Total synthesis of natural products based on hydrogenation of aromatic rings

• Haoxiang Wu and
• Xiangbing Qi

Beilstein J. Org. Chem. 2026, 22, 88–122, doi:10.3762/bjoc.22.4

• mutually compatible, and rationalized facial selectivity through insights from asymmetric styrene hydrogenation. In 2024, Glorius and co-workers developed a chemoselective hydrogenation strategy capable of selectively reducing benzene rings in the presence of pyridine rings (Scheme 4) [47]. Supported by

• hydrogenation of the polycyclic aromatic compound PyBQ to PyBTHQ using this catalyst in HFIP (Scheme 5) [50]. Under the optimized conditions, only the heteroaromatic part of quinoline was reduced selectively, while the benzene ring and pyridine remained unchanged. In 2020, Beller and co-workers used a manganese

• 53 while retaining the benzene ring structure using an iridium catalyst to selectively hydrogenate indoles and benzofurans (Scheme 7) [59]. The hydrogenated products were obtained in 90% yield with 98% ee on average. In 2024, Yin and co-workers reported an innovative palladium-catalyzed asymmetric

Advances in Zr-mediated radical transformations and applications to total synthesis

• Hiroshige Ogawa and
• Hugh Nakamura

Beilstein J. Org. Chem. 2026, 22, 71–87, doi:10.3762/bjoc.22.3

• available materials, in benzene afforded the Zr(RCNN)2 complex 18. Investigation of the photoredox properties of the synthesized complex revealed trends similar to those of known photosensitizers, suggesting its potential utility as a photosensitizer [15]. Accordingly, the Zr(MeCNN)2 complex was employed as

Synthesis and applications of alkenyl chlorides (vinyl chlorides): a review

• Daniel S. Müller

Beilstein J. Org. Chem. 2026, 22, 1–63, doi:10.3762/bjoc.22.1

• vary widely across the literature, with solvents ranging from neat conditions to cyclohexane, hexanes, toluene, benzene, carbon tetrachloride, dichloromethane, and diethyl ether. Reaction temperatures span from −10 °C to 100 °C. The first detailed investigation of this transformation was reported by

• Kagan and co-workers [48], who demonstrated that the reaction of acetophenone (1) with PCl5 in refluxing benzene affords a complex product mixture (Scheme 2). A second, very detailed investigation of this reaction was presented by Jung and Kwon [49]. Focusing on the synthesis of efavirenz (21), a potent

Synthesis of new tetra- and pentacyclic, methylenedioxy- and ethylenedioxy-substituted derivatives of the dibenzo[c,f][1,2]thiazepine ring system

• Gábor Berecz,
• András Dancsó,
• Mária Tóthné Lauritz,
• Loránd Kiss,
• Gyula Simig and
• Balázs Volk

Beilstein J. Org. Chem. 2025, 21, 2645–2656, doi:10.3762/bjoc.21.205

• Group, Magyar tudósok krt. 2, H-1117 Budapest, Hungary 10.3762/bjoc.21.205 Abstract New tetra- and pentacyclic derivatives of the dibenzo[c,f][1,2]thiazepine ring system have been synthesized. The target compounds contain methylenedioxy or ethylenedioxy substituents linked to the benzene ring. The key

Ni-promoted reductive cyclization cascade enables a total synthesis of (+)-aglacin B

• Si-Chen Yao,
• Jing-Si Cao,
• Jian Xiao,
• Ya-Wen Wang and
• Yu Peng

Beilstein J. Org. Chem. 2025, 21, 2548–2552, doi:10.3762/bjoc.21.197

• followed by reaction with CH(OMe)3 afforded acetal 17, which was then subjected to a CH2Cl2 solution of TMSOTf and iPr2NEt. A mixture of enol methyl ethers 18 were thus produced by an elimination reaction. Eventually, a site-selective bromination of the double bond over the electron-rich benzene rings with

Pentacyclic aromatic heterocycles from Pd-catalyzed annulation of 1,5-diaryl-1,2,3-triazoles

