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

• compounds catalyzed by copper triflate under ultrasound irradiation allowed the one-pot formation of 1H-benzo[f]chromen-2-yl(phenyl)methanones (naphthopyranes) 37. The comparison with conventional method showed better yields and shorter reaction times. The suggested reaction mechanism showed the formation

Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

• addition to form the corresponding trispyrazole 35 (Scheme 10) [61]. Similarly, aromatic aldehydes furnish the corresponding bispyrazolylmethanes either under ultrasound irradiation in low-boiling solvents [62] or under Ag/TiO2 catalysis [63]. In addition to 1,3-dicarbonyl compounds, 1,3,5-tricarbonyl

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

• bonding with polar species [114]. The nanoparticle of choice was CuO, which had already displayed several varied catalytic applications, so the P4VPy–CuO nanoparticles were synthesized through an ultrasound irradiation protocol and tested in the reaction between p-chlorobenzaldehyde and indole. An amount

Synthesis of 5-arylidenerhodanines in L-proline-based deep eutectic solvent

• Stéphanie Hesse

Beilstein J. Org. Chem. 2023, 19, 1537–1544, doi:10.3762/bjoc.19.110

• reaction of benzofuranone and aldehydes in good to excellent yields in a few minutes under ultrasound irradiation. Results and Discussion As a part of our ongoing research in DES chemistry, we were mainly interested in the conditions reported by Detsi [20], and attempted to apply them for rhodanine

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

• amines 50 were reacted with 2,5-DMTHF (2) in 5 mol % Bi(NO3)3·5H2O in solvent-free conditions under ultrasound irradiation at room temperature. The main advantages of this procedure are its simple isolation process, excellent product yield without using expensive or sensitive solvents and reagents

First example of organocatalysis by cathodic N-heterocyclic carbene generation and accumulation using a divided electrochemical flow cell

• Daniele Rocco,
• Ana A. Folgueiras-Amador,
• Richard C. D. Brown and
• Marta Feroci

Beilstein J. Org. Chem. 2022, 18, 979–990, doi:10.3762/bjoc.18.98

• was added to the catholyte and the mixture was left under ultrasound irradiation for 30 minutes. The solvent was removed under reduced pressure and the residue was purified by column chromatography on silica gel. The first experiment (Table 1, entry 1) was carried out using stainless steel as cathode

• to the catholyte. The mixture was left under ultrasound irradiation for 30 minutes. The solvent was removed under reduced pressure and the residue was purified by column chromatography on silica gel (petroleum ether/ethyl acetate 7:3), affording the corresponding pure 1a as an off-white solid. 1

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

• ultrasound irradiation, obtaining quantitative yields when compared to the mechanical stirring procedure, thus demonstrating the best efficiency of the method [103]. In 2002, Arai and co-workers reported studies involving epoxidation reactions of menadione (10) using H2O2 as oxidant and a chiral salt derived

• a quantitative yield. Still about reduction reactions, Niemczyk and Van Arnum described a green methodology for reduction of menadione (10), during the pegylation of 14 to improving the solubility of the studied compounds [118]. The authors reduced 10 with sodium dithionite under ultrasound

• irradiation, generating the reduced adduct in 79% yield (Scheme 20). Depending on the type of solvent used, the yield may vary due to oxidation of the alcohol 14 back to 10 because of its low stability in solution. The pegylation strategy involved monomethoxypoly(ethyleneglycol)succinimide carbonate (mPEG-SC

Ultrasound-assisted Strecker synthesis of novel 2-(hetero)aryl-2-(arylamino)acetonitrile derivatives

• Emese Gal,
• Luiza Gaina,
• Hermina Petkes,
• Alexandra Pop,
• Castelia Cristea,
• Gabriel Barta,
• Dan Cristian Vodnar and
• Luminiţa Silaghi-Dumitrescu

Beilstein J. Org. Chem. 2020, 16, 2929–2936, doi:10.3762/bjoc.16.242

• heterocyclic compounds, the use of ultrasound irradiation became a powerful tool by proving to be superior in terms of reaction rates, yields, and the purity of the products as compared to traditional convective heating methods [2]. Sonochemical syntheses can be successfully performed in homogeneous media

• chemistry protocol capable of inducing a more efficient energy input. Indeed, the reaction rate was significantly increased by applying the new protocol modified by means of an indirect ultrasound irradiation technique and high yields of the α-(arylamino)acetonitrile products were obtained after 30 minutes

