Formaldehyde surrogates in multicomponent reactions

• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Bernhard Westermann

Beilstein J. Org. Chem. 2025, 21, 564–595, doi:10.3762/bjoc.21.45

• this context, quinoline and its derivatives are privileged structures in several natural products and biologically active compounds, rendering this scaffold an important synthetic target. An attractive strategy to afford tetrahydroquinolines and quinolines is the Povarov reaction, a type of aza-Diels

• remarkable example, when formaldehyde was used, the reaction did not provide the desired quinoline 6 as the main product but rather julolidines 7 (Scheme 7) [31]. However, the use of paraformaldehyde and glycine can produce the desired products with low yields, but very expensive catalysts and complex

• compound and MMS, undergoes an aza-Diels–Alder cyclization with the alkyne, and after oxidation and aromatization steps generates quinoline II. Unfortunately, under these gentle and greener conditions, aliphatic alkynes remain unreacted, compared to the metal-catalyzed version developed by Xu et al. [37

Heteroannulations of cyanoacetamide-based MCR scaffolds utilizing formamide

• Marios Zingiridis,
• Danae Papachristodoulou,
• Despoina Menegaki,
• Konstantinos G. Froudas and
• Constantinos G. Neochoritis

Beilstein J. Org. Chem. 2025, 21, 217–225, doi:10.3762/bjoc.21.13

• reaction of 2 with formamide was performed within only 3 h (Scheme 3), yielding the N-substituted thienopyrimidones 5a–e in 30–99% total yield (2 steps), as well with aliphatic and (hetero)aromatic substituents. Quinoline derivatives are prevalent in nature, and many exhibit a range of biological

• obtained 15 diversely substituted heteroannulated pyrimidones, employing privileged thiophene, quinoline and indole scaffolds in a rapid fashion, without the need of column chromatography, in a parallel setup. Heteroannulated pyrimidones in drug discovery: blockbuster drugs that are based on the privileged

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

• motifs such as a benzofuran, indazole, and quinoline were also shown to undergo the desired Markovnikov amidation with high efficiency (23j–l). Several mechanistic experiments were performed to rationalize the reaction pathways. As shown in Figure 7, copper hydride, generated from a copper precatalyst

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

• , Huang, and Mei et al. explored Cu-catalyzed electrochemical C(sp2)–H bromination of 8-aminoquinoline amide at the C5 site of quinoline using NH4Br as a brominating reagent under anoxic oxidation conditions (Figure 13) [64]. This catalytic reaction has a broad substrate scope, and further investigation

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 coupling with copper triflate as catalyst, without ligand, co-catalyst or other additives. The reaction involved the formation of the imine XVII followed by alkynylation to propargylamine XVIII, cyclization, and oxidation to quinoline 23 (Scheme 17) [34]. Three component oxidative annulation to

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

• reacted with aminoarylaldehydes 5 to form axially chiral 2-arylquinoline derivatives 6 (Scheme 2). Using the pyrrolidine derivative C2 as the most efficient organocatalyst, a range of quinoline derivatives were obtained in high yields and enantiomeric purities. The postulated mechanism consists of iminium

• thiourea organocatalyst was prepared. Hou et al. investigated a way to prepare axially chiral compounds that contain both benzimidazole and quinoline rings 189 (Scheme 55) [83]. One route to access such compounds was possible through the reaction of 2-alkynylbenzimidazoles 187 with o-aminophenylketones 188

Intramolecular C–H arylation of pyridine derivatives with a palladium catalyst for the synthesis of multiply fused heteroaromatic compounds

• Yuki Nakanishi,
• Shoichi Sugita,
• Kentaro Okano and
• Atsunori Mori

Beilstein J. Org. Chem. 2024, 20, 3256–3262, doi:10.3762/bjoc.20.269

• reaction of the corresponding heteroaromatic carboxylic acids with thionyl chloride followed by treatment with N-octyl-2-bromoaniline [15]. The reactions proceeded smoothly affording products 1a–c in good yields as shown in Scheme 1. We then studied the reaction of quinoline amide 1a under several

Non-covalent organocatalyzed enantioselective cyclization reactions of α,β-unsaturated imines

• Sergio Torres-Oya and
• Mercedes Zurro

Beilstein J. Org. Chem. 2024, 20, 3221–3255, doi:10.3762/bjoc.20.268

• quinuclidine moiety can act as a base activating a nucleophile, secondly the secondary hydroxy group can participate in hydrogen bonding or can behave as a Brønsted acid (Figure 5). Additionally, the quinoline moiety can interact through π–π stacking with the reactants. On the other hand, the (DHQD)2-based

