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

• standard Cu-catalyzed electrochemical protocol. Based on mechanistic studies, the proposed mechanism is shown in Figure 9. First, hydroquinone 34 is oxidized at the anode to generate a quinone intermediate 38. Meanwhile, the chiral copper catalyst reacts with the Schiff base 33, generating a nucleophilic

• sterically hindered hydroquinone promotes 1,4-addition, resulting in the formation of an α-arylated intermediate 40, and different products are generated depending on the substituents on the Schiff base. For example, a methyl-substituted Schiff base provided a chiral quinone 35 after 1,4-addition and

• electrochemical oxidation. In contrast, the naphthyl-substituted Schiff base generated the corresponding enantioenriched product 36 through 1,4-addition followed by intramolecular annulation. When 2,6-disubstituted hydroquinone was used as the starting material, 1,6-addition occurred due to steric hindrance

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

• -methylthiazole-2-carboxaldehyde as chelating agent, in the presence of copper triflate and the chiral diamine ligand 28. The stereoselectivity was directed by the formation of a proposed catalyst complex 29 involving two molecules of Schiff base (Scheme 22) [39]. The three-component annulation of aldehydes

The Groebke–Blackburn–Bienaymé reaction in its maturity: innovation and improvements since its 21st birthday (2019–2023)

• Cristina Martini,
• Muhammad Idham Darussalam Mardjan and
• Andrea Basso

Beilstein J. Org. Chem. 2024, 20, 1839–1879, doi:10.3762/bjoc.20.162

Ugi bisamides based on pyrrolyl-β-chlorovinylaldehyde and their unusual transformations

• Alexander V. Tsygankov,
• Vladyslav O. Vereshchak,
• Tetiana O. Savluk,
• Serhiy M. Desenko,
• Valeriia V. Ananieva,
• Oleksandr V. Buravov,
• Yana I. Sakhno,
• Svitlana V. Shishkina and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2024, 20, 1773–1784, doi:10.3762/bjoc.20.156

• -4CR proceeds through the formation of an azomethine (Schiff base) in the first stage [39][40]. Therefore, considering the results of our previous work [39] on the nature and properties of azomethines based on β-chlorovinylaldehyde 1 (Figure 1), we decided to study the possibility of using the three

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

• a condensation reaction with benzaldehyde to yield the Schiff base 1’-benzylidine-4’-(cholest-5-ene-3-yl)thiosemicarbazone (81) in 77% yield. Subsequently, the resulting product was subjected to a reaction with thioglycolic acid in dioxane, affording intermediate 82 in 70% yield. Upon treatment of

Towards an asymmetric β-selective addition of azlactones to allenoates

• Behzad Nasiri,
• Ghaffar Pasdar,
• Paul Zebrowski,
• Katharina Röser,
• David Naderer and
• Mario Waser

Beilstein J. Org. Chem. 2024, 20, 1504–1509, doi:10.3762/bjoc.20.134

• thus wondering if we could extend this ammonium salt-catalyzed β-selective allenoate functionalization strategy to other amino acid classes. Azlactones 1 have previously been used for γ-selective additions to allenoates under chiral phosphine catalysis [28]. In addition, glycine Schiff base derivatives

Synthesis of 2-benzyl N-substituted anilines via imine condensation–isoaromatization of (E)-2-arylidene-3-cyclohexenones and primary amines

• Lu Li,
• Na Li,
• Xiao-Tian Mo,
• Ming-Wei Yuan,
• Lin Jiang and
• Ming-Long Yuan

Beilstein J. Org. Chem. 2024, 20, 1468–1475, doi:10.3762/bjoc.20.130

• -substituent as compared to their ortho- or meta-substituted counterparts. It might be explained by the less obvious steric resistance of the former in the process of Schiff base formation. In addition, an alkylidenyl-equipped 3-cyclohexanone was found to be incompatible with the current reaction system, only

Competing electrophilic substitution and oxidative polymerization of arylamines with selenium dioxide

• Vishnu Selladurai and
• Selvakumar Karuthapandi

Beilstein J. Org. Chem. 2024, 20, 1221–1235, doi:10.3762/bjoc.20.105

• into acetanilide using acetonitrile as acetylating agent. The resulting acetanilide underwent α-CH oxidation with SeO2 to give 2-oxo-N-phenylacetamide, which undergoes Schiff base formation with aniline. The resulting Schiff base undergoes further α-CH oxidation with SeO2 to give the oxamide 3. A

A laterally-fused N-heterocyclic carbene framework from polysubstituted aminoimidazo[5,1-b]oxazol-6-ium salts

• Andrew D. Gillie,
• Matthew G. Wakeling,
• Bethan L. Greene,
• Louise Male and
• Paul W. Davies