• the ultrasound irradiation technique as a greener chemical protocol affording significantly enhanced reaction rates and higher crystallite size of the products, thus increasing the energy efficiency of the Strecker synthesis. An initial screening of the mutagenic potential of the newly synthetized α

Natural dolomitic limestone-catalyzed synthesis of benzimidazoles, dihydropyrimidinones, and highly substituted pyridines under ultrasound irradiation

• Kumar Godugu,
• Venkata Divya Sri Yadala,
• Mohammad Khaja Mohinuddin Pinjari,
• Trivikram Reddy Gundala,
• Lakshmi Reddy Sanapareddy and
• Chinna Gangi Reddy Nallagondu

Beilstein J. Org. Chem. 2020, 16, 1881–1900, doi:10.3762/bjoc.16.156

• pyridines via C–N, C–C, and C–S bond formations in a mixture of ethanol and H2O under ultrasound irradiation. The catalyst is characterized by XRD, FTIR, Raman spectroscopy, SEM, and EDAX analysis. The main advantages of this methodology include the wide substrate scope, cleaner reaction profile, short

• : benzimidazoles; dihydropyrimidinones; highly substituted pyridines; natural dolomitic limestone; ultrasound irradiation; Introduction Nitrogen heterocycles are recognized as “privileged medicinal scaffolds” because these compounds are found in a wide variety of bioactive natural products and pharmaceuticals [1

• synthesis of 1-benzyl-2-phenyl-1H-benzo[d]imidazole (3a). At first, a control experiment was conducted by using model substrates, 1 and 2a, in H2O in the absence of catalyst under ultrasound irradiation for 60 min at 45–50 °C. It was found that the reaction did not proceed in the absence of a catalyst

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions

• Pezhman Shiri and
• Jasem Aboonajmi

Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52

• heterogeneous nanocatalyst in “click” reactions for the multicomponent synthesis of triazole products in water with ultrasound irradiation and 0.017 mol % catalyst loading. As such, a series of aryl/alkyl-substituted oxiranes was treated with sodium azide and nonactivated terminal alkynes, giving 1,2,3-triazole

Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• could be conducted under ultrasound irradiation using sodium ethoxide as catalyst, thus generating steroid ring A-fused 3,4-dihydropyrimidinones and 3,4-dihydropyrimidinthiones 44 in very good yields. Mohamed et al. [44] reported a 4CR for the synthesis of pyridopyrimidines fused to ring D of

Ammonium-tagged ruthenium-based catalysts for olefin metathesis in aqueous media under ultrasound and microwave irradiation

• Łukasz Gułajski,
• Andrzej Tracz,
• Katarzyna Urbaniak,
• Stefan J. Czarnocki,
• Michał Bieniek and
• Tomasz K. Olszewski

Beilstein J. Org. Chem. 2019, 15, 160–166, doi:10.3762/bjoc.15.16

• research on synthesis of catalysts for olefin metathesis and to expand the utility of ammonium-tagged ruthenium-based catalysts [69][70][71][72][73][74][75][76], herein we present the use of such catalysts for olefin metathesis in aqueous media promoted by microwave and ultrasound irradiation. Results and

• the RCM (Table 1, entries 1 and 2) both tested catalysts (1 mol %) under classical conditions exhibited similar activities with 4b being slightly less active (52 vs 48%, respectively). The reaction performed under ultrasound irradiation proved to be ca. 10% more productive with both catalysts compared

• catalysts (5 mol %) produced the desired product again with quite similar yields under classical conditions. However, the use of microwave or ultrasound irradiation promoted the undesired isomerisation of the C=C bond, thus lowering the yields of the desired product 9 (Table 1, entries 3 and 4). This result

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

• -aminopyrazole 16 and 4-hydroxycoumarin (50) with isatin 54 under ultrasound irradiation in water (Scheme 11). Solvent and catalytic screening for the reaction have shown that water in presence of p-TSA at 60 °C on heating for 6 hours provide best results with excellent yields. Recently, Wang et al. [57] also

• reported a similar reaction of 5-aminopyrazole 16, arylaldehyde 47 with ethyl cyanoacetate (94) under ultrasound irradiation in presence of p-TSA in water for the synthesis of 3-methyl-6-oxo-4-aryl-4,5,6,7-tetrahydro-4H-pyrazolo[3,4-b]pyridine-5-carbonitrile derivatives 95 (Scheme 27). All the synthesized

