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

• , trimethylsilylacetylene (TMSA) was selected for coupling with aryl iodides in the presence of a catalytic amount of Pd–Cu/C and PPh3 using Et2NH as a base in methanol at 120 °C under microwave irradiation for 20 min. In the next step, the azide derivative was added to the reaction mixture. Finally, the reaction mixture

Ultrasonic-assisted unusual four-component synthesis of 7-azolylamino-4,5,6,7-tetrahydroazolo[1,5-a]pyrimidines

• Yana I. Sakhno,
• Maryna V. Murlykina,
• Oleksandr I. Zbruyev,
• Anton V. Kozyryev,
• Svetlana V. Shishkina,
• Dmytro Sysoiev,
• Vladimir I. Musatov,
• Sergey M. Desenko and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2020, 16, 281–289, doi:10.3762/bjoc.16.27

• such interactions can be tuned, for example, by application of a condition-based divergence strategy [25], which is based on the variation of solvents, catalysts, and activation methods [16][26][27][28][29]. Thus, using nonclassical activation methods such as ultrasonication and microwave irradiation

• applying different temperatures in the range of 0–110 °C (both with the help of conventional heating and microwave irradiation) and by using different solvents and catalysts, such as HOAc, DMSO, primary alcohols with and without the presence of HCl, Yb(OTf)3, or Et3N. In all these cases, mixtures of

Combination of multicomponent KA² and Pauson–Khand reactions: short synthesis of spirocyclic pyrrolocyclopentenones

• Riccardo Innocenti,
• Elena Lenci,
• Gloria Menchi and
• Andrea Trabocchi

Beilstein J. Org. Chem. 2020, 16, 200–211, doi:10.3762/bjoc.16.23

• following the reported method [48] employing copper catalysis, and tested on our starting material upon variation of copper salts, solvents and temperature, resulting in the neat reaction under CuI catalysis being optimal when carried out for 2 h at 100 °C under microwave irradiation (see Supporting

• mixture was heated under microwave irradiation to 100 °C for 2 h. Then, EtOAc was added and the organic phase was washed with 5% NH4OH (3 × 20 mL) and brine. The organic phase was dried with Na2SO4 and concentrated under reduced pressure. The crude product was purified by flash chromatography using the

Efficient method for propargylation of aldehydes promoted by allenylboron compounds under microwave irradiation

• Jucleiton J. R. Freitas,
• Queila P. S. B. Freitas,
• Silvia R. C. P. Andrade,
• Juliano C. R. Freitas,
• Roberta A. Oliveira and
• Paulo H. Menezes

Beilstein J. Org. Chem. 2020, 16, 168–174, doi:10.3762/bjoc.16.19

• -560, Brazil Universidade Federal de Campina Grande, Centro de Educação e Saúde: Cuité, Paraíba, Brazil 10.3762/bjoc.16.19 Abstract The propargylation of aldehydes promoted by microwave irradiation using allenylboron compounds in a chemo- and regioselective way is described. The corresponding products

• pharmaceutical synthesis [29]. Moreover, the removal of tributyltin residues from reaction mixtures is also a major issue. The use of microwave irradiation for the formation of new C–C bonds is nowadays widely used and offers several advantages such as the increment in the product yield, reduction of reaction

• shortest time necessary for the formation of the products at 100 °C under microwave irradiation was evaluated. The results are shown in Table 2. From Table 2, it can be seen that the increment in the reaction time resulted in higher yields without major changes in the ratio of 2a:3a. The optimized reaction

Functionalization of the imidazo[1,2-a]pyridine ring in α-phosphonoacrylates and α-phosphonopropionates via microwave-assisted Mizoroki–Heck reaction

• Damian Kusy,
• Agata Wojciechowska,
• Joanna Małolepsza and
• Katarzyna M. Błażewska

Beilstein J. Org. Chem. 2020, 16, 15–21, doi:10.3762/bjoc.16.3

• ][17]). However, we did not observe any change in this ratio under the applied conditions of the Mizoroki–Heck reaction. On applying microwave irradiation (100 °C, 40 min), we achieved 70% conversion into product 3 (Table 1, entry 2). In order to improve the conversion into the product, we increased

• , synthesis of these compounds by standard thermal Heck protocols was ineffective, thus highlighting the importance of employing microwave irradiation for this transformation. Eighteen new compounds were obtained using the developed method. The advantages of the proposed method include operational simplicity

