Facile access to pyridinium-based bent aromatic amphiphiles: nonionic surface modification of nanocarbons in water

• Lorenzo Catti,
• Shinji Aoyama and
• Michito Yoshizawa

Beilstein J. Org. Chem. 2024, 20, 32–40, doi:10.3762/bjoc.20.5

• -solubilities. It is noteworthy that an AA derivative featuring three nonionic –O(CH2CH2O)2CH3 side-chains on the phenylene spacer is insoluble in water (see Figure S45 in Supporting Information File 1), emphasizing the importance of the hydrophilic pyridinium core for the observed water-solubility. Formation

• below 0.1 mM (Figures S28 and S32, Supporting Information File 1), which is around 10 times lower than that of AA [12][13]. The increased stability against dilution likely arises from reduced electrostatic repulsion and increased anthracene-based π-stacking interactions due to the absence of o-alkoxy

Cycloaddition reactions of heterocyclic azides with 2-cyanoacetamidines as a new route to C,N-diheteroarylcarbamidines

• Pavel S. Silaichev,
• Tetyana V. Beryozkina,
• Vsevolod V. Melekhin,
• Valeriy O. Filimonov,
• Andrey N. Maslivets,
• Vladimir G. Ilkin,
• Wim Dehaen and
• Vasiliy A. Bakulev

Beilstein J. Org. Chem. 2024, 20, 17–24, doi:10.3762/bjoc.20.3

• Pavel S. Silaichev Tetyana V. Beryozkina Vsevolod V. Melekhin Valeriy O. Filimonov Andrey N. Maslivets Vladimir G. Ilkin Wim Dehaen Vasiliy A. Bakulev Department of Organic Chemistry, Perm State University, 15 Bukireva st., Perm 614990, Russia TOS Department, Ural Federal University, 19 Mira st

Synthesis of N-acyl carbazoles, phenoxazines and acridines from cyclic diaryliodonium salts

• Nils Clamor,
• Mattis Damrath,
• Thomas J. Kuczmera,
• Daniel Duvinage and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2024, 20, 12–16, doi:10.3762/bjoc.20.2

• with a 47% yield. A method for the synthesis of similar annulated N-heterocycles from iodanes with nitriles is described by Chen et al. [34]. Next, we investigated O-bridged dibenzo[b,e][1,4]iodaoxin-5-ium salts as substrates, as was shown in a recent work [29]. Following the trend, we already observed

Aldiminium and 1,2,3-triazolium dithiocarboxylate zwitterions derived from cyclic (alkyl)(amino) and mesoionic carbenes

• Nedra Touj,
• François Mazars,
• Guillermo Zaragoza and
• Lionel Delaude

Beilstein J. Org. Chem. 2023, 19, 1947–1956, doi:10.3762/bjoc.19.145

• applications [24][25][26][27][28]. N-Heterocyclic carbenes and their enetetramine dimers readily add to the central carbon atom of allenes and heteroallenes X=C=Y (X, Y = CR2, NR, O, S) to afford zwitterionic adducts [29]. In particular, their reaction with carbon disulfide affords stable azolium-2

• excess to compensate for the possible formation of sodium O-tert-butyl xanthate [72][73][74]. We reasoned that these conditions should favor a quantitative deprotonation of the starting triazolium salts and the concomitant trapping of the free carbenes by CS2 prior to their potential decomposition

Construction of diazepine-containing spiroindolines via annulation reaction of α-halogenated N-acylhydrazones and isatin-derived MBH carbonates

• Xing Liu,
• Wenjing Shi,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2023, 19, 1923–1932, doi:10.3762/bjoc.19.143

• efficient synthesis of spiro[azepine-4,3'-indoline] derivatives via the [4 + 3] cycloaddition reaction of bromo-substituted isatin-derived MBH adducts and N-(o-chloromethyl)arylamides. In this efficient protocol, the reactive allylic phosphonium ylides and aza-o-quinone methides were generated in situ and

