Synthesis of pyrimido[1,6-a]quinoxalines via intermolecular trapping of thermally generated acyl(quinoxalin-2-yl)ketenes by Schiff bases

• Svetlana O. Kasatkina,
• Ekaterina E. Stepanova,
• Maksim V. Dmitriev,
• Ivan G. Mokrushin and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2018, 14, 1734–1742, doi:10.3762/bjoc.14.147

• quinoxalin-2-ylideneacetates [9], multicomponent Mannich–Ritter transformations of quinoxalin-2(1H)-ones under the action of nitriles and 3,4-dihydro-2H-pyran [10] and a microwave-assisted cascade strategy via in situ-generated N-acyliminium ion precursors and amines [11] (Figure 2). To develop a new

Design, synthesis and structure of novel G-2 melamine-based dendrimers incorporating 4-(n-octyloxy)aniline as a peripheral unit

• Cristina Morar,
• Pedro Lameiras,
• Attila Bende,
• Gabriel Katona,
• Emese Gál and
• Mircea Darabantu

Beilstein J. Org. Chem. 2018, 14, 1704–1722, doi:10.3762/bjoc.14.145

• go to completion. The crude isolated products exhibited very low solubility in solvents usually recommended for standard N-acylations (acetone, THF, 1,4-dioxane, pyridine, etc.). Treatment of these acid chlorides with G-1 dendron D-N

  NH (3 equiv) under various conditions (microwave-assisted organic

Synthesis of pyrazolopyrimidinones using a “one-pot” approach under microwave irradiation

• Mark Kelada,
• John M. D. Walsh,
• Robert W. Devine,
• Patrick McArdle and
• John C. Stephens

Beilstein J. Org. Chem. 2018, 14, 1222–1228, doi:10.3762/bjoc.14.104

• the microwave-assisted synthesis of substituted pyrazolo[1,5-a]pyrimidinones, a core scaffold in many bioactive and pharmaceutically relevant compounds, has been established. A variety of substituents was tolerated at the 2 and 5 positions, including functionalized aryls, heterocycles, and alkyl

• groups. Keywords: microwave-assisted synthesis; nitrogen-fused heterocycle; one-pot; pyrimidinone; Introduction The pyrazolo[1,5-a]pyrimidinone is a fused nitrogen-containing heterocyclic system and is of interest due to its role as a basic core scaffold in many bioactive and pharmaceutically relevant

• . Herein, we report such a strategy for the simple synthesis of functionalized pyrazolo[1,5-a]pyrimidinones that employs a one-pot microwave-assisted approach. Findings A number of synthetic approaches have been developed for the synthesis of privileged nitrogen-fused bicyclic systems such as the pyrazolo

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

• sequence-specific DNA binding, the lack of viable strategies for facile synthesis of library of structural variants of these classes of conjugates remains a huge challenge for the researchers. In order to resolve this issue, Dervan et al. recently published a modular microwave-assisted Fmoc-based solid

The first Pd-catalyzed Buchwald–Hartwig aminations at C-2 or C-4 in the estrone series

• Ildikó Bacsa,
• Dávid Szemerédi,
• János Wölfling,
• Gyula Schneider,
• Lilla Fekete and
• Erzsébet Mernyák

Beilstein J. Org. Chem. 2018, 14, 998–1003, doi:10.3762/bjoc.14.85

• with benzophenone imine and subsequent hydrogenolysis. Keywords: aminoestrones; Buchwald–Hartwig amination; 13α-estrone; functionalization; microwave assisted reactions; Introduction Aminoestrones are of particular interest thanks to their diverse biological applications [1][2][3][4]. There exist

• in the amination step [9]. They also found that X-Phos is an outstanding ligand with increased activity and stability compared to those based on BINAP [10]. There are a number of literature methods with respect to microwave-assisted Buchwald–Hartwig couplings [11][12][13]. Many publications have

• reported remarkable advantages of microwave-assisted syntheses, including shorter reaction times, higher yields and chemoselectivity [14][15][16]. Concerning the aromatic ring A of estrone, the Pd-catalyzed Buchwald–Hartwig amination was carried out exclusively at position C-3, starting from the 3-triflate