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

• position of quinoline N-oxides and pyridine N-oxides, utilizing hypervalent iodine salts as the arylation reagents. The reaction was facilitated by visible light in conjunction with a photocatalyst. The absence of either the photocatalyst or light resulted in only trace amounts of the product, underscoring

• their essential roles in product formation. Optimized conditions comprised the reaction of the quinoline N-oxides 25 (1 equiv) with diaryliodonium tetrafluoroborates 26 (2 equiv) as the arylating agent, 1,4-benzoquinone (BQ) as an additive (2 equiv), the photocatalyst eosin Y (10 mol %), and Cs2CO3 (1

• state, eosin Y*. This excited state further undergoes oxidation via a single-electron-transfer (SET) reaction with Ar2IBF4 26, producing eosin Y+ and a phenyl radical 30 (Scheme 10). The radical intermediate 30 selectively binds to the C2 position of either quinoline or pyridine N-oxide, forming

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

• late-stage functionalizations. In 2020, Ackermann and coworkers reported the challenging C–H alkoxylation of (hetero)arenes with sterically encumbered secondary alcohols via a nickel electrocatalyzed protocol [49]. A traceless removable quinoline amide in the meta position was employed as a directing

Stereoselective mechanochemical synthesis of thiomalonate Michael adducts via iminium catalysis by chiral primary amines

• Michał Błauciak,
• Dominika Andrzejczyk,
• Błażej Dziuk and
• Rafał Kowalczyk

Beilstein J. Org. Chem. 2024, 20, 2313–2322, doi:10.3762/bjoc.20.198

• stabilized by an intramolecular hydrogen bond with a protonated amine unit activates the Michael acceptor (Scheme 4). Moreover, a strong but reversible covalent bond locates the electrophile upon the quinoline unit of the catalyst and thus subsequently blocks the bottom approach of the thiomalonate. Hence

Efficacy of radical reactions of isocyanides with heteroatom radicals in organic synthesis

• Akiya Ogawa and
• Yuki Yamamoto

Beilstein J. Org. Chem. 2024, 20, 2114–2128, doi:10.3762/bjoc.20.182

• acid [58]. Rainier et al. reported the thiol-mediated 5-exo cyclization of o-alkynylaryl isocyanides, which successfully afforded dithiolated indoles 22 (Scheme 15) [59]. However, depending on the reaction conditions, quinoline derivatives were also produced as byproducts (vide infra). The photoinduced

• electrocyclization reaction, the aza-Bergmann cyclization, takes place, selectively yielding nitrogen-containing 6-membered cyclization products (Scheme 19) [67]. The aza-Bergmann cyclization of ortho-alkynyl isocyanides proceeds under milder conditions than the Bergmann cyclization of endiynes, forming quinoline

• -2,4-biradical intermediates. When diselenide, ditelluride, and diiodide are used as radical mediators, seleno, telluro, and iodo groups are introduced at the 2,4-positions of the quinoline, respectively [68][69][70]. On the other hand, in the case of germyl hydride, hydrosilane (TTMSS), selenol, and

Harnessing the versatility of hydrazones through electrosynthetic oxidative transformations

• Aurélie Claraz

Beilstein J. Org. Chem. 2024, 20, 1988–2004, doi:10.3762/bjoc.20.175

• synthesis of pyrazolo[4,3-c]quinoline derivatives 22 from 7-chloro-4-hydrazinoquinolines 20 and aromatic aldehydes 21 (Scheme 5) [40]. In 1992, Chiba and Okimoto reported the electrooxidative cyclization of aldehyde and ketone-derived N-acylhydrazones 23a and 23b to build 1,3,4-oxadiazoles 24a and Δ3-l,3,4

• engaged aromatic aldehyde-derived NH-tosylhydrazones 83 in an iodide-catalyzed electrochemical formal (3 + 2)-cycloaddition with quinolines 84 to build [1,2,4]triazolo[4,3-a]quinoline derivatives 85. Better yields were obtained with hydrazones bearing an electron-rich substituent on the aromatic ring. The

• reaction initiated with anodic formation of iodine. The latter would react with hydrazone 83 to form the zwitterionic species 86 under basic conditions. Subsequent formal (3 + 2)-cycloaddition with the quinoline 84 formed fused system 87 which underwent elimination of iodide and sulfinic acid to furnish

