An atom-economical addition of methyl azaarenes with aromatic aldehydes via benzylic C(sp³)–H bond functionalization under solvent- and catalyst-free conditions

• Divya Rohini Yennamaneni,
• Vasu Amrutham,
• Krishna Sai Gajula,
• Rammurthy Banothu,
• Murali Boosa and
• Narender Nama

Beilstein J. Org. Chem. 2020, 16, 3093–3103, doi:10.3762/bjoc.16.259

• times [30]. Rao et al. performed similar reactions without catalyst under microwave irradiation in the presence of water as a solvent [31], but when considering an industrial scale, there are numerous factors that serves as obstacles for the usage of microwave reactors, such as escalated heat loss

Selective and reversible 1,3-dipolar cycloaddition of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes with 1,3-diphenylprop-2-en-1-ones under microwave irradiation

• Alexander P. Molchanov,
• Mariia M. Efremova,
• Mariya A. Kryukova and
• Mikhail A. Kuznetsov

Beilstein J. Org. Chem. 2020, 16, 2679–2686, doi:10.3762/bjoc.16.218

• that the Lewis acid-catalyzed reaction of diaziridines with donor–acceptor cyclopropanes and aziridines affords the perhydropyridazine or triazine derivatives, respectively, in good yields [31][32][33]. The use of microwave irradiation in organic synthesis complies with the principles of green

• chemistry and has attracted much interest. For 1,3-dipolar cycloaddition reactions microwave irradiation not only allows to reduce the reaction time and to increase yields, but in some cases also can affect the selectivity of the reaction [34][35][36]. The efficiency of microwave irradiation has been shown

• cycloaddition reaction of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes 1a–d (DABCH) with 1,3-diarylpropenones 2a–l at 110 °С under microwave irradiation using a microwave oven Discover SP in a 10 mL glass reactor. It was found that under these conditions the (3 + 2) cycloaddition products – perhydropyrazolopyrazoles

Synthesis and characterization of S,N-heterotetracenes

• Astrid Vogt,
• Florian Henne,
• Christoph Wetzel,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2020, 16, 2636–2644, doi:10.3762/bjoc.16.214

• 3-nitro-2,2’-bithiophene with triethyl phosphite under microwave irradiation and surprisingly obtained targeted heterotriacene H-DTP (vide supra) with only 11% yield [45]. This result prompted us to have a closer look on the applicability of the Cadogan reaction/cyclization in order to provide S,N

Synergy between supported ionic liquid-like phases and immobilized palladium N-heterocyclic carbene–phosphine complexes for the Negishi reaction under flow conditions

• Edgar Peris,
• Raúl Porcar,
• María Macia,
• Jesús Alcázar,
• Eduardo García-Verdugo and
• Santiago V. Luis

Beilstein J. Org. Chem. 2020, 16, 1924–1935, doi:10.3762/bjoc.16.159

• of methylimidazolium units leading to a Pd(II)-SILLP system 11 with 0.56 mequiv of Pd/g of SILLP and 3.79 mequiv of IL-like units/g of SILLP (Scheme 4). This system was treated with either NaBH4 or EtOH under microwave irradiation to produce the corresponding PdNPs immobilized onto SILLPs (12a,b

Tuneable access to indole, indolone, and cinnoline derivatives from a common 1,4-diketone Michael acceptor

• Dalel El-Marrouki,
• Sabrina Touchet,
• Abderrahmen Abdelli,
• Hédi M’Rabet,
• Mohamed Lotfi Efrit and
• Philippe C. Gros

Beilstein J. Org. Chem. 2020, 16, 1722–1731, doi:10.3762/bjoc.16.144

• as the main product, with the best yield being obtained in butanol (43%, Table 1, entry 11), however, with the formation of 6b occurring only in 10% yield. Switching to microwave irradiation formed exclusively 7b in 60% yield after 3 h (Table 1, entry 13). Note, that to check the effect of a shorter

Microwave-assisted efficient one-pot synthesis of N²-(tetrazol-5-yl)-6-aryl/heteroaryl-5,6-dihydro-1,3,5-triazine-2,4-diamines

• Moustafa Sherief Moustafa,
• Ramadan Ahmed Mekheimer,
• Saleh Mohammed Al-Mousawi,
• Mohamed Abd-Elmonem,
• Hesham El-Zorba,
• Afaf Mohamed Abdel Hameed,
• Tahany Mahmoud Mohamed and
• Kamal Usef Sadek

Beilstein J. Org. Chem. 2020, 16, 1706–1712, doi:10.3762/bjoc.16.142

• developed by reacting 5-amino-1,2,3,4-tetrazole with aromatic aldehydes and cyanamide in pyridine under controlled microwave heating with high yields. X-ray crystallography confirmed the structure of the obtained products. Keywords: microwave irradiation; N2-(tetrazol-5-yl)-6-aryl/heteroaryl-1,3,5-triazine

• favorable due to the high nucleophilicity of the exocyclic amino function attached to the electron-rich tetrazole ring [45]. In support of this assumption we stopped the reaction after 4 minutes of heating under microwave irradiation and inspected the prior formation of 9 via comparison with an authentic

• ://www.ccdc.cam.ac.uk CCDC1961565 for compound 4i. All reactions were monitored by TLC with 1:1 ethyl acetate/petroleum ether as eluent and were carried out until starting materials were completely consumed. After 7 min microwave irradiation was stopped and the reaction mixture was analyzed by TLC; after further

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• endotermic process is the rate-limiting step and long reaction times are generally associated to this. However, the reaction can be accelerated in conditions that facilitate the dissociation of CO ligands such as heating, microwave irradiation [37][38], visible light, or ultrasonication [39]. Alternatively

