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

• (CuCl2, NaNO2, TEMPO) using molecular oxygen as a terminal oxidant have also been used [12]. Nevertheless, neither of these conditions was successful when they were applied to methanol to generate formaldehyde, because overoxidation is an important side reaction in these cases [12][13][14][15]. However

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

• % CuCl2 catalyst was required, and anodic oxidation was employed instead of stoichiometric chemical oxidants. This cascade strategy is compatible with various substituted N-arylenamines 57 that bear electron-withdrawing and electron-donating groups, facilitating the production of quinoxaline scaffolds 59

Facile one-pot reduction of β-nitrostyrenes to phenethylamines using sodium borohydride and copper(II) chloride

• Laura D’Andrea and
• Simon Jademyr

Beilstein J. Org. Chem. 2025, 21, 39–46, doi:10.3762/bjoc.21.4

• Aalborg, Denmark current address: Centre for Analysis and Synthesis, Lund University, Naturvetarvägen 14, 223 62 Lund, Sweden 10.3762/bjoc.21.4 Abstract Phenethylamines and phenylisopropylamines of scientific relevance can be prepared with a NaBH4/CuCl2 system in 10 to 30 minutes via reduction of

• substituted β-nitrostyrenes. This one-pot procedure allows the quick isolation of substituted β-nitrostyrene scaffolds with 62–83% yield under mild conditions, without the need for special precautions, inert atmosphere, and time-consuming purification techniques. Keywords: 2C-X; CuCl2; NaBH4; β-nitrostyrene

• NaBH4/CuCl2 system effectively facilitates this transformation and provide an account of its application to the β-nitrostyrene examples presented in Figure 1. Result and Discussion Herein, we demonstrate that NaBH4, in combination with catalytic amounts of CuCl2, is a simple and higher yielding method

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

• trione 1 in hands, we explored the Scholl reaction and thionation reaction of it (Scheme 1b) because these reactions can potentially allow π-expansion of 1. A variety of Scholl reaction conditions, such as AlCl3/NaCl, AlCl3/CuCl2, FeCl3, and DDQ/TfOH, were tested. However, these reactions either left the

Advances in the use of metal-free tetrapyrrolic macrocycles as catalysts

• Mandeep K. Chahal

Beilstein J. Org. Chem. 2024, 20, 3085–3112, doi:10.3762/bjoc.20.257

• -catalyzed aziridination of styrene (22) by chloramine-T (23, NaCl=NTs) as a source of nitrene in acetonitrile (Figure 5) [40]. No aziridine product was formed either without any source of copper or in the presence of a different copper salt, such as CuCl, CuCl2·2H2O, or CuOTf. Calix[4]pyrrole itself is

Challenge N- versus O-six-membered annulation: FeCl₃-catalyzed synthesis of heterocyclic N,O-aminals

• Giacomo Mari,
• Lucia De Crescentini,
• Gianfranco Favi,
• Fabio Mantellini,
• Diego Olivieri and
• Stefania Santeusanio

Beilstein J. Org. Chem. 2024, 20, 1412–1420, doi:10.3762/bjoc.20.123

• goal, different Lewis acids (10 mol %) such as Zn(OTf)2, CuCl2, and FeCl3 were screened at room temperature in different solvents, employing compound 4a as the model substrate (Table 1). From the set of data collected, both the formation of N,O-aminal 5a and corresponding hemiaminal 6a were observed

Advancements in hydrochlorination of alkenes

• Daniel S. Müller

Beilstein J. Org. Chem. 2024, 20, 787–814, doi:10.3762/bjoc.20.72

• leading to anti-Markovnikov products via several pathways. We have chosen not to present a fourth class of reactions involving either HCl gas or CuCl2 and a Pd catalyst, as reported by Alper [20] and Sigman [21], as these reactions are somewhat exotic and are sufficiently discussed in Yang’s review [14

