(Bio)isosteres of ortho- and meta-substituted benzenes

• H. Erik Diepers and
• Johannes C. L. Walker

Beilstein J. Org. Chem. 2024, 20, 859–890, doi:10.3762/bjoc.20.78

• substituted ortho-benzene. Stephenson and co-workers accessed 1,2-BCHeps 79a–c by insertion of alkenes into BCPs 78, and proposed the 1,2-BCHeps as isosteres of ortho-benzenes (Scheme 7A) [46]. The reaction proceeded via homolytic cleavage of a C–C bond adjacent to the imine functionality and stepwise alkene

Regioselective quinazoline C2 modifications through the azide–tetrazole tautomeric equilibrium

• Dāgs Dāvis Līpiņš,
• Andris Jeminejs,
• Una Ušacka,
• Anatoly Mishnev,
• Māris Turks and
• Irina Novosjolova

Beilstein J. Org. Chem. 2024, 20, 675–683, doi:10.3762/bjoc.20.61

• techniques employing transition-metal and photocatalysis [15][16]. These methods facilitate C–C bond formation, enabling the introduction of alkyl groups at the C2 position of quinazoline derivatives. While arylsulfanyl group rearrangement reactions have been documented by us for modifying 2,4-substituted

Enhanced reactivity of Li⁺@C₆₀ toward thermal [2 + 2] cycloaddition by encapsulated Li⁺ Lewis acid

• Hiroshi Ueno,
• Yu Yamazaki,
• Hiroshi Okada,
• Fuminori Misaizu,
• Ken Kokubo and
• Hidehiro Sakurai

Beilstein J. Org. Chem. 2024, 20, 653–660, doi:10.3762/bjoc.20.58

• likely due to the steric effect caused by the methyl group directly connected to the alkenyl C=C bond in reactant 1. After optimizing the reaction conditions, compounds 5a and 5b were isolated in 71% and 53% yields, respectively. Importantly, the generation of multiadducts in the thermal [2 + 2

Recent developments in the engineered biosynthesis of fungal meroterpenoids

• Zhiyang Quan and
• Takayoshi Awakawa

Beilstein J. Org. Chem. 2024, 20, 578–588, doi:10.3762/bjoc.20.50

• molecular species withdraws a hydrogen atom, and the generated radical induces various reactions such as hydroxylation, unsaturation, epoxidation, halogenation, endoperoxidation, and C–C bond reconstruction, leading to the formation of diverse chemical structures [22][26][27][28][29][30][31]. Structure

Possible bi-stable structures of pyrenebutanoic acid-linked protein molecules adsorbed on graphene: theoretical study

• Yasuhiro Oishi,
• Motoharu Kitatani and
• Koichi Kusakabe

Beilstein J. Org. Chem. 2024, 20, 570–577, doi:10.3762/bjoc.20.49

• activation barrier. This steric hindrance effect is analogous to the well-known steric hindrance effect of the rotation around the C–C bond in ethane. Indeed, on the graphene surface, the possible conformations resulting from the rotation are effectively limited to conformation 2, due, in part, to the

• rotation at the alkyl chain (conformation II), as shown in Figure 1d. Rotational motion at the alkyl chain inevitably involves steric hindrance effects around the C–C bond. In particular, for motions corresponding to rotations around the C–C bond in PASE represented by the solid red line in Figure 1a and b

• how an activation barrier appears on the potential energy surface in PASE adsorbed on graphene. The conformational change between two bi-stable PASE structures can be regarded as rotational motion around a C–C bond in the alkyl chain. An origin of an activation barrier is the steric hindrance coming

Entry to new spiroheterocycles via tandem Rh(II)-catalyzed O–H insertion/base-promoted cyclization involving diazoarylidene succinimides

• Alexander Yanovich,
• Anastasia Vepreva,
• Ksenia Malkova,
• Grigory Kantin and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2024, 20, 561–569, doi:10.3762/bjoc.20.48

• from each of the bromo-substituted alcohols used by us have two main pathways of transformation under the action of base: 1) exo-tet cyclization with substitution of the bromine atom and formation of the spirocycle, and 2) migration of the exocyclic double C=C bond into the imide cycle (the process is

• )ethanol. In the latter case, the predominant process was found to be the base-promoted migration of the C=C bond of the arylidene fragment into the cycle. Examples of biologically active compounds and natural products based on THF/THP spiro-conjugates with pyrrolidine rings. DAS spirocyclizations reported

Synthesis of photo- and ionochromic N-acylated 2-(aminomethylene)benzo[b]thiophene-3(2Н)-ones with a terminal phenanthroline group

• Vladimir P. Rybalkin,
• Sofiya Yu. Zmeeva,
• Lidiya L. Popova,
• Irina V. Dubonosova,
• Olga Yu. Karlutova,
• Oleg P. Demidov,
• Alexander D. Dubonosov and
• Vladimir A. Bren

Beilstein J. Org. Chem. 2024, 20, 552–560, doi:10.3762/bjoc.20.47

• a terminal phenanthroline receptor substituent was synthesized. Upon irradiation in acetonitrile or DMSO with light of 436 nm, they underwent Z–E isomerization of the C=C bond, followed by very fast N→O migration of the acyl group and the formation of nonemissive O-acylated isomers. These isomers

• vibrations of the thiophene and amide carbonyl groups were observed at 1663–1678 and 1705–1713 cm−1, respectively. The 1H NMR spectra contained signals of methine protons (=CH–) in the region 7.92–9.02 ppm, which corresponded to the Z-configuration of the C=C bond. According to data previously obtained [14

• photoisomerization of the C=C bond, followed by very fast thermal N→O migration of the acyl group and the formation of O-acylated isomers. This rearrangement was accompanied by a decrease of the initial fluorescence intensity at 465–468 nm up to zero, since the resulting OAc− form was nonemissive. The reverse

Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

• their solvation sphere occupy part of the cavity and prevent non-coordinating guests from entering the binding cavity. By extending the spacer between the terpy and the arms from a single C–C bond to an amide functional group that also participates in the coordination of the Zn2+, non-coordinating

Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

• Periklis X. Kolagkis,
• Eirini M. Galathri and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36

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