions and the increase in exchange and dispersion interactions in CHCl3 compared to DMSO are the driving forces for the placement of the sec-amine molecules

Synthesis and biological evaluation of Argemone mexicana-inspired antimicrobials

• Jessica Villegas,
• Bryce C. Ball,
• Katelyn M. Shouse,
• Caleb W. VanArragon,
• Ashley N. Wasserman,
• Hannah E. Bhakta,
• Allen G. Oliver,
• Danielle A. Orozco-Nunnelly and
• Jeffrey M. Pruet

Beilstein J. Org. Chem. 2023, 19, 1511–1524, doi:10.3762/bjoc.19.108

• considered ways to further enhance this activity. We first explored the effects of structural modifications to berberine itself. The cationic iminium within berberine and its derivatives is susceptible to nucleophilic attack [10][14]. Through use of an acetone enolate, as well as partial or full reduction by

• typically less active when compared to the B1 variant. Exceptions to this were the markedly improved activity of compound B13 towards C. pseudodiphtheriticum, as well as its unique Gram-negative activity (Table 2). Given the partial reduction of berberine to B10 gave promising improvement for a single

• desired derivatives. Unexpected oxidation side-product B2, B4, and B6 were also isolated from certain reaction mixtures. Direct modification of the original berberine structure. Preparation of non-cyclic charged variants of B1. Partial reduction of compound B1 to B14. Synthesis of the substituted 2

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• Scheme 31. Initially, homolytic cleavage of thiosulfonate 70 generated PhS· and PhSO2· radicals. The reduction of Ni(II) to Ni(0) in the presence of Cs2CO3 and the reaction with 68 formed alkynyl-Ni species I. Then, the PhS· radical reacted with I to generate alkenyl radical II, which can react with the

• heterogeneous medium coming from H2O and toluene was beneficial for the progress of the transformation. In 2014, Denmark and Chi successfully synthesized a wide variety of pyrrolidines 99, piperidines 100, and azepanes via intramolecular sulfenoamination of olefins 98 (Scheme 40) [75]. The reduction of endo to

• reduction of II by silane. On the other hand, most of II were converted to intermediate III, which underwent hydride reduction to render product 140 (Scheme 61). Another organocatalysis system was disclosed by Liu and co-workers for sulfenylation of α-fluoro-β-ketoamides 143 and azlactones 145 (Scheme 62

Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• complex 57 was obtained through reduction of the phenoxyimine-imidazolium bromide 55a (R = t-Bu) with NaBH4 followed by successive alkylation with iPrBr and reaction with Cu2O (Scheme 19) [32]. The use of the synthesized complexes 56a and 57 as precatalysts for the 1,4-conjugate addition to enones and the

• ]. Later in 2003, Buchwald, Sadighi and Jurkauskas [47] succeeded in the application of [(IPr)CuCl] as NHC–Cu(I) complex to catalyze the conjugate reduction of α,β-unsaturated carbonyl compounds. In the decade following these initial reports, the field has blossomed and NHC–Cu(I) complexes have been

One-pot nucleophilic substitution–double click reactions of biazides leading to functionalized bis(1,2,3-triazole) derivatives

• Hans-Ulrich Reissig and
• Fei Yu

Beilstein J. Org. Chem. 2023, 19, 1399–1407, doi:10.3762/bjoc.19.101

• the alkynyl-substituted 1,2-oxazin-4-ol derivative 19 which is smoothly available from the corresponding ketone 6 by highly stereoselective reduction with sodium borohydride [53]. Starting from 1,3- (8) or 1,4-bis(bromomethyl)benzene (16), respectively, the approved conditions in the presence of TBTA

• quantitatively available by sodium borohydride reduction of 7, we encountered the first problems. Under similar conditions of the hydrogenolysis the expected product 24 could be isolated as major component and characterized (Scheme 7, reaction 2), but the obtained sample contained unknown byproducts. It is

