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

• 5-aminopyrazole-4/3-ethylcarboxylates 126 with trifluoromethyl-β-diketones 17 in acetic acid under microwave heating, which were subsequently hydrolyzed to the corresponding pyrazolo[1,5-a]pyrimidine carboxylic acids 128 by treating with sodium hydroxide in ethanol at 65 °C. The compounds were

Fluorescent nucleobase analogues for base–base FRET in nucleic acids: synthesis, photophysics and applications

• Mattias Bood,
• Sangamesh Sarangamath,
• Moa S. Wranne,
• Morten Grøtli and
• L. Marcus Wilhelmsson

Beilstein J. Org. Chem. 2018, 14, 114–129, doi:10.3762/bjoc.14.7

• yields, was effectively obtained in 86% yield by using an excess of KF in ethanol and microwave heating at 140 °C. Conveniently, at the same time all the three acetyl protecting groups were cleaved and the free nucleobase was isolated via precipitation. A 5´-DMTr protection followed by 2´-TBDMS

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

• of the bisdioxines becomes severely hindered in cyclic derivatives, so that the 38-membered ring compound 32 requires microwave heating at 170 °C to form tetraoxaadamantane 33, and the catenated compound 36 and calix[6]arene derivative 37 did not form tetraoxaadamantanes. The reaction mechanisms of

Phosphonic acid: preparation and applications

• Charlotte M. Sevrain,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2017, 13, 2186–2213, doi:10.3762/bjoc.13.219

• microwave heating. The final product was isolated in 63% yield [223]. The Moedritzer–Irani reaction was also applied to introduce phosphonic acid functions on polymer or dendrimers possessing reactive amine. Accordingly, phosphonic acids were introduced on polyethyleneglycol 113 [188], polyethylene imine

Synthesis of substituted Z-styrenes by Hiyama-type coupling of oxasilacycloalkenes: application to the synthesis of a 1-benzoxocane

• James R. Vyvyan,
• Courtney A. Engles,
• Scott L. Bray,
• Erik D. Wold,
• Christopher L. Porter and
• Mikhail O. Konev

Beilstein J. Org. Chem. 2017, 13, 2122–2127, doi:10.3762/bjoc.13.209

• yield of the cyclic ether was still low (Table 2, entry 6). Microwave heating was not helpful (Table 2, entry 7). The non-nucleophilic base DBU was not effective in promoting the cyclization, either (Table 2, entry 8). We observed small amounts of products arising from the dehydration of 15 in the 1H

An efficient Pd–NHC catalyst system in situ generated from Na₂PdCl₄ and PEG-functionalized imidazolium salts for Mizoroki–Heck reactions in water

• Nan Sun,
• Meng Chen,
• Liqun Jin,
• Wei Zhao,
• Baoxiang Hu,
• Zhenlu Shen and
• Xinquan Hu

Beilstein J. Org. Chem. 2017, 13, 1735–1744, doi:10.3762/bjoc.13.168

• media became more and more attractive [11]. Despite there are several strategies for palladium-catalyzed cross-coupling reactions in water, such as microwave heating [12], ultrasonic irradiation [13][14] and ligand-free methodology [15][16], the more efficient and preferable one is the use of water

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

• facilitate the conversion [52][53][54][55]. Unfortunately most of these methods suffer from the disadvantages of prolonged reaction time, poor yield and competing oxidative dealkylation of 4-benzyl and sec-alkyl-substituted DHP substrates. Alternative strategies involving transition metals and microwave

• heating, ultrasonication and solvent-free conditions alleviated the drawbacks to a major extent [56][57][58][59][60][61]. One such useful strategy include manganese dioxide (MnO2)-mediated oxidative aromatization of 1,4-DHP 45 to afford substituted pyridine derivatives 46 under microwave conditions

