Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

Synthesis of π-conjugated polycyclic compounds by late-stage extrusion of chalcogen fragments

• Aissam Okba,
• Pablo Simón Marqués,
• Kyohei Matsuo,
• Naoki Aratani,
• Hiroko Yamada,
• Gwénaël Rapenne and
• Claire Kammerer

Beilstein J. Org. Chem. 2024, 20, 287–305, doi:10.3762/bjoc.20.30

• recognized as valuable synthetic tools in organic chemistry [54], with the most famous S-extrusion process to generate new C–C bonds probably being the Ramberg–Bäcklund reaction [55]. In the case of heteropines, chalcogen extrusion leads to a six-membered ring via the intramolecular formation of a C–C bond

• synthesis and a final closure of the 7-membered ring by C–C bond formation. This is in sharp contrast with the widely adopted strategy relying on the late-stage insertion of the sulfur atom with concomitant ring closure, using either electrophilic or nucleophilic sulfur reagents. By way of example, thiepine

Photochromic derivatives of indigo: historical overview of development, challenges and applications

• Gökhan Kaplan,
• Zeynel Seferoğlu and
• Daria V. Berdnikova

Beilstein J. Org. Chem. 2024, 20, 228–242, doi:10.3762/bjoc.20.23

• melting point of indigo is bifurcated intra- and intermolecular hydrogen bonding [11], and face-to-face π–π stacking of parallel aromatic rings (Figure 2) [12]. Single crystal X-ray diffraction analysis showed that the indigo molecule is almost planar and exists in the E-conformation. The central C=C bond

Metal-catalyzed coupling/carbonylative cyclizations for accessing dibenzodiazepinones: an expedient route to clozapine and other drugs

• Amina Moutayakine and
• Anthony J. Burke

Beilstein J. Org. Chem. 2024, 20, 193–204, doi:10.3762/bjoc.20.19

• been used in a multitude of reactions [16][17]. The present approach enables the formation of two C–N bonds along with a C–C bond and provides a good alternative to previously reported strategies, as it enables the formation of these structures in a multicomponent fashion in the presence of a CO

Tandem Hock and Friedel–Crafts reactions allowing an expedient synthesis of a cyclolignan-type scaffold

• Viktoria A. Ikonnikova,
• Cristina Cheibas,
• Oscar Gayraud,
• Alexandra E. Bosnidou,
• Nicolas Casaretto,
• Gilles Frison and
• Bastien Nay

Beilstein J. Org. Chem. 2024, 20, 162–169, doi:10.3762/bjoc.20.15

• C–C bond adjacent to the hydroperoxide group (Scheme 1a). The best-known application of this reaction is the cumene process, which allows the production of millions of tons of phenol each year [2]. The reaction has also been used in an industrial synthesis of artemisinin [3]. Allylic hydroperoxides

Electron-beam-promoted fullerene dimerization in nanotubes: insights from DFT computations

• Laura Abella,
• Gerard Novell-Leruth,
• Josep M. Ricart,
• Josep M. Poblet and
• Antonio Rodríguez-Fortea

Beilstein J. Org. Chem. 2024, 20, 92–100, doi:10.3762/bjoc.20.10

• isomer, the formation energies with respect to C60 + C60 are up to −300 kcal mol−1, which reflects the high degree of C–C bond reorganization needed to obtain this fullerene isomer that satisfies the so-called isolated pentagon rule (IPR) [19]. We corroborated our results for the gas-phase products using

• distance is around 1.60–1.70 Å. Formation of the second C–C bond to yield dimer 1-Cs requires to overcome a second transition state TS-2 with energy barriers that range between 10–13 kcal mol−1 from the immediate intermediate depending on the profile. The interdimer C···C distance of the forming bond is

• shorter than the one observed for the gas phase reaction. The transition state TS corresponds now to the formation of the second interdimer C···C distance, around 2.15 Å (Figure 3), once the first C–C bond is already formed. All the attempts to obtain an intermediate with a single C–C interdimer bond