• )benzenesulfonamides to give chiral azepane spirooxindoles with excellent stereoselectivity (reaction 2 in Scheme 1) [55][56]. Du and co-workers reported a DABCO-mediated [4 + 3] cycloaddition reaction between o-quinone methides and isatin-derived MBH carbonates to give functionalized benzo[b]oxepine derivatives in

Biphenylene-containing polycyclic conjugated compounds

• Cagatay Dengiz

Beilstein J. Org. Chem. 2023, 19, 1895–1911, doi:10.3762/bjoc.19.141

• subjecting α,α,α′,α′-tetrabromo-o-xylene (16) to t-BuOK to anhydrous conditions, biphenylene derivative 17 was obtained with a yield of 69% (Scheme 3). In the final step of the synthesis, a halogen–lithium exchange was carried out, followed by treatment with MeOH, resulting in a 79% yield of benzo[b

N-Boc-α-diazo glutarimide as efficient reagent for assembling N-heterocycle-glutarimide diads via Rh(II)-catalyzed N–H insertion reaction

• Grigory Kantin,
• Pavel Golubev,
• Alexander Sapegin,
• Alexander Bunev and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2023, 19, 1841–1848, doi:10.3762/bjoc.19.136

• also highly regioselective, proceeding via attack on the 2-N atom to give products 6m–o. In the instance of unsubstituted benzotriazole, a minor regioisomer 6m' was identified with a calculated yield of 6% using NMR data. Benzotriazoles featuring electron-withdrawing substituents showed incomplete

A novel recyclable organocatalyst for the gram-scale enantioselective synthesis of (S)-baclofen

• Gyula Dargó,
• Dóra Erdélyi,
• Balázs Molnár,
• Péter Kisszékelyi,
• Zsófia Garádi and
• József Kupai

Beilstein J. Org. Chem. 2023, 19, 1811–1824, doi:10.3762/bjoc.19.133

• the other components of the reaction mixture. The lipophilic O-alkylated gallic acid unit increases the solubility of the organocatalyst in less polar solvents, such as DCM or toluene but leads to the precipitation of the organocatalyst in polar solvents, including MeOH or MeCN. As a result, the

• applied between the catalytic and lipophilic units to avoid a decrease in the catalytic activity. The demethylated cinchona squaramide 6 was reacted with O-p-toluenesulfonyl-N-Boc-ethanolamine. The protecting group was removed using trifluoroacetic acid, followed by a neutralization step, gaining the

Synthetic approach to 2-alkyl-4-quinolones and 2-alkyl-4-quinolone-3-carboxamides based on common β-keto amide precursors

• Yordanka Mollova-Sapundzhieva,
• Plamen Angelov,
• Danail Georgiev and
• Pavel Yanev

Beilstein J. Org. Chem. 2023, 19, 1804–1810, doi:10.3762/bjoc.19.132

• -mediated domino reaction of chromone-3-carboxaldehydes and amines [41], Pd-catalyzed redox-neutral C–N coupling reaction of iminoquinones with electron-deficient alkenes [42], NH3 insertion into o‑haloarylynones [43], gold(III)-catalyzed azide-yne cyclization [44], Michael/Truce-Smiles rearrangement

• reductive cyclizations of o-nitrobenzoyl ketones [57][58], enamines [59][60], or isoxazoles [61]. The scope of these reductive cyclizations is limited by the availability of the necessary intermediates and has remained largely underexplored, especially with regard to 4-quinolones with long-chain

• key o-nitrobenzoyl intermediates 3 in a reaction with o-nitrobenzoyl chloride (Scheme 1, conditions ii). The acylation of 2 to 3 proceeded with variable yields, depending on the substituents R1 and R2. Derivatives 2 with a primary carboxamide group (R2 = H) gave generally lower and poorly reproducible