• Kaylen D. Lathrum,
• Emily M. Hanneken,
• Katelyn R. Grzelak and
• James T. Fletcher

Beilstein J. Org. Chem. 2025, 21, 2524–2534, doi:10.3762/bjoc.21.194

• with ortho-bromo(trimethylsilylethynyl)benzene produced 1,5-diaryl-1,2,3-triazole products 25–30, each possessing an ortho-bromoaryl reactive site necessary for the annulation step. The tandem deprotection/click reaction was used to successfully prepare 1,5-diaryl-1,2,3-triazoles 25–30 in yields

Synthesis of the tetracyclic skeleton of Aspidosperma alkaloids via PET-initiated cationic radical-derived interrupted [2 + 2]/retro-Mannich reaction

• Ru-Dong Liu,
• Jian-Yu Long,
• Zhi-Lin Song,
• Zhen Yang and
• Zhong-Chao Zhang

Beilstein J. Org. Chem. 2025, 21, 2470–2478, doi:10.3762/bjoc.21.189

• difference can be attributed to a subtle discrepancy between the spin localizations of IN4 and TS2. As depicted in Figure 2b, the spin density of IN4 is predominantly concentrated at the benzene ring, whereas in TS2 it is primarily localized at C19, C12, C3, and N9 (Figure 2a) [32]. Therefore, the

Transformation of the cyclohexane ring to the cyclopentane fragment of biologically active compounds

• Natalya Akhmetdinova,
• Ilgiz Biktagirov and
• Liliya Kh. Faizullina

Beilstein J. Org. Chem. 2025, 21, 2416–2446, doi:10.3762/bjoc.21.185

• ]undec-7-ene (DBU) in benzene resulted in high yield of β-hydroxyaldehyde 6. Through a series of synthetic transformations, the target products (−)-taiwaniaquinones A (7), F (8), G (9), and H (11), (−)-taiwaniaquinol B (10) and (−)-dichroanone (12) were obtained from intermediate 6 (Scheme 2). An

• -Ethylformylation of compound 35 and subsequent oxidation of ketoenol 36 with 30% aqueous H2O2 in the presence of a 28% MeONa/MeOH solution resulted in the formation of a diacid, which was then converted into dimethyl ester 37 with a yield of 55%. Refluxing ester 37 with an excess of t-BuOK in benzene gave acid 39

• ethylenedioxy fragment (see below) are attractive substrates for studying the possibility of a photochemically induced contraction of the cyclohexane ring. Photoirradiation of keto oxirane 146 [76] in benzene containing 1% methanol afforded cyclopentane annulated derivative 147a along with keto ester 148a, a

The high potential of methyl laurate as a recyclable competitor to conventional toxic solvents in [3 + 2] cycloaddition reactions

• Ayhan Yıldırım and
• Mustafa Göker

Beilstein J. Org. Chem. 2025, 21, 2389–2415, doi:10.3762/bjoc.21.184

• for the preparation of such cyclic compounds and/or their fused cyclic systems typically necessitate the use of toxic solvents, including chloroform, benzene, toluene etc. [32][53][54][55][56][57][58][59]. Indeed, the selection of conventional organic solvents, including benzene, toluene and

• , the conventional solvents that are typically employed as reaction media encompass a range of options, including tetrahydrofuran (THF) (a problematic solvent, p), dioxane (considered hazardous, h), benzene (designated as highly hazardous, hh), toluene (p), chloroform (hh), acetonitrile (p), sulfolane

Conformational effects on iodide binding: a comparative study of flexible and rigid carbazole macrocyclic analogs

• Guang-Wei Zhang,
• Yong Zhang,
• Le Shi,
• Chuang Gao,
• Hong-Yu Li and
• Lei Xue