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

• subsequently dissolved in methanol with CuCl2, yielding the desired Cu–isatin Schiff base complex. The optimum reaction conditions between benzaldehyde and indole were obtained at a nanocatalyst loading of only 0.25 mol % after 2 hours of heating at 80 °C with water as the medium. In the absence of the Cu

Copper-promoted C5-selective bromination of 8-aminoquinoline amides with alkyl bromides

• Changdong Shao,
• Chen Ma,
• Li Li,
• Jingyi Liu,
• Yanan Shen,
• Chen Chen,
• Qionglin Yang,
• Tianyi Xu,
• Zhengsong Hu,
• Yuhe Kan and
• Tingting Zhang

Beilstein J. Org. Chem. 2024, 20, 155–161, doi:10.3762/bjoc.20.14

• quinoline ring of 1a in this reaction. Other competitive site-selective C–H bromination products and multiple brominated products were not observed. Subsequently, the bromination reaction was examined with various catalysts such as CoCl2·6H2O, Ni(OAc)2·4H2O, MnSO4·H2O, CuCl, CuBr, CuCl2, CuBr2, and Cu(OAc)2

Tying a knot between crown ethers and porphyrins

• Maksym Matviyishyn and
• Bartosz Szyszko

Beilstein J. Org. Chem. 2023, 19, 1630–1650, doi:10.3762/bjoc.19.120

• 1.70–2.50 ns. An apparent colour change was observed upon treatment of 42 with AgSbF6 and CuCl2, indicating radical cation formation 42•+. ESR spectra and coulometric oxidation experiments further supported the presence and stability of the radical species. The reactions of 38 with a pre-functionalized

• single crystal XRD. Compound 43 formed stable cation radicals upon adding different oxidising agents, such as AgSbF6, TFA, and CuCl2. The cation radicals showed relative stability and remained undeteriorated on air for over a week. The crowned porphyrinoids incorporating two pyrroloindole units 44 were

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• , CoCl2, NiCl2, MnCl2, FeCl2, Fe(acac)3 and copper salts such as Cu(OAc)2, CuBr2, CuBr, CuCl2, and CuCN·2LiCl were evaluated in this coupling reaction, in which Cu(OAc)2 showed highest product yields. Moreover, phthalimides with SCF3, SCN, and SePh groups also worked well in this approach. Because of the

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

• , K2CO3, or Cs2CO3) in the presence of copper chlorides (Scheme 11). However, this protocol required environmental unfriendly solvents such as 3-chloropyridine and high temperatures. In general, CuCl gave higher yields than CuCl2·2H2O typically ranging from 70 to 99% [24]. Furthermore, an IMes–CuCl

• respectively, incorporating NHC–Cu(I) bromide and Cu(II) phenoxymine coordination. These complexes could be independently prepared through transmetallation by reacting NHC–AgBr 74 with copper(II) precursors Cu(SO3CF3)2 or CuCl2·2H2O (Scheme 26) [32]. Oro and co-workers synthesized new NHC–CuX complexes 78a,b

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

• synthesis of compounds with quaternary centers and natural products with high structural complexity. In 2014, Li et al. reported a CuCl2-catalyzed cross-dehydrogenation coupling reaction of C(sp3)–H bonds adjacent to an ether oxygen and the C(sp3)–H bonds at the α-position of a carbonyl functionality in the

• terminal alkynyl aldehydes with ethers in the presence of CuCl2 and TBHP (Scheme 15b) [68]. The reaction is compatible with various functional groups including cyclic ethers and open chain ethers. Studies on the reaction mechanism showed that the reaction is a catalytic cycle involving a radical process

Copper-catalyzed N-arylation of amines with aryliodonium ylides in water

• Kasturi U. Nabar,
• Bhalchandra M. Bhanage and
• Sudam G. Dawande

Beilstein J. Org. Chem. 2023, 19, 1008–1014, doi:10.3762/bjoc.19.76

• , CuCl2, CuBr2, and CuSO4·5H2O (Table 1, entries 4–7) with maintaining the same reaction conditions. Among these salts, CuSO4·5H2O afforded a relatively higher yield of the product diphenylamine (3a, Table 1, entry 4). Inspired by this observation, we carried out the N-arylation of aniline (1a) with

Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• excellent yields. To obtain the best reaction conditions, various Lewis acid catalysts (e.g., FeCl3 CuCl2, InCl3, Cu(OTf)2, Mg(OTf)2, Zn(OTf)2, Yb(OTf)3, Y(OTf)3, Bi(OTf)3, La(OTf)3 and Sc(OTf)3), different solvents (e.g., CH2Cl2, CHCl3, CH3CN, CH3NO2, n-hexane, and dioxane), temperatures (90–110 °C), and

• , and simple operation in a more environmentally benign environment. Among various catalysts (CuO, CuSO4, Cu(OAc)2, CuF2, CuBr2, CuCl, CuI, Cu2O, CuCl2), solvents (THF, EtOAc, EtOH, CH2Cl2, CH3CN, H2O) and amount of catalyst loading (5, 10, 15 mol %) to optimize the reaction conditions, CuCl2 as the

• hydrolysis of 2,5-DMTHF (2), which provide intermediate C after the removal of methanol in the presence of CuCl2. In the next steps, nucleophilic addition reaction of amines 34 with intermediate C, dehydration, and intramolecular aromatization affords N-substituted pyrroles 35. In 2018, Patil and Kumar [70

Mechanochemical solid state synthesis of copper(I)/NHC complexes with K₃PO₄

• Ina Remy-Speckmann,
• Birte M. Zimmermann,
• Mahadeb Gorai,
• Martin Lerch and
• Johannes F. Teichert

Beilstein J. Org. Chem. 2023, 19, 440–447, doi:10.3762/bjoc.19.34

• protocol, complexes 7a–d were obtained with acceptable yields, with similar yields compared to previous methods. In some cases, the homoleptic cationic copper(I) complexes [(NHC)2Cu]+CuCl2− were observed as side products [48][53]. We decided to directly compare complex 5 from mechanochemical synthesis (5bm

Catalytic aza-Nazarov cyclization reactions to access α-methylene-γ-lactam heterocycles

• Bilge Banu Yagci,
• Selin Ezgi Donmez,
• Onur Şahin and
• Yunus Emre Türkmen

Beilstein J. Org. Chem. 2023, 19, 66–77, doi:10.3762/bjoc.19.6

• ester 36 with an n-propyl group at the β-position is that it does not have the volatility issues of the ethyl-substituted ester, and that it is sterically less hindered than the isobutyl-substituted ester. When a broad range of Lewis and Brønsted acids such as AgOTf, Zn(OTf)2, ZnBr2, CuCl2, BF3·OEt2

Synthesis of meso-pyrrole-substituted corroles by condensation of 1,9-diformyldipyrromethanes with pyrrole

• Baris Temelli and
• Pinar Kapci

Beilstein J. Org. Chem. 2022, 18, 1403–1409, doi:10.3762/bjoc.18.145

• positive effect on the reaction yield (Table 1, entries 14 and 15), p-chloranil formed a product with a lower yield than DDQ (Table 1, entries 16–18). The activities of different copper catalysts were also tested in the model reaction. Only CuCl2 formed the product in 5% yield and the other salts did not

Amamistatins isolated from Nocardia altamirensis

• Till Steinmetz,
• Wolf Hiller and
• Markus Nett

Beilstein J. Org. Chem. 2022, 18, 360–367, doi:10.3762/bjoc.18.40

• thiamin·HCl (1 mg/mL), 10 mL trace elements solution (0.05 g/L EDTA, 0.84 mg/L ZnCl2, 0.13 mg/L CuCl2×2H2O, 0.01 mg/L CoCl2×2H2O, 0.01 mg/L H3BO3, 0.0016 mg/L MnCl2×4H2O). The cultivation was conducted on a rotary shaker at 130 rpm and 30 °C for three weeks. Afterwards, adsorber resin (XAD-7, 20 g/L) was