• reaction time and the fairly high amount of catalyst employed. As an alternative method, which should be more chemoselective, we examined the reduction with samarium diiodide [60]. This versatile one-electron transfer reagent is known to cleave N–O bonds with high selectivity [61][62] and was applied

Visible-light-induced nickel-catalyzed α-hydroxytrifluoroethylation of alkyl carboxylic acids: Access to trifluoromethyl alkyl acyloins

• Feng Chen,
• Xiu-Hua Xu,
• Zeng-Hao Chen,
• Yue Chen and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2023, 19, 1372–1378, doi:10.3762/bjoc.19.98

• ) reduction of intermediate H (Ered(NiI/Ni0) = −1.17 V vs SCE [41]) by photoexcited HE* (Ered(HE*/HE·+) = −2.28 V vs SCE [42]) regenerates the active Ni(0) species E and closes the catalytic cycle. Conclusion In conclusion, we have demonstrated a visible-light-induced nickel-catalyzed radical cross coupling

Synthesis of ether lipids: natural compounds and analogues

• Marco Antônio G. B. Gomes,
• Alicia Bauduin,
• Chloé Le Roux,
• Romain Fouinneteau,
• Wilfried Berthe,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2023, 19, 1299–1369, doi:10.3762/bjoc.19.96

• ) KO mouse which is a mouse model that stop the biosynthesis of ELs [22]. In that case, a reduction of the levels of various neurotransmitters were evidenced likely due to an alteration of the transport efficacy assumed by the synaptic vesicles. The phenotype of these KO mouse shows impaired social

• phosphoglycerolipids [30]. This is likely due to a reduction of the lateral area per molecule and an increase in lipid tail-ordering [31]. It must be however emphasis that the variability of the structure of the lipid chains can deeply influence the biophysical properties meaning that general conclusions could be

• phosphate moiety was introduced via the use of bromoethyl dichlorophosphate 11.4 to produce 11.5. The reduction of the ketone with NaBH4 produced 11.6, and then the incorporation of the trimethylammonium group produced deoxy-lyso-PAF 11.7. Finally, the acetylation of the secondary alcohol produced racemic

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

• (Figure 3, Table 1). The reduction wave has a quasi-reversible character with the E1/2 at −1.50 V, which is 260 mV shifted to higher potential when compared with 4CzIPN (−1.76 V) under similar conditions in THF [15]. Compounds 4BGIPN and 4CzIPN experience a reduction process at the benzonitrile core (see

• , the LUMO isosurface in Figure 6, vide infra). Therefore, the higher reduction potential for 4BGIPN suggests that the benzonitrile core has a lower electron density, which is likely associated with extended π-conjugation and two additional electron withdrawing aza-type nitrogen atoms in the

• aerated MCH solution. The reduction in quantum yield on exposure to oxygen is due to quenching of the triplet excited states indicating a TADF luminescence mechanism. PLQY in Zeonex films is 39% in air, which is lower than the PLQY of 87% reported for 4CzIPN [17]. The two-component excited state lifetime

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

• are widespread as essential building blocks in various drugs, natural products, agrochemicals, and materials. Modern economy requires developing green strategies with improved efficiency and reduction of waste. Due to its atom and step-economy, the cross-dehydrogenative coupling (CDC) reaction has

• dihydropyrans (DHPs) and aldehydes in the presence of Zn(II) (Scheme 37) [102]. The method has good enantioselectivity and functional group tolerance and provides a practical and economical route towards a series of enantiopure α-substituted DHPs through CDC, through an in situ NaBH4 reduction two-step sequence

Acetaldehyde in the Enders triple cascade reaction via acetaldehyde dimethyl acetal

• Alessandro Brusa,
• Debora Iapadre,
• Maria Edith Casacchia,
• Alessio Carioscia,
• Giuliana Giorgianni,
• Giandomenico Magagnano,
• Fabio Pesciaioli and
• Armando Carlone

