Features of the behavior of 4-amino-5-carboxamido-1,2,3-triazole in multicomponent heterocyclizations with carbonyl compounds

• Eugene S. Gladkov,
• Katerina A. Gura,
• Svetlana M. Sirko,
• Sergey M. Desenko,
• Ulrich Groth and
• Valentin A. Chebanov

Beilstein J. Org. Chem. 2012, 8, 2100–2105, doi:10.3762/bjoc.8.236

• ; heterocycle; microwave-assisted synthesis; multicomponent reaction; ultrasound-assisted synthesis; Introduction Multicomponent reactions (MCRs) [1][2][3][4] involving polyfunctional aminazoles as a key reagent are challenging objectives in the modern chemistry of heterocyclic compounds dealing with the

• boiling dry ethanol or under MW heating in methanol. The same procedure also allowed us to obtain compounds 5a,b. The best results in this case were observed when the microwave-assisted procedure (Method D) was applied. It should be noted that for similar treatments involving 3-amino-1,2,4-triazole [7][29

• '-cyclopentane}-3-carboxamide (4a) or 5,6,7,8-tetrahydro-4H-spiro{[1,2,3]triazolo[5,1-b]quinazoline-9,1'-cyclohexane}-3-carboxamide (4b) under all the conditions tested. The best results were observed in the case of microwave-assisted synthesis in methanol at 120 °C. Spirocompound 4c may be obtained by a

Exploring chemical diversity via a modular reaction pairing strategy

• Joanna K. Loh,
• Sun Young Yoon,
• Thiwanka B. Samarakoon,
• Alan Rolfe,
• Patrick Porubsky,
• Benjamin Neuenswander,
• Gerald H. Lushington and
• Paul R. Hanson

Beilstein J. Org. Chem. 2012, 8, 1293–1302, doi:10.3762/bjoc.8.147

• Methodologies and Library Development (KU-CMLD), 2034 Becker Drive, Shankel Structural Biology Center, West Campus, Lawrence, KS 66047-3761, USA 10.3762/bjoc.8.147 Abstract The efficient synthesis of an 80-member library of unique benzoxathiazocine 1,1-dioxides by a microwave-assisted, intermolecular

• the design and synthesis of an 80-member library of benzofused sultams by a microwave-assisted, intermolecular SNAr diversification of core benzoxathiazocine 1,1-dioxide scaffolds [33][34][35][36] (Scheme 1). Results and Discussion Initial efforts focused on the synthesis of eight core scaffolds 1–8

• . Conclusion In conclusion, an efficient microwave-assisted intermolecular-SNAr protocol for the synthesis of an 80-member library of amino benzoxathiazocine 1,1-dioxides has been developed. Employing a variety of commercially available chiral, non-racemic amines, the 80-member library of bridged, benzofused

Multistep organic synthesis of modular photosystems

• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2012, 8, 897–904, doi:10.3762/bjoc.8.102

• and alkylation with ethyl bromoacetate (10) gave ethyl ester 11, and final ester hydrolysis lead to the desired acid 7. The peripheral NDIs 12, designed to template for stack exchange on initiator 2, were prepared from naphthalenedianhydride (NDA) 13. Microwave-assisted imidation [15] with the two

• NDI 18 of initiator 2, designed to initiate and template for SOSIP, was accessible from NDA 13 as well. The synthesis of NDI 19 by microwave-assisted imidation with Boc-protected lysine 20 has been reported before in the literature [15]. Reaction with Cbz-hydrazine gave the Cbz-protected NDI hydrazide

• crude dibromo cNDA 32. Microwave-assisted reaction [15] with amines 14 and 15 gave the mixed cNDI 44 together with the symmetric side products. The obtained mixture of 2,6- and 3,7-regioisomers was not separated throughout the entire synthesis of photosystem 1. Nucleophilic aromatic substitution with

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

• analytical pure sample of 6g (identical with an authentic sample, MS, 1H NMR and 13C NMR). ORTEP diagram of compound 6a. ORTEP diagram of compound 5. ORTEP diagram of compound 6e. ORTEP diagram of compound 6g. Microwave-assisted synthesis of 4 and 6. A proposed mechanism to account for the formation of

