Identification and removal of a cryptic impurity in pomalidomide-PEG based PROTAC

• Bingnan Wang,
• Yong Lu and
• Chuo Chen

Beilstein J. Org. Chem. 2025, 21, 407–411, doi:10.3762/bjoc.21.28

• develop a method to facilitate the elimination of this impurity. We first attempted scavenging 6 by solid-phase supported amines. Incubating a mixture of 3 and 6 with TentaGel S-NH2 in DMF led to a gradual decrease of 6 over four days. Whereas this method is applicable to removing 9 of different PEG-OH

The effect of neighbouring group participation and possible long range remote group participation in O-glycosylation

• Rituparna Das and
• Balaram Mukhopadhyay

Beilstein J. Org. Chem. 2025, 21, 369–406, doi:10.3762/bjoc.21.27

• protecting groups in the C-2 position in glycosyl donors, on the elimination of the activated leaving group from the anomeric position, the flattened oxocarbenium ion formed causes the incoming nucleophilic acceptor to attack from either the β or the α-face of the sugar ring, thereby leading to the formation

• ether-type groups are less electron-withdrawing than the ester groups [55][145][146] making the corresponding glycosyl donors more reactive (armed) than the corresponding donors with ester group protection. However, the use of ether groups works on the protocol of elimination 1,2-trans selectivity

Red light excitation: illuminating photocatalysis in a new spectrum

• Lucas Fortier,
• Corentin Lefebvre and
• Norbert Hoffmann

Beilstein J. Org. Chem. 2025, 21, 296–326, doi:10.3762/bjoc.21.22

• reaction mixture. This step allows the oxidative addition of nickel on the aryl bromide 9 followed by the reductive elimination giving the desired product 11. Besides the innovative synthetic results obtained in this study, the authors underline a major advantage to switch to red light as it enables a

Molecular diversity of the reactions of MBH carbonates of isatins and various nucleophiles

• Zi-Ying Xiao,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2025, 21, 286–295, doi:10.3762/bjoc.21.21

• derivatives. At first, a Lewis base attack at the α-position of the MBH nitrile of isatin resulted in the intermediate A with elimination of carbon dioxide and tert-butoxide ion. Secondly, the product 3 was produced by the SN2 substitution of the Lewis base by the arylamine. When MBH maleimides of isatin were

• used in the reaction, a direct Michael addition of the arylamine to the C=C bond of the maleimide unit and sequential elimination of carbon dioxide and tert-butoxide ion gives the intermediate B, which in turn undergoes an allylic rearrangement to afford the product 5. In this process, no extra

• addition of Lewis base is needed. When triphenylphosphine or tri(n-butyl)phosphine were involved in the reaction, the similar SN2’ substitution of tri(n-butyl)phosphine with the elimination of carbon dioxide and tert-butoxide anion gives the phosphonium salt C. Then, the deprotonation of phosphonium salt C

Dioxazolones as electrophilic amide sources in copper-catalyzed and -mediated transformations

• Seungmin Lee,
• Minsuk Kim,
• Hyewon Han and
• Jongwoo Son

Beilstein J. Org. Chem. 2025, 21, 200–216, doi:10.3762/bjoc.21.12

• , providing the corresponding products (16g–k). Mechanistically, the reaction begins with the generation of the active copper species 17, successively forming INT-19 and INT-20 (Figure 5). The penta-coordinated copper nitrenoid species INT-20, as suggested by DFT calculations, undergoes reductive elimination

• 20 is afforded through protonolysis, regenerating the active copper species to complete the catalytic cycle. 2 Amidation via oxidative insertion to N–O bonds and reductive elimination 2.1 Hydroamidation of vinylarenes Amines bearing stereogenic centers have been widely investigated in the research

• and silane, undergoes the enantio-determining hydrocupration of the vinylarene, affording INT-25 [25]. Next, oxidative insertion of INT-25 into the N–O bond of the dioxazolone, forms INT-26, followed by decarboxylative reductive elimination to generate INT-27. Further incorporation of silane delivers