Beilstein J. Org. Chem. 2025, 21, 2369–2375, doi:10.3762/bjoc.21.181

• fluorescence quenching efficiency upon iodide binding compared to the rigid WDG (KPBG/KWDG = 22.78), demonstrating its potential as a highly sensitive optical probe and offering a novel strategy for engineering dynamic supramolecular receptors. Two carbazole-based macrocyclic probes, PBG (flexible benzene ring

• variations in fluorescence properties, leading to deviations from the linear Stern–Volmer relationship governing the quenching mechanism. The flexible benzene ring of the PBG allows the cavity to be conformationally adjusted to fit the size of I−, while the rigid fluorenyl group of the WDG results in steric

• computational schematic (Figures S16 and S17 in Supporting Information File 1), the anions are positioned within the macrocycle cavity, exhibiting close contacts to hydrogen atoms on the bridging benzene rings, peripheral substituted phenyl groups, and carbazole moieties. These spatial interactions suggest a

Insoluble methylene-bridged glycoluril dimers as sequestrants for dyes

• Suvenika Perera,
• Peter Y. Zavalij and
• Lyle Isaacs

Beilstein J. Org. Chem. 2025, 21, 2302–2314, doi:10.3762/bjoc.21.176

• environmental concern. We report the design, synthesis, and characterization of a series of methylene-bridged glycoluril dimers G2W1–G2W4 that are insoluble in water and that differ in the nature of their aromatic sidewalls (G2W4: benzene, G2W3: naphthalene, G2W1 and G2W2: triphenylene). We tested G2W1–G2W4

• glycoluril tetramer-derived acyclic CB[n] (e.g., M1) containing benzene, naphthalene, and anthracene aromatic sidewalls bearing O(CH2)3SO3Na water-solubilizing groups and found that the hosts with larger sidewalls displayed higher affinity toward hydrophobic alicyclic cationic guests [42][43]. Conversely, we

•  1). The removal efficiency was calculated using Equation 1, where c0 is the initial dye concentration, and ct is the dye concentration after sequestration. The results of these experiments are shown in Figure 4. Quite disappointingly, Figure 4 shows that the benzene, naphthalene, and triphenylene

Pathway economy in cyclization of 1,n-enynes

• Hezhen Han,
• Wenjie Mao,
• Bin Lin,
• Maosheng Cheng,
• Lu Yang and
• Yongxiang Liu

Beilstein J. Org. Chem. 2025, 21, 2260–2282, doi:10.3762/bjoc.21.173

• structures, demonstrating notable utility in the synthesis of this biologically significant alkaloid. In 2020, Sanz and co-workers developed a gold(I)-catalyzed strategy achieving stereoselective construction of alkylidenecyclopentenes and benzene derivatives (Scheme 31) [44]. Notably, this study pioneered

• intermediate 150. Subsequent aromatization and ring expansion afforded benzene derivatives 151 (Scheme 31, path a). Conversely, E-configured substrates underwent gold-catalyzed alkyne activation, triggering terminal alkene 5-exo-dig cyclization to form carbocationic intermediate 152. Alcohols nucleophilically

Pd-catalyzed dehydrogenative arylation of arylhydrazines to access non-symmetric azobenzenes, including tetra-ortho derivatives

• Loris Geminiani,
• Kathrin Junge,
• Matthias Beller and
• Jean-François Soulé

Beilstein J. Org. Chem. 2025, 21, 2234–2242, doi:10.3762/bjoc.21.170

• reported in Buchwald–Hartwig reactions, enhances yield by facilitating the reduction of Pd(II) to Pd(0) and improving the solubility of the base [56]. To ensure the generality of the conditions, 1-bromo-2-(trifluoromethoxy)benzene was also tested, yielding the desired azobenzene 3c in 69% yield with the

• proved to be a suitable coupling partner, enabling the preparation of azoarene 3p in 70% yield. Moreover, starting from 1,4-dibromobenzene and 2 equivalents of 1a, a double reaction occurred, enabling the one-step synthesis of 1,4-bis[(E)-2-phenyldiazenyl]benzene (3q) in high yield. We next investigated