Construction of trisubstituted chromone skeletons carrying electron-withdrawing groups via PhIO-mediated dehydrogenation and its application to the synthesis of frutinone A

• Qiao Li,
• Chen Zhuang,
• Donghua Wang,
• Wei Zhang,
• Rongxuan Jia,
• Fengxia Sun,
• Yilin Zhang and
• Yunfei Du

Beilstein J. Org. Chem. 2019, 15, 2958–2965, doi:10.3762/bjoc.15.291

• also be realized by DDQ-mediated dehydrogenation of chromanones under heating in dioxane (Scheme 1b) [3][59][60]. In 2005, Yang and co-workers reported that chromones could be formed by microwave irradiation of the corresponding chromanone reactants and N-bromosuccinimide (NBS) in the presence of a

Diversity-oriented synthesis of spirothiazolidinediones and their biological evaluation

• Sambasivarao Kotha,
• Gaddamedi Sreevani,
• Lilya U. Dzhemileva,
• Milyausha M. Yunusbaeva,
• Usein M. Dzhemilev and
• Vladimir A. D’yakonov

Beilstein J. Org. Chem. 2019, 15, 2774–2781, doi:10.3762/bjoc.15.269

• bromide (6a) in the presence of Mo(CO)6 in acetonitrile at 90 °C under microwave irradiation (MWI) conditions to give the co-trimerized spiro derivative 8a (Scheme 2). The free NH moiety of thiazolidinedione 3 was alkylated using alkyl or aryl halides in the presence of Et3N using DCM as solvent. To our

Combining the Ugi-azide multicomponent reaction and rhodium(III)-catalyzed annulation for the synthesis of tetrazole-isoquinolone/pyridone hybrids

• Gerardo M. Ojeda,
• Prabhat Ranjan,
• Pavel Fedoseev,
• Lisandra Amable,
• Upendra K. Sharma,
• Daniel G. Rivera and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2019, 15, 2447–2457, doi:10.3762/bjoc.15.237

• aldehydes were reacted in parallel with trimethylsilyl azide and tritylamine under microwave irradiation – followed by removal of the trityl group and acylation to afford the N-acylaminomethyltetrazoles 1a–s and 2a–l. The functionalized tetrazoles were obtained in moderate to excellent yields over three

In water multicomponent synthesis of low-molecular-mass 4,7-dihydrotetrazolo[1,5-a]pyrimidines

• Irina G. Tkachenko,
• Sergey A. Komykhov,
• Vladimir I. Musatov,
• Svitlana V. Shishkina,
• Viktoriya V. Dyakonenko,
• Vladimir N. Shvets,
• Mikhail V. Diachkov,
• Valentyn A. Chebanov and
• Sergey M. Desenko

Beilstein J. Org. Chem. 2019, 15, 2390–2397, doi:10.3762/bjoc.15.231

• , Ukraine Bar-Ilan University Ramat Gan, 5290002, Israel 10.3762/bjoc.15.231 Abstract The three-component reaction of 5-aminotetrazole with aliphatic aldehydes (formaldehyde, acetaldehyde) and acetoacetic ester derivatives in water under microwave irradiation leads to the selective formation of 4,7

• in this case. The three-component reactions of 5-aminotetrazole (1) with aldehydes 7a,b (paraformaldehyde, acetaldehyde) and a set of acetoacetic ester derivatives 8a–d in water under microwave irradiation at 100 °C led to the formation of the corresponding 5,6,7-trisubstituted 4,7-dihydrotetrazolo

• product is the 5-hydroxy-containing tetrahydro derivative. In our experiments, the three-component reaction of amine 1 with aldehyde 7b and compound 13 in water under microwave irradiation afforded tetrahydro derivative 14 as a mixture of two stereoisomers. Inspection of the mixture by 1H NMR revealed

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• ]pyridines under microwave irradiation [115]. 1-Butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) was used as ionic liquid for this three-component reaction of pyridine-2(1H)-one 70, acetophenone 71 and o-tosylhydroxylamine (72, Scheme 25). The reason behind the use of an ionic liquid as reaction

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

• with a thiosemicarbazide and 2-bromo-1-phenylethan-1-one under microwave irradiation to form the steroid–thiazole hybrid 35 in very good yield. As previously mentioned, due to the poor reactivity of steroidal ketones and their imine derivatives, most MCRs with ketosteroids described in the literature