Recent advances in electrochemical copper catalysis for modern organic synthesis

• Yemin Kim and
• Won Jun Jang

Beilstein J. Org. Chem. 2025, 21, 155–178, doi:10.3762/bjoc.21.9

• through oxidative addition, followed by transmetalation and reductive elimination, to obtain the desired product. Throughout the catalytic cycle, the catalyst undergoes conversion between [M]n and [M]n+2 (Figure 1) [11]. However, using alkyl electrophiles as coupling partners in cross-coupling reactions

• remains a significant challenge owing to the high energy barrier required for oxidative addition and facile β-hydride elimination [12]. The development of radical approaches facilitated by transition-metal catalysis has provided a promising solution to overcome the limitations of conventional coupling

• elimination, produces C–H alkynylated arene 10, which then forms the final product 3 through intramolecular cyclization. Finally, the Cu(I) complex 9 produced via reductive elimination is reoxidized at the anode to regenerate the Cu(II) complex 4, completing the catalytic cycle. Yao and Shi developed the

Nickel-catalyzed cross-coupling of 2-fluorobenzofurans with arylboronic acids via aromatic C–F bond activation

• Takeshi Fujita,
• Haruna Yabuki,
• Ryutaro Morioka,
• Kohei Fuchibe and
• Junji Ichikawa

Beilstein J. Org. Chem. 2025, 21, 146–154, doi:10.3762/bjoc.21.8

• successfully synthesize a range of 2-arylbenzofurans with various substituents. The reaction, which proceeded under mild conditions, involved β-fluorine elimination from nickelacyclopropanes formed by the interaction of 2-fluorobenzofurans with zero-valent nickel species. This protocol facilitates orthogonal

• developed efficient metal-mediated methods for activating (i) vinylic [8][9][10][11][12][13] and (ii) allylic C–F bonds [14][15][16][17][18] using β-fluorine elimination under mild conditions. In these studies, (i) we discovered zirconium-mediated β-fluorine elimination from zirconacyclopropanes A, which

• -(trifluoromethyl)-1-alkenes strongly interact with electron-rich zero-valent nickel species to form nickelacyclopropanes C [15][16][17]. These intermediates enable C–F bond activation through the formation of nickelacyclopentenes D with alkynes, followed by β-fluorine elimination, leading to defluorinative

Cu(OTf)₂-catalyzed multicomponent reactions

• Sara Colombo,
• Camilla Loro,
• Egle M. Beccalli,
• Gianluigi Broggini and
• Marta Papis

Beilstein J. Org. Chem. 2025, 21, 122–145, doi:10.3762/bjoc.21.7

• the mechanism is the attack of the protonated pyridin-2-one to the copper-complex of the enamine XXXII resulting from the reaction between acetophenone and O-tosylhydroxylamine, which occurs with elimination of TsOH. The so-obtained imino–copper complex XXXIII gives rise to an intramolecular C–N bond

• formation releasing Cu(OTf)2. The final bicyclic product 33 arises from isomerization and water elimination. Recently, Singh's research group developed a cascade process to access imidazo[1,2-a]pyridines-linked isoxazoles 35. Isoxazole carbaldehydes treated with 2-aminopyridines and isonitriles in the

• of an ortho-quinone methide intermediate XXXVII formed through nucleophilic attack of the 2-naphthol to the aldehyde followed by reaction with 1,3-dicarbonyl compound coordinated by the copper. The subsequent intramolecular nucleophilic attack of the oxygen to the enol and water elimination resulted

Recent advances in organocatalytic atroposelective reactions

• Henrich Szabados and
• Radovan Šebesta

Beilstein J. Org. Chem. 2025, 21, 55–121, doi:10.3762/bjoc.21.6

• [27]. This transformation led to a series of axially chiral cycl[3.2.2]azines 24 in good yields and high enantiomeric purities (Scheme 8). The proposed mechanism comprises enamine activation, condensation with nitroolefin 23, ring closure, and catalyst elimination to provide the axially chiral product