Halogen-containing thiazole orange analogues – new fluorogenic DNA stains

• Aleksey A. Vasilev,
• Meglena I. Kandinska,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• David Sucunza,
• Juan J. Vaquero,
• Obis D. Castaño,
• Stanislav Baluschev and
• Silvia E. Angelova

Beilstein J. Org. Chem. 2017, 13, 2902–2914, doi:10.3762/bjoc.13.283

• TO-7Cl. The condensation of 2-methylbenzothiazolium salt 2a and 4,7-dichloroquinolinium methyl sulfate 4a was conducted in water, methanol or ethanol by stirring the reaction mixture at room temperature or by ultrasound irradiation for not more than 40 minutes. Prolonged sonication causes heating of

• the samples in the ultrasonic bath and this makes external cooling difficult. In addition, the ultrasound irradiation promotes side reactions and thus leads to slightly lower reaction yields when compared to the room temperature conditions. It is well known that water is one of the most useful green

Synthesis, effect of substituents on the regiochemistry and equilibrium studies of tetrazolo[1,5-a]pyrimidine/2-azidopyrimidines

• Elisandra Scapin,
• Paulo R. S. Salbego,
• Caroline R. Bender,
• Alexandre R. Meyer,
• Anderson B. Pagliari,
• Tainára Orlando,
• Geórgia C. Zimmer,
• Clarissa P. Frizzo,
• Helio G. Bonacorso,
• Nilo Zanatta and
• Marcos A. P. Martins

Beilstein J. Org. Chem. 2017, 13, 2396–2407, doi:10.3762/bjoc.13.237

• using ultrasound irradiation promoted shorter reaction times, high regioselectivity, and excellent yields, when compared with conventional thermal heating [30]. Presently, we demonstrate an eco-friendly synthesis of 5- and 7-substituted tetrazolo[1,5-a]pyrimidine isomers, in good to excellent yields

Solvent-free copper-catalyzed click chemistry for the synthesis of N-heterocyclic hybrids based on quinoline and 1,2,3-triazole

• Martina Tireli,
• Silvija Maračić,
• Stipe Lukin,
• Marina Juribašić Kulcsár,
• Dijana Žilić,
• Mario Cetina,
• Ivan Halasz,
• Silvana Raić-Malić and
• Krunoslav Užarević

Beilstein J. Org. Chem. 2017, 13, 2352–2363, doi:10.3762/bjoc.13.232

• , there is a persistent incentive to find greener alternatives, which would reduce time and energy requirements as well as waste generated by these reactions. Among other non-conventional approaches such as microwave and ultrasound irradiation [7][12][13], mechanochemistry has emerged as a viable approach

Solvent-free sonochemistry: Sonochemical organic synthesis in the absence of a liquid medium

• Deborah E. Crawford

Beilstein J. Org. Chem. 2017, 13, 1850–1856, doi:10.3762/bjoc.13.179

• success of both of these reactions by ultrasound irradiation in the absence of solvent creates potential for organic synthesis to be carried out by applying a milder form of mechanical energy, i.e., sound waves. As a result, it may be possible that reactions which are particularly sensitive to intense

Ultrasound-promoted organocatalytic enamine–azide [3 + 2] cycloaddition reactions for the synthesis of ((arylselanyl)phenyl-1H-1,2,3-triazol-4-yl)ketones

• Gabriel P. Costa,
• Natália Seus,
• Juliano A. Roehrs,
• Raquel G. Jacob,
• Ricardo F. Schumacher,
• Thiago Barcellos,
• Rafael Luque and
• Diego Alves

Beilstein J. Org. Chem. 2017, 13, 694–702, doi:10.3762/bjoc.13.68

• DMSO using Et2NH (1 mol %) was also performed under ultrasound irradiation. The reaction performed under ultrasound irradiation with 20% of the amplitude for 20 minutes (followed by TLC until the total consumption of the starting materials) yielded product 3a in 92% (conditions B, Scheme 2). Inspired

• by results described under conditions B, we performed additional experiments using ultrasound irradiation with Et2NH as organocatalyst (Table 1). Initially, substrates 1a and 2a were reacted in DMSO under ultrasound irradiation for 20 min using different amplitudes (Table 1, entries 1–4). We observed

• (Scheme 3) after 5 minutes reaction under ultrasound irradiation (40% of amplitude) at room temperature. Comparing these results with already published ones under conventional conditions, our methodology using ultrasound irradiation affords the products in 5 minutes and in comparable yields while the