Beilstein J. Org. Chem. 2024, 20, 621–627, doi:10.3762/bjoc.20.54

• ][26][27]. The unique Schiff base 6 can however be stored without precautions for several months without degradation and is prepared with minimal processing in 75% yield by telescoping the annulation and condensation steps. As the 4-aminooxazole motif appeared to be a poor nucleophile, we sought to

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

• combatted some disadvantages of the use of iron oxides, the catalytic approach presented had handicaps that held back its broader applications [108]. In 2016, Sobhani et al. expanded on the use of iron oxide as an effective magnetic nanoparticle by creating a Cu–isatin Schiff base complex supported on nano

• -iron oxide compounds for the synthesis of BIMs [109][110]. These compounds were synthesized through the reaction between the amino-functionalized modified magnetic nanoparticles (MNPs), which were obtained by a sol–gel methodology, and isatin, producing isatin Schiff base-γ-Fe2O3, which was

• 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

Facile approach to N,O,S-heteropentacycles via condensation of sterically crowded 3H-phenoxazin-3-one with ortho-substituted anilines

• Eugeny Ivakhnenko,
• Vasily Malay,
• Pavel Knyazev,
• Nikita Merezhko,
• Nadezhda Makarova,
• Oleg Demidov,
• Gennady Borodkin,
• Andrey Starikov and
• Vladimir Minkin

Beilstein J. Org. Chem. 2024, 20, 336–345, doi:10.3762/bjoc.20.34

• ][12]. At the first stage, this reaction follows one of three possible reaction pathways, including Schiff base formation (attack at the C(3) center), Michael addition at C(1), or nucleophilic substitution (SNH) at the C(2) center [13][14][15]. Most readily used is the pathway involving carbonyl–amine

• condensation and Schiff base formation, which is then cyclized [12][16]. The reaction of 1 with arylamines 2a is performed in toluene solution in the presence of a catalytic amount of p-toluenesulfonic acid. This readily affords 6,8-di-tert-butyl-N-aryl-3H-phenoxazin-3-imines 3 but proceeds smoothly only with

• fragment gave rise to the appearance of an additional long-wavelength absorption band with λmax = 520 nm and ε = 9200 M−1⋅сm−1. Subjecting o-phenylenediamines 2с to the reaction with 3H-phenoxazin-3-one makes the simultaneous activation of two principle reaction pathways (SNH and Schiff base formation

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

• ]. The field remained practically unexplored until 2005 when the Love group reported Schiff-base calixpyrrole macrocycles introducing crown ether segments [66][67]. The hybrid systems were demonstrated to form a plethora of coordination compounds with transition metals. In 2019 Ravikanth developed

• hybrids, such as crownphyrins and Schiff-base calixpyrroles, has been discussed, providing some new directions in the field. The continued development of hybrid systems is anticipated to provide exciting opportunities for further explorations and bring many intriguing molecular systems with fascinating

pH-Responsive fluorescent supramolecular nanoparticles based on tetraphenylethylene-labelled chitosan and a six-fold carboxylated tribenzotriquinacene

• Nan Yang,
• Yi-Yan Zhu,
• Wei-Xiu Lin,
• Yi-Long Lu and
• Wen-Rong Xu

Beilstein J. Org. Chem. 2023, 19, 635–645, doi:10.3762/bjoc.19.45

• the mixture was heated at 70 °C with stirring for 6–10 h. The resulting mixture was then allowed to stand overnight, and the solvent was removed under reduced pressure to obtain the crude Schiff base as a pale-yellow solid. Without further purification, the Schiff base was dispersed in methanol (60 mL

A new oxidatively stable ligand for the chiral functionalization of amino acids in Ni(II)–Schiff base complexes

• Alena V. Dmitrieva,
• Oleg A. Levitskiy,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2023, 19, 566–574, doi:10.3762/bjoc.19.41

• )-1-benzylpyrrolidine-2-carboxamide) and its Ni(II)–Schiff base complexes formed of glycine, serine, and dehydroalanine are reported. A bulky tert-butyl substituent in the phenylene fragment precludes unwanted oxidative dimerization of the Schiff base complex, making it suitable for targeted

• complex. Solubility of the t-Bu-containing ligand and its Schiff base complexes is increased, facilitating scaling-up the reaction procedure and isolation of the functionalized amino acid. Keywords: asymmetric synthesis; chiral auxiliaries; cysteine derivatives; Ni–Schiff base complexes; voltammetry

• )) and includes a chiral auxiliary, an amino acid, and a bifunctional linker capable to arrange the components in the Schiff base complex. Such templates provide a significant C–H acidity at the α-amino acid carbon and a possibility for recycling of the chiral auxiliaries (for reviews see [5][14][15][16