• products 6. The factors that determine the nature of the end product are, however, at present unclear. Microwave-assisted synthesis of 4 and 6. Selected bond lengths and bond angles for compound 6a. Selected bond lengths and bond angles for compound 6e. Selected bond lengths and bond angles for compound 6g

Synthesis of 2-amino-3-arylpropan-1-ols and 1-(2,3-diaminopropyl)-1,2,3-triazoles and evaluation of their antimalarial activity

• Matthias D’hooghe,
• Stéphanie Vandekerckhove,
• Karen Mollet,
• Karel Vervisch,
• Stijn Dekeukeleire,
• Liesbeth Lehoucq,
• Carmen Lategan,
• Peter J. Smith,
• Kelly Chibale and
• Norbert De Kimpe

Beilstein J. Org. Chem. 2011, 7, 1745–1752, doi:10.3762/bjoc.7.205

• )methyl]aziridines by Cu(I)-catalyzed azide-alkyne cycloaddition, followed by microwave-assisted, regioselective ring opening by dialkylamine towards 1-(2,3-diaminopropyl)-1,2,3-triazoles. Although most of these compounds exhibited weak antiplasmodial activity, six representatives showed moderate

• , which were shown to be of great importance as novel antiplasmodial agents (Figure 1) [6]. More recently, we reported 1,2,3-triaminopropanes 2 as a new class of antimalarial compounds (Figure 1), prepared through microwave-assisted, regioselective ring opening of the corresponding 2-(aminomethyl

• dimethylaminopropanes 16f,g in good yields (Scheme 3). This result showed that this microwave-assisted methodology for the ring opening of nonactivated aziridines can be further extended towards the use of other secondary amines. In order to introduce structural diversity within these molecules, different substituent

Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series

• Cécile Verrier,
• Pierrik Lassalas,
• Laure Théveau,
• Guy Quéguiner,
• François Trécourt,
• Francis Marsais and
• Christophe Hoarau

Beilstein J. Org. Chem. 2011, 7, 1584–1601, doi:10.3762/bjoc.7.187

• with aryliodides under base-free and ligandless conditions in DMF as solvent [42][43]. However under the developed conditions, the direct coupling of oxazole proved to be inefficient (Scheme 7). More recently, Piguel disclosed an original, ligandless, microwave-assisted, Pd(0)/Cu(I)-catalyzed protocol

Continuous preparation of carbon-nanotube-supported platinum catalysts in a flow reactor directly heated by electric current

• Alicja Schlange,
• Antonio Rodolfo dos Santos,
• Ulrich Kunz and
• Thomas Turek

Beilstein J. Org. Chem. 2011, 7, 1412–1420, doi:10.3762/bjoc.7.165

• hot spots. This can lead to temperature gradients in the reacting solution, resulting in poor dispersion of Pt on the carbon support. For this reason, in the past few years heating by means of microwave ovens was introduced. The microwave-assisted polyol synthesis method has many advantages over the

Translation of microwave methodology to continuous flow for the efficient synthesis of diaryl ethers via a base-mediated S_NAr reaction

• Charlotte Wiles and
• Paul Watts

Beilstein J. Org. Chem. 2011, 7, 1360–1371, doi:10.3762/bjoc.7.160

• large scale, whilst increasing, is not as well established, largely due to the challenges associated with the uniform irradiation of large reactor vessels [16]. In a critical assessment of microwave-assisted organic synthesis, Moseley and Kappe [17] recently concluded that on a small scale (1 to 50 mL

Scaling up of continuous-flow, microwave-assisted, organic reactions by varying the size of Pd-functionalized catalytic monoliths

• Ping He,
• Stephen J. Haswell,
• Paul D. I. Fletcher,
• Stephen M. Kelly and
• Andrew Mansfield

Beilstein J. Org. Chem. 2011, 7, 1150–1157, doi:10.3762/bjoc.7.133

• to scale up the rate of product formation without a loss in the intrinsic reaction performance, by using a continuous-flow, microwave-assisted, Pd-supported silica-monolith reactor. The Pd-monolith-3.2 and Pd-monolith-6.4 (both with the same length of 3 cm) were used to perform the model reaction (1

• the setup for continuous-flow, microwave-assisted Suzuki–Miyaura reactions. Supporting Information File 330: Additional material.

