Practical synthesis of aryl-2-methyl-3-butyn-2-ols from aryl bromides via conventional and decarboxylative copper-free Sonogashira coupling reactions

• Andrea Caporale,
• Stefano Tartaggia,
• Andrea Castellin and
• Ottorino De Lucchi

Beilstein J. Org. Chem. 2014, 10, 384–393, doi:10.3762/bjoc.10.36

• in piperidine as the solvent [39][78] or by using aminophosphines [18] as well as phenanthryl imidazolium carbenes as the catalyst ligands [79]. A more practical methodology has been reported by Shirakawa in which a Pd(OAc)2/PPh3 catalyst system in DMSO and in the presence of K3PO4 as the base was

Cyclic phosphonium ionic liquids

• Sharon I. Lall-Ramnarine,
• Joshua A. Mukhlall,
• James F. Wishart,
• Robert R. Engel,
• Alicia R. Romeo,
• Masao Gohdo,
• Sharon Ramati,
• Marc Berman and
• Sophia N. Suarez

Beilstein J. Org. Chem. 2014, 10, 271–275, doi:10.3762/bjoc.10.22

• ) are composed primarily of nitrogen-centered (particularly imidazolium, pyridinium, pyrrolidinium, and related quaternary ammonium) cations with a wide range of anions [1]. While a number of these ILs have been applied successfully to commercial processes [1], efforts are continually underway to

• ]. While dialkylimidazolium ILs can be efficient extraction media for nuclear separations [17][18][19], the imidazolium cation is also a good acceptor of radiolytically produced excess electrons. The resultant radical participates in radiation damage mechanisms that alter the IL's properties [20]. On the

• ILs with aryl groups attached directly to the nitrogen atoms of imidazolium cations are reported [31]. The melting points of the phenylphosphonium ILs are both above room temperature (see Table 1), however C4PhPphol NTf2 is persistently metastable as a supercooled liquid under ambient conditions. The

Advancements in the mechanistic understanding of the copper-catalyzed azide–alkyne cycloaddition

• Regina Berg and
• Bernd F. Straub

Beilstein J. Org. Chem. 2013, 9, 2715–2750, doi:10.3762/bjoc.9.308

• substrate with formation of the corresponding azolium salt is highly favoured, as copper-coordinated alkynes are much more acidic than imidazolium or imidazolinium cations. For example, the pKa value of copper-coordinated propyne was calculated to be around 15 [13], whereas N,N-diarylimidazolium and N,N

• -diarylimidazolinium chloride salts have pKa values of about 19.8 to 21.1 and 20.7 to 21.5, respectively, for example pKa [1,3-bis(2,6-diisopropylphenyl)imidazolium chloride] = 21.1 ± 0.5 and pKa [1,3-bis(2,6-diisopropylphenyl)imidazolinium chloride] = 21.5 ± 0.5 in aqueous solution at 25 °C [154]. In contrast to free

Garner’s aldehyde as a versatile intermediate in the synthesis of enantiopure natural products

• Mikko Passiniemi and
• Ari M.P. Koskinen

Beilstein J. Org. Chem. 2013, 9, 2641–2659, doi:10.3762/bjoc.9.300

• organorhodium nucleophiles with aldehydes (Scheme 12) [65]. They screened catalysts, ligands and bases in order to find the best conditions for the alkylation reaction. They found RhCl3·3H2O together with imidazolium chloride 26 as the ligand precursor and the base NaOMe to be the catalyst system of choice

Synthesis, characterization and luminescence studies of gold(I)–NHC amide complexes

• Adrián Gómez-Suárez,
• David J. Nelson,
• David G. Thompson,
• David B. Cordes,
• Duncan Graham,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2013, 9, 2216–2223, doi:10.3762/bjoc.9.260

• reported the synthesis of [AuX(NHC)] (X = Cl, Br, I) complexes, directly from imidazolium and imidazolidinium salts and a suitable gold source, such as [AuCl(SMe2)], using K2CO3 as a base [13]. Moreover, we have also reported the synthesis of the first mononuclear gold(I) hydroxide species, [Au(OH)(IPr

Synthesis of guanidinium–sulfonimide ion pairs: towards novel ionic liquid crystals