Methyl isocyanide as a convertible functional group for the synthesis of spirocyclic oxindole γ-lactams via post-Ugi-4CR/transamidation/cyclization in a one-pot, three-step sequence

• Amarendar Reddy Maddirala and
• Peter R. Andreana

Beilstein J. Org. Chem. 2018, 14, 875–883, doi:10.3762/bjoc.14.74

• '-pyrrolidine]-2,5'-diones. Zhu et al. [38] reported 3-substituted-2-indolinones via a microwave-assisted post-Ugi-4CR/Buchwald–Hartwig reaction and another similar approach was illustrated by Van der Eycken et al. [39] for spiro[indoline-3,2'-pyrrole]-2,5'(1'H)-diones. In previous efforts to study 3

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• the desired 1-amidoalkyl-2-naphthol derivatives. This second step can also be considered as a nucleophilic addition of the amide to the o-QM component. Various catalysts and conditions were used to optimize reaction conditions considering economical and environmental aspects. These include microwave

• -assisted reactions, solvent-free conditions and the reusability of the catalyst (Table 1). Procedures are carried out as one-pot multicomponent transformations without the isolation of the intermediates formed. Therefore, with the application of nontoxic, readily available and inexpensive reagents, both

Latest development in the synthesis of ursodeoxycholic acid (UDCA): a critical review

• Fabio Tonin and
• Isabel W. C. E. Arends

Beilstein J. Org. Chem. 2018, 14, 470–483, doi:10.3762/bjoc.14.33

• systems. In addition, a microwave-assisted Wolff–Kishner reduction has been examined with good results in a 30 seconds reaction [45]. Another option is the production of hydrazine in situ, using chemical methods. Also enzymatic activities towards hydrazine have been discovered [46], however, not enough

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

• -arylmaleimides 44 in a solvent-free methodology based on microwave-assisted (80 W, 80 °C, 1.5 h) hetero-Diels–Alder reaction for the synthesis of pyrazolo[3,4-b]pyridine derivatives 45 (Scheme 8). Jiang et al. [54] described the synthesis of macrocyclane-fused pyrazolo[3,4-b]pyridine derivatives 49 by the

• of NaCl from 2.5 to 10 mol % resulted in gradual increase of the yield of the desired product 63 from 85% to 89% and 93%, respectively (Scheme 14). Recently, Jiang et al. [61] have also developed a microwave-assisted synthesis of spiropyrazolo[3,4-b]pyridines 66 via a similar type of three-component

• [2,3-e]pyrazolo[3,4-b]pyridine 77 was formed in the reaction when indandione 58 was used as β-diketone which was attributed to the loss of the benzyl fragment from 5-aminopyrazole derivative 75. Microwave-assisted reactions went to completion in very short time (5 min) compared to reactions under

Recent applications of click chemistry for the functionalization of gold nanoparticles and their conversion to glyco-gold nanoparticles

• Vivek Poonthiyil,
• Thisbe K. Lindhorst,
• Vladimir B. Golovko and
• Antony J. Fairbanks

Beilstein J. Org. Chem. 2018, 14, 11–24, doi:10.3762/bjoc.14.2

• the surface of AuNPs [61]. Herein microwave-assisted CuAAC was used to attach a variety of alkyne derivatives (5, 8, and 18–23) to azide-functionalized AuNPs (Scheme 8). The use of the microwave heating for the CuAAC reduced the reaction time to 5–10 minutes, and also gave almost quantitative

• ]. Surface modification of AuNPs using microwave-assisted CuAAC. Reagents and conditions: (a) HS(CH2)11N3, C6H6, rt, 7 h; (b) dioxane/t-BuOH/H2O or THF, CuSO4, sodium ascorbate, microwave heating (1000 W), 5–10 minutes [61]. AuNP functionalization and efficient CuAAC with a range of alkynes reported by