Multi-redox indenofluorene chromophores incorporating dithiafulvene donor and ene/enediyne acceptor units

• Christina Schøttler,
• Kasper Lund-Rasmussen,
• Line Broløs,
• Philip Vinterberg,
• Ema Bazikova,
• Viktor B. R. Pedersen and
• Mogens Brøndsted Nielsen

Beilstein J. Org. Chem. 2024, 20, 59–73, doi:10.3762/bjoc.20.8

• lengths of the bonds (b–f) within the five-membered rings of the cores as well as the exocyclic C=C double bond (a) that is present in compounds 25 and 26 (for bond labels, see Figure 11). A small difference in the exocyclic C=C bond length is observed between 25 and 26, with the bond in 26 being slightly

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

• opening of triazole 6 to form diazo compound anti-7, followed by rotation around the C‒C bond of the amidine group to furnish rotamer syn-7 which then undergoes 1,5-dipolar cyclization to products 3. The second path involves a Dimroth-type cyclization to form products 3′, which however, were not

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

• state, in line with their cross-conjugated or pseudo-cross-conjugated nature [80][81]. Indeed, an average C1–C2 distance of 1.49 Å indicated that the adducts were essentially assembled via the formation of a single rather than a double C–C bond (1.51 vs 1.34 Å) [78]. These data are in line with the

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

• methods. Because there are one C=C bond and one C=N bond in the molecules 3a–m, no diastereoisomers are obtained. Therefore, the 1H NMR spectra gave simple absorptions for the characteristic groups in the molecules. For further developing the scope of the [4 + 3] cycloaddition reaction, MBH esters of

• ylide B. Thirdly, the intermediate C is formed by the nucleophilic substitution of a halide ion in substrate 1 by the allylic ylide B. Then, Michael addition of the amino group to the C=C bond results in the cyclic intermediate D. Finally, the spiro[indoline-3,5'-[1,2]diazepine] 3 is produced by the

Benzoimidazolium-derived dimeric and hydride n-dopants for organic electron-transport materials: impact of substitution on structures, electrochemistry, and reactivity

• Swagat K. Mohapatra,
• Khaled Al Kurdi,
• Samik Jhulki,
• Georgii Bogdanov,
• John Bacsa,
• Maxwell Conte,
• Tatiana V. Timofeeva,
• Seth R. Marder and
• Stephen Barlow

Beilstein J. Org. Chem. 2023, 19, 1651–1663, doi:10.3762/bjoc.19.121

• -1,1',3,3'-tetramethyl-2,2',3,3'-tetrahydro-2,2'-bibenzo[d]imidazole, has been obtained from addition of HPO3Et2 across the central C=C bond of bis(1,3-dimethylbenzoimidazolinidin-2-ylidene) [25], 12 dimers have generally been obtained by reductive electrochemical or chemical dimerization of 1+ cations

• crystallographic inversion (Ci) symmetry, and approximate molecular C2h symmetry, and so has a perfectly staggered conformation around the central C–C bond and thus a Y–C–C–Y torsion angle of precisely 180°; the structure closely resembles those of the two inequivalent molecules in the structure of the previously

• mostly somewhat folded towards a puckered envelope conformation, generally with the Y group in a pseudo-axial position and the 1,3-methyl groups and the central C–C bond in pseudo-equatorial positions, although for one of the monomers in the unsymmetrical conformer in the structure of (N-DMBI)2, 1b2, the

Unraveling the role of prenyl side-chain interactions in stabilizing the secondary carbocation in the biosynthesis of variexenol B

• Moe Nakano,
• Rintaro Gemma and
• Hajime Sato

Beilstein J. Org. Chem. 2023, 19, 1503–1510, doi:10.3762/bjoc.19.107

• of the neighboring prenyl side chain interacts and promptly induce C–C bond formation. There have been no reports published where, as in our case, the cation is stabilized without bond formation. We have also considered other transannular cation–π interactions in this system. In this case, the