C2 to C6 biobased carbonyl platforms for fine chemistry

• Jingjing Jiang,
• Muhammad Noman Haider Tariq,
• Florence Popowycz,
• Yanlong Gu and
• Yves Queneau

Beilstein J. Org. Chem. 2025, 21, 2103–2172, doi:10.3762/bjoc.21.165

• aqueous-phase reforming (APR) technology for the production of light hydrocarbons and hydrogen in a single step from aqueous organic phases [97] containing 1-hydroxypropan-2-one (acetol), ethanol, benzene-1,2-diol (catechol), acetic acid or mixtures thereof. The process was conducted over various Ni-based

• catalysts including Ni/CeO2-γAl2O3, spinal NiAl2O4 and Ni/La2O3-αAl2O3, at 230 °C and 3.2 MPa. Using a chiral catalyst composed of [RuCl2(benzene)]2 and SunPhos, an effective asymmetric hydrogenation of α-hydroxy ketones was reported, yielding chiral terminal 1,2-diols in up to 99% ee. This Ru-catalyzed

Aryl iodane-induced cascade arylation–1,2-silyl shift–heterocyclization of propargylsilanes under copper catalysis

• Rasma Kroņkalne,
• Rūdolfs Beļaunieks,
• Armands Sebris,
• Anatoly Mishnev and
• Māris Turks

Beilstein J. Org. Chem. 2025, 21, 1984–1994, doi:10.3762/bjoc.21.154

• techniques, indicating that the observed arylation–cyclization cascade reaction is highly stereospecific. With this result in hand, we performed copper catalyst screening (Table 3). We observed that CuCl and the CuOTf benzene complex gave similarly good yields (82–84% by NMR, Table 3, entries 2 and 4), while

Synthesis of N-doped chiral macrocycles by regioselective palladium-catalyzed arylation

• Shuhai Qiu and
• Junzhi Liu

Beilstein J. Org. Chem. 2025, 21, 1917–1923, doi:10.3762/bjoc.21.149

• ][21][22][23]. In addition to benzene-based systems, pyridine-embedded aza[1n]metacyclophanes have been synthesized by Wang [24]. Despite these advances, N-doped chiral macrocycles incorporating extended π-conjugated moieties remain largely underexplored. To date, only a few examples, carbazole-based

• could be viewed as the aza[14]metacyclophane derivatives, in which two benzene rings are replaced by two pyrenes. The Pd-catalyzed arylation of 3a with Pd(OAc)2, PMe(t-Bu)2·HBF4 and DBU under microwave conditions gave two isomeric macrocycles MC1 and MC2 with four newly formed C–C bonds in yields of 5

Chiral phosphoric acid-catalyzed asymmetric synthesis of helically chiral, planarly chiral and inherently chiral molecules

• Wei Liu and
• Xiaoyu Yang

Beilstein J. Org. Chem. 2025, 21, 1864–1889, doi:10.3762/bjoc.21.145

• electrophilic amination reaction of the aniline moiety with azodicarboxylates [37][38], the introduction of a bulky hydrazine group restricted the free flipping of the benzene ring, leading to the formation of planar chiral macrocycle 33 with high enantioselectivity (Scheme 9). Substrate scope studies

• restrict the benzene ring flipping (see 33c). Notably, the use of a bulkier NHBn directing group allowed for the extension of the ansa chain to 15–19 members (see 33d,e), while preserving planar chirality and functional group compatibility. Remarkably, the chiral paracyclophane product 33a could be

Photoswitches beyond azobenzene: a beginner’s guide

• Michela Marcon,
• Christoph Haag and
• Burkhard König

Beilstein J. Org. Chem. 2025, 21, 1808–1853, doi:10.3762/bjoc.21.143

• coupling with aryl iodides. The monosubstituted product 78 can be further functionalised with any of the previous methods [67]. Hemiindigos 81 and 82 are synthesised by generation of 80 via reaction with (diacetoxyiodo)benzene (PIDA) in the presence of base, followed by reaction with the corresponding