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

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

Activated carbon as catalyst support: precursors, preparation, modification and characterization

• Melanie Iwanow,
• Tobias Gärtner,
• Volker Sieber and
• Burkhard König

Beilstein J. Org. Chem. 2020, 16, 1188–1202, doi:10.3762/bjoc.16.104

• be produced by salt templating or ultrasonic spray pyrolysis as well as by microwave irradiation. The resulting activated carbon materials are characterized by a variety of techniques such as SEM, FTIR, nitrogen adsorption, Boehm titrations, adsorption of phenol, methylene blue and iodine, TPD, CHNS

• ]. Microwave irradiation is a promising alternative with some advantages. In contrast to conventional heating, which is based on the convection mechanism involving conduction and radiation, the sample can be heated uniformly and contactless by the heat generated from electromagnetic energy, resulting in

• surface areas by microwave-induced ZnCl2 activation within minutes. The porosity of the materials can be tailored by the carbon precursor to ZnCl2 ratio and the microwave irradiation time [104]. Foo et al. investigated the activated carbon preparation by microwave heating with K2CO3 activation from wood

Fluorinated phenylalanines: synthesis and pharmaceutical applications

• Laila F. Awad and
• Mohammed Salah Ayoup

Beilstein J. Org. Chem. 2020, 16, 1022–1050, doi:10.3762/bjoc.16.91

• product 2-[18F]FPhe 46 in 43% yield, whereas under microwave irradiation a 34% yield was obtained. Under the optimized conditions, the enantiomeric purity was reported to be ≥94% ee [46] (Scheme 10). 1.3. Photooxidative cyanation of fluorinated benzylamine A convenient, protecting group-free, and

Diversity-oriented synthesis of 17-spirosteroids

• Benjamin Laroche,
• Thomas Bouvarel,
• Martin Louis-Sylvestre and
• Bastien Nay

Beilstein J. Org. Chem. 2020, 16, 880–887, doi:10.3762/bjoc.16.79

• at 170 °C for 17-(4-penten-1-yloxy)steroids, for 1 h under microwave irradiation. The solvent was removed by evaporation, and the resulting crude material was purified by chromatography on silica gel (petroleum ether/EtOAc 99:1) to afford the spirocyclic diene. General procedure C for one-pot RCEYM

• /Diels–Alder reaction The enyne (1 mmol) was dissolved in dry toluene (c 0.03 M). The solution was placed in a sealed microwave tube containing a magnetic stirrer under argon. The Grubbs second generation catalyst (2 mol %) was added and the reaction mixture was stirred at 120 °C for 1 h under microwave

• irradiation. The microwave tube was opened and the dienophile (1.2 mmol) was added in one portion. The mixture was stirred at 150 °C for 35 min. The solvent was removed and the crude material was purified by chromatography on silica gel (petroleum ether/EtOAc 8:3) to afford the product. Structure of four 17

Efficient synthesis of piperazinyl amides of 18β-glycyrrhetinic acid

• Dong Cai,
• ZhiHua Zhang,
• Yufan Meng,
• KaiLi Zhu,
• LiYi Chen,
• ChangXiang Yu,
• ChangWei Yu,
• ZiYi Fu,
• DianShen Yang and
• YiXia Gong

Beilstein J. Org. Chem. 2020, 16, 798–808, doi:10.3762/bjoc.16.73

• yields (<19%) of the desired compound 8 were obtained after a longer reaction time (Table 2, entries 1–4). A further investigation of the reaction using microwave irradiation to heat at reflux temperature also failed to produce the target product (Table 2, entry 2). The intermediate 6 exhibited very low

Synthesis of C₇₀-fragment buckybowls bearing alkoxy substituents

• Yumi Yakiyama,
• Shota Hishikawa and
• Hidehiro Sakurai

Beilstein J. Org. Chem. 2020, 16, 681–690, doi:10.3762/bjoc.16.66

• using 20 mol % of Pd(PPh3)2Cl2 and 150 mol % DBU in DMF at 150 °C under microwave irradiation conditions to afford the desired dimethoxy derivative 5a in 75% yield. In contrast, when the reaction of 4b was performed, not only the desired product 5b but also the unexpected regioisomer 5c was obtained

• . The temperature dependency of the product ratio between 5b and 5c was investigated and the results are shown in Table 1. The cyclization did not proceed under 140 °C, and at 140 °C the total yield is low (41% after 40 min microwave irradiation) but the ratio of 5b was the highest (5b/5c = 10:1). The

Microwave-assisted efficient and facile synthesis of tetramic acid derivatives via a one-pot post-Ugi cascade reaction

• Yong Li,
• Zheng Huang,
• Jia Xu,
• Yong Ding,
• Dian-Yong Tang,
• Jie Lei,
• Hong-yu Li,
• Zhong-Zhu Chen and
• Zhi-Gang Xu

Beilstein J. Org. Chem. 2020, 16, 663–669, doi:10.3762/bjoc.16.63

• developed through an Ugi/Dieckmann cyclization strategy with DBU. This two-step one-pot procedure afforded the targeted tetramic acid analogues in good yields. With commercially available Ugi starting materials, microwave irradiation, a simple operation, excellent yields, and a broad scope, this reaction

• investigated the effect of different inorganic and organic bases (Table 1). It was interesting to note that all of the bases tested in the study afforded the desired enol tetramic acid derivative 7a after the reaction was heated under the microwave irradiation conditions. The ketone compound 6a could be the

•  1, entries 9–12. DMF was superior to other solvents with the highest yield. Then the microwave irradiation temperature was varied: at 80 °C for 10 min, a large fraction of the Ugi adduct 5a was still present in the product mixture (LC–MS determination); at 120 °C, the desired compound 7a was

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