• the final step of the reaction, ring opening by the C–C bond cleavage yields the desired product 203. The first phosphoric acid C39-catalyzed asymmetric cycloaddition–elimination cascade reaction of 2-naphthol or phenol enamide derivatives 204 with azonaphthalenes 205 was done by Xu et al. in 2021

• cyclization takes place, subsequent β-H elimination, and C–N-bond cleavage lead to the axially chiral indolylaniline 212. Heterobiaryl aldehydes 217a–o and aminobenzamides 218a–g reacted in the presence of CPA C50 leading to axially chiral products 219 (Scheme 64) [94]. Investigating various combinations of

Synthesis, structure and π-expansion of tris(4,5-dehydro-2,3:6,7-dibenzotropone)

• Yongming Xiong,
• Xue Lin Ma,
• Shilong Su and
• Qian Miao

Beilstein J. Org. Chem. 2025, 21, 1–7, doi:10.3762/bjoc.21.1

• -membered ring to an eight-membered ring [2]. Results and Discussion As shown in Scheme 1a, the synthesis of trione 1 started from the bromination of 4-bromo-2,3:6,7-dibenzotropone (4) [24], giving tribromide 5 in a yield of 64%. The subsequent elimination reaction of 5 with KOH afforded dibromide 6 in a

Ceratinadin G, a new psammaplysin derivative possessing a cyano group from a sponge of the genus Pseudoceratina

• Shin-ichiro Kurimoto,
• Kouta Inoue,
• Taito Ohno and
• Takaaki Kubota

Beilstein J. Org. Chem. 2024, 20, 3215–3220, doi:10.3762/bjoc.20.267

• ]. Despite the absence of an HMBC correlation directly indicating a connection between C-8 and C-9, the HMBC correlation between the N-methylene protons H2-10 (δH 3.66) and the carbonyl carbon C-9 (δC 161.5), along with the molecular formula of compound 1 by process of elimination, suggested that C-8 and 9-N

Direct trifluoroethylation of carbonyl sulfoxonium ylides using hypervalent iodine compounds

• Radell Echemendía,
• Carlee A. Montgomery,
• Fabio Cuzzucoli,
• Antonio C. B. Burtoloso and
• Graham K. Murphy

Beilstein J. Org. Chem. 2024, 20, 3182–3190, doi:10.3762/bjoc.20.263

• reductive elimination (path 1) [37][38][39]. This pathway initiates by formation of a halogen bond complex between 1a and the trifuoroethyl(mesityl)iodonium ion 2a’, where adduct XB-1 is presumably in equilibrium with isomeric XB-2. Reductive elimination of the iodoarene from XB-2 would furnish B, whose

• arene moieties. These observations confirmed the LUMO as an appropriate lobe for nucleophilic attack via the SN2 pathway (path 2), and confirmed the LUMO+1 as an appropriate lobe for substitution via reductive elimination (path 1). As such, neither mechanism could be immediately discarded, and we were

• mesh) as a stationary phase (eluent n-hex/AcOEt 5:95%). Representative examples of fluorine containing, biologically active compounds. Possible mechanisms for the reaction of 1a and 2a leading to 3a (via B), proceeding via either halogen-bonded adducts and reductive elimination (path 1) or directly via

Hypervalent iodine-mediated intramolecular alkene halocyclisation

• Charu Bansal,
• Oliver Ruggles,
• Albert C. Rowett and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 3113–3133, doi:10.3762/bjoc.20.258

• ring A (Scheme 2). The Pd(II) intermediate is oxidised by PhI(OPiv)2/AgF, forming Pd(IV). Formation of the product can occur either by reductive elimination by Pd(IV) or SN2 nucleophilic attack by fluorine with concomitant palladium reduction. Reductive elimination of the Pd(II) intermediate forms the