• Martin Butschies,
• Manuel M. Neidhardt,
• Markus Mansueto,
• Sabine Laschat and
• Stefan Tussetschläger

Beilstein J. Org. Chem. 2013, 9, 1093–1101, doi:10.3762/bjoc.9.121

• anions and imidazolium cations with short alkyl chains were studied by DesMarteau resulting in room-temperature ionic liquids [21]. In contrast, ILCs with bistriflimide anions are much less explored, because the sterically demanding anion often inhibits the formation of a mesophase [6][22]. Liquid

• -crystalline phases were found for viologen salts [23][24][25][26][27][28], imidazolium ILCs [29][30][31], pyrrolidinium ILCs [32][33] and ionic polymers [34][35][36][37]. Sulfonimides, which are directly bound to a mesogenic group, have not been described until now. We have recently described the concept of

1-n-Butyl-3-methylimidazolium-2-carboxylate: a versatile precatalyst for the ring-opening polymerization of ε-caprolactone and rac-lactide under solvent-free conditions

• Astrid Hoppe,
• Faten Sadaka,
• Claire-Hélène Brachais,
• Gilles Boni,
• Jean-Pierre Couvercelle and
• Laurent Plasseraud

Beilstein J. Org. Chem. 2013, 9, 647–654, doi:10.3762/bjoc.9.73

• under vacuo (method A) or by addition of NaBPh4 (method B). Possible catalytic and deactivation mechanisms are proposed. Keywords: aliphatic polyesters; green polymerization reaction; imidazolium-2-carboxylates; N-heterocarbene precursor; organocatalysis; Introduction Poly(ε-caprolactone) (PCL) and

• concept was extended to the synthesis of aliphatic polycarbonates, involving the transesterification of DMC with linear alkane diols under solvent-free conditions, and based on a two-step polymerization process [50]. The high reactivity of imidazolium-2-carboxylates can be explained by their facile

• -CO2, the mixture of ε-caprolactone or rac-lactide and initiator alcohols remained unchanged under otherwise identical conditions, even for an extended period of time, underlining the decisive role of the imidazolium-2-carboxylate species in the polymerization process. Moreover and under atmospheric

Chemoenzymatic synthesis and biological evaluation of enantiomerically enriched 1-(β-hydroxypropyl)imidazolium- and triazolium-based ionic liquids

• Paweł Borowiecki,
• Małgorzata Milner-Krawczyk and
• Jan Plenkiewicz

Beilstein J. Org. Chem. 2013, 9, 516–525, doi:10.3762/bjoc.9.56

• diastereomeric derivatives (Figure 2) confirmed the results of the above equations. The chiral environment provided by the derivatizing agent (MPA) covalently associated with the respective alcohol leads to significant differences in chemical shifts (δ = 0.91 ppm), especially in the case of the imidazolium

• (+)-8a–c and (+)-8e–f, which are exceedingly viscous liquids (gums), all of the chiral hydroxy-functionalized imidazolium and one of the triazolium salts are liquid at room temperature. Final products were characterized by 1H, 13C NMR and FTIR spectroscopy as well as high-resolution electrospray

• 5). Moreover, the chemical nature of the cationic head group influenced the overall toxicity of the CILs, which is in good agreement with several previous studies [60]. The imidazolium CILs exhibited visibly stronger antibacterial and antifungal activity than triazolium CILs (Tables 4–6). However

N-Heterocyclic carbene–palladium(II)-1-methylimidazole complex catalyzed Mizoroki–Heck reaction of aryl chlorides with styrenes

• Ting-Ting Gao,
• Ai-Ping Jin and
• Li-Xiong Shao

Beilstein J. Org. Chem. 2012, 8, 1916–1919, doi:10.3762/bjoc.8.222

• -diisopropylphenyl)imidazolium chloride], and 1-methylimidazole in a one-step procedure in high yield, was an effective catalyst in C–C and C–N bond-formation reactions [37][38][39][40][41][42][43][44]. In our continuing investigations on the further applications of this complex in organic synthesis, we found that