From betaines to anionic N-heterocyclic carbenes. Borane, gold, rhodium, and nickel complexes starting from an imidazoliumphenolate and its carbene tautomer

• Ming Liu,
• Jan C. Namyslo,
• Martin Nieger,
• Mika Polamo and
• Andreas Schmidt

Beilstein J. Org. Chem. 2016, 12, 2673–2681, doi:10.3762/bjoc.12.264

• bis(3-butyl-1-(2-phenolate)-1H-imidazolium-2-yl)gold (10): A solution of 0.066 g (0.10 mmol) of bis(3-butyl-1-(2-hydroxyphenyl)-1H-imidazolium-2-yl)gold chloride (9) and 0.014 g (0.10 mmol) of K2CO3 in 5 mL of methanol was stirred for 30 minutes under ultrasound irradiation. After concentrating the

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

An efficient access to the synthesis of novel 12-phenylbenzo[6,7]oxepino[3,4-b]quinolin-13(6H)-one derivatives

• Wentao Gao,
• Guihai Lin,
• Yang Li,
• Xiyue Tao,
• Rui Liu and
• Lianjie Sun

Beilstein J. Org. Chem. 2012, 8, 1849–1857, doi:10.3762/bjoc.8.213

• hydrochloric acid. Subsequently, we reported a similar reaction under ultrasound irradiation conditions by using KHSO4 as catalyst [36]. Although the two methodologies are elegant and impressive, our attempts to follow both routes to synthesize 2 were frustrated by very low yields. In this regard, Bose et al

Regioselectivity in the multicomponent reaction of 5-aminopyrazoles, cyclic 1,3-diketones and dimethylformamide dimethylacetal under controlled microwave heating

• Kamal Usef Sadek,
• Ramadan Ahmed Mekheimer,
• Tahany Mahmoud Mohamed,
• Moustafa Sherief Moustafa and
• Mohamed Hilmy Elnagdi

Beilstein J. Org. Chem. 2012, 8, 18–24, doi:10.3762/bjoc.8.3

• ., either kinetic or thermodynamic [11][12][13]. It has been reported that the use of microwave or ultrasound irradiation provides an additional parameter for synthetic selectivity [14][15][16][17]. Results and Discussion The multicomponent reaction of 5-aminopyrazoles, dimedone and aromatic aldehydes was

First synthesis of 2-(benzofuran-2-yl)-6,7-methylene dioxyquinoline-3-carboxylic acid derivatives

• Wentao Gao,
• Jia Liu,
• Yun Jiang and
• Yang Li

Beilstein J. Org. Chem. 2011, 7, 210–217, doi:10.3762/bjoc.7.28

• ethyl 4-chloro-3-oxobutanoate using KHSO4 as catalyst under ultrasound irradiation conditions. The targeted compounds 3a–h were obtained in good yields of 52–82% and their structures were established based on spectral data and elemental analyses. Keywords: benzofuran; Friedländer condensation

• carried out under ultrasound irradiation conditions at 80 °C using KHSO4 as catalyst in 80% EtOH as solvent. The resulting product 5 was obtained in good yield (74%) after purification by a flash chromatography on silica gel (eluent: petroleum ether/ethyl acetate = 5:1). The next step involves the

An improved synthesis of 1,3,5-triaryl- 2-pyrazolines in acetic acid aqueous solution under ultrasound irradiation

• Ji-Tai Li,
• Xiao-Hui Zhang and
• Zhi-Ping Lin

Beilstein J. Org. Chem. 2007, 3, No. 13, doi:10.1186/1860-5397-3-13

• used in organic synthesis in the last three decades. A large number of organic reactions can be carried out in higher yields, shorter reaction time or milder conditions under ultrasound irradiation. Results Preparation of a series of 1,3,5-triaryl-2-pyrazolines through the reaction of chalcones and

• phenylhydrazine hydrochloride was carried out in 83–96% yield within 1.5–2 h in sodium acetate-acetic acid aqueous solution under ultrasound irradiation. Conclusion We have described a practical and convenient procedure for the synthesis of 1,3,5-triaryl-2-pyrazolines in sodium acetate-acetic acid aqueous

• solution at room temperature under ultrasound irradiation. Background Pyrazoline derivatives have been found to possess a broad spectrum of biological activities such as tranquillizing, muscle relaxant, psychoanaleptic, anticonvulsant, antihypertensive, and antidepressant activities. [1][2][3][4][5][6