From dipivaloylketene to tetraoxaadamantanes

• Gert Kollenz and
• Curt Wentrup

Beilstein J. Org. Chem. 2018, 14, 1–10, doi:10.3762/bjoc.14.1

• tetraoxaadamantanes. Inward-pointing isocyanate, urethane and carbamate groups in bisdioxines. The diisocyanate is obtained by Curtius and Hofmann rearrangements of the diazides and diamides [38][39]. Microwave-assisted tetraoxaadamantane formation. Cyclic bisdioxine ester derivative 34 forming a single mono

New bio-nanocomposites based on iron oxides and polysaccharides applied to oxidation and alkylation reactions

• Daily Rodríguez-Padrón,
• Alina M. Balu,
• Antonio A. Romero and
• Rafael Luque

Beilstein J. Org. Chem. 2017, 13, 1982–1993, doi:10.3762/bjoc.13.194

• -assisted oxidation of benzyl alcohol reached 45% conversion after 10 min. The conversion of the alkylation of toluene in both microwave-assisted and conventional heating methods was higher than 99% after 3 min and 30 min, respectively. The transformation of benzyl alcohol and toluene into valuable product

• in both the oxidation and alkylation reaction reveals a potential method for the valorization of lignocellulosic biomass. Keywords: alkylation; benzyl alcohol; benzyl chloride; iron oxide; mechanochemistry; microwave-assisted oxidation; polysaccharide; toluene; Introduction Heterogeneous catalysis

• alkylation of toluene with benzyl chloride, either via microwave-assisted or with conventional heating (60 °C). For the microwave-assisted reaction (Scheme 2), after three minutes, the conversion was higher than 99% for all of the three materials (Figure 6). For the Fe2O3-PS4-MNP nanocatalyst, even after

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• K-10 and Pd/C as catalysts. The microwave-assisted synthesis of β-carboline 96 from tetrahydro-β-carboline 95 using catalytic Pd/C and lithium carbonate at high temperature is also reported [96]. This high yielding procedure gets completed within a few minutes (Scheme 36). Although the reaction

• mechanisms (radical and metal-catalyzed) of the transformation. Ferric chloride-catalyzed, TBHP-oxidized synthesis of substituted quinazolinones and arylquinazolines. Iridium-catalyzed oxidative dehydrogenation of quinolines. Microwave-assisted synthesis of β-carboline with a catalytic amount of Pd/C in

Syntheses of 3,4- and 1,4-dihydroquinazolines from 2-aminobenzylamine

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

Beilstein J. Org. Chem. 2017, 13, 1470–1477, doi:10.3762/bjoc.13.145

• transformations like conversion of amides into nitriles [52][53] or the Beckmann rearrangement [52][54]. They have also been widely employed in heterocyclic synthesis, including microwave-assisted reactions. The recognized wide functional group tolerance, stability and low environmental impact are additional

• nucleus almost unexplored. To our knowledge, this is the first general method available for synthesis of these compounds. The products were synthesized by microwave-assisted ring closure of different aminoamides promoted by PPE. The yields and reaction times involved in the heterocyclization step compare

• required functionalization of both amino groups present in 2-ABA was achieved by different routes involving selective N-acylation and cesium carbonate-mediated N-alkylation reactions, avoiding protection/deprotection steps. The heterocycles were efficiently synthesized in short reaction times by microwave

1-Imidoalkylphosphonium salts with modulated C_α–P⁺ bond strength: synthesis and application as new active α-imidoalkylating agents

• Jakub Adamek,
• Roman Mazurkiewicz,
• Anna Węgrzyk and
• Karol Erfurt

Beilstein J. Org. Chem. 2017, 13, 1446–1455, doi:10.3762/bjoc.13.142

• 9aa, 9ab, 9bb, 9db, 9e, 9f, 9g, 9ia were recrystallized from toluene or toluene/hexane 1:1, v/v. Microwave assisted synthesis of N-(1-arylalkyl)imides 9: A suspension of the 1-(N-imido)alkyltriarylphosphonium salt 5 (0.25 mmol) in an aromatic compound (2.5 cm3) was placed in a glass vial sealed with a