Beilstein J. Org. Chem. 2023, 19, 1243–1250, doi:10.3762/bjoc.19.92

• reason, the use of MCRs is appealing in the construction of natural or synthetic products [2][3][4][5] or libraries of compounds [2], and is generally considered an advantage in organic synthesis for atom economy, waste reduction and time saving. Cascade reactions are defined as chemical processes in

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

• overcome the challenges faced by other strategies (Scheme 1). At its core, RLT involves the outer sphere transfer of an anionic, X-type ligand coordinated to a redox-active metal to a radical intermediate, resulting in formation of a new C–ligand bond with concomitant single electron reduction of the metal

• 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

Unravelling a trichloroacetic acid-catalyzed cascade access to benzo[f]chromeno[2,3-h]quinoxalinoporphyrins

• Chandra Sekhar Tekuri,
• Pargat Singh and
• Mahendra Nath

Beilstein J. Org. Chem. 2023, 19, 1216–1224, doi:10.3762/bjoc.19.89

• /toluene 1:10 mixture under inert atmosphere to afford 2-amino-3-nitro-meso-tetraarylporphyrins which on reduction through sodium borohydride in the presence of 10% Pd/C in CH2Cl2/MeOH provided the desired porphyrins 1 in good yields as key starting materials for the synthesis of newly designed benzo[f

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

• cycle to reduce and fixate carbon dioxide [7]. Quite sensibly, many research groups investigating artificial photosynthesis develop components and systems for water splitting and carbon dioxide reduction separately before they or others seek to combine them. This modular approach is hugely beneficial

• because it can allow coupling of different reaction systems [2][8]. This strategy also works well for developing photoelectrochemical systems where the oxidation and reduction can be confined at separate electrodes. When developing reactions for carbon dioxide reduction in a modular fashion isolated from

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

• was shown to be a key player in lanostane triterpenoid cytotoxicity; increased activity was demonstrated either by its esterification with glucose or by its reduction into a hydroxymethylene group unlike its presence as a free carboxylic acid moiety [23]. Thus, our findings provide further insights

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

• resulted in a significant reduction in kinetics and selectivity (Table 1, entry 3). Other more green and biobased solvent alternatives, such as ethanol [36], can effectively replace the acetonitrile (for the complete scope of solvents, please consult Supporting Information File 1, Table S2), but reaction

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

• , commercially available aryl halides are chlorides [37][38], with potentials for reduction that almost exclusively lie beyond the threshold of monophotonically-excited photoredox catalysts (i.e., more deeply negative than E1/2 = −2.0 V vs SCE). Considering this, state-of-the-art developments have focused on the

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

• reduction wave was observed at −1.78 V (vs Fc/Fc+) due to the reduction of the NI unit. For all the dyads containing a native PTZ unit, the oxidation potentials are virtually the same. However, the reduction potential changes to some extent, which is consistent with our molecular design to keep the donor

• after oxidation, and there was still a reversible reduction potential at −1.53 V (vs Fc/Fc+). Slightly cathodically shifted reduction waves were observed for other dyads containing an oxidized PTZ unit, i.e., NI-PTZ-Ph-O and NI-PTZ-C5-O. The redox potentials of the compounds are collected in Table 3

Five new sesquiterpenoids from agarwood of Aquilaria sinensis

• Hong Zhou,
• Xu-Yang Li,
• Hong-Bin Fang,
• He-Zhong Jiang and
• Yong-Xian Cheng

Beilstein J. Org. Chem. 2023, 19, 998–1007, doi:10.3762/bjoc.19.75

• (Table 3). The difference is that the carboxylic acid at C-4 in 3 undergoes reduction to form a hydroxymethyl group at C-4 in 5. This alteration is supported by the analysis of the HMBC correlations (Figure 2) of H-3/C-4 (δC 128.6), C-14 (δC 63.5) and H-14/C-4, C-5 (δC 141.9). Thus, the planar structure