Imidazolinium and amidinium salts as Lewis acid organocatalysts

• Oksana Sereda,
• Nicole Clemens,
• Tatjana Heckel and
• René Wilhelm

Beilstein J. Org. Chem. 2012, 8, 1798–1803, doi:10.3762/bjoc.8.205

• electrochemical processes [1]. Several of these solvents can contribute to the research field of “green chemistry” [2]. The most common used ionic liquids are based on imidazolium cations. Next to their application in catalytic reactions [3][4][5][6], they are also capable of catalyzing reactions themselves

• , either in substoichiometric amounts or as reaction medium due to hydrogen-bond activation of the protons of the imidazolium cation [7][8][9][10] and other variables, such as π-orbital and charge–charge interactions [8][9][10]. Recently, we applied saturated imidazolium salts with an aryl substituent at

• –Alder reaction with ethyl crotonthioate (1) and cyclopentadiene (2). Diels–Alder reaction catalysed with imidazolinium salts. Ring opening of thiirane 12. Ring opening of epoxide 14. Synthesis of bis-imidazolium salt 17. Synthesis of amidinium salt 21. Diels–Alder reaction with 10 mol % catalyst

Extending the utility of [Pd(NHC)(cinnamyl)Cl] precatalysts: Direct arylation of heterocycles

• Anthony R. Martin,
• Anthony Chartoire,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2012, 8, 1637–1643, doi:10.3762/bjoc.8.187

• preparation of the palladium complex 4. Following the strategy recently reported by Markó [23], we were successful in the synthesis of the IPr*Tol·HCl imidazolium salt 5 in a 53% overall yield (see Supporting Information File 1). Subsequently, 5 was treated with KOt-Bu in dry THF to generate the corresponding

Polysiloxane ionic liquids as good solvents for β-cyclodextrin-polydimethylsiloxane polyrotaxane structures

• Narcisa Marangoci,
• Rodinel Ardeleanu,
• Laura Ursu,
• Constanta Ibanescu,
• Maricel Danu,
• Mariana Pinteala and
• Bogdan C. Simionescu

Beilstein J. Org. Chem. 2012, 8, 1610–1618, doi:10.3762/bjoc.8.184

• Polymers, “Gheorghe Asachi” Technical University of Iasi, 700050 Iasi, Romania 10.3762/bjoc.8.184 Abstract An ionic liquid based on polydimethylsiloxane with imidazolium salt brushes was synthesized as a good solvent for β-cyclodextrin-polydimethylsiloxane rotaxane. As expected the PDMS-Im/Br ionic liquid

• interactions. The structure is stable in the 20 to 80 °C domain as proved by the oscillatory and rotational rheological tests. Keywords: cyclodextrins; imidazolium salt; ionic liquid; polyrotaxanes; polysiloxanes; Introduction Ionic liquids (ILs) are environmentally friendly solvents with great potential for

• decreases when their glass-transition temperature (Tg) increases [23]. In this respect, we have synthesized ILs based on polydimethylsiloxane with imidazolium salt brushes (PDMS-Im/S) with low Tg values in order to avoid a macroscopic phase separation in a mixture of ILs and CD-polydimethylsiloxane

N-Heterocyclic carbene-catalyzed direct cross-aza-benzoin reaction: Efficient synthesis of α-amino-β-keto esters

• Takuya Uno,
• Yusuke Kobayashi and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2012, 8, 1499–1504, doi:10.3762/bjoc.8.169

• -coupling of 1a was obtained. Encouraged by this result, we then attempted the other precatalysts 3b–e depicted in Figure 2. Imidazolium salt 3b and simple triazolium salt 3c gave no coupled product 5a (Table 1, entries 2 and 3). Further screening revealed that bicyclic triazolium salt 3d could catalyze the

A quantitative approach to nucleophilic organocatalysis

• Herbert Mayr,
• Sami Lakhdar,
• Biplab Maji and
• Armin R. Ofial

Beilstein J. Org. Chem. 2012, 8, 1458–1478, doi:10.3762/bjoc.8.166

• -unsaturated aldehydes can thus be explained by the low acidity of imidazolium ions [59]. Unlike triazolium and tetrazolium ions, imidazolium ions are unable to transfer a proton to the enamine unit in 16 (corresponding to 5 in the general Figure 2), which is necessary to close the catalytic cycle shown in

