N-Methylphthalimide-substituted benzimidazolium salts and PEPPSI Pd–NHC complexes: synthesis, characterization and catalytic activity in carbon–carbon bond-forming reactions

• Senem Akkoç,
• Yetkin Gök,
• İlhan Özer İlhan and
• Veysel Kayser

Beilstein J. Org. Chem. 2016, 12, 81–88, doi:10.3762/bjoc.12.9

• ligands [12][13]. As catalysts, palladium N-heterocyclic carbene (Pd–NHC) complexes display remarkable activities in coupling reactions [5][14][15][16][17]. Among various Pd–NHC complexes such as [Pd(NHC)(dmba)Cl] (dmba = N,N-dimethylbenzylamine) and [Pd(NHC)(Im)Cl2] (Im = imidazole) [18][19], [PEPPSI Pd

Enantioselective additions of copper acetylides to cyclic iminium and oxocarbenium ions

• Jixin Liu,
• Srimoyee Dasgupta and
• Mary P. Watson

Beilstein J. Org. Chem. 2015, 11, 2696–2706, doi:10.3762/bjoc.11.290

• ,N ligand, StackPhos, for enantioselective alkynylations of quinolinium ions [35]. They hypothesized that their imidazole-based P,N ligand would provide a different bite angle than Quinap or Pinap ligands and thus enable higher ee’s than previously obtained in the alkynylation of these challenging

Synthesis of bi- and bis-1,2,3-triazoles by copper-catalyzed Huisgen cycloaddition: A family of valuable products by click chemistry

• Zhan-Jiang Zheng,
• Ding Wang,
• Zheng Xu and
• Li-Wen Xu

Beilstein J. Org. Chem. 2015, 11, 2557–2576, doi:10.3762/bjoc.11.276

• diazo transfer agent (imidazole-1-sulfonyl azide) was performed to convert the amine group into the corresponding azide group, which provided a polymeric substrate for the second CuAAC reaction to give the desired bistriazoles (Scheme 23). In 2009, Zhu and co-workers found that copper(II) acetate (Cu

Copper-catalyzed stereoselective conjugate addition of alkylboranes to alkynoates

• Takamichi Wakamatsu,
• Kazunori Nagao,
• Hirohisa Ohmiya and
• Masaya Sawamura

Beilstein J. Org. Chem. 2015, 11, 2444–2450, doi:10.3762/bjoc.11.265

• not been used for these methods [11]. As related studies we reported earlier the copper-catalyzed conjugate addition of alkylboranes (alkyl-9-BBN) to imidazole-2-yl α,β-unsaturated ketones [12][13][14] and the copper-catalyzed three-component coupling with alkylboranes, alkynoates, and tributyltin

A concise and efficient synthesis of benzimidazo[1,2-c]quinazolines through CuI-catalyzed intramolecular N-arylations

• Xinlong Pang,
• Chao Chen,
• Ming Li and
• Chanjuan Xi

Beilstein J. Org. Chem. 2015, 11, 2365–2369, doi:10.3762/bjoc.11.258

• showing the cleavage of the quinazoline ring rather than the imidazole ring [26]. Conclusion We have demonstrated a CuI-catalyzed pathway to produce functionalized benzimidazo[1,2-c]quinazoline derivatives from bromo-substituted quinazolin-4(3H)-imines through a selective intramolecular N-arylation

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

• chloride or benzyl bromide seem to be ideal candidates to prepare 1,3-dibenzylimidazolium salts via a double alkylation of imidazole. Indeed, these primary alkyl halides are highly reactive toward nucleophiles and do not undergo elimination reactions. Accordingly, numerous procedures were reported for the

Evidencing an inner-sphere mechanism for NHC-Au(I)-catalyzed carbene-transfer reactions from ethyl diazoacetate

• Manuel R. Fructos,
• Juan Urbano,
• M. Mar Díaz-Requejo and
• Pedro J. Pérez

Beilstein J. Org. Chem. 2015, 11, 2254–2260, doi:10.3762/bjoc.11.245

• Abstract Kinetic experiments based on the measurement of nitrogen evolution in the reaction of ethyl diazoacetate (N2CHCO2Et, EDA) and styrene or methanol catalyzed by the [IPrAu]+ core (IPr = 1,3-bis(diisopropylphenyl)imidazole-2-ylidene) have provided evidence that the transfer of the carbene group