• required a high temperature set by classic heating or microwave irradiation. Using cholic acid as carboxylic acid component, Cui and co-workers [37] developed a novel MCR resembling the Ugi-4CR, but relying on the reactivity of ynamides as surrogates of the isocyanide component. Ynamides are alkynes with a

• strong oxidizing Jones reagent, because the oxidizing power of sulfuric acid was not enough to achieve oxidation. Interestingly, the use of microwave irradiation instead of classic heating allowed obtaining the Biginelli product in only 10 min, instead of 12 h as required for the synthesis of pyrimidines

Extending mechanochemical porphyrin synthesis to bulkier aromatics: tetramesitylporphyrin

• Qiwen Su and
• Tamara D. Hamilton

Beilstein J. Org. Chem. 2019, 15, 1149–1153, doi:10.3762/bjoc.15.111

• -solvent-added routes to porphyrins, including high-temperature sealed-bomb methods [15][16][17], gas-phase synthesis [9], and microwave irradiation [10] do not employ a second oxidation step. Presumably for the latter two methods open to air, dioxygen serves as a rapid oxidizer under high-temperature

Switchable selectivity in Pd-catalyzed [3 + 2] annulations of γ-oxy-2-cycloalkenones with 3-oxoglutarates: C–C/C–C vs C–C/O–C bond formation

• Yang Liu,
• Julie Oble and
• Giovanni Poli

Beilstein J. Org. Chem. 2019, 15, 1107–1115, doi:10.3762/bjoc.15.107

• . Using DMF and DMA as solvents at 130 °C (Table 1, entries 10 and 11), and [Pd(η3-C3H5)Cl]2, dppf] as the catalytic system in DMSO (Table 1, entry 12) did not allow further improvements for the formation of compound 5a. Furthermore, after 1 h at 130 °C under microwave irradiation, the desired compound 5a

• at 130 °C, 6 h (conditions B), or 1 h under microwave irradiation (conditions C)]. Scope The scope of the C–C/O–C [3 + 2] annulation between dimethyl 3-oxoglutarate (1a) and six- (2a), five- (2b) and seven-membered (2c) cyclic α,β-unsaturated-γ-oxycarbonyls was next studied (Scheme 3). Under the

• thermal conditions or microwave irradiation. Surprisingly, application of these protocols to the seven-membered bis-electrophile 2c led to the corresponding bicyclo[5.3.0]decane-3,9-dione (5c) with a low yield of 24% under thermal conditions B, while microwave irradiation was ineffective. Moderate yields

Synthesis of (macro)heterocycles by consecutive/repetitive isocyanide-based multicomponent reactions

• Angélica de Fátima S. Barreto and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2019, 15, 906–930, doi:10.3762/bjoc.15.88

• four consecutive IMCRs were employed. The strategy allowed the synthesis of a cyclic heptapeptoid in only 8 steps using microwave irradiation in seven of these steps allowing short reaction times (3–5 minutes) and excellent yields of the intermediates (88–98%). The non-optimized low yield of the last

Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors

• Kirill B. Polyanskii,
• Kseniia A. Alekseeva,
• Pavel V. Raspertov,
• Pavel A. Kumandin,
• Eugeniya V. Nikitina,
• Atash V. Gurbanov and
• Fedor I. Zubkov

Beilstein J. Org. Chem. 2019, 15, 769–779, doi:10.3762/bjoc.15.73

• ) by a reaction of 2-(2-bromoethyl)benzyl bromide with secondary amines under microwave irradiation followed by the decomposition of the products under the action of potassium tert-butoxide [46]. All of the above routes offer some advantages but they all are rather expensive. Thus, the initial stage of

Solid-phase synthesis of biaryl bicyclic peptides containing a 3-aryltyrosine or a 4-arylphenylalanine moiety

• Iteng Ng-Choi,
• Àngel Oliveras,
• Lidia Feliu and
• Marta Planas

Beilstein J. Org. Chem. 2019, 15, 761–768, doi:10.3762/bjoc.15.72

• degassed 1,2-dimethoxyethane (DME)/EtOH/H2O (9:9:2) under microwave irradiation at 120 °C for 30 min (Scheme 2). An aliquot of the resulting resin 5 was cleaved, and HPLC and mass spectrometry analysis of the crude reaction mixture revealed the formation of the biaryl cyclic peptide 6 in 18% purity. Mass