Hybrid super electron donors – preparation and reactivity

• Jean Garnier,
• Douglas W. Thomson,
• Shengze Zhou,
• Phillip I. Jolly,
• Leonard E. A. Berlouis and
• John A. Murphy

Beilstein J. Org. Chem. 2012, 8, 994–1002, doi:10.3762/bjoc.8.112

• organic electron donors incorporating a "stronger" donor component and a "weaker" component, e.g., 9 or 10 would be prime candidates, as the driving force for the loss of their first electron should exceed that for the loss of their second. The electrochemical properties of some hybrid imidazolium

• adopted as targets for synthesis. Of these, 10 and 11 are imidazolylidenes derived from an imidazolium salt. Donors derived from imdazolium salts are highly reactive and unstable; CV studies in MeCN have shown [15] that two-electron reduction of 13, bearing a single trimethylene bridge, which was intended

• trimethylene tethers. As compounds 10 and 11 are derived from imidazolium precursors, we were keen to explore their reactivity. The redox properties of the donors were first measured by cyclic voltammetry. Either the electron donors or their oxidized salts could, in principle, be used as a starting point for

N-Heterocyclic carbene/Brønsted acid cooperative catalysis as a powerful tool in organic synthesis

• Rob De Vreese and
• Matthias D’hooghe

Beilstein J. Org. Chem. 2012, 8, 398–402, doi:10.3762/bjoc.8.43

• preparation and characterization of a metal carbene complex in 1964 through nucleophilic attack of phenyllithium at tungsten hexacarbonyl followed by O-alkylation [1], and Arduengo described the preparation of the first free and stable N-heterocyclic carbene 2 by deprotonation of the corresponding imidazolium

Synthesis of mesomeric betaine compounds with imidazolium-enolate structure

• Nina Gonsior,
• Fabian Mohr and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 390–397, doi:10.3762/bjoc.8.42

• -bezoquinone to obtain novel mesomeric betaine materials with imidazolium-enolate structure. Results and Discussion The quaternization of 1-butylimidazole (2) with tetrabromo-1,4-benzoquinone (p-bromanil (1)) in acetonitrile and the subsequent quenching of the reaction mixture with water yielded dipole 2,3

• and IR spectroscopy, as well as X-ray single-crystal analysis. The 1H NMR spectrum of 3 is depicted in Figure 1. The signals for all structural features were found, e.g., at 9.21 ppm, 7.81 ppm and 7.64 ppm, for the imidazolium protons, and in the range of 4.23–0.92 ppm for the butyl moiety

• molecule symmetry. The characteristic peaks of imidazolium appeared at 137.3 ppm, 124.7 ppm, and 120.8 ppm. The peaks of the benzoquinone carbons were recorded in the range of 175.4 to 111.4 ppm, whereas the signals for the butyl group appeared in the range from 48.5 to 13.3 ppm. Furthermore, the specific

(How) does 1,3,5-triethylbenzene scaffolding work? Analyzing the abilities of 1,3,5-triethylbenzene- and 1,3,5-trimethylbenzene-based scaffolds to preorganize the binding elements of supramolecular hosts and to improve binding of targets

• Xing Wang and
• Fraser Hof

Beilstein J. Org. Chem. 2012, 8, 1–10, doi:10.3762/bjoc.8.1

• imidazolium-based hosts 5 (used for anion binding) [18][19] as instructive systems for computational analysis (Figure 2). These hosts were chosen because (1) they are typical of the kinds of heterocycles often used as recognition elements in this family of hosts; (2) we wished to examine the effects of charge

• calculations were used to identify the global minimum-energy conformation for each host, and to determine the relative energies for each of the other conformations in each series (Table 5). Unlike simple hexaethylbenzene, the imidazolium groups of 5Et provided a very different result when examined by gas-phase

• the benzene, and “uud,” in which one binding arm is directed toward the opposite face of the benzene from the other two. Imidazolium-substituted hosts 5Me and 5H both show a preference for the nonideal uud conformation in the gas phase, which we can again attribute to the mutual repulsion of the