Hyperbranched polyethylenimine bearing cyclodextrin moieties showing temperature and pH controlled dye release

• Indra Böhm,
• Susanne Katharina Kreth and
• Helmut Ritter

Beilstein J. Org. Chem. 2011, 7, 1130–1134, doi:10.3762/bjoc.7.130

• , Scheme S1). Briefly, compound 3 can be obtained through polymer-analogous amidation with 5-hexynoic acid and subsequent reaction with mono-(6-azido-6-desoxy)-β-cyclodextrin by click reaction under microwave assisted conditions. Synthesis of 1,4-di-N-adamantylaminoanthraquinone (2): 2 was synthesized

Chemistry in flow systems II

• Andreas Kirschning

Beilstein J. Org. Chem. 2011, 7, 1046–1047, doi:10.3762/bjoc.7.119

• microwave-assisted synthesis, for which almost two decades passed until it became a broadly accepted enabling heating technology, and which will continue to have a strong impact on practical organic chemistry. Flow systems have already been implemented in various areas in organic chemistry with very

Unusual behavior in the reactivity of 5-substituted-1H-tetrazoles in a resistively heated microreactor

• Bernhard Gutmann,
• Toma N. Glasnov,
• Tahseen Razzaq,
• Walter Goessler,
• Dominique M. Roberge and
• C. Oliver Kappe

Beilstein J. Org. Chem. 2011, 7, 503–517, doi:10.3762/bjoc.7.59

• ]. High-temperature processing offers many distinct advantages as demonstrated by the recent success of microwave-assisted organic synthesis [14][15][16][17][18]. In microwave chemistry, reaction times can often be reduced from hours to minutes by efficient and rapid direct dielectric heating of the

• effects in flow chemistry are also discussed. Results and Discussion Flow degradation of 5-benzhydryl-1H-tetrazole As a model system for tetrazole formation the microwave-assisted cycloaddition of diphenylacetonitrile (1) with NaN3 was studied (Scheme 1). After considerable experimentation [25] an optimum

• analysis. All solvents and chemicals were obtained from standard commercial vendors and were used without any further purification. Pd concentrations from the leaching experiments of a “palladated” steel coil and the metal screening of the “NMP/AcOH/H2O mixtures” were determined after microwave assisted

SbCl₃-catalyzed one-pot synthesis of 4,4′-diaminotriarylmethanes under solvent-free conditions: Synthesis, characterization, and DFT studies

• Ghasem Rezanejade Bardajee

Beilstein J. Org. Chem. 2011, 7, 135–144, doi:10.3762/bjoc.7.19

• acids such as zinc chloride, zeolites, montmorillonite K-10, and polymer-supported sulfonic acid (NKC-9) [35][36][37][38][39][40]. Microwave-assisted synthesis of DTMs in the presence of aniline hydrochloride has also been described [41]. Recently, bismuth(III) nitrate and zirconium(IV) dichloride oxide

• heterocyclic aldehydes in the presence of SbCl3 to produce the corresponding DTMs in good to excellent yields. At first we focused on the reaction of benzaldehyde and N,N-dimethylaniline as a model reaction under various reaction conditions (with solvent, solvent-free, and microwave-assisted). Various protic

Formation of epoxide-amine oligo-adducts as OH-functionalized initiators for the ring-opening polymerization of ε-caprolactone

• Julia Theis and
• Helmut Ritter

Beilstein J. Org. Chem. 2010, 6, 938–944, doi:10.3762/bjoc.6.105

• Julia Theis Helmut Ritter Institut für Organische Chemie und Makromolekulare Chemie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany 10.3762/bjoc.6.105 Abstract Epoxide-amine oligo-adducts were synthesized via a one-pot microwave assisted heterogeneous

• former work on the formation of hyperbranched epoxide-amine adducts via microwave-assisted heterogeneous catalytic transfer hydrogenation [22], we report herein the synthesis of an linear oligo(amino alcohol). The hydroxy groups of the latter were then used as an initiator for the ring-opening