A facile three-component route to powerful 5-aryldeazaalloxazine photocatalysts

• Ivana Weisheitelová,
• Radek Cibulka,
• Marek Sikorski and
• Tetiana Pavlovska

Beilstein J. Org. Chem. 2024, 20, 1831–1838, doi:10.3762/bjoc.20.161

• purification. Thus, it significantly improves existing approaches. Keywords: catalysis; deazaalloxazine; flavin; multicomponent approach; one-pot reaction; Introduction Heterocyclic compounds containing pyrimidine and quinoline motifs in their structure, both of natural and synthetic origin, find a wide set

• Discussion Regarding the synthesis of 5-aryldeazaalloxazines 2 (5-arylpyrimido[4,5-b]quinoline-2,4(1H,3H)-diones), the data in the literature are quite limited, and the known methodology describes the dehydrogenation of initially formed 5,10-dihydro analogues (5-aryl-5,10-dihydropyrimido[4,5-b]quinoline-2,4

• , water), which has become a common method for the synthesis of these derivatives [3][22][25][30][31][32][33]. In our previous studies [14][15][16][17][18][19] we have shown that the 5-aryl and 7,8-substitutients of the pyrimido[4,5-b]quinoline core have a significant effect on the photocatalytic activity

Syntheses and medicinal chemistry of spiro heterocyclic steroids

• Laura L. Romero-Hernández,
• Ana Isabel Ahuja-Casarín,
• Penélope Merino-Montiel,
• Sara Montiel-Smith,
• José Luis Vega-Báez and
• Jesús Sandoval-Ramírez

Beilstein J. Org. Chem. 2024, 20, 1713–1745, doi:10.3762/bjoc.20.152

Electrocatalytic hydrogenation of cyanoarenes, nitroarenes, quinolines, and pyridines under mild conditions with a proton-exchange membrane reactor

• Koichi Mitsudo,
• Atsushi Osaki,
• Haruka Inoue,
• Eisuke Sato,
• Naoki Shida,
• Mahito Atobe and
• Seiji Suga

Beilstein J. Org. Chem. 2024, 20, 1560–1571, doi:10.3762/bjoc.20.139

• anilines were obtained. The quinoline reduction was efficiently promoted by adding a catalytic amount of p-toluenesulfonic acid (PTSA) or pyridinium p-toluenesulfonate (PPTS). Pyridine was also reduced to piperidine in the presence of PTSA. Keywords: cyanoarene; nitroarene; PEM reactor; pyridine

• ; quinoline; Introduction Nitrogen-containing molecules are important bioactive compounds and intermediates in chemical synthesis. Therefore, the chemical transformations of nitrogen-containing compounds have been widely studied in the field of organic synthesis [1][2][3][4]. For instance, the reduction of

• more π-extended aniline was easily obtained in a high yield. Reduction of quinolines to tetrahydroquinolines The electrochemical reduction of quinolines was performed using a PEM reactor. First, several different cathode catalyst were examined for the reduction of quinoline (6a) (Table 5). Because 4.0

Benzylic C(sp³)–H fluorination

• Alexander P. Atkins,
• Alice C. Dean and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 1527–1547, doi:10.3762/bjoc.20.137

• with nucleophilic fluoride sources too (Figure 30) [77]. This process involved an initial quinoline-directed C–H activation by Pd(II), followed by oxidation to generate a Pd(IV)–fluoride complex capable of C–F reductive elimination to generate the primary benzyl fluoride. Under this protocol, eleven 8

Synthesis and optical properties of bis- and tris-alkynyl-2-trifluoromethylquinolines

• Stefan Jopp,
• Franziska Spruner von Mertz,
• Peter Ehlers,
• Alexander Villinger and
• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 1246–1255, doi:10.3762/bjoc.20.107

• steady state absorption and fluorescence spectroscopy which give insights of the influence of the substitution pattern and of the type of substituents on the optical properties. Keywords: alkynes; catalysis; fluorescence; heterocycles; palladium; Introduction Quinoline is a well-known core structure

• which can be found in several natural and synthetic products and many of them show interesting pharmacological properties [1][2][3]. Quinine, for example, is a widely known natural product which was first isolated from the cinchona tree besides many other quinoline-containing cinchona alkaloids [4]. It

• is applied as antimalarial agent and furthermore as a bitter flavour component. Mefloquin [5] and ciprofloxacin [6], on the other hand, are synthetic compounds containing a fluorinated quinoline and quinolone core structure and are used as antimalarial and antibacterial agents, respectively (Figure 1

Manganese-catalyzed C–C and C–N bond formation with alcohols via borrowing hydrogen or hydrogen auto-transfer

• Mohd Farhan Ansari,
• Atul Kumar Maurya,
• Abhishek Kumar and
• Saravanakumar Elangovan