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• Pd-catalyzed cross-coupling approach starting from 1-chloro-2-iodobenzenes, phenylacetylene and a variety of primary amines [28][29]. The sequential three-component reaction was performed with the aid of an N-heterocyclic carbene-palladium complex generated in situ, derived from imidazolium salt 50

Efficient and selective chemical transformations under flow conditions: The combination of supported catalysts and supercritical fluids

• M. Isabel Burguete,
• Eduardo García-Verdugo and
• Santiago V. Luis

Beilstein J. Org. Chem. 2011, 7, 1347–1359, doi:10.3762/bjoc.7.159

• productivity and operational costs should be also considered and have not yet been analyzed. The system has been further improved through the use of different Xantphos-related ligands containing imidazolium subunits to favor the solubility in the IL phase [62]. A system involving the immobilization of the

• lipase onto a covalently supported ionic liquid-like phase (SILLP) [105][106]. Those SILLPs are prepared by functionalization of PS–DVB surfaces with IL-like (imidazolium) moieties [107][108]. Experimental results have shown that the resulting surfaces have similar physico-chemical properties to those of

NMR studies of anion-induced conformational changes in diindolylureas and diindolylthioureas

• Damjan Makuc,
• Jennifer R. Hiscock,
• Mark E. Light,
• Philip A. Gale and
• Janez Plavec

Beilstein J. Org. Chem. 2011, 7, 1205–1214, doi:10.3762/bjoc.7.140

• extensively employed in synthetic anion receptors comprising groups such as amides, pyrroles, indoles, ureas and triazoles, as well as in ammonium, guanidinium and imidazolium moieties used as hydrogen bond donors [16][17][18][19][20][21][22][23]. Amongst neutral anion receptor systems, indole and related

Fluorometric recognition of both dihydrogen phosphate and iodide by a new flexible anthracene linked benzimidazolium-based receptor

• Kumaresh Ghosh and
• Debasis Kar

Beilstein J. Org. Chem. 2011, 7, 254–264, doi:10.3762/bjoc.7.34

• hydrogen bond donors and acceptors are of considerable importance. Among the different binding motifs for anions, the hydrogen bonding properties of NH groups in neutral amines [13], amides [14], ureas/thioureas [15][16], indoles [17][18][19] and pyrroles [20] as well as in guanidinium [21] and imidazolium

Recent advances in the development of alkyne metathesis catalysts

• Xian Wu and
• Matthias Tamm

Beilstein J. Org. Chem. 2011, 7, 82–93, doi:10.3762/bjoc.7.12

• isolobal to phosphoraneimides (R3PN−) and cyclopentadienides (C5R5−) [48][49][50][51][52], can be described by the resonance structures shown in Scheme 4, indicating that the ability of the imidazolium ring to stabilize a positive charge affords highly basic ligands with a strong electron-donating capacity

A new fluorescent chemosensor for fluoride anion based on a pyrrole–isoxazole derivative

• Zhipei Yang,
• Kai Zhang,
• Fangbin Gong,
• Shayu Li,
• Jun Chen,
• Jin Shi Ma,
• Lyubov N. Sobenina,
• Albina I. Mikhaleva,
• Guoqiang Yang and
• Boris A. Trofimov

Beilstein J. Org. Chem. 2011, 7, 46–52, doi:10.3762/bjoc.7.8

• reported in recent years, those employing polarized NH groups as anion-binding motifs have attracted considerable attention. Typical examples are charge neutral receptors containing pyrrole, amide, indolocarbazole, guanidium, imidazolium and urea/thiourea moieties. Usually, the anions are recognized via H

Synthesis of some novel hydrazono acyclic nucleoside analogues

• Mohammad N. Soltani Rad,
• Ali Khalafi-Nezhad and
• Somayeh Behrouz

Beilstein J. Org. Chem. 2010, 6, No. 49, doi:10.3762/bjoc.6.49

• that among published methods for N-alkylation of imidazole derivatives [26][27][28][29][30][31][32][33][34], the method developed by Liu et al. [35] was the most appropriate one for N-alkylation of azoles and their derivatives, since in this method the formation of quaternary imidazolium salts is