• to an intramolecular Suzuki–Miyaura reaction using Pd2(dba)3 (0.2 equiv), SPhos (0.4 equiv) and KF (4 equiv) in degassed DME/EtOH/H2O (9:9:2) under microwave irradiation at 120 ºC for 30 min. Mass spectrometry analysis of the crude reaction mixture from the cleavage of an aliquot of the resulting

Efficient synthesis of 4-substituted-ortho-phthalaldehyde analogues: toward the emergence of new building blocks

• Clémence Moitessier,
• Ahmad Rifai,
• Pierre-Edouard Danjou,
• Isabelle Mallard and
• Francine Cazier-Dennin

Beilstein J. Org. Chem. 2019, 15, 721–726, doi:10.3762/bjoc.15.67

• -dimethylformamide system was tested according to the study of Fang et al. [25] revealing that the methoxy group in the meta-position of an electron-withdrawing substituents can be removed under microwave irradiation. However, when testing the system on 5b, no reaction occurred. Another experiment with lithium

• ) in the presence of different Brønsted acids. While investigating these conditions in combination with microwave irradiation (Scheme 4), the desired compound 4-HO-OPA (6) was successfully obtained in only 30 minutes, with a good yield (75%) when reacting with methanesulfonic acid (MsOH) as catalyst

• compound 5b (200 mg, 1.2 mmol), p-TsOH (1.68g, 9.8 mmol) and [Bmim]Br (4.0 g, 18.3 mmol) was placed in a sealed vial and irradiated under microwave irradiation for 30 minutes at 150 °C under strong agitation. After cooling, the mixture was vigorously extracted with Et2O overnight. The ether layer was

Synthesis and SAR of the antistaphylococcal natural product nematophin from Xenorhabdus nematophila

• Frank Wesche,
• Hélène Adihou,
• Thomas A. Wichelhaus and
• Helge B. Bode

Beilstein J. Org. Chem. 2019, 15, 535–541, doi:10.3762/bjoc.15.47

• bond formation was achieved using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl), 1-hydroxybenzotriazole (HOBt) and N,N-diisopropylethylamine (DIPEA) in DMF under microwave irradiation (Scheme 1). Racemic 1 was synthesized using tryptamine and (rac)-3-methyl-2-oxopentanoic acid

• phthalimides 16 and 23 [29]. These intermediary compounds 16 and 23 also allowed an N-methylation of the azaindole moiety with sodium hydride (NaH) and methyl iodide (MeI) to yield 17 and 24. By ethanolic hydrazinolysis and microwave irradiation the phthalimides (16, 17, 23, and 24) were deprotected yielding

Design of indole- and MCR-based macrocycles as p53-MDM2 antagonists

• Constantinos G. Neochoritis,
• Maryam Kazemi Miraki,
• Eman M. M. Abdelraheem,
• Ewa Surmiak,
• Tryfon Zarganes-Tzitzikas,
• Beata Łabuzek,
• Tad A. Holak and
• Alexander Dömling

Beilstein J. Org. Chem. 2019, 15, 513–520, doi:10.3762/bjoc.15.45

• optimization, we improved the Ugi-macrocyclization procedure compared to our previous findings utilizing microwave irradiation (see Supporting Information File 1); Firstly, the corresponding amino acid was irradiated with indole-3-carboxaldehyde derivatives 6 using MeOH as solvent (5 mL) at 120 °C for 1 h

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

• to the classical conditions. On the other hand, microwave irradiation turned out to be less effective leading to a drop in the reaction yield for 1a (48%) and a slightly increased yield in the case of 4b (55%). In the homometathesis reaction of allyl alcohol 8 (Table 1, entries 3 and 4) both

• is in agreement with the known fact that in protic solvents ruthenium hydrides are formed leading to isomerisation byproducts [66]. Finally, we were pleased to see that the use of ultrasound or microwave irradiation were beneficial for the CM of alcohol 8 with methyl acrylate (10, Table 1, entries 5

• justifying the use of modified catalysts. For the ammonium NHC-tagged catalysts (0.25 mol %), the use of microwave irradiation was more productive than ultrasound treatment. This effect was most pronounced in the case of catalysts with low solubility in water such as 1b or the insoluble catalysts 1d and 2c