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

Transition-metal-catalyzed synthesis of phenols and aryl thiols

• Yajun Liu,
• Shasha Liu and
• Yan Xiao

Beilstein J. Org. Chem. 2017, 13, 589–611, doi:10.3762/bjoc.13.58

• CsOH to weaker KOH showed comparable yields. In 2010, Leadbeater and co-workers used N,N′-dimethylethylenediamine (DMEDA) as ligand and performed the reaction using CuI as catalyst in the presence of K3PO4 [32] (Scheme 10). Under microwave heating, the reactions were accomplished within 30 min. A

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

• the presence of trifluoroacetic acid (TFA) at 120 °C (4 hours). The authors have proved that the microwave heating would significantly shorten the reaction time up to 20 minutes under the same reaction conditions (TFA, 120 °C, Scheme 42). The cell growth inhibitory properties of the synthesized 1

Stereoselective synthesis of fused tetrahydroquinazolines through one-pot double [3 + 2] dipolar cycloadditions followed by [5 + 1] annulation

• Xiaofeng Zhang,
• Kenny Pham,
• Shuai Liu,
• Marc Legris,
• Alex Muthengi,
• Jerry P. Jasinski and
• Wei Zhang

Beilstein J. Org. Chem. 2016, 12, 2204–2210, doi:10.3762/bjoc.12.211

• , and MeCN as a solvent, the three-component reaction for 2a was completed under microwave heating at 115 °C for 25 min. Without work-up, the reaction mixture was directly reacted with 1.0 equiv of N-benzylmaleimide (6a) under microwave heating at 125 °C for 25 min to give 7a as a major diastereomer of

Tandem processes promoted by a hydrogen shift in 6-arylfulvenes bearing acetalic units at ortho position: a combined experimental and computational study

• Mateo Alajarin,
• Marta Marin-Luna,
• Pilar Sanchez-Andrada and
• Angel Vidal

Beilstein J. Org. Chem. 2016, 12, 260–270, doi:10.3762/bjoc.12.28

• into fulvenes 24 by the usual procedure, whereas its microwave heating (DMSO, 120 °C, 120 W) yielded a mixture of the benz[f]indenes 25 and 26 in the habitual 2:1 ratio. These conversions most probably occur, in mechanistic terms, similarly to those of the acetal-fulvenes 3 (Scheme 4), although in the

Hydroquinone–pyrrole dyads with varied linkers

• Hao Huang,
• Christoffer Karlsson,
• Maria Strømme,
• Martin Sjödin and
• Adolf Gogoll

Beilstein J. Org. Chem. 2016, 12, 89–96, doi:10.3762/bjoc.12.10

• microwave heating [22], allowing the reaction to be completed in half an hour with 95% yield. A second Sonogashira reaction of 10 with 3-iodo-1-(triisopropylsilyl)-1H-pyrrole afforded the protected pyrrole derivative 4d. For this second Sonogashira reaction, these conditions, when attempting to couple 10 to

• absorption maxima from DFT calculations for each linker compound are indicated by vertical red lines. Calculated HOMO for 3a (a) and 3d (b). Synthetic route for 3-(2,5-dimethoxybenzyl)-1H-pyrrole (3a). Conditions: i) Pd(PPh3)4, Na2CO3 (2 M aq), MeOH/toluene, microwave heating, 110 °C, 4 h, 56%; ii) TBAF, THF

• -(triisopropylsilyl)-1H-pyrrole-3-carbaldehyde, 80 °C, 3 h, 40%; iv) TBAF, THF, rt, 0.5 h, 86%. Synthesis of 3-((2,5-dimethoxyphenyl)ethynyl)-1H-pyrrole (3d). Conditions: i) Ethynyltrimethylsilane, Pd(PPh3)2Cl2, CuI, PPh3, diethylamine, DMF, microwave heating, 120 °C, 30 min, 95%; ii) NaOH (1 M, aq), MeOH/CHCl3, rt

Efficient synthetic protocols for the preparation of common N-heterocyclic carbene precursors

• Morgan Hans,
• Jan Lorkowski,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2015, 11, 2318–2325, doi:10.3762/bjoc.11.252