Beilstein J. Org. Chem. 2024, 20, 1111–1166, doi:10.3762/bjoc.20.98

• conditions were followed for the methylation of several ketones with methanol, which gave yields of up to 99% (Scheme 40). Very recently, a quinoline-based manganese catalyst was studied by Chakraborty and co-workers for the alkylation of methyl aryl ketones with alcohols (Scheme 41) [70]. Several methyl

• in methanol at 110 °C for 24 h under a N2 atmosphere, giving the desired products with 60 to 99% yields (Scheme 64). In 2023, Elias et al. reported that an air-stable, phosphine-free manganese complex generated from 8-quinoline could α-alkylate 2-oxindole with primary and secondary alcohols [92

• that the metal–ligand cooperation plays a crucial role in the acceptorless dehydrogenation of ethylene glycol to glycolaldehyde and the HA process. In 2018, Maji’s group reported the Friedländer quinoline synthesis using a phosphine-free manganese catalyst generated in situ from Mn(CO)5Br and L3 [58

Carbonylative synthesis and functionalization of indoles

• Alex De Salvo,
• Raffaella Mancuso and
• Xiao-Feng Wu

Beilstein J. Org. Chem. 2024, 20, 973–1000, doi:10.3762/bjoc.20.87

• substrate. In the second case the reaction was catalyzed under the same conditions except for changing the solvent to iPrOH and the catalyst to [Pd(tfa)2L] (Scheme 5). Furthermore, Gabriele and co-workers developed the oxidative carbonylation of 1-(2-aminoaryl)-2-yn-1-ols to quinoline-3-carboxylic esters

(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

• microsomes (CLint) improved significantly. The increase in solubility is particularly marked at low pH. A related observation was made by Poole and co-workers for quinoline-substituted 1,2,3-BCPs, where larger increases in the lipophilicity of the bioisosteric compound were also found at low pH [68]. One

HPW-Catalyzed environmentally benign approach to imidazo[1,2-a]pyridines

• Luan A. Martinho and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2024, 20, 628–637, doi:10.3762/bjoc.20.55

• ], pyrazolo-fused benzophenazines [45], 4,5-dioxopyrrolidines [46], 1,2-dihydropyridine (1,2-DHPs) [47], pyrimido[4,5-b]quinoline-tetraones [48], tetrahydrobenzo[b]pyrans and indazolo[2,1-b]phthalazinetriones [49]. Herein, we report the synthesis of imidazo[1,2-a]pyridines via the GBB-3CR using HPW as

Chemical and biosynthetic potential of Penicillium shentong XL-F41

• Ran Zou,
• Xin Li,
• Xiaochen Chen,
• Yue-Wei Guo and
• Baofu Xu

Beilstein J. Org. Chem. 2024, 20, 597–606, doi:10.3762/bjoc.20.52

• reports on the biosynthetic pathways from tryptophan to quinoline rings. Through our analysis, we discovered that tryptophan in the primary metabolic pathway is primarily catalyzed by indoleamine 2,3-dioxygenase and tryptophan 2,3-dioxygenase (IDO and TDO), as well as canine urinary tryptophan 3

• -monooxygenase, to form quinoline rings [26]. Quinine is frequently cited as one of the primary forms of quinoline rings in secondary metabolic pathways. Francesco Trenti et al. [27] studied some of the biosynthesis processes of quinine, in which enzymes involved are much more complex than primary metabolism

• 1 and those previously reported. This suggests that the formation of the quinoline ring in compound 1 may represent a new and unreported biosynthetic pathway. Moreover, to address the low yields that hindered the determination of absolute stereochemistry, we attempted to boost the production of

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

• ). Additionally, Minisci-type additions were carried out in the presence of protonated quinoline radical acceptor 83, affording product 84 (Scheme 16A). Mechanistically, this activation mode involves an intra-complex SET that forms the Ph3P–NaI radical cation species 85 and the corresponding radical anion 86

• ] (Scheme 33A). The mechanism of this redox neutral reaction involves reductive fragmentation of the radical precursor 3 mediated by the cathode under constant-current electrolysis (Scheme 33B). The resulting alkyl radical 9 attacks the protonated quinoline 168, forming radical cation intermediate 169

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

• bronze in refluxing quinoline, thus triggering a S-extrusion along with a decarboxylation reaction (Scheme 3) [56]. From a retrosynthetic point of view, this example nicely illustrates the fact that polyannelated thiepines, and more generally S-, Se- and Te-based heteropines, are straightforward