• interaction between the secondary carbocation at C10 and the C2=C3 double bond or the exomethylene group at C7 should be considered. However, moving it closer to the C2=C3 bond would result in IM2 as shown in Figure 1 and a C–C bond would be formed. The exomethylene group at C7 is also very reactive, so if it

• gets close, it would easily form a C–C bond. Therefore, we believe that no other transannular cation–π interactions need to be considered in this system. In systems without cation–π interactions, such as in the biosynthesis of variediene [39] and spiroviolene [40], bonds around the secondary

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 second protonation of the C=C bond is hampered due to a strong acceptor character of the substituents, contrary to other more donating enones. As a continuation of the research on the electrophilic activation of electron-poor alkenes bearing two electron-withdrawing substituents at the C=C bond

• of the C=C bond of species Ba is very unfavorable. Moreover, the corresponding O,C-diprotonated form Da was found to be extremely unstable and spontaneously rearranges into species Ea via a shift of a chlorine atom. Therefore, the DFT calculations and NMR data for enones 2 in TfOH (Table 2) indicate

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

• (I) complex at the β-carbon atom of the activated C=C bond thereby catalyzing the reaction. The NHC–Cu(I) complexes have been found to be effective catalysts for conjugate addition reactions because they stabilize the intermediate species involved in the reaction, which can otherwise be highly

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

• adjacent C=C bond, various conjugated alkenyl C–H bonds can also be activated to construct functionalized ethers. In 2013, Wang et al. achieved a mild Cu(OTf)2-catalyzed CDC of (benzo)thiazoles with cyclic ethers in the presence of K2S2O8 (Scheme 9) [59]. The catalytic system is also suitable for

• coupling process. Initially, ether 64 interacts with tert-butoxyl radicals via hydrogen atom transfer reaction to generate radical A with release of tert-butyl alcohol. Subsequently, the radical A adds to the C=C bond of α-oxo ketene dithioacetal 107 to form radical B, which further reacts with Fe(III) to

• 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

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

• , or it is trapped with pyrrole derivatives 3 in a C–C bond formation to afford arylated products 4. Based on the ultrashort lifetime of *PDI•− (τ = 145 ps), the notion of its photochemistry has attracted skepticism and it has been suggested decomposition products of *PDI•− may instead serve as

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

• formation of a new C–C bond [21]. The reaction requires an electrophilic reagent/intermediate present in the reaction system on which an electrophilic attack by the π-electron cloud of the aromatic ring can occur spontaneously to form a dearomatized species. The latter is rearomatized in a succeeding step

• . The C2-symmetric P9 promoted the reaction between 2-methoxyfuran (1) and β,γ-alkynyl-α-imino esters 24 to effect a C–C bond formation at the C2’ position of the heterocyclic ring. Only two examples were shown by varying the alkynyl substituent. The authors further extended the scope by studying the

• substrates (see transition state 75, Scheme 18). This C–C-bond formation affords a 3-indolinone moiety bearing an aza-quaternary stereocenter at the C2 position. In addition, the reaction allows to obtain axially chiral products 70/72/74 through restriction of the C–C bond rotation around the heteroaryl and

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

• accomplish by more conventional procedures, enables the synthesis of ergot alkaloid precursors. In addition, this work describes a mild, environmentally friendly method to activate, reductively and oxidatively, natural carboxylic acids for decarboxylative C–C bond formation by exploiting the same

• to forge the desired six-membered ring through a key C–C bond formation while furnishing secondary radical VI and the undesired seven-membered-ring compound VII. Closure of the photoredox catalytic cycle would then involve either SET reduction of the radical VI and VII (which upon protonation would