Recent advancements in iodide/phosphine-mediated photoredox radical reactions

• Tinglan Liu,
• Yu Zhou,
• Junhong Tang and
• Chengming Wang

Beilstein J. Org. Chem. 2023, 19, 1785–1803, doi:10.3762/bjoc.19.131

• catalysis has risen to prominence as an incredibly effective methodology, establishing itself as a powerful tool for crafting various C–X (X = C, N, O, F, Cl…) bonds owing to its advantageous traits, such as sustainability, practicality, and environmental compatibility [5]. Despite its broad synthetic

• materials science. In recent years, the combination of dual photoredox with first-row transition-metal catalysis has emerged as a powerful tool for achieving various cross-coupling reactions involving C–N, C–O, C–S, and other chemical bonds [3][23]. In this context, Guan et al. theoretically designed a

• novel metallaphotoredox catalysis by combining the NaI/PPh3 photoredox catalyst with a Cu(I) catalyst to accomplish diverse C–O/N cross-couplings of alkyl N-hydroxyphthalimide esters 3 with various phenols/secondary amines 30 (Scheme 13) [24]. It was anticipated the utilization of computational methods

Charge carrier transport in perylene-based and pyrene-based columnar liquid crystals

• Alessandro L. Alves,
• Simone V. Bernardino,
• Carlos H. Stadtlober,
• Edivandro Girotto,
• Giliandro Farias,
• Rodney M. do Nascimento,
• Sergio F. Curcio,
• Thiago Cazati,
• Marta E. R. Dotto,
• Juliana Eccher,
• Leonardo N. Furini,
• Hugo Gallardo,
• Harald Bock and
• Ivan H. Bechtold

Beilstein J. Org. Chem. 2023, 19, 1755–1765, doi:10.3762/bjoc.19.128

• 1712 cm−1 which corresponds to C=O stretching [27]. The pair at 1390 and 1417 cm−1 is attributed to perylene ring stretching [28]. As observed for bis(phenethylimido)perylene (PhPTCD) [29] only a small number of peaks is observed. In contrast, compound 2 presents a larger number of peaks, with the

• 1758 cm−1 (C=O). X-ray diffraction (XRD) measurements of 1 and 2 are shown in Figure 2. The Miller indices indicate the Colhex and Colrect character of the mesophases [31]. Despite crystallization of 2, the Colrect order is partially preserved at room temperature. The Colhex lattice parameter (a

Trifluoromethylated hydrazones and acylhydrazones as potent nitrogen-containing fluorinated building blocks

• Zhang Dongxu

Beilstein J. Org. Chem. 2023, 19, 1741–1754, doi:10.3762/bjoc.19.127

• , 1,4-naphthoquinones, o-trimethylsilylphenyl triflate and chalcones have all been reacted with fluorinated nitrile imines to give a series of fluoroalkylated pyrazoles by Jasiński’s team [67][68][69][70][71][72] (Scheme 11a). Subsequently, Hu et al., Nie et al., and Ma et al. have all independently

Unprecedented synthesis of a 14-membered hexaazamacrocycle

• Anastasia A. Fesenko and
• Anatoly D. Shutalev

Beilstein J. Org. Chem. 2023, 19, 1728–1740, doi:10.3762/bjoc.19.126

• (KBr, cm−1) ν: 3313 (s), 3113 (br s), 1705 (s), 1624 (s), 1573 (s), 1521 (m), 1304 (m), 1249 (s), 1155 (m), 872 (s), 761 (m); 1H NMR (600.13 MHz, DMSO-d6, 30 °C) δ 9.68 (br s, 1Н, NHC=O), ≈9.50 (very br s, 1Н, C=NH, signal partly overlaps with the signal of the NHC=O proton), 8.24 (br s, 1Н, H-6), 8.06