• oligomeric initiator. This oligomer can be obtained in a one-pot microwave assisted heterogeneous catalytic transfer hydrogenation, starting from 4-nitroanisole (2) in the presence of the diglycidyl ether of bisphenol A (1). Product 4 consists of oligomers because of some side reactions. The hydroxy groups

Synthesis and crystal structures of multifunctional tosylates as basis for star-shaped poly(2-ethyl-2-oxazoline)s

• Richard Hoogenboom,
• Martin W. M. Fijten,
• Guido Kickelbick and
• Ulrich S. Schubert

Beilstein J. Org. Chem. 2010, 6, 773–783, doi:10.3762/bjoc.6.96

• might cause side reactions during the polymerizations. Subsequently, this tetrafunctional initiator was applied for the microwave-assisted cationic ring-opening polymerization of EtOx. The polymerization of EtOx with TetraTos-B as initiator was performed with 2 M monomer concentration in CH3CN at 140 °C

Calix[4]arene-click-cyclodextrin and supramolecular structures with watersoluble NIPAAM-copolymers bearing adamantyl units: “Rings on ring on chain”

• Bernd Garska,
• Monir Tabatabai and
• Helmut Ritter

Beilstein J. Org. Chem. 2010, 6, 784–788, doi:10.3762/bjoc.6.83

• 5,11,17,23-tetra-tert-butyl-25,27-dipropargylether-26,28-hydroxy-calix[4]arene (calix[4]arene-dipropargylether) (2) onto 6I-azido-6I-deoxycyclomaltoheptaose (3) under microwave assisted conditions. The coupling was proven by MALDI-TOF mass spectrometry, 1H NMR and IR-spectroscopy. The pH dependent

• (2) onto 6I-azido-β-CD (3) under microwave assisted conditions. Results and Discussion Synthesis and characterization of compound 4 The calixarene-click-CD compound (4) was synthesized as shown in Scheme 1. The successful microwave assisted cycloaddition of 5,11,17,23-tetra-tert-butyl-25,27

• 500 nm) of the solution heated at 1 K/min in a magnetically stirred cell; cloud points were defined as the temperature at which the transmission decreases by 50%. Microwave assisted synthesis was performed using a CEM Discover synthesis unit (monomode system). The temperature was measured by infrared

Solvent-free and time-efficient Suzuki–Miyaura reaction in a ball mill: the solid reagent system KF–Al₂O₃ under inspection

• Franziska Bernhardt,
• Ronald Trotzki,
• Tony Szuppa,
• Achim Stolle and
• Bernd Ondruschka

Beilstein J. Org. Chem. 2010, 6, No. 7, doi:10.3762/bjoc.6.7

• titanium silicalite, TiSiO4, showed moderate conversions in the range of basic γ-Al2O3 SRS3. Contrary to microwave-assisted reactions, MgO showed only little conversion when used as a base under ball milling conditions [34], whereas neutral oxides SiO2 and CeO2 did not show any conversion. Since the

• neutral to basic aluminas has been recently shown in three-component reactions affording thiochromeno[2,3-b]pyridine derivatives [24]. The results were in clear contrast to that of the microwave-assisted Pd(PPh3)4-catalyzed solid-state Suzuki–Miyaura reaction protocol presented by Saha et al., revealing

• acid and surface oxygen of alumina (ArB(OH)2–O–Al(O–)3). The reported results also confute the results from microwave-assisted cross-coupling with pure basic alumina, which was seen to be completely inert for this type of reaction [33]. Apparently co-grinding of all reactants in a ball mill leads to in

A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis

• Magnus Rueping and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2010, 6, No. 6, doi:10.3762/bjoc.6.6

• . A gold(I)-catalyzed hydroarylation of indoles with styrenes as well as with aliphatic and cyclic alkenes was developed by Che et al. [64]. [AuCl(PPh3)]/AgOTf was the catalyst system of choice and the reaction was, depending on the substrate, performed under thermal or microwave-assisted conditions

Gold film- catalysed benzannulation by Microwave- Assisted, Continuous Flow Organic Synthesis (MACOS)