• on the alkene gave low yields of product. A mechanism was proposed involving the activation of iodosylbenzene 9 with BF3·Et2O to form an HVI intermediate that activates the alkene to form an iodonium species. Intramolecular nucleophilic attack of nitrogen, elimination of PhI and attack by fluoride

• ) whereby AgBF4 first activates the fluoroiodane 12 for alkene coordination. Intramolecular nucleophilic attack of oxygen on the more substituted carbon forms the cyclised intermediate A and eliminates fluoride. Phenonium intermediate B is formed with elimination of the iodoarene and subsequent attack of

Synthesis of the 1,5-disubstituted tetrazole-methanesulfonylindole hybrid system via high-order multicomponent reaction

• Cesia M. Aguilar-Morales,
• América A. Frías-López,
• Nadia V. Emilio-Velázquez,
• Alejandro Islas-Jácome,
• Angelica Judith Granados-López,
• Jorge Gustavo Araujo-Huitrado,
• Yamilé López-Hernández,
• Hiram Hernández-López,
• Luis Chacón-García,
• Jesús Adrián López and
• Carlos J. Cortés-García

Beilstein J. Org. Chem. 2024, 20, 3077–3084, doi:10.3762/bjoc.20.256

• first catalytic cycle begins with the coupling of 1,5-disubstituted tetrazole-alkyne 19 and methanesulfonyl-2-iodoaniline 17 forming the intermediate 23. Following a reductive elimination, the Sonogashira-like product 24 is produced, which then progresses into the second catalytic cycle. In this cycle

Advances in radical peroxidation with hydroperoxides

• Oleg V. Bityukov,
• Pavel Yu. Serdyuchenko,
• Andrey S. Kirillov,
• Gennady I. Nikishin,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2024, 20, 2959–3006, doi:10.3762/bjoc.20.249

• action of radical A leads to intermediate E. The recombination of intermediate E with tert-butylperoxy radical B, following elimination of TsH, and oxidation of oxazole G provides the target peroxide 82 formation. Non-activated С(sp3)–H A number of studies [77][78][79][80][81] are devoted to the

• , which transforms into alkyl radical D via CO elimination. Radical D adds to the double bond of alkene 130, to form the C-centered radical E, which recombines with radical B to yield the target product 132. Later, the same authors reported a four-component radical coupling of two different alkenes 133

• reaction mechanism includes the formation of α-dicarbonyl compound A and elimination of CO which results in aldehyde B. tert-Butoxy E and tert-butylperoxy F radicals are formed during the redox Cu(I)/Cu(II) cycle. The acyl radical C generated via hydrogen atom abstraction with tert-butoxy radical E adds to

gem-Difluorovinyl and trifluorovinyl Michael acceptors in the synthesis of α,β-unsaturated fluorinated and nonfluorinated amides

• Monika Bilska-Markowska,
• Marcin Kaźmierczak,
• Wojciech Jankowski and
• Marcin Hoffmann

Beilstein J. Org. Chem. 2024, 20, 2946–2953, doi:10.3762/bjoc.20.247

• anticipated α-substituted compound (Table 1, entry 9). The NMR analysis revealed that the obtained compounds were Michael addition products. The formation of the presented compounds (Table 1) was due to the earlier generation of gem-difluoroalkenes by the elimination of one of the fluorine atoms from the CF3

• scope, we observed that gem-difluoroalkenes produced β-fluoro-unsaturated amides 11a–d (Scheme 3). In these reactions, we used conditions previously optimised for derivatives 1a–d (n-BuLi 4 equiv, THF, −78 °C, 3 h). The amides 11a–d preferred HF elimination over engaging in another Michael reaction

• , such a reaction pathway was absent for derivatives 11a–d, where the alpha-positioned proton exhibited a low pKa, favouring an easy elimination reaction. This is supported by the higher yields of products 12a–d compared to their 11a–d counterparts. The exclusive formation of E isomers in compounds 11a–d