• weaken the hydrogen bonds between N–H and the ester moieties of the rotor and the stator. The Cigáň group focused on the synthesis of benzoylpyridine hydrazones with different substitutions in the rotor benzene [97]. The p-NMe2 group causes red-shift of both absorption maxima of the E- and Z-isomer

Research progress on calixarene/pillararene-based controlled drug release systems

• Liu-Huan Yi,
• Jian Qin,
• Si-Ran Lu,
• Liu-Pan Yang,
• Li-Li Wang and
• Huan Yao

Beilstein J. Org. Chem. 2025, 21, 1757–1785, doi:10.3762/bjoc.21.139

• , connected via methylene bridges. The most common CAs usually consist of 4, 6, or 8 phenolic units (Figure 2) [47][48][49][50][51][52][53]. The upper rim of CAs is equipped with hydrophobic alkyl groups, which, together with the benzene rings, form a hydrophobic cavity. In contrast, the lower rim consists of

Unique halogen–π association detected in single crystals of C–N atropisomeric N-(2-halophenyl)quinolin-2-one derivatives and the thione analogue

• Mai Uchibori,
• Nanami Murate,
• Kanako Shima,
• Tatsunori Sakagami,
• Ko Kanehisa,
• Gary James Richards,
• Akiko Hori and
• Osamu Kitagawa

Beilstein J. Org. Chem. 2025, 21, 1748–1756, doi:10.3762/bjoc.21.138

• -electron on the quinolinone benzene ring, while that in optically pure forms is caused by an n–π* interaction between a lone electron pair on the halogen atom and a π* orbital of the quinolinone. In contrast to the formation of the homochiral layered polymer in quinolinones, in racemic N-(2-bromophenyl

• vapour diffusion of hexane into a methanol solution of the compound at room temperature) and their X-ray crystal structural analyses were performed (Figure 2) [33]. In the crystals of rac-1a, a π-type intermolecular interaction between the bromine atom and the benzene ring of the quinolinone was found

• , the chlorine atom interacts with two carbon atoms (C5 and C6) of the benzene ring, the two bond distances (Cl···C5,6) and two bond angles (C–Cl···C5,6) were 3.42, 3.27 Å and 164.5, 154.4°, respectively. The formation of homochiral layered polymers through intermolecular halogen–π interactions was also

On the aromaticity and photophysics of 1-arylbenzo[a]imidazo[5,1,2-cd]indolizines as bicolor fluorescent molecules for barium tagging in the study of double-beta decay of ¹³⁶Xe

• Eric Iván Velazco-Cabral,
• Fernando Auria-Luna,
• Juan Molina-Canteras,
• Miguel A. Vázquez,
• Iván Rivilla and
• Fernando P. Cossío

Beilstein J. Org. Chem. 2025, 21, 1627–1638, doi:10.3762/bjoc.21.126

• of this second reaction was calculated to be of 28 kcal/mol, slightly lower than the aromatic stabilization energy (ASE) and isomerization stabilization energy (ISE) calculated for benzene [20] (see reaction D in Scheme 1). Most likely this lowering stems from the strain imposed to the ortho

• stabilization energy of benzene (15). Combination of these latter equations yields This second averaged equation results in a computed stabilization energy of ⟨ΔECD⟩ = −20.5 kcal/mol, 2.1 kcal/mol lower than that calculated for ⟨ΔEAB⟩. These results indicate that there is a noticeable interplay between the

• possible. The role of the crown ether and the para-phenylene moieties was also analyzed. The interactions of different sized crown ethers with Ba2+ and coordination with the aromatic ring modeled by means of benzene (14, highlighted in yellow in Scheme 2) were studied computationally. Although the

Transition-state aromaticity and its relationship with reactivity in pericyclic reactions

• Israel Fernández

Beilstein J. Org. Chem. 2025, 21, 1613–1626, doi:10.3762/bjoc.21.125

• [1][2][3]. Initially introduced to account for the remarkable stability, low reactivity, and unique structural features of benzene and related aromatic hydrocarbons, the concept has undergone a significant evolution [4]. Since the introduction of the famous Hückel’s (4n + 2) rule [5], first clearly