• of a gold(I) source and a diazo compound. It was not until 2005 that the first example of this transformation was reported by our group [15][16], when the complex IPrAuCl (1) (IPr = 1,3-bis(diisopropylphenyl)imidazole-2-ylidene), in the presence of NaBArF4 (BArF4− = tetrakis(3,5-bis(trifluoromethyl

Synthesis of α,β-unsaturated esters via a chemo-enzymatic chain elongation approach by combining carboxylic acid reduction and Wittig reaction

• Yitao Duan,
• Peiyuan Yao,
• Yuncheng Du,
• Jinhui Feng,
• Qiaqing Wu and
• Dunming Zhu

Beilstein J. Org. Chem. 2015, 11, 2245–2251, doi:10.3762/bjoc.11.243

• 4 °C, and disrupted by high pressure homogenizer after re-suspension in binding buffer (20 mM sodium phosphate buffer, 0.5 M NaCl, 20 mM imidazole, pH 7.4). His-CAR or His-PPTase protein in the supernatant fraction was collected from the crude cell lysate by centrifugation at 12 000g for 20 min

• . Protein purification was performed on a HisTrapTM FF crude column (GE Healthcare, Piscataway, USA), and the protein was desorbed with an elution buffer (20 mM sodium phosphate, 0.5 M NaCl, 0.5 M imidazole, pH 7.4). The purified proteins His-CAR or His-PPTase were dialyzed in a sodium phosphate buffer (50

Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

• Kevin Lafaye,
• Cyril Bosset,
• Lionel Nicolas,
• Amandine Guérinot and
• Janine Cossy

Beilstein J. Org. Chem. 2015, 11, 2223–2241, doi:10.3762/bjoc.11.241

• hindrance may be invoked to explain the absence of catalyst deactivation (Scheme 24). Similarly, 15- to 18-membered ring macrocycles that incorporate an imidazole group were synthesized using a RCM of the corresponding dienes using GII as the catalyst (Scheme 25) [64][65][66]. By examining all these

• . Enyne ring-closing metathesis. Synthesis of (R)-(+)-muscopyridine using a RCM strategy. Synthesis of a tris-pyrrole macrocycle. Synthesis of a bicyclic imidazole. RCM using Schrock’s catalyst 44. Synthesis of 1,6-pyrido-diazocine 46 by using a RCM. Synthesis of fused pyrimido-azepines through RCM. RCM

• involving alkenes containing various N-heteroaromatics. Synthesis of dihydroisoquinoline using a RCM. Formation of tricyclic compound 59. RCM in the synthesis of normuscopyridine. Synthesis of macrocycle 64. Synthesis of macrocycles possessing an imidazole group. Retrosynthesis of an analogue of

2-Hetaryl-1,3-tropolones based on five-membered nitrogen heterocycles: synthesis, structure and properties

• Yury A. Sayapin,
• Inna O. Tupaeva,
• Alexandra A. Kolodina,
• Eugeny A. Gusakov,
• Vitaly N. Komissarov,
• Igor V. Dorogan,
• Nadezhda I. Makarova,
• Anatoly V. Metelitsa,
• Valery V. Tkachev,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2015, 11, 2179–2188, doi:10.3762/bjoc.11.236

• ]imidazole failed, no expected 1,3-tropolones were formed under the above described conditions. The ratio of the products was inversed when running the reaction under prolonged (3–4 days) heating of acetic acid solution of reactants at about 50 °С (method B). In this case, 4,5,6,7-tetrachloro-1,3-tropolones

C–H bond halogenation catalyzed or mediated by copper: an overview

• Wenyan Hao and
• Yunyun Liu

Beilstein J. Org. Chem. 2015, 11, 2132–2144, doi:10.3762/bjoc.11.230

• -halogenated phenols 41/42 in good to excellent yield and regioselectivity. In addition, the C-3 chlorination of indoles 43 and C-4 chlorination of imidazole (45) were also achieved under the standard reaction conditions to provide products 44 and 46, respectively (Scheme 16). Because of the attractive

Stereoselective synthesis of hernandulcin, peroxylippidulcine A, lippidulcines A, B and C and taste evaluation

• Marco G. Rigamonti and
• Francesco G. Gatti

Beilstein J. Org. Chem. 2015, 11, 2117–2124, doi:10.3762/bjoc.11.228

• ) TBAF, MeCN, rt, 2 h. Reagents and conditions: (a) cat. methylene blue, light, bubbling O2, CH2Cl2/MeOH 4:1, rt, 15 h; (b) imidazole, TBDPSCl, cat. DMAP, DMF, rt, 24 h; (c) TBAF, THF, rt, 12 h; (d) TMSCl, cat. DMAP, CH2Cl2/pyridine 2:1, 0 °C/rt, 24 h; (e) acidic-aqueous work-up then PPh3, CH2Cl2, rt, 15