• (s, 1Н, H-3), 3.82 (s, 3Н, NCH3), 2.03 (br s, 3Н, CH3 in Ac); 1H NMR (600.13 MHz, DMSO-d6, 85 °C) δ 8.19 (s, 1Н, H-6), 8.02 (s, 1Н, H-3), 3.83 (s, 3Н, NCH3), 2.10 (s, 3Н, CH3 in Ac), signals of the NH protons are not observed; 13C NMR (150.90 MHz, DMSO-d6, 85 °C) δ 168.22 (C=O), 151.71 (С-7a), 146.22

Effects of the aldehyde-derived ring substituent on the properties of two new bioinspired trimethoxybenzoylhydrazones: methyl vs nitro groups

• Dayanne Martins,
• Roberta Lamosa,
• Talis Uelisson da Silva,
• Carolina B. P. Ligiero,
• Sérgio de Paula Machado,
• Daphne S. Cukierman and
• Nicolás A. Rey

Beilstein J. Org. Chem. 2023, 19, 1713–1727, doi:10.3762/bjoc.19.125

• around the conjugated amide single bond (N–C=O). N-Acylhydrazones have also gained attention in literature due to other applications, ranging from medicine to supramolecular chemistry [7][8]. Among their applicability is the area of optoelectronic devices, in which they are used for the manufacture of

• -withdrawing nitro substituent in hdz-NO2 makes the intramolecular H-bond stronger. Regarding lattice organization, both structures exhibit stacked motifs. In hdz-CH3, the planes were organized by C–H···O non-conventional H-bonds comprising the methoxy groups (Figure 2B). In the columns, there are

• Hirshfeld surfaces and evidence the strong flatness of the structures (Figures S2B and S3B in Supporting Information File 1). Important contributions of hydrogen bonds (O···H/H···O) can also be found, especially for hdz-NO2. Besides the interaction maps, crystal structures themselves may be used to

Tying a knot between crown ethers and porphyrins

• Maksym Matviyishyn and
• Bartosz Szyszko

Beilstein J. Org. Chem. 2023, 19, 1630–1650, doi:10.3762/bjoc.19.120

• attraction between the two parts. Boitrel developed a crown ether-double-capped zinc(II) porphyrin 11 (Figure 9) [42]. The tritopic receptor incorporated symmetrically positioned diaza-crown-6 units above and below the central porphyrin core. The metalation of the tetrakis(o-aminophenyl)porphyrin (TAPP) core

• water molecule was accommodated within the cleft of the Pacman-shaped macrocycle, occupying the axial position. The V–O bond length of 2.111(3) Å indicated the coordinated entity's V(III)–OH2 character. The water molecule in the cleft was further stabilised by hydrogen bonding to the ether oxygens

A series of perylene diimide cathode interlayer materials for green solvent processing in conventional organic photovoltaics

• Kathryn M. Wolfe,
• Shahidul Alam,
• Eva German,
• Fahad N. Alduayji,
• Maryam Alqurashi,
• Frédéric Laquai and
• Gregory C. Welch

Beilstein J. Org. Chem. 2023, 19, 1620–1629, doi:10.3762/bjoc.19.119

• saturated solution at 19.4 mg/mL, CN-PDIN-FB a saturated solution at 3.2 mg/mL, and CN-PDIN-FB a saturated solution at 1.2 mg/mL. The compounds are also soluble in other organic solvents such as toluene, o-xylenes, and chloroform at concentrations of >100 mg/mL. However, in conventional OPVs, it is critical

Sulfur-containing spiroketals from Breynia disticha and evaluations of their anti-inflammatory effect

• Ken-ichi Nakashima,
• Naohito Abe,
• Masayoshi Oyama,
• Hiroko Murata and
• Makoto Inoue

Beilstein J. Org. Chem. 2023, 19, 1604–1614, doi:10.3762/bjoc.19.117

• electrospray ionization HRESIMS analysis, and quantum chemical electronic CD calculations. Furthermore, the absolute configurations of sugar residues were determined by derivatization of the hydrolysates with ʟ-cysteine methyl ester and o-tolyl isothiocyanate followed by HPLC analysis. The anti-inflammatory