• Gjergji Shore,
• Michael Tsimerman and
• Michael G. Organ

Beilstein J. Org. Chem. 2009, 5, No. 35, doi:10.3762/bjoc.5.35

• regioselective, and proceeds in good to excellent conversion. Keywords: benzannulation; flow synthesis; gold catalysis; microwave; thin metal film; Introduction Microwave-assisted organic synthesis (MAOS) has had a significant impact on organic and medicinal chemistry by dramatically shortening reaction times

• of gold, copper, silver, and gold-on-silver were prepared and evaluated for their catalytic activity in the microwave-assisted, continuous flow benzannulation of aryl, alkyl and silylalkynes with alkynylbenzaldehydes. Only the gold-on-silver films possessed both the high level of catalytic activity

An expedient synthesis of 5-n-alkylresorcinols and novel 5-n-alkylresorcinol haptens

• Kirsti Parikka and
• Kristiina Wähälä

Beilstein J. Org. Chem. 2009, 5, No. 22, doi:10.3762/bjoc.5.22

• way for the immunochemical detection techniques of alkylresorcinols. Keywords: 5-n-alkylresorcinols; haptens; microwave assisted synthesis; Wittig reaction; Introduction 5-Alk(en)ylresorcinols and related compounds are phenolic lipids present in several families of plants (e.g. Gramineae

N-acylation of ethanolamine using lipase: a chemoselective catalyst

• Mazaahir Kidwai,
• Roona Poddar and
• Poonam Mothsra

Beilstein J. Org. Chem. 2009, 5, No. 10, doi:10.3762/bjoc.5.10

• lipase (Novozym® 435) are described and optimum conditions for selective N-acylation rather than O-acylation are also discussed. Microwave assisted solution phase, solid supported and conventional methods were investigated and results were compared. There is a synergy between the enzyme catalysis and

• microwave irradiation. Keywords: chemoselective; lipase; microwave irradiation; zein number; Introduction Microwave assisted enzyme catalysis is a popular developing methodology in the field of green chemistry [1]. Enzymes have gained pivotal importance in the production of fine chemicals, pharmaceuticals

• irradiation has advantages over conventional heating (CH), in the control of reaction rate, yield, stereoselectivity or chemoselectivity [15]. Microwave assisted heating under controlled conditions is an invaluable technology for organic synthesis because it often dramatically reduces reaction times

Microwave assisted synthesis of triazoloquinazolinones and benzimidazoquinazolinones

• Aboul-Fetouh E. Mourad,
• Ashraf A. Aly,
• Hassan H. Farag and
• Eman A. Beshr

Beilstein J. Org. Chem. 2007, 3, No. 11, doi:10.1186/1860-5397-3-11

ADDP and PS-PPh₃: an efficient Mitsunobu protocol for the preparation of pyridine ether PPAR agonists

• Paul S. Humphries,
• Quyen-Quyen T. Do and
• David M. Wilhite

Beilstein J. Org. Chem. 2006, 2, No. 21, doi:10.1186/1860-5397-2-21

• esters, we then sought an expedient method for obtaining the final carboxylic acids. We opted for a microwave-assisted procedure for this basic hydrolysis step. As shown in Scheme 3, the carboxylic acids (e.g. 25) could be obtained in a matter of minutes [see Supporting Information File 1 and Supporting

Microwave- assisted ring closure reactions: Synthesis of 8-substituted xanthine derivatives and related pyrimido- and diazepinopurinediones

• Joachim C. Burbiel,
• Jörg Hockemeyer and
• Christa E. Müller

Beilstein J. Org. Chem. 2006, 2, No. 20, doi:10.1186/1860-5397-2-20

• high yield by microwave-assisted ring closure reaction. Results and Discussion A key step in the classical synthetic route towards xanthines is the ring closure of the imidazole ring [15]. An improved ring closure method leading to 8-unsubstituted xanthines by microwave-assisted ring closure reaction

• poor mixing. Microwave-assisted synthesis has been extensively applied in the field of heterocyclic chemistry, especially when high temperatures are needed for ring formation with conventional heating [24]. Based on these findings the preparation of 8-substituted xanthine derivatives and related

• solution or suspension of the starting compounds in a mixture of HMDS and tetrahydrofuran. The addition of THF as a co-solvent proved to be crucial. Yields were generally improved by the new method. The new microwave-assisted cyclization procedure allowed the preparation of a previously unaccessible 2