The marine sponge Agelas citrina as a source of the new pyrrole–imidazole alkaloids citrinamines A–D and N-methylagelongine

• Christine Cychon,
• Ellen Lichte and
• Matthias Köck

Beilstein J. Org. Chem. 2015, 11, 2029–2037, doi:10.3762/bjoc.11.220

• Christine Cychon Ellen Lichte Matthias Kock Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven, Germany 10.3762/bjoc.11.220 Abstract The chemical investigation of the Caribbean sponge Agelas citrina revealed four new pyrrole–imidazole

• citrinamine C (3) is derived from the PIA dimer nagelamide B (8). Citrinamine D (4) shows an uncommon linkage between the imidazole rings of both monomeric units as it is only observed in the benzocyclobutane ring moiety of benzosceptrins A–C (9–11). Compound 5 is the N-methyl derivative of agelongine (12

• ) which consist of a pyridinium ring and an ester linkage instead of the aminoimidazole moiety and the common amide bond in PIAs. Keywords: Agelas citrina; marine sponges; mauritiamine; NMR; pyrrole–imidazole alkaloids; Introduction The family of pyrrole-imidazole alkaloids (PIAs) represents a

Stereochemistry of ring-opening/cross metathesis reactions of exo- and endo-7-oxabicyclo[2.2.1]hept-5-ene-2-carbonitriles with allyl alcohol and allyl acetate

• Piotr Wałejko,
• Michał Dąbrowski,
• Lech Szczepaniak,
• Jacek W. Morzycki and
• Stanisław Witkowski

Beilstein J. Org. Chem. 2015, 11, 1893–1901, doi:10.3762/bjoc.11.204

• -tolyl substituted NHC ligand in [Ru]5 exerts a smaller steric effect than the -PCy3 residue in [Ru]1–4. Furthermore, the bulky phosphine ligand (PCy3) expands away from the transition metal center (coordination sphere), while the N,N’-o-tolyl substituent attached to the central imidazole ring penetrates

Influence of bulky yet flexible N-heterocyclic carbene ligands in gold catalysis

• Alba Collado,
• Scott R. Patrick,
• Danila Gasperini,
• Sebastien Meiries and
• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 1809–1814, doi:10.3762/bjoc.11.196

• modifying the architecture of the imidazole ring, typically, by changing the N-substituents or the backbone [13][14][15][16][17][18][19][20]. One of our research interests is the study of the electronic and steric properties of new N-heterocyclic carbenes and their influence in catalysis upon coordination

Fe(II)/Et₃N-Relay-catalyzed domino reaction of isoxazoles with imidazolium salts in the synthesis of methyl 4-imidazolylpyrrole-2-carboxylates, its ylide and betaine derivatives

• Ekaterina E. Galenko,
• Olesya A. Tomashenko,
• Alexander F. Khlebnikov,
• Mikhail S. Novikov and
• Taras L. Panikorovskii

Beilstein J. Org. Chem. 2015, 11, 1732–1740, doi:10.3762/bjoc.11.189

• reaction with sulfur affording the corresponding imidazolethiones under very mild conditions. Keywords: imidazole; isoxazole; NHC carbene; pyrrole-2-carboxylate; relay catalysis; Introduction Pyrrole-2-carboxyate and imidazole units are present in bioactive pyrrole-imidazole alkaloids and pyrrole

• -imidazole polyamides [1][2][3][4][5]. Derivatives of 4-imidazolylpyrrole-2-carboxylic acid are much less known, though some of these compounds showed various bioactivities [6][7][8][9] and were patented as inhibitors of c-Met protein kinase [8] and as anti-inflammatory agents [9]. Additionally, 5

• ][27] and coenzyme pyrroloquinoline quinone [28]. The synthesis of 4-imidazolylpyrrole-2-carboxylic acid derivatives usually involves the corresponding pyrrole with a functional group allowing the formation of a imidazole ring [8][9]. Recently we developed a new approach to 3-(1H-pyrrol-3-yl)-1H

A facile synthetic route to benzimidazolium salts bearing bulky aromatic N-substituents