Cyclodextrin-based Schiff base pro-fragrances: Synthesis and release studies

• Attila Palágyi,
• Jindřich Jindřich,
• Juraj Dian and
• Sophie Fourmentin

Beilstein J. Org. Chem. 2022, 18, 1346–1354, doi:10.3762/bjoc.18.140

• ; imine; kinetics; pro-fragrance; Schiff base; Introduction The fragrance and flavor industry is one of the most intensively developing sectors of the chemical industry. Encapsulation techniques are widely used in both food and cosmetic industries to control the delivery of the encapsulated guest

• (hydrogen of the imine group of Schiff base) were compared to the integral of the signal belonging to the same proton of the starting compound 3d measured in DMSO-d6 (without a buffer) used as a blank. We note that the experiment was conducted in a closed system with a 50% content of DMSO-d6 to enable

• intervals were 2 h to several days for up to 3 months (for basic pH). The integrals of the signal at 8.30 ppm, corresponding to the hydrogen of the imine group of the non-hydrolyzed Schiff base, were compared to the integral of the signal corresponding to the same proton of the pro-fragrance measured in

Reductive opening of a cyclopropane ring in the Ni(II) coordination environment: a route to functionalized dehydroalanine and cysteine derivatives

• Oleg A. Levitskiy,
• Olga I. Aglamazova,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2022, 18, 1166–1176, doi:10.3762/bjoc.18.121

• ) coordination environment in the form of a Schiff base is considered as a route to electrochemical broadening of the donor–acceptor cyclopropane concept in combination with chirality induction in the targeted products. A tendency to the reductive ring-opening and the follow-up reaction paths of thus formed

• -activity and chirality provided by the Ni–Schiff base template, supported with the protection from redox-destruction of the amino acid skeleton, makes the suggested approach a convenient route to various types of non-proteinogenic amino acids [9][10][12][13]. Recently, several practical approaches to α,α

• -cyclopropanated amino acids in the form of Ni(II)–Schiff base complexes were suggested [16][17][18][19], including electrochemical ones [15]. Cyclopropane-containing amino acids are important components of various pharmaceuticals [20][21] and bio-additives [22]. Meanwhile, the cyclopropane fragment not only

Facile and diastereoselective arylation of the privileged 1,4-dihydroisoquinolin-3(2H)-one scaffold

• Dmitry Dar’in,
• Grigory Kantin,
• Alexander Bunev and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2022, 18, 1070–1078, doi:10.3762/bjoc.18.109

• cinnamaldehyde gave no desired product (11t–v). Quite surprisingly, the Schiff base derived from methyl o-formylbenzoate also gave no desired product while cyclization led to isobenzofuran-1(3H)-one 14 (Scheme 1). Having secured a supply of diversely substituted 3(2H)-isoquinolones 11a–s, we proceeded to

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

• ) complexes showing the best catalytic activities with high selectivity compared to the Pt(II) complex, leading to 95–99% conversion and 60–65% selectivity (Table 1, entry 12) [58]. Sönmez and co-workers applied mononuclear complexes of ruthenium(III), chromium(III), and iron(III) with Schiff base ligands as

Recent developments and trends in the iron- and cobalt-catalyzed Sonogashira reactions

• Surendran Amrutha,
• Sankaran Radhika and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 262–285, doi:10.3762/bjoc.18.31

• product of reductive elimination regenerates the catalyst. Javidi and co-workers reported a sequence of magnetically separable catalysts which consisted of Schiff base complexes of metal ions supported on superparamagnetic Fe3O4 nanoparticles (Scheme 16) [32]. To examine their catalytic activity, a

• Sonogashira coupling was carried out with these magnetic nanoparticles. The model substrates chosen were iodobenzenes and phenylacetylene that were reacted in the presence of 0.6 mol % of Fe3O4@SiO2/Schiff base complex of Fe(II) ions and 2 equivalents of K2CO3 in DMF at 110 °C for 4 h. The magnetically

• -substituted iodobenzenes catalyzed by in situ-generated α-Fe2O3 nanoparticles. One-pot synthesis of 2-arylbenzo[b]furans via tandem Sonogashira coupling–cyclization protocol. Suggested mechanism of the Fe(III) catalyzed coupling of o-iodophenol with acetylene derivatives. Fe3O4@SiO2/Schiff base/Fe(II

Anomeric 1,2,3-triazole-linked sialic acid derivatives show selective inhibition towards a bacterial neuraminidase over a trypanosome trans-sialidase