Synthesis of tetrahydrofuro[3,2-c]pyridines via Pictet–Spengler reaction

• Elena Y. Mendogralo and
• Maxim G. Uchuskin

Beilstein J. Org. Chem. 2023, 19, 991–997, doi:10.3762/bjoc.19.74

• construction of tetrahydrofuro[3,2-c]pyridines is based on a Bischler–Napieralski cyclocondensation followed by the C=N bond reduction (Scheme 1d) [36][37][38][39]. Despite the simplicity of the latter approach and availability of 2-(furan-2-yl)ethanamine, the instability of intermediate dihydrofuro[3,2-c

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

• after recrystallization. Subsequent ozonolysis of the terminal alkene functionality with a follow-up reduction furnished primary alcohol 134 which was transformed into the azide 135. Reduction of the azide 135 was accompanied by debenzylation, was followed by tosylation of the primary amine and exchange

• of the Boc-protecting group with the Teoc group then gave phenol 136. Compound 136 was then subjected to a highly diastereoselective oxidative phenolic coupling giving fused tetracyclic architecture 137. Follow-up acid-mediated intramolecular aza-Michael addition and subsequent alkene reduction

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

• carboxylate anion and/or reduction of the corresponding N-hydroxyphthalimide- (NHPI)-derived redox-active ester, although it destroys their stereochemical information [46][47][48][49][50][51]. In addition, the side-chains of aromatic amino acids (mainly electron-rich tryptophan and tyrosine) can be

• intramolecularly with the C4-pendant prenyl side-chain previously oxidized [76]. Closure of the photoredox catalytic cycle would then involve SET reduction, and protonation would deliver the desired carbocyclic ring (Figure 1c). If this cyclization reaction could be realized in either way, it would shorten the

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

• aligns well with the observed increase in the degree of unsaturation and the reduction in mass by 2 Da. Compound 4 (0.5 mg) was obtained as a brown oil. It possesses a molecular ion at m/z 276.0985 [M + H]+, which suggests a molecular formula of C15H17NO2S (calcd. for C15H18NO3S, 276.1002) and is in

Synthesis of aliphatic nitriles from cyclobutanone oxime mediated by sulfuryl fluoride (SO₂F₂)

• Xian-Lin Chen and
• Hua-Li Qin

Beilstein J. Org. Chem. 2023, 19, 901–908, doi:10.3762/bjoc.19.68

• nitriles 3ba–da in excellent yields. Interestingly, when the loading of CH3COOK was reduced to 2 equivalents, we obtained a mixture of unsaturated nitrile 3aa and saturated nitrile 4 after column chromatography (Scheme 4). We speculated that the reduction of the base equivalent may induce the ionization of

• oxime derivatives with alkenes was proposed (Scheme 6). Initially, cyclobutanone oxime reacts with SO2F2, generating an oxime sulfonyl ester intermediate (fluorosulfonate) I promoted by the base. Subsequently, the intermediate fluorosulfonate I undergoes single-electron reduction by [Cun] in situ to

• ) was stirred at 100 °C under an SO2F2 atmosphere (balloon) for 12 h; yields refer to isolated compounds. Competition between two reactions caused by the reduction of base equivalent. Mechanistic investigations. A proposed plausible mechanism. Screening the optimized reaction conditions.a Supporting

Asymmetric tandem conjugate addition and reaction with carbocations on acylimidazole Michael acceptors

• Brigita Mudráková,
• Renata Marcia de Figueiredo,
• Jean-Marc Campagne and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 881–888, doi:10.3762/bjoc.19.65

• ]. These non-traditional electrophiles allow access to structurally highly interesting motifs. In addition, they are amenable to valuable synthetic transformations such as oxidative ring contraction of the cycloheptatrienyl ring or reduction of the benzodithiolyl group. In this context, we decided to study