Recent advances in transition-metal-free arylation reactions involving hypervalent iodine salts

• Ritu Mamgain,
• Kokila Sakthivel and
• Fateh V. Singh

Beilstein J. Org. Chem. 2024, 20, 2891–2920, doi:10.3762/bjoc.20.243

• formation of the Nu–Ar product and aryl iodide [21]. Second, the arylation can take place in the presence of a metal catalyst via oxidative addition, followed by reduction elimination [48][49]. Thirdly, it proceeds through a ligand-coupled arylation which involves a five-membered transition state to yield

• reductive elimination in exceptional yields (Scheme 20) [71]. Although screening studies indicated the possibility of achieving the N-arylation at both, the N1- and N2-positions of the triazoles, N2-arylation was predominantly observed. It was incredible to achieve splendid regioselectivity without the

• the study. The results demonstrated that the diphenyliodonium triflate has a feasible energy barrier of 21.5 kcal/mol and can be readily converted into a stable iodonium thiolate species. This species can further undergo a C–S bond-forming reductive elimination, providing the sulfide product. As a

N-Glycosides of indigo, indirubin, and isoindigo: blue, red, and yellow sugars and their cancerostatic activity

• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 2840–2869, doi:10.3762/bjoc.20.240

• steps from indigo (1a). The reaction of 1a with potassium permanganate afforded product 12 which was transformed to dehydroindigo (13) by pyridine-mediated elimination of acetic acid. The reaction of 13 with tetra-O-trimethylsilyl-ʟ-rhamnopyranose (4b) in the presence of trimethylsilyl iodide, addition

Synthesis of tricarbonylated propargylamine and conversion to 2,5-disubstituted oxazole-4-carboxylates

• Kento Iwai,
• Akari Hikasa,
• Kotaro Yoshioka,
• Shinki Tani,
• Kazuto Umezu and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2024, 20, 2827–2833, doi:10.3762/bjoc.20.238

• ,O-acetal derived from diethyl mesoxalate (DEMO) undergoes elimination of acetic acid upon treatment with a base, leading to the formation of N-acylimine in situ. Lithium acetylide readily attacks the imino group to afford N,1,1-tricarbonylated propargylamines. When the resulting propargylamine

• anhydride, the intermediately formed hemiacetal underwent acetylation, leading to N,O-acetals 1. In this method, an acid amide can be used as an amine masked with an acyl group. Subsequent elimination of acetic acid occurred to afford 2 in situ upon treatment with a base, enabling nucleophilic addition with

• acid amides and acetylides, respectively. When adduct 4 was treated with a base or ammonium acetate, ring closure proceeded to form a five-membered ring, accompanied by the elimination of the ethoxycarbonyl group. 2,5-Disubstituted oxazole-4-carboxylic acid derivatives are frequently found in

Access to optically active tetrafluoroethylenated amines based on [1,3]-proton shift reaction

• Yuta Kabumoto,
• Eiichiro Yoshimoto,
• Bing Xiaohuan,
• Masato Morita,
• Motohiro Yasui,
• Shigeyuki Yamada and
• Tsutomu Konno

Beilstein J. Org. Chem. 2024, 20, 2776–2783, doi:10.3762/bjoc.20.233

• at room temperature for 24 h gave the corresponding [1,3]-proton shift adduct (S)-20b in 31% yield (Table 1, entry 1). In this case, the HF-elimination product 21b was also obtained in 16% [37], and the starting material was recovered in 53%. As shown in entries 2–7 of Table 1, the reactions in

• various solvents were next examined. When CH3CN or CH2Cl2 was used, 17% or 36% of the target product (S)-20b were obtained and almost no HF-elimination product 21b was formed, while about 40% of the azocine derivative 22b was afforded as a byproduct [38], along with the recovery of (R)-16b. In the case of

Synthesis of fluoroalkenes and fluoroenynes via cross-coupling reactions using novel multihalogenated vinyl ethers