• Peterson de Andrade,
• Sanaz Ahmadipour and
• Robert A. Field

Beilstein J. Org. Chem. 2022, 18, 208–216, doi:10.3762/bjoc.18.24

• , it is known that PLP is a TcTS weak inhibitor [35][38] and its inhibition does not involve formation of a Schiff-base intermediate [38]. However, an allosteric modulation of neuraminidase activity has been attributed to a selective modification of murine respirovirus neuraminidase via specific PLP

Ready access to 7,8-dihydroindolo[2,3-d][1]benzazepine-6(5H)-one scaffold and analogues via early-stage Fischer ring-closure reaction

• Irina Kuznetcova,
• Felix Bacher,
• Daniel Vegh,
• Hsiang-Yu Chuang and
• Vladimir B. Arion

Beilstein J. Org. Chem. 2022, 18, 143–151, doi:10.3762/bjoc.18.15

• Schiff base reaction to give undesired 5-(2-nitrobenzyl)-2-phenyl-1,2-dihydro-3H-pyrazol-3-one [37]. Note that hypothetically two Fischer indole products could arise from this reaction, namely 1a and methyl 1-benzyl-2-(2-nitrobenzyl)-1H-indole-3-carboxylate, where the ester and nitroaryl moieties are

Study on the interactions between melamine-cored Schiff bases with cucurbit[n]urils of different sizes and its application in detecting silver ions

• Jun-Xian Gou,
• Yang Luo,
• Xi-Nan Yang,
• Wei Zhang,
• Ji-Hong Lu,
• Zhu Tao and
• Xin Xiao

Beilstein J. Org. Chem. 2021, 17, 2950–2958, doi:10.3762/bjoc.17.204

• host–guest interactions. Among them, Q[7]-TBT is selected as a UV detector for the detection of silver ions (Ag+). This work makes full use of the characteristics of each cucurbituril and melamine-cored Schiff base to construct a series of complexes and these are applied to metal detection. Keywords

• : cucurbiturils; melamine; Schiff base; silver ion; Introduction Schiff bases [1] are usually synthesized by the condensation of amines and active carbonyl compounds, endowing them both nitrogen and oxygen donor atoms [2][3][4][5]. Schiff bases are not only easy to coordinate with various transition metal ions

• electropositivity can be a perfect candidate for the study of outer-surface interaction of cucurbit[n]urils [21][22][23][24]. In this work, nitrogen-rich melamine is used as the center molecule to synthesize the Schiff base 2,4,6-tris(((4-(4-carboxybutyl)phenyl)methylene)amino)-1,3,5-triazine (TBT) through the

Photophysical, photostability, and ROS generation properties of new trifluoromethylated quinoline-phenol Schiff bases

• Inaiá O. Rocha,
• Yuri G. Kappenberg,
• Wilian C. Rosa,
• Clarissa P. Frizzo,
• Nilo Zanatta,
• Marcos A. P. Martins,
• Isadora Tisoco,
• Bernardo A. Iglesias and
• Helio G. Bonacorso

Beilstein J. Org. Chem. 2021, 17, 2799–2811, doi:10.3762/bjoc.17.191

• trifluoromethylated hybrid system comprising the Schiff base scaffolds from some 6-aminoquinolines and salicylaldehyde derivatives in order to analyze and evaluate their photophysical, photostability, and antioxidant properties for possible future applications in the pharmacological areas or materials sciences

• the respective 2-alkenylquinoline or to simultaneous reaction products from both moieties (6-amino and 2-methyl substituents). However, at the end of the reaction only the Schiff base 3aa could be isolated and the 2-alkenylquinoline derivative was not identified by GC or 1H NMR. In contrast to the

• the three solvents are depicted in Figure 3. The values of maximum molar absorption coefficients (in log ε) and wavelengths (nm) of all compounds are listed in Table 1. The absorption spectra of the studied Schiff base series presented electronic transitions in the 250–500 nm UV–vis region. In the

Cationic oligonucleotide derivatives and conjugates: A favorable approach for enhanced DNA and RNA targeting oligonucleotides

• Mathias B. Danielsen and
• Jesper Wengel

Beilstein J. Org. Chem. 2021, 17, 1828–1848, doi:10.3762/bjoc.17.125

• research. This has been explored utilizing the reactivity between primary amines and the aldehyde moiety of a 2’-O-(2-oxoethyl)uridine nucleotide, incorporated centrally in an 11-mer TFO, to form a Schiff base (monomers 41–45) [80]. All aminoalkylated moieties improved the triplex stability. Notably, a

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

• tandem reaction proceeds via formation of a Schiff-base 39 and subsequently 1,3-dipolar cycloaddition to produce the intermediate 42. Then, the intermediate 42 affords the final product 43 via an oxidative aromatization process in the presence of air or iodine (Scheme 15). To propose a precise mechanism