BODIPY-based fluorescent liposomes with sesquiterpene lactone trilobolide

• Ludmila Škorpilová,
• Silvie Rimpelová,
• Michal Jurášek,
• Miloš Buděšínský,
• Jana Lokajová,
• Roman Effenberg,
• Petr Slepička,
• Tomáš Ruml,
• Eva Kmoníčková,
• Pavel B. Drašar and
• Zdeněk Wimmer

Beilstein J. Org. Chem. 2017, 13, 1316–1324, doi:10.3762/bjoc.13.128

• compound is shown in Scheme 1, part B. Propargyl-ChL [35] was introduced into Huisgen copper-catalyzed 1,3-dipolar cycloaddition [36] (CuAAC) with BODIPY 3. This microwave-assisted reaction catalyzed by CuSO4·5H2O, sodium ascorbate and a catalytic amount of TBTA (tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl

New tricks of well-known aminoazoles in isocyanide-based multicomponent reactions and antibacterial activity of the compounds synthesized

• Maryna V. Murlykina,
• Maryna N. Kornet,
• Sergey M. Desenko,
• Svetlana V. Shishkina,
• Oleg V. Shishkin,
• Aleksander A. Brazhko,
• Vladimir I. Musatov,
• Erik V. Van der Eycken and
• Valentin A. Chebanov

Beilstein J. Org. Chem. 2017, 13, 1050–1063, doi:10.3762/bjoc.13.104

• National Academy of Sciences of Ukraine, Nauky Ave., 60, 61001, Kharkiv, Ukraine Laboratory for Organic & Microwave-Assisted Chemistry (LOMAC), KU Leuven, Celestijnenlaan 200F, B-3001, Leuven, Belgium Laboratory of Biotechnology of Physiologically Active Substances, Zaporizhzhya National University

Fluorescent carbon dots from mono- and polysaccharides: synthesis, properties and applications

• Stephen Hill and
• M. Carmen Galan

Beilstein J. Org. Chem. 2017, 13, 675–693, doi:10.3762/bjoc.13.67

• glucose, this particular monosaccharide has been extensively used as an ideal carbon source for CD formation, under a range of experimental conditions. The microwave-assisted synthesis of FCDs from a glucose solution in the presence of poly(ethylene glycol)-200 (PEG-200) by Yang et al. is, to the best of

• and polymerisation in the presence of amino groups makes it a cheap and suitable candidate as a molecular precursor for CD synthesis. To that end, Liu et al. demonstrated in 2011 that the microwave-assisted pyrolysis of glycerol in the presence of TTDDA afforded blue-emissive CDs with a QY of 12

N-Propargylamines: versatile building blocks in the construction of thiazole cores

• S. Arshadi,
• E. Vessally,
• L. Edjlali,
• R. Hosseinzadeh-Khanmiri and
• E. Ghorbani-Kalhor

Beilstein J. Org. Chem. 2017, 13, 625–638, doi:10.3762/bjoc.13.61

• precursors 31. (a) Microwave-assisted cyclization of N-propargyl thiocarbamate 34. (b) Synthesis of thiazoles 39 through a tandem coupling–cyclization–isomerization sequential process. Synthesis of thiazolidines 42 (42’) from the reaction of β-oxodithioesters 40 (40’) with N-propargylamine (41) through an N

• dihydrothiazol-2-ylamides 54. (b) Possible reaction pathway for the generation of product 54. Proposed mechanism for the generation of the iodine-substituted 4H-1,3-thiazines 56 and 4,5-dihydrothiazoles 57. Au(III)-catalyzed synthesis of 5-alkylidenedihydrothiazoles 58 developed by Stevens. Microwave-assisted

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• -arylpropanoic and 4-arylbutanoic acids has been reported in 2015 by Le et al. [22]. The authors applied a microwave-assisted intramolecular Friedel–Crafts acylation catalyzed by metal triflate in triflate-anion containing ionic liquids. This synthesis proceeded with the goals of green chemistry and allowed to

• -indanones 69 were synthesized from benzyl Meldrum’s acids derivatives 67 in two steps [47]. In this synthesis, they underwent microwave-assisted hydrolysis to carboxylic acids 68, followed by chlorosulfonic acid-mediated Friedel–Crafts cyclization to give halo-1-indanones 69 (Scheme 23). Quaternized