• by acid hydrolysis of 1 using the method developed by Tanaka et al. [16], in which the hydrolysates are derivatized with ʟ-cysteine methyl ester and o-tolyl isothiocyanate followed by HPLC analysis. For compound 1, peaks were observed at retention times of 13.96, 20.83, and 22.16 min. The peaks at

• -rhamnose (22.16 min) derivatives in this study, it is reasonable to assign the peak at 20.83 min to the ᴅ-apiose derivative. Therefore, 1 was identified as breynogenin-α-S-oxide 3-O-β-ᴅ-apiofuranosyl-(1→2)-[α-ʟ-rhamnopyranosyl-(1→3)]-β-ᴅ-glucopyranosyl-(1→2)-β-ᴅ-glucopyranoside. Epibreynin J (2) was also

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

• based on the radical polymerization of catechol derivatives. Catechols are known as easily oxidizable compounds and are prone to undergo oxidation by losing one or two electrons [3]. This way, either semiquinone radicals or o-quinones are formed by single or double-electron oxidation, respectively [4

• –substrate interface. The mfp's contain up to 27 mol % of DOPA (ʟ-3,4-dihydroxyphenylalanine), which plays a crucial role on mussel adhesion [11]. Although the crucial role of DOPA in mussel adhesion is not fully understood, a prevailing view suggests that DOPA can be oxidized to o-quinones at an acidic pH

• and the quinones react with unoxidized catechols to form o-semiquinone radicals afterwards [12]. The semiquinone radicals can help DOPA adhere onto organic surfaces. At a basic pH, the system is cured and mechanically stabilized through the formation of DOPA-metal coordination bonds. The cohesion of

Cyclodextrins permeabilize DPPC liposome membranes: a focus on cholesterol content, cyclodextrin type, and concentration

• Ghenwa Nasr,
• Hélène Greige-Gerges,
• Sophie Fourmentin,
• Abdelhamid Elaissari and
• Nathalie Khreich

Beilstein J. Org. Chem. 2023, 19, 1570–1579, doi:10.3762/bjoc.19.115

• time because it does not fully consider the complexation process between the CDs and the membrane components. Another finding obtained by Nishijo and his co-workers [30] may further clarify this idea. The authors studied the interaction of various CDs with CHOL: heptakis(2,6-di-O-methyl)-β-CD (DOM-β-CD

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

• . Conversion of naphthols to naphthylamines is typically achieved through a three-step sequence whereby the naphthol is first O-alkylated with 2-bromo-2-methylpropionamide and this ether undergoes a Smiles rearrangement to the hydroxyamide, which is hydrolyzed to the free naphthylamine [44][45]. It has

• previously been shown in the literature that the first two steps of this Smiles-rearrangement approach can be effectively performed in one pot [49]. Therefore, after allowing the O-alkylation to proceed at room temperature in dimethylethyleneurea (DMEU), we proceeded directly to the hydroxyamides 7 and 8

• (R3/R4). Compound C4 is the known compound O-methylfagaronine, which has previously been synthesized through a variety of methods [50][51][52]. The antileukemia activity, antitumor activity, and inhibition of reverse transcriptase of O-methylfagaronine (C4) have previously been explored [51][52][53

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

• products in moderate to excellent yields. In 2019, Gao and Yang et al. disclosed a new protocol for the synthesis of 4‑aryl/alkylsulfenylisoxazoles 48 from sulfenylation of 2-alkyn-1-one O-methyloximes 46 with N-sulfenylsuccinimides 1 (Scheme 20) [57]. The transformation proceeded via an electrophilic

• reacted with N-(arylthio)succinimide 1 or N-(arylthio)phthalimide 14 as the sulfenylating reagents in the presence of cinchona-derived thiourea O as a catalyst to afford the corresponding chiral naphthalenone products 126 under mild reaction conditions. Another work from Anbarasan and Chaitanya on the use