• Gabriele Grieco,
• Olivier Blacque and
• Heinz Berke

Beilstein J. Org. Chem. 2015, 11, 1656–1666, doi:10.3762/bjoc.11.182

• -step synthesis avoiding chromatographic work-up. In the key step triethyl orthoformate is reacted with the corresponding N1,N2-diarylbenzene-1,2-diamines and then further transformed in situ, by alkoxy abstraction using trimethylsilyl chloride (TMSCl), and concomitant imidazole ring closure. Keywords

• : benzimidazolium salts; bulky ligands; cyclization; ligand design; N-heterocyclic carbenes (NHC); ring formation; Introduction Imidazole-based N-heterocyclic carbenes (NHCs) are stable systems serving as ancillary ligands mainly to construct organometallic complexes. These NHCs are sterically and electronically

• used as electroluminescent materials (OLEDs) [16][17][18][19]. After the discovery of NHCs in 1968 by Wanzlick and Öfele, who isolated stable diamino-substituted carbenes, around 20 years later Arduengo further stabilized these potential ligand groups by embedding them into imidazole rings and

Deproto-metallation of N-arylated pyrroles and indoles using a mixed lithium–zinc base and regioselectivity-computed CH acidity relationship

• Mohamed Yacine Ameur Messaoud,
• Ghenia Bentabed-Ababsa,
• Madani Hedidi,
• Aïcha Derdour,
• Floris Chevallier,
• Yury S. Halauko,
• Oleg A. Ivashkevich,
• Vadim E. Matulis,
• Laurent Picot,
• Valérie Thiéry,
• Thierry Roisnel,
• Vincent Dorcet and
• Florence Mongin

Beilstein J. Org. Chem. 2015, 11, 1475–1485, doi:10.3762/bjoc.11.160

• reacted with 2 equiv of imidazole in the presence of 0.1 equiv of copper(I) oxide, 2 equiv of caesium carbonate as the base in dimethylsulfoxide (DMSO) at 110 °C [47]. Under these conditions, the imidazole-substituted compounds 5b, 5d and 6d were generated in 85, 67 and 40% yield, respectively (Scheme 8

• compounds 3d and 4d. Procedure 7 for the N-arylation of imidazole [47]. A mixture of the prepared iodide (1.0 mmol), Cu2O (0.10 g, 0.10 mmol), Cs2CO3 (0.65 g, 2.0 mmol), imidazole (0.14 g, 2.0 mmol) and DMSO (0.5 mL) was stirred for 24 h at 110 °C under argon. After cooling to room temperature, the mixture

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

Synthesis of novel N-cyclopentenyl-lactams using the Aubé reaction

• Madhuri V. Shinde,
• Rohini S. Ople,
• Ekta Sangtani,
• Rajesh Gonnade and
• D. Srinivasa Reddy

Beilstein J. Org. Chem. 2015, 11, 1060–1067, doi:10.3762/bjoc.11.119

• . To begin with, the azido alcohol 3 required for the present work was envisaged from Vince lactam (±)-1. The known amino alcohol [31] (prepared from Vince lactam by following literature procedures) was treated with triflyl azide or imidazole sulfonyl azide [32][33] using standard conditions to furnish

Highly selective palladium–benzothiazole carbene-catalyzed allylation of active methylene compounds under neutral conditions

• Antonio Monopoli,
• Pietro Cotugno,
• Carlo G. Zambonin,
• Francesco Ciminale and
• Angelo Nacci

Beilstein J. Org. Chem. 2015, 11, 994–999, doi:10.3762/bjoc.11.111

• of the different behavior displayed by these two carbene ligands can be found in the different aromatic character of their (benzothiazole and imidazole) heterocyclic rings. It is well known that this feature can strongly affect the nucleophilicity of these NHC species, and ultimately can influence

• benzothiazole–carbene ligand deriving from V, should be more active (being a better σ-donor) than the corresponding imidazole (deriving from VI) due to its higher aromatic character. Studies are in progress to verify this assumption. With optimized conditions in hand, we widened the scope of our investigation

• favourably also with the analogous and more widely used NHC carbenes deriving from imidazole. Complexes and ligands employed. Pd-catalyzed α-allylation of active methylene compounds. Optimization of reaction conditions.a α-allylation of 1,3-dicarbonyl compoundsa. Supporting Information Supporting

Multivalent dendritic polyglycerolamine with arginine and histidine end groups for efficient siRNA transfection

• Fatemeh Sheikhi Mehrabadi,
• Hanxiang Zeng,
• Mark Johnson,
• Cathleen Schlesener,
• Zhibin Guan and
• Rainer Haag