• Yukiko Karuo,
• Keita Hirata,
• Atsushi Tarui,
• Kazuyuki Sato,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2024, 20, 2691–2703, doi:10.3762/bjoc.20.226

• and 11). We predicted that the product yield would decrease because 2k is labile in column chromatography. Utilizing a boronic acid bearing an n-butyl group as a primary alkyl group (4m), the cross-coupling did not proceed due to β-elimination (Table 3, entry 12). In contrast, the reaction with

A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis

• Nian Li,
• Ruzal Sitdikov,
• Ajit Prabhakar Kale,
• Joost Steverlynck,
• Bo Li and
• Magnus Rueping

Beilstein J. Org. Chem. 2024, 20, 2500–2566, doi:10.3762/bjoc.20.214

• generated tert-butyl peroxide to form an allylic peroxide, which ultimately transforms into an enone upon elimination of t-BuOH (Scheme 24). One year later, they developed an electrochemical transformation closely related to their electrochemical allylic oxidation, i.e. the oxidation of unactivated C(sp3)–H

• form a cyclic alkyl radical. The alkyl radical is further oxidized by [Co(III)] to produce the target amination product and a [Co(II)–H] species via direct hydrogen transfer or β-hydride elimination. Deprotonation of [Co(II)–H] by MeO− regenerates the [Co(I)] complex, which is subsequently oxidized

• carboxylate substrate and [Ru(p-cymene)Cl2]2. Subsequently, the Ru complex coordinates with the aniline substrate, followed by C–H activation to form a six-membered Ru species. The final product is generated through reductive elimination, releasing Ru(0), which is then reoxidized on the anode to regenerate

Visible-light-mediated flow protocol for Achmatowicz rearrangement

• Joachyutharayalu Oja,
• Sanjeev Kumar and
• Srihari Pabbaraja

Beilstein J. Org. Chem. 2024, 20, 2493–2499, doi:10.3762/bjoc.20.213

• towards investigating for the selective elimination of the waste solvent using an integrated one-flow work-up procedure to generate 3a with maximum practicality. Initially, the individual stages of the liquid–liquid extraction was achieved using the droplet micro fluidic method for extracting the compound

• OH). The Achmatowicz product is formed by addition of water to oxocarbenium intermediate A followed by elimination of L. Conclusion In conclusion, an integrated continuous PFR platform for photocatalytic functionalization of furfuryl alcohols to dihydropyranones through an Achmatowicz rearrangement

Phenylseleno trifluoromethoxylation of alkenes

• Clément Delobel,
• Armen Panossian,
• Gilles Hanquet,
• Frédéric R. Leroux,
• Fabien Toulgoat and
• Thierry Billard

Beilstein J. Org. Chem. 2024, 20, 2434–2441, doi:10.3762/bjoc.20.207

• finally be reopened by trifluoroacetate (Scheme 3). Although the selenylated compounds 2 are of interest, the presence of the PhSe moiety allows other transformations to be considered. First, the oxidative elimination of the selenyl moiety to generate a double bond was first studied. However, regardless

Facile preparation of fluorine-containing 2,3-epoxypropanoates and their epoxy ring-opening reactions with various nucleophiles

• Yutaro Miyashita,
• Sae Someya,
• Tomoko Kawasaki-Takasuka,
• Tomohiro Agou and
• Takashi Yamazaki

Beilstein J. Org. Chem. 2024, 20, 2421–2433, doi:10.3762/bjoc.20.206

• carried out for the verification of the intermediate leading to the product 11. Although we initially assumed that the epoxy ring opening occurred by hydride generated through the β-elimination of the n-C10H21MgBr-based cuprate species, the TLC analysis of the reaction mixture did not show any evidence of

• of the reductive elimination very slow, the intermediary Cu(III) species safely existed until the addition of D2O. Because the significant overlap of NMR peaks was observed due to the quite similar structure of 11a and 11a-D, quantitative analysis of the deuterium content of 11a-D was not possible