• of N-(arylsulfanyl)succinimide 1 and N-(arylseleno)succinimide 1’’ in an oxychalcogenation process was reported in 2018 (Scheme 54) [86]. In this method, they succeeded in applying methanesulfonic acid (MsOH) as a promoter for oxythiolation and oxyselenation of o-vinylanilides 127 through the

Cyclization of 1-aryl-4,4,4-trichlorobut-2-en-1-ones into 3-trichloromethylindan-1-ones in triflic acid

• Vladislav A. Sokolov,
• Andrei A. Golushko,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2023, 19, 1460–1470, doi:10.3762/bjoc.19.105

• , the O-protonated forms ArC(=OH+)CH=CHCCl3, which are then cyclized into the target CCl3-indanones. These cations have been studied experimentally by means of NMR spectroscopy in TfOH and theoretically by DFT calculations. Under the same superacidic conditions in TfOH, CCl3-hydroxy ketones (1-aryl

• conjugated enones afford O,C-diprotonated forms under superelectrophilic activation conditions. These dications can participate in electrophilic aromatic substitution reactions with arenes ([11] and references therein). Recently, we have shown that the reaction of (E)-5,5,5-trichloropent-3-en-2-one [Cl3CCH

• =CHC(=O)Me] with arenes in Brønsted superacid TfOH (triflic acid, CF3SO3H) furnishes 3-methyl-1-trichloromethylindenes (Scheme 1a) [11]. Based on NMR analysis in TfOH and theoretical DFT calculations, it has been found that the reaction proceeds through an intermediate formation of the O-protonated

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

• on carbon and provided the expected (propyloxy)methyl-substituted aminopyran 22 in 81% yield (Scheme 7, reaction 1). The reductive removal of the N-benzyl group and the cleavage of the N–O bond occurred apparently without problems. With the second model compound, 1,2,3-triazole 23, which is almost

• possible, that the N-benzyl group attached to the 1,2,3-triazole moiety is partially removed under these conditions and/or that even the C–O bond connecting the 1,2,3-triazole part with the aminopyran part is reductively cleaved since this bond also has benzylic character. In earlier investigations with

• 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

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

• correspond, for instance, to biosynthesized intermediates (e.g., 1-O-alkyl-glycerol-3-phosphate [4], lyso-PAF [5]) or neutral ether lipids (e.g., diacyl ether glycerol [6]). Ether glycerolipids are present in mammalian but also in anaerobic bacteria [7], archea (with an inverted stereochemistry at the sn-2

• of the phenotypes associated to peroxisomal disorders (e.g., brain abnormality, mental retardation, premature death) emphasizes the essential role of ether lipids in physiology of cells and tissues. This implication of ELs was also confirmed by producing glyceronephosphate O-acyltransferase (Gnpat

• interactions and memory deficiency [23]. In another domain, it was reported that centenarians feature a specific profile of ELs in plasma with, in particular, higher level of O-alkyl form of phosphatidylcholine EL and a decreased level of phosphatidylethanolamine plasmalogen (alkenyl) [24]. It must be also

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

• oxidative alkylation of cyclic benzyl ethers with malonates or ketones. Oxygen is used as a terminal oxidant at atmospheric pressure. The key intermediate of this oxidative coupling reaction is benzyl alcohol intermediate C (Scheme 4) [52]. The generation of N–O radicals from NHPI in the presence of oxygen

• of ethers to obtain symmetric and asymmetric 1,1-bis-indolylmethane derivatives (Scheme 23) [84]. The reaction proceeds through the tandem oxidative coupling of the C–O bond and cleavage of the C–H bond. Fe plays a dual role in catalysing the C–C bond coupling and C–O bond cleavage as Lewis acid

• to afford internal alkynes from substrates with the C(sp3)–H bond mainly located in the α-position to N, O, or S atoms. This method provides a direct and atom-economical alternative for the construction of structurally complex alkyne compounds (Scheme 26) [87]. In addition to iron, various other