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

• ][26][27][28][29], a synthesis method for δ-olefin-containing aliphatic nitriles by the radical C–C bond cleavage of cycloketone oxime ester derivatives was developed by Shi’s group (Scheme 2a) [30], which emerged as an efficient strategy to construct C(sp2)–C(sp3) bonds [31][32][33]. Later, Xiao [34

• works, we contemplated that the N–O bond of cyclobutanone oxime derivatives could be activated by SO2F2 in situ to enable cleavage of the C–C bond, which could achieve this transformation without going through inefficient pre-introduction of electrophores. Herein, we describe how this concept has been

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

• reactive allenes (reaction e), which serve as synthetic intermediates for polyfunctionalized enynes [8]. The ring strain of the cyclopropane ring facilitates the cleavage of the C–C bond, and both cation and anion are stabilized by the adjacent phenyl group and ester functions, respectively (reaction f

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

• obtained by other conjugate addition reactions. Keywords: acylimidazole; asymmetric catalysis; carbocation; conjugate addition; enolate; Introduction Asymmetric metal-catalyzed conjugate additions provide access to numerous chiral scaffolds. This type of C–C bond formation efficiently enables the

Pyridine C(sp²)–H bond functionalization under transition-metal and rare earth metal catalysis

• Haritha Sindhe,
• Malladi Mounika Reddy,
• Karthikeyan Rajkumar,
• Akshay Kamble,
• Amardeep Singh,
• Anand Kumar and
• Satyasheel Sharma

Beilstein J. Org. Chem. 2023, 19, 820–863, doi:10.3762/bjoc.19.62

• also achieving selectivity is difficult due to its ubiquitous nature [40]. The metal-catalyzed C–H bond functionalization is a good strategy for synthesizing highly functionalized organic frameworks. In this context, the C–H alkylation is one of the most important C–C bond-formation reactions [41][42

• NHC aryl part with trans-styrene was highly important for the reaction to proceed and for the enantiocontrolled formation of the products. Alkenylation The C–H alkenylation is another important C–C bond-forming reaction. Olefinated organic molecules like vinylarenes play a significant role as key

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

• precursors. Review seco-HBC-based chiral NGs In the HBC synthesis, a small fraction of a partially cyclodehydrogenated intermediate was indeed isolated during the conversion of hexaphenylbenzene to HBC [32]. Conceptually, the partially ring-closed intermediate by cutting one C–C bond of HBC can be treated as

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

• applied for the synthesis of seven to fourteen-membered phostam, phostone, and phostine derivatives. 1.1 Synthesis via C–C bond formation Most medium and large phostams, phostones, and phostines were prepared via C–C bond formation, especially via ring-closing metathesis (RCM). 1.1.1 Synthesis via C–C

• bond formation through RCM reaction: Ring-closing metathesis (RCM) is an efficient strategy for the construction of common to large cyclic compounds via the formation of a C=C bond [26], which can be further reduced to a C–C bond. To prepare phostam-derived antitumor agents, ethyl N-allyl-N-(but-3-en-1

• -azaphosphepane 2-oxide and 1,2-azaphosphocane 2-oxide derivatives. Thus, the strategy is an efficient method for the synthesis of 1,2-azaphosphepine 2-oxides, 1,2-azaphosphocine 2-oxides, 1,2-azaphosphepane 2-oxides, and 1,2-azaphosphocane 2-oxides via C–C bond formation. All phostams 5, 6, 9 and 10 are

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

• molecule 5b. In the crystal packing (Figure S66 in Supporting Information File 1), molecules 5e tend to approach π-donor DMAN and π-acceptor p-nitrophenyl fragments, and the shortest distance between the two molecules is 2.810 Å (Figure S67 in Supporting Information File 1). The alternation of the C–C bond

• -terminated butadiyne 5 gradually underwent demethylation/acid-catalyzed heterocyclization involving one of the dimethylamino groups and the adjacent C≡C bond of the butadiyne linker, forming the corresponding benzo[g]indole derivative. Proton sponge-based 1,4-diaryl-1,3-butadiynes synthesized previously and