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

• Gerardo M. Ojeda Prabhat Ranjan Pavel Fedoseev Lisandra Amable Upendra K. Sharma Daniel G. Rivera Erik V. Van der Eycken Laboratory for Organic & Microwave-Assisted Chemistry (LOMAC), Department of Chemistry, University of Leuven (KU Leuven), Celestijnenlaan 200F, B-3001 Leuven, Belgium Center for

• 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

Effect of ring size on photoisomerization properties of stiff stilbene macrocycles

• Sandra Olsson,
• Óscar Benito Pérez,
• Magnus Blom and
• Adolf Gogoll

Beilstein J. Org. Chem. 2019, 15, 2408–2418, doi:10.3762/bjoc.15.233

• well-established reactions (Scheme 2). The indanone is formed by intramolecular Friedel–Crafts acylation of 2 under microwave radiation as reported by Oliverio et al. [23]. The second step is the demethylation of indanone methyl ether 3 by aluminium trichloride in toluene at reflux [24]. Two indanone

• dichloromethane (DCM), ethyl acetate, pentane, tetrahydrofuran (THF) and toluene that were distilled before use. N,N-Dimethylformamide (DMF) was used as supplied (biotech. grade, ≥99.9%). Unless stated differently, all reactions were carried out under atmospheric pressure and with argon atmosphere. Microwave (MW

• ) heating was carried out in a Biotage+ Initiator microwave using 10–20 mL Biotech MW vials, applying MW irradiation at 2.45 GHz, with a power setting up to 40 W and an average pressure of 4–5 bar when DCM was the solvent and 90 W/1 bar when the solvent was DMF. Analytical TLC was performed using Merck

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 in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• transformation employed Pd2(dba)3/t-BuBrettPhos and CsF to convert aryl alcohols to aryl fluorides at 180 °C under microwave conditions (Scheme 14). The proposed catalytic cycle of this aryl fluorination is also shown. Only reductive elimination was investigated by Larhed, because this reaction step is crucial

Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors

• Christoph W. Grathwol,
• Nathalie Wössner,
• Sören Swyter,
• Adam C. Smith,
• Enrico Tapavicza,
• Robert K. Hofstetter,
• Anja Bodtke,
• Manfred Jung and
• Andreas Link

Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214

• = quartet, m = multiplet and combinations thereof, br = broad. Infrared (IR) spectra were recorded on a Bruker Alpha FT-IR spectrometer equipped with a diamond ATR unit and are indicated in terms of absorbance frequency [cm−1]. Microwave synthesis was conducted in a Monowave 300 microwave synthesis reactor

• a microwave reaction vessel 3a (1.01 g, 5.00 mmol, 1.00 equiv) was mixed with styrene (651 mg, 6.25 mmol, 1.25 equiv), tris(o-tolyl)phosphine (61 mg, 0.20 mmol, 0.04 equiv), Pd2(dba)3 (92 mg, 0.10 mmol, 0.02 equiv) and NEt3 (863 ΜL, 0.63 g, 6.25 mmol, 1.25 equiv) and suspended in anhydrous DMF (6 mL

• ). The reaction was conducted at 120 °C for 40 min in a microwave reactor. After cooling to room temperature the mixture was taken up in EtOAc and filtered through a pad of Celite®. The filtrate was washed with water (3 × 30 mL) and sat. aq. NaCl solution (30 mL), dried over MgSO4 and concentrated under

Synthesis of 1-azaspiro[4.4]nonan-1-oxyls via intramolecular 1,3-dipolar cycloaddition

• Yulia V. Khoroshunova,
• Denis A. Morozov,
• Andrey I. Taratayko,
• Polina D. Gladkikh,
• Yuri I. Glazachev and
• Igor A. Kirilyuk

Beilstein J. Org. Chem. 2019, 15, 2036–2042, doi:10.3762/bjoc.15.200

• loss of a hydrogen atom is consistent with the susceptibility of 7c to oxidative decay (Scheme 3). Intramolecular cycloaddition of similar nitrones is known to lead to hexahydro-1H-cyclopenta[c]isoxazoles [6][12]. Indeed, heating of 7а–с at 145 °C in toluene for 30–60 min in a microwave oven produced

Archangelolide: A sesquiterpene lactone with immunobiological potential from Laserpitium archangelica

• Silvie Rimpelová,
• Michal Jurášek,
• Lucie Peterková,
• Jiří Bejček,
• Vojtěch Spiwok,
• Miloš Majdl,
• Michal Jirásko,
• Miloš Buděšínský,
• Juraj Harmatha,
• Eva Kmoníčková,
• Pavel Drašar and
• Tomáš Ruml