• -methylphenyl)imidazolium chloride (IDip*·HCl or IPr*·HCl). Keywords: cyclization; experimental procedure; imidazolinium salt; imidazolium salt; microwave heating; Introduction Since Arduengo and co-workers successfully isolated and characterized the first imidazol-2-ylidene derivative in 1991 [1][2], stable

Half-sandwich nickel(II) complexes bearing 1,3-di(cycloalkyl)imidazol-2-ylidene ligands

• Johnathon Yau,
• Kaarel E. Hunt,
• Laura McDougall,
• Alan R. Kennedy and
• David J. Nelson

Beilstein J. Org. Chem. 2015, 11, 2171–2178, doi:10.3762/bjoc.11.235

• much shorter reaction times by using microwave heating [21]. As the microwave apparatus heats the solvent directly, rather than applying heat to the outer walls of a glass vessel, it was proposed that this might allow for better yields. Optimisation of the reaction conditions (20 min at 110 °C in THF

• [NiCl(Cp)(IMes)] (2). Synthesis of [NiCl(Cp)(ICy)] using conventional heating. Synthesis of (a) [NiCl(Cp)(ICy)] (3) and (b) [NiCl(Cp)(IDD)] (4) with microwave heating. Model Suzuki–Miyaura reaction for the evaluation of the new complexes as cross-coupling pre-catalysts. Experimental data for single

New palladium–oxazoline complexes: Synthesis and evaluation of the optical properties and the catalytic power during the oxidation of textile dyes

• Rym Hassani,
• Mahjoub Jabli,
• Yakdhane Kacem,
• Jérôme Marrot,
• Damien Prim and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2015, 11, 1175–1186, doi:10.3762/bjoc.11.132

• /Micromass) device with a resolution of 5000 RP at 5%. Thin-layer chromatography (TLC) was carried out on aluminium sheets precoated with silica gel 60 F254. Microwave irradiations were realized using an Anton Paar Monowave 300 apparatus. Microwave heating was performed with a single mode cavity Discover

Thiazole formation through a modified Gewald reaction

• Carl J. Mallia,
• Lukas Englert,
• Gary C. Walter and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2015, 11, 875–883, doi:10.3762/bjoc.11.98

• range, microwave heating was introduced. This allowed access to higher temperatures above the boiling points of the solvents used at atmospheric pressure. Optimisation and scoping of thiazole formation The reaction of ethyl phenylcyanoacetate (16) with pro-aldehyde 10 was used as a model system applying

Matsuda–Heck reaction with arenediazonium tosylates in water

• Ksenia V. Kutonova,
• Marina E. Trusova,
• Andrey V. Stankevich,
• Pavel S. Postnikov and
• Victor D. Filimonov

Beilstein J. Org. Chem. 2015, 11, 358–362, doi:10.3762/bjoc.11.41

• for the first time. A range of alkenes was arylated in good to quantitative yields in water. The reaction is significantly accelerated when carried out under microwave heating. The arylation of haloalkylacrylates with diazonium salts has been implemented for the first time. Keywords: alkyl cinnamates

• were recorded on a Bruker Avance 300 and a Perkin Elmer BXII, respectively. Melting points were obtained with a melting point system MP50, Mettler Toledo (values are given uncorrected). HPLC–MS measurements were obtained with a Thermo Scientific DFS High Resolution GC–MS. Microwave heating was carried

• . Arylation of methyl acrylate (1a) with arenediazonium tosylate 2a. Study of reaction conditions. Arylation of alkenes with arenediazonium tosylates in water under microwave heating. Supporting Information Supporting Information File 354: Additional experimental data. Acknowledgements This research was

Efficient deprotection of F-BODIPY derivatives: removal of BF₂ using Brønsted acids

• Mingfeng Yu,
• Joseph K.-H. Wong,
• Cyril Tang,
• Peter Turner,
• Matthew H. Todd and
• Peter J. Rutledge