1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis

• Ruan Carlos B. Ribeiro,
• Patricia G. Ferreira,
• Amanda de A. Borges,
• Luana da S. M. Forezi,
• Fernando de Carvalho da Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 53–69, doi:10.3762/bjoc.18.5

• the presence of CuCl2 formed two isomers of 4-arylated-N-butylbenzo[c]carbazole-5,6-dione 60 and 4-amino-benzo[a]carbazol-5,6-dione 61 in 39% and 13% yields, respectively. These two reactions demonstrate the importance of the catalyst in complex formation with carbonyls of 18 that promote nucleophilic

Exfoliated black phosphorous-mediated CuAAC chemistry for organic and macromolecular synthesis under white LED and near-IR irradiation

• Azra Kocaarslan,
• Zafer Eroglu,
• Önder Metin and
• Yusuf Yagci

Beilstein J. Org. Chem. 2021, 17, 2477–2487, doi:10.3762/bjoc.17.164

• ), CuCl2 (1 equiv) and PMDETA (1 equiv) were placed in a Schlenk tube. The tube was degassed by three freeze pump-thaw cycles. Then the tube was irradiated under NIR light for 48 h. After the given time, the mixture was diluted with THF and the copper complex was removed by passing through a neutral

A novel methodology for the efficient synthesis of 3-monohalooxindoles by acidolysis of 3-phosphate-substituted oxindoles with haloid acids

• Li Liu,
• Yue Li,
• Tiao Huang,
• Dulin Kong and
• Mingshu Wu

Beilstein J. Org. Chem. 2021, 17, 2321–2328, doi:10.3762/bjoc.17.150

• , AlCl3, Cu (CF3SO3)2, and CuCl2, on the reaction was also examined, but no significant improvement in the yield was found (Table 1, entries 17–21). Considering all of the reaction parameters, the optimal reaction conditions were chosen as shown in Table 1, entry 13. Once the optimization studies were

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• amines with cyanoguanidine in refluxing water in the presence of CuCl2. The pink copper complexes were then treated with hydrogen sulfide to release the desired compounds. As a representative example, N1-butylbiguanide (buformin) was obtained as a hydrochloride salt, with a 47% yield (Scheme 2). Other

Amino- and polyaminophthalazin-1(2H)-ones: synthesis, coordination properties, and biological activity

• Zbigniew Malinowski,
• Emilia Fornal,
• Agata Sumara,
• Renata Kontek,
• Karol Bukowski,
• Beata Pasternak,
• Dariusz Sroczyński,
• Joachim Kusz,
• Magdalena Małecka and
• Monika Nowak

Beilstein J. Org. Chem. 2021, 17, 558–568, doi:10.3762/bjoc.17.50

• time intervals of 0 h, 1 h, and 24 h starting from mixing the solutions containing equimolar amounts of the ligand and CuCl2. Unexpectedly, compound 6d (L1) did not show any complexing properties. In all spectra a signal of the same ligand, despite long reaction times, was only observed (ESIMS

• compound 7 (L3) and CuCl2 showed the presence of two types of complexes containing one and two phthalazinone ligands: [(L3)Cu(II)Cl]+ and [(L3)2Cu2(II)Cl3]+. The most abundant peak at m/z = 422.3 Da corresponded to the complex [(L3)Cu(II)Cl]+. The MS/MS fragmentation of the ions at m/z = 422.3 Da for 63Cu

4-Hydroxy-3-methyl-2(1H)-quinolone, originally discovered from a Brassicaceae plant, produced by a soil bacterium of the genus Burkholderia sp.: determination of a preferred tautomer and antioxidant activity

• Dandan Li,
• Naoya Oku,
• Yukiko Shinozaki,
• Yoichi Kurokawa and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 1489–1494, doi:10.3762/bjoc.16.124

• without test compounds were mixed in 50 mM boric acid/sodium hydroxide buffer (pH 9.0). To this mixture was added CuCl2 (100 μM) to initiate the Fenton reaction, and after 5 min of incubation, the chemiluminescence at 500 nm was recorded on a microplate reader. The experiments were run in triplicate, and