Beilstein J. Org. Chem. 2019, 15, 1933–1944, doi:10.3762/bjoc.15.189

• solution) and TBTA (3 mg, 5.6 µmol) were added. The mixture was placed into a microwave reactor and irradiated for 2 h at 70 °C. Then, the solvent was evaporated under reduced pressure and the residue was chromatographed (hexanes/AcOEt, 1:1). The obtained product 5 was re-chromatographed twice to obtain

Synthesis of a [6]rotaxane with singly threaded γ-cyclodextrins as a single stereoisomer

• Jason Yin Hei Man and
• Ho Yu Au-Yeung

Beilstein J. Org. Chem. 2019, 15, 1829–1837, doi:10.3762/bjoc.15.177

• first heated at 100 °C for 5 minutes in a microwave reactor to facilitate the dissolution of the CB[6] (Scheme 2). The solution was then added to a solution mixture of the biphenylene building block 1 and γ-CD at different ratios, and the mixture was heated at 60 °C overnight. The products were analyzed

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

One-pot activation–alkynylation–cyclization synthesis of 1,5-diacyl-5-hydroxypyrazolines in a consecutive three-component fashion

• Christina Görgen,
• Katharina Boden,
• Guido J. Reiss,
• Walter Frank and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 1360–1370, doi:10.3762/bjoc.15.136

• -methoxyethanol not only gave high yields of 5b, but also proved to be practical with respect to work-up. Upon comparison between dielectric and conductive heating the reaction in the microwave cavity gave no detectable difference in reaction time and yield. All these optimized conditions were therefore directly

Mechanochemical Friedel–Crafts acylations

• Mateja Đud,
• Anamarija Briš,
• Iva Jušinski,
• Davor Gracin and
• Davor Margetić

Beilstein J. Org. Chem. 2019, 15, 1313–1320, doi:10.3762/bjoc.15.130

• mixture of 19 and 18 (3:2 ratio), accompanied with a small amount of 22. As a substitute for dianthracene 19, thermally more stable substrate, anthracene-N-methyl maleimide adduct 25 [54] was prepared by Diels–Alder reaction under high pressure conditions as well as by microwave-assisted reaction and

Doebner-type pyrazolopyridine carboxylic acids in an Ugi four-component reaction

• Maryna V. Murlykina,
• Oleksandr V. Kolomiets,
• Maryna M. Kornet,
• Yana I. Sakhno,
• Sergey M. Desenko,
• Victoriya V. Dyakonenko,
• Svetlana V. Shishkina,
• Oleksandr A. Brazhko,
• Vladimir I. Musatov,
• Alexander V. Tsygankov,
• Erik V. Van der Eycken and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2019, 15, 1281–1288, doi:10.3762/bjoc.15.126

• , State Scientific Institution “Institute for Single Crystals” of National Academy of Sciences of Ukraine, Nauky Ave., 60, 61072, Kharkiv, Ukraine Faculty of Chemistry, V. N. Karazin Kharkiv National University, Svobody sq., 4, 61077, Kharkiv, Ukraine Laboratory for Organic & Microwave-Assisted Chemistry

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

• groups on Ugi-4CRs with spirostanic, androstanic, pregnanic and cholestanic carboxylic acids, later on Chowdhury and co-workers published a similar strategy for the multicomponent derivatization of cholestanes using microwave assisted Ugi-4CR [27]. 2.1.3 Steroids as the isocyanide component: To our

• 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

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

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• aromatic, heteroaromatic and aliphatic amines in ethanol, under microwave heating, and without metal catalyst [83]. Very good yields of 35 are obtained in a very simple and cost-effective manner. A rather similar approach was disclosed shortly later by Han and co-workers [84], who used β-ketoacids (34 R3

• improvement on this multicomponent approach, making use of β-cyclodextrine as promoter, water as a solvent, and microwave heating (route C, Scheme 16) [98]. Under these neutral conditions, they prepared up to nineteen compounds (60–95%, R1 = H, Cl, R2 = alkyl, benzyl, aryl), including two derivatives

• comprising three palladium-catalysed reactions: Sonogashira, Heck and Suzuki–Miyaura (Scheme 37) [113][114][115]. In this methodology, N-arylpropiolamides 128 reacted with aryl iodides 129 and aryl- or styrylboronic acids 130 under microwave activation to yield 3-(diarylmethylene)oxindoles 131 or 3-(1,3

A three-component, Zn(OTf)₂-mediated entry into trisubstituted 2-aminoimidazoles

• Alexei Lukin,
• Anna Bakholdina,
• Anna Kryukova,
• Alexander Sapegin and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2019, 15, 1061–1064, doi:10.3762/bjoc.15.103