• 2-bromo-6-methoxy-3-phenyl-1-indanone (130, Scheme 41). An efficient microwave-assisted synthesis of 1-indanones 132a–s related to combretastatin A-4 has been proposed by Lawrence et al. [68]. Two of the indanones were obtained via a Nazarov cyclization of chalcones 131 without using microwaves, in

NMR reaction monitoring in flow synthesis

• M. Victoria Gomez and
• Antonio de la Hoz

Beilstein J. Org. Chem. 2017, 13, 285–300, doi:10.3762/bjoc.13.31

• reaction system, including the main reaction pathways and also the side reactions, and to detect several intermediates including the formation of an ether bridge (Figure 11). Gomez et al. [48] reported the first contribution that combines microstructured NMR probes with microliter continuous-flow microwave

• -assisted organic reactions. A microfluidic NMR chip with a planar microcoil and a detection volume of 6 nL was used for detection (Figure 12a). The specially designed microwave reactor has a small cavity in which a WeflonTM (15% carbon filled PTFE) bar is introduced to ensure almost instantaneous heating

The synthesis of α-aryl-α-aminophosphonates and α-aryl-α-aminophosphine oxides by the microwave-assisted Pudovik reaction

• Erika Bálint,
• Ádám Tajti,
• Anna Ádám,
• István Csontos,
• Konstantin Karaghiosoff,
• Mátyás Czugler,
• Péter Ábrányi-Balogh and
• György Keglevich

Beilstein J. Org. Chem. 2017, 13, 76–86, doi:10.3762/bjoc.13.10

• and α-aryl-α-aminophosphine oxides was synthesized by the microwave-assisted solvent-free addition of dialkyl phosphites and diphenylphosphine oxide, respectively, to imines formed from benzaldehyde derivatives and primary amines. After optimization, the reactivity was mapped, and the fine mechanism

Synthesis of spiro[isoindole-1,5’-isoxazolidin]-3(2H)-ones as potential inhibitors of the MDM2-p53 interaction

• Salvatore V. Giofrè,
• Santa Cirmi,
• Raffaella Mancuso,
• Francesco Nicolò,
• Giuseppe Lanza,
• Laura Legnani,
• Agata Campisi,
• Maria A. Chiacchio,
• Michele Navarra,
• Bartolo Gabriele and
• Roberto Romeo

Beilstein J. Org. Chem. 2016, 12, 2793–2807, doi:10.3762/bjoc.12.278

• . Experimental General: Solvents and reagents are commercial. Microwave assisted synthesis was performed in a CEM Discover microwave oven using sealed reaction vessels. The temperature was monitored using a vertically focused IR temperature sensor. In order to have a homogenous system all the batches were

Electron-transfer-initiated benzoin- and Stetter-like reactions in packed-bed reactors for process intensification

• Anna Zaghi,
• Daniele Ragno,
• Graziano Di Carmine,
• Carmela De Risi,
• Olga Bortolini,
• Pier Paolo Giovannini,
• Giancarlo Fantin and
• Alessandro Massi

Beilstein J. Org. Chem. 2016, 12, 2719–2730, doi:10.3762/bjoc.12.268

• with ESI-L low concentration tuning mix from m/z 118 to 2700 to yield an accuracy below 5 ppm. Accurate mass data were collected by directly infusing samples in 40/60 H2O/ACN 0.1% TFA into the system at a flow-rate of 0.4 mL/min. Microwave-assisted reactions were carried out using a single-mode cavity

Continuous-flow synthesis of primary amines: Metal-free reduction of aliphatic and aromatic nitro derivatives with trichlorosilane

• Riccardo Porta,
• Alessandra Puglisi,
• Giacomo Colombo,
• Sergio Rossi and
• Maurizio Benaglia

Beilstein J. Org. Chem. 2016, 12, 2614–2619, doi:10.3762/bjoc.12.257

• conditions, but the presence of noble metal catalysts, packed into disposable cartridges, suffers from functional group compatibility and catalyst poisoning during time. In 2012 Kappe’s research group reported the microwave-assisted continuous-flow synthesis of anilines from nitroarenes using hydrazine as