• been introduced [7][8][9][10][11]. The concept of aromaticity was also extended to the transition states (TSs) of concerted pericyclic reactions as early as 1938 when Evans and Warhurst [12] recognized the relationship between the six π-electrons of benzene and the six delocalized electrons in the

• transition structure of the Diels–Alder cycloaddition reaction between butadiene and ethylene “…Very qualitatively, we may say that whereas in the initial state the mobile electrons are those characteristics of an ethylene and a butadiene structure, in the TS they simulate the behavior of a benzene molecule

Synthesis of optically active folded cyclic dimers and trimers

• Ena Kumamoto,
• Kana Ogawa,
• Kazunori Okamoto and
• Yasuhiro Morisaki

Beilstein J. Org. Chem. 2025, 21, 1603–1612, doi:10.3762/bjoc.21.124

• ]paracyclophanes via Wurtz-type intramolecular cyclization [3]. [2.2]Paracyclophane has a molecular structure in which two benzene rings are stacked face-to-face with ethylene chains at the para positions. Various studies have been conducted on their reactivities and physical properties derived from their unique

• molecular structure with stacked π-electron clouds [1][4][5][6]. The distance between benzene rings in [2.2]paracyclophane is extremely short (2.8–3.1Å), and thus the rotational motion of benzene rings is completely suppressed; therefore, planar chirality without chiral centers [7] appears by introducing

• substituent(s) at appropriate position(s) on the benzene rings [8]. Enantiopure planar chiral [2.2]paracyclophanes have been used as chiral auxiliaries and chiral ligands for transition metals in the fields of organic and organometallic chemistry [9][10][11][12][13][14][15][16][17][18][19][20]. In 2012

3-Aryl-2H-azirines as annulation reagents in the Ni(II)-catalyzed synthesis of 1H-benzo[4,5]thieno[3,2-b]pyrroles

• Julia I. Pavlenko,
• Pavel A. Sakharov,
• Anastasiya V. Agafonova,
• Derenik A. Isadzhanyan,
• Alexander F. Khlebnikov and
• Mikhail S. Novikov

Beilstein J. Org. Chem. 2025, 21, 1595–1602, doi:10.3762/bjoc.21.123

• an ortho-substituent into the benzene ring also has no effect on the synthesis efficiency (compound 3f). A slight decrease in yield was observed only for the naphthyl-substituted annulation product 3k. The plausible mechanism of the reaction involves the nucleophilic addition of the Ni-enolate of 1

Thermodynamic equilibrium between locally excited and charge transfer states in perylene–phenothiazine dyads

• Issei Fukunaga,
• Shunsuke Kobashi,
• Yuki Nagai,
• Hiroki Horita,
• Hiromitsu Maeda and
• Yoichi Kobayashi

Beilstein J. Org. Chem. 2025, 21, 1577–1586, doi:10.3762/bjoc.21.121

• the degree of electronic interaction between the donor PTZ and acceptor Pe moieties, as indicated by the decreased overlap between HOMO and LUMO. UV–vis absorption spectra of the Pe–PTZ derivatives were recorded in benzene at room temperature (Figure 3a). All compounds exhibited characteristic

• does not necessarily depend on the number of TPA groups. The relative emission quantum yields (Φf) in benzene solution were 2.4, 3.1, 2.4, and 20% for Pe–PTZ, Pe–PTZ(TPA), Pe–PTZ(TPA)2, and Pe–Ph–PTZ(TPA)2, respectively. This order corresponds to the relative intensities of the CT band compared to the

• the transient absorption spectra and EAS of Pe–PTZ(TPA)2 in benzene excited at 350 nm. The excitation at 350 nm predominantly corresponds to an absorption band enhanced by the introduction of TPA groups, suggesting preferential excitation of the PTZ(TPA)2 moiety. Immediately after excitation, ground