Beilstein J. Org. Chem. 2015, 11, 37–41, doi:10.3762/bjoc.11.6

• : potassium tert-butoxide in tert-butanol/water with microwave heating to 90–140 °C (26–98% yield) [15][16]. Kusaka et al. built on this strategy to achieve deboration of F-BODIPYs using sodium tert-butoxide in refluxing toluene (59–83% yield) en route to bis(dipyrrinato)zinc(II) complexes [17]. Two very

The unexpected influence of aryl substituents in N-aryl-3-oxobutanamides on the behavior of their multicomponent reactions with 5-amino-3-methylisoxazole and salicylaldehyde

• Volodymyr V. Tkachenko,
• Elena A. Muravyova,
• Sergey M. Desenko,
• Oleg V. Shishkin,
• Svetlana V. Shishkina,
• Dmytro O. Sysoiev,
• Thomas J. J. Müller and
• Valentin A. Chebanov

Beilstein J. Org. Chem. 2014, 10, 3019–3030, doi:10.3762/bjoc.10.320

• and microwave heating did not produce any positive results. Thus, refluxing of the reactants in water, ethanol, dioxane, or application of microwave irradiation at temperatures up to 140 °C only gave rise to the formation of imine 8 (Scheme 3). The reaction time in these cases reached 3 h. On the

• effect of different catalysts on the reaction was studied. It should be noted that in the case of catalytic processes both conventional and microwave heating were also inefficacious. The only noteworthy result was the detection of trace amounts of 4-(2-hydroxyphenyl)-N-(2-methoxyphenyl)-3,6-dimethyl-4,7

Synthesis of trifluoromethyl-substituted pyrazolo[4,3-c]pyridines – sequential versus multicomponent reaction approach

• Barbara Palka,
• Angela Di Capua,
• Maurizio Anzini,
• Gyté Vilkauskaité,
• Algirdas Šačkus and
• Wolfgang Holzer

Beilstein J. Org. Chem. 2014, 10, 1759–1764, doi:10.3762/bjoc.10.183

• due to its preeminent synthetic efficiency, also in the construction of heterocyclic and condensed heterocyclic systems [23][24][25][26][27]. After testing different reaction conditions we found that microwave heating of the chloroaldehyde 2 with tert-butylamine in the presence of 6 mol % of Pd(PPh3

Automated solid-phase peptide synthesis to obtain therapeutic peptides

• Veronika Mäde,
• Sylvia Els-Heindl and
• Annette G. Beck-Sickinger

Beilstein J. Org. Chem. 2014, 10, 1197–1212, doi:10.3762/bjoc.10.118

• special features such as automated monitoring (e.g., via chromophors [67] or conductivity [68]), microwave heating, capability for inert atmosphere and automated peptide cleavage [65]. The systems are mostly based on filtration by vacuum or pressure application [69], or centrifugation [70] and can work in

Rapid pseudo five-component synthesis of intensively blue luminescent 2,5-di(hetero)arylfurans via a Sonogashira–Glaser cyclization sequence

• Fabian Klukas,
• Alexander Grunwald,
• Franziska Menschel and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 672–679, doi:10.3762/bjoc.10.60

• under microwave heating (the temperature optimum of 130 °C was quickly identified by screening experiments), the water/KOH ratio, and the concentrations were varied. In the course of our studies a related work using copper catalysts with the electronrich DMEDA (N,N’-dimethylethylenediamine) or the

• electronpoor 1,10-phenanthroline as ligands was published [32], however, in our hands no favorable effect on the isolated yields of 2a was found (Table 1, entries 4–8). The cyclization works equally well with conductive heating in an oil bath instead of microwave heating (Table 1, entry 8). At higher

Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

• Gijs Koopmanschap,
• Eelco Ruijter and
• Romano V.A. Orru

Beilstein J. Org. Chem. 2014, 10, 544–598, doi:10.3762/bjoc.10.50

• 79%. Recently, another UDC-based synthesis of DKP scaffolds using the cheaper and commercial available n-butylisocyanide as convertible component was reported [149]. The scaffolds were obtained in good yields in a 1:1 diastereomeric ratio. However, microwave heating was required to induce cyclization