Beilstein J. Org. Chem. 2015, 11, 763–772, doi:10.3762/bjoc.11.86

• polymeric backbone (dPG). The functionalization degree for each polymer was determined by comparing the peak integral of either the methylene groups of arginine in high field or the imidazole ring of histidine in the aromatic area (7.2–8.7 ppm) with the assignable dPG backbone signal (Supporting Information

• NHCH2CH2CH2CHNH2CO of arginine groups, NH2COCHCH2C and NH2COCHCH2C of histidine groups), 7.4 (s, CHNHCHN, 1H of imidazole groups) and 8.7 (s, CHNHCHN, 1H of imidazole groups) ppm. dPG-13Arg: δ = 1.6 (s, NHCH2CH2CH2CH, 2H), 1.9 (s, NHCH2CH2CH2CH, 2H), 3–4.5 (m, dPG backbone, NHCH2CH2CH2CH and NHCH2CH2CH2CHNH2CO of

• arginine groups) ppm. dPG-13His: δ = 3–4.5 (m, dPG backbone, NH2COCHCH2C and NH2COCHCH2C of histidine groups), 7.4 (s, CHNHCHN, 1H of imidazole groups) and 8.7 (s, CHNHCHN, 1H of imidazole groups) ppm. dPG-8Arg30His: δ = 1.6 (s, NHCH2CH2CH2CH, 2H), 1.9 (s, NHCH2CH2CH2CH, 2H), 3–4.5 (m, dPG backbone

Sequence-specific RNA cleavage by PNA conjugates of the metal-free artificial ribonuclease tris(2-aminobenzimidazole)

• Friederike Danneberg,
• Alice Ghidini,
• Plamena Dogandzhiyski,
• Elisabeth Kalden,
• Roger Strömberg and
• Michael W. Göbel

Beilstein J. Org. Chem. 2015, 11, 493–498, doi:10.3762/bjoc.11.55

• %; b: 1) 1,1‘-thiocarbonyldiimidazole, imidazole, MeCN, 0 °C to rt, 1 h; 2) methyl 3,4-diaminobenzoate, MeCN, 50 °C, 4 h, rt, overnight, 79%; c: Mukaiyama’s reagent, NEt3, DMF, 20 h, rt, 88%; d: 1) SOCl2, MeOH, 0 °C to rt, 3 h; 2) 2-nitrophenylisothiocyanate, NEt3, EtOH, 0 °C to rt, overnight, 90%; e

Selective methylation of kaempferol via benzylation and deacetylation of kaempferol acetates

• Qinggang Mei,
• Chun Wang,
• Weicheng Yuan and
• Guolin Zhang

Beilstein J. Org. Chem. 2015, 11, 288–293, doi:10.3762/bjoc.11.33

• work-up. We turned to employ thiophenol with imidazole in N-methylpyrrolidinone (NMP) at 0 °C [26], for selective removal of the most electrophilic 7-O-acetyl group from the fully acetylated kaempferol. 3,4′,5-Tri-O-acetylkaempferol (2) was obtained in excellent yield (91%). Methylation of 2 with 1.3

• . Kaempferol. Reagents and conditions: (a) PhSH, imidazole, NMP (N-methylpyrrolidinone), 0 °C, 91%; (b) Me2SO4 (1.3 equiv), K2CO3, acetone, rt, 87%; (c) NH3 (g), MeOH, 97%; (d) Me2SO4 (3 equiv), K2CO3, acetone, MeOH, reflux, 90%; (e) i: AlCl3, CH2Cl2, CH3CN, reflux, ii: 1 M HCl (aq), 89%; (f) i: Me2SO4 (2.6

3α,5α-Cyclocholestan-6β-yl ethers as donors of the cholesterol moiety for the electrochemical synthesis of cholesterol glycoconjugates

• Aneta M. Tomkiel,
• Adam Biedrzycki,
• Jolanta Płoszyńska,
• Dorota Naróg,
• Andrzej Sobkowiak and
• Jacek W. Morzycki

Beilstein J. Org. Chem. 2015, 11, 162–168, doi:10.3762/bjoc.11.16

• with TBDMSCl in DMF in the presence of imidazole and DMAP. All of these compounds proved to be electrochemically active. Cyclic voltammograms measured in dichloromethane on a platinum electrode indicated that the main oxidation peak for the substances occurred within 1.8–2.0 V (vs Ag/AgNO3 in MeCN