Ring-closing-metathesis-based synthesis of annellated coumarins from 8-allylcoumarins

• Christiane Schultze and
• Bernd Schmidt

Beilstein J. Org. Chem. 2018, 14, 2991–2998, doi:10.3762/bjoc.14.278

• the past few years. Starting materials are allyl ethers of salicylic aldehydes or ketones 5 and the stable ylide ethyl (triphosphoranylidene)acetate (6), which upon microwave irradiation undergo a tandem Claisen rearrangement/Wittig olefination/cyclization sequence. This sequence was pioneered by the

Pd-Catalyzed microwave-assisted synthesis of phosphonated 13α-estrones as potential OATP2B1, 17β-HSD1 and/or STS inhibitors

• Rebeka Jójárt,
• Szabolcs Pécsy,
• György Keglevich,
• Mihály Szécsi,
• Réka Rigó,
• Csilla Özvegy-Laczka,
• Gábor Kecskeméti and
• Erzsébet Mernyák

Beilstein J. Org. Chem. 2018, 14, 2838–2845, doi:10.3762/bjoc.14.262

• reacted with diethyl phosphite or diphenylphosphine oxide using Pd(PPh3)4 as catalyst under microwave irradiation. The influence of the new compounds on the transport function of the organic anion transporting polypeptide OATP2B1 was investigated by measuring Cascade Blue uptake. Derivatives bearing a 3

• . Here we disclose the synthesis of novel 2- or 4-substituted 13α-estrone derivatives 8–13 via the Hirao reaction (Scheme 1). Diethyl phosphite (7a) or diphenylphosphine oxide (7b) were chosen as >P(O)H reagents and C–P couplings were planned under microwave irradiation using Pd-based catalysis

• , but the important benefits of microwave-irradiation have also been utilized in this field [29]. The optimization of reaction conditions was carried out using 2-bromo- or 2-iodo-13α-estrone 3-methyl ether (1 or 1I) as starting compounds and diethyl phosphite (7a) as the reagent (Table 1, Scheme 1). Two

An overview on recent advances in the synthesis of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials and their catalytic applications in chemical processes

• Hashem Sharghi,
• Pezhman Shiri and
• Mahdi Aberi

Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253

• polyhydroquinoline derivatives 118 under microwave irradiation. Several substituted aldehydes 7 with dimedone (20), acetoacetate ester 34a, and ammonium acetate in ethanol under microwave irradiation were reacted to produce corresponding products in high yields. In addition to the catalytic role of strong acid

Synthesis of dihydroquinazolines from 2-aminobenzylamine: N³-aryl derivatives with electron-withdrawing groups

• Nadia Gruber,
• Jimena E. Díaz and
• Liliana R. Orelli

Beilstein J. Org. Chem. 2018, 14, 2510–2519, doi:10.3762/bjoc.14.227

• -aryl-2-iminoazacycloalkanes [84] and 2-oxazolines or their higher homologues [85], using polyphosphoric acid esters PPE (ethyl polyphosphate) [86] and PPSE (trimethylsilyl polyphosphate) [87] under microwave irradiation. PPE and PPSE are aprotic irreversible dehydrating agents of the Lewis acid-type

• esters are their low cost, operational simplicity and minimum environmental impact. Besides, their use together with microwave irradiation brings about shorter reaction times, cleaner crude products and consequently higher yields. On the basis of our previous work on DHQs [41], we explore herein the use

• latter [85][88]. Additionally, the classical work-up procedure of PPSE-promoted reactions involves basic conditions [85]. In fact, treatment of 3b with PPSE/Cl2CH2 under microwave irradiation afforded the desired product 1b with 90% yield (Table 3). In a control experiment, 3b was reacted with PPE/Cl3CH

Synergistic approach to polycycles through Suzuki–Miyaura cross coupling and metathesis as key steps

• Sambasivarao Kotha,
• Milind Meshram and
• Chandravathi Chakkapalli

Beilstein J. Org. Chem. 2018, 14, 2468–2481, doi:10.3762/bjoc.14.223

• , Claisen rearrangement (CR) of 77 under microwave irradiation (MWI) conditions on a silica gel support followed by O-allylation of the resulting CR product furnished diallyl compound 78. Treatment of diallyl compound 78 with G-I catalyst 1 delivered the expected naphthoxepine derivative 79 (96%). Next