• co-workers describing Zn(OTf)2-catalyzed, microwave-promoted conversion of a mixture of a secondary propargylamide and an amine into a trisubstituted imidazole 1 [1][2] inspired us to explore several variants of this methodology. Last year, we described the synthesis of differently substituted

Novel (2-amino-4-arylimidazolyl)propanoic acids and pyrrolo[1,2-c]imidazoles via the domino reactions of 2-amino-4-arylimidazoles with carbonyl and methylene active compounds

• Victoria V. Lipson,
• Tetiana L. Pavlovska,
• Nataliya V. Svetlichnaya,
• Anna A. Poryvai,
• Nikolay Yu. Gorobets,
• Erik V. Van der Eycken,
• Irina S. Konovalova,
• Svetlana V. Shiskina,
• Alexander V. Borisov,
• Vladimir I. Musatov and
• Alexander V. Mazepa

Beilstein J. Org. Chem. 2019, 15, 1032–1045, doi:10.3762/bjoc.15.101

• , Ukraine Laboratory for Organic & Microwave-Assisted Chemistry (LOMAC), Katholieke Universiteit Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium Peoples' Friendship University of Russia (RUDN University) 6 Miklukho-Maklaya street, Moscow, 117198, Russia Enamine Ltd., 23 Chervonotkats’ka str., Kyiv

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

• amounts of each reagent. Neither room-temperature reactions nor reflux conditions led to satisfactory results. However, microwave heating of 11 at 120 °C for 30 min in trifluoroethanol as solvent allowed the obtention of the desired tetrazole-ketopiperazines 12 in yields ranging from 20–72% (1:1 to 9:1

• isocyanide-based multicomponent reactions in the synthesis of macrocycles containing a tetrazole nucleus [30]. The strategy was based on the use of α-isocyano-ω-carboxylic esters 71 via a microwave-mediated Ugi-azide reaction at the beginning of the synthesis and an intramolecular Ugi reaction of

• backbone could be easily exchanged. Later on, our group introduced the use of microwave heating to this same synthetic strategy for the synthesis of a cyclic peptoid (Scheme 18) [33]. The combination of these two tools (microwave heating and consecutive IMCRs) has proved to be a particularly attractive

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• supramolecular chemistry are dynamic combinatorial chemistry [11], subcomponent self-assembly approach [12][13][14], and systems chemistry [15][16][17][18], etc. There also has been growing interest towards exploration of nontraditional energy sources like visible light [19][20], microwave [21], mechanochemical

An improved synthesis of adefovir and related analogues

• David J. Jones,
• Eileen M. O’Leary and
• Timothy P. O’Sullivan

Beilstein J. Org. Chem. 2019, 15, 801–810, doi:10.3762/bjoc.15.77

• were unable to access 2 (Scheme 7). Instead, the major product isolated in both cases was novel heterocycle 35. It is likely that cleavage of one of the pivaloxymethyl groups, followed by intramolecular cyclisation, results in the formation of 35. Microwave heating of 33 in the presence of DBU also

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

• -Tyr motif has been devised. This approach comprises two key steps. The first one involves the cyclization of a linear peptidyl resin containing the corresponding halo- and boronoamino acids via a microwave-assisted Suzuki–Miyaura cross coupling. This step is followed by the macrolactamization of the

• 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

• )-βAla-Glu(Rink-MBHA)-OpNB (7), followed by microwave-assisted intramolecular Suzuki–Miyaura reaction, Boc group removal, and final macrolactamization. Boc-Tyr(3-B(OH)2,Me)-OH was prepared in solution through Miyaura borylation of Boc-Tyr(3-I,Me)-OMe [31], followed by hydrolysis of the pinacolate and

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

• through a reaction of furfuryl alcohol with propargyl bromide, as is referred in the study of Cao et al. (Scheme 1) [17]. As a matter of fact, a modification of the purification step was done in order to quantitatively enhance the yield. An alternative solvent-free microwave-assisted organic synthesis

• -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

Intramolecular cascade annulation triggered by rhodium(III)-catalyzed sequential C(sp²)–H activation and C(sp³)–H amination

• Liangliang Song,
• Guilong Tian,
• Johan Van der Eycken and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2019, 15, 571–576, doi:10.3762/bjoc.15.52

• Liangliang Song Guilong Tian Johan Van der Eycken Erik V. Van der Eycken Laboratory for Organic & Microwave-Assisted Chemistry (LOMAC), Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001, Leuven, Belgium Laboratory for Organic and Bio-Organic Synthesis, Department of Organic and