From betaines to anionic N-heterocyclic carbenes. Borane, gold, rhodium, and nickel complexes starting from an imidazoliumphenolate and its carbene tautomer

• Ming Liu,
• Jan C. Namyslo,
• Martin Nieger,
• Mika Polamo and
• Andreas Schmidt

Beilstein J. Org. Chem. 2016, 12, 2673–2681, doi:10.3762/bjoc.12.264

• .12.264 Abstract The mesomeric betaine imidazolium-1-ylphenolate forms a borane adduct with tris(pentafluorophenyl)borane by coordination with the phenolate oxygen, whereas its NHC tautomer 1-(2-phenol)imidazol-2-ylidene reacts with (triphenylphosphine)gold(I) chloride to give the cationic NHC complex [Au

• , MICs) and vice versa [34]. Herein, conjugated mesomeric betaine 2-(1-butyl-1H-imidazolium-3-yl)phenolate, its tautomeric NHC and its anionic NHC are shown to serve as monodentate and bidentate ligands, respectively. Results and Discussion Salt 5 is available via a three-step procedure [35

• ppm. Minute traces of water protonate the anionic NHC 7 spontaneously to give 6A/B without any traces of decomposition products. The betaine 6A reacted with tris(pentafluorophenyl)borane in dioxane at reflux temperature to give the borane adduct 8. The proton attached to C-2 of the imidazolium ring

Ionic liquids as transesterification catalysts: applications for the synthesis of linear and cyclic organic carbonates

• Maurizio Selva,
• Alvise Perosa,
• Sandro Guidi and
• Lisa Cattelan

Beilstein J. Org. Chem. 2016, 12, 1911–1924, doi:10.3762/bjoc.12.181

• screening guide. IL-based catalysts for transesterification reactions Synthesis of IL-catalysts: IL-based catalysts for transesterification reactions mostly comprise imidazolium, phosphonium, ammonium, sulfonium and pyridinium salts. The conventional syntheses of such compounds usually start from the

• of glycerol trioleate with methanol: both, acidic ionic liquids (e.g., 1-allyl-3-(butyl-4-sulfonyl)imidazolium trifluoromethanesulfonate [BsAIm][OTf]) supported onto sulfhydryl-group-modified SiO2 (MPS-SiO2) [38], and imidazolium salts (e.g., 1-allyl-dodecylimidazolium hydroxide ([ADIm][OH

• conversion of rapeseed oils into FAMEs products [45]. A series of Brønsted acidic imidazolium ILs has been investigated for the catalytic synthesis of sec-butanol by transesterification of sec-butyl acetate with methanol (Scheme 5) [46]. The reaction is of interest for the preparation of less toxic

Experimental and theoretical investigations on the high-electron donor character of pyrido-annelated N-heterocyclic carbenes

• Michael Nonnenmacher,
• Dominik M. Buck and
• Doris Kunz

Beilstein J. Org. Chem. 2016, 12, 1884–1896, doi:10.3762/bjoc.12.178

• (current address of corresponding author) 10.3762/bjoc.12.178 Abstract Rh(CO)2Cl(NHC) complexes of dipyrido-annelated N-heterocyclic carbenes were prepared. From the C–H coupling constant of the respective imidazolium salts and the N–C–N angle of the N-heterocyclic carbene (NHC), a weaker σ-donor

• abilities was limited to determining the overall donor character and taking into account the σ-donor character. The latter is dependant on the s-character of the σ-orbital and thus can be obtained directly from the 1JCH coupling constant of the imidazolium salt [37][38][39] (which can be regarded as the H

• -donor character (deduced directly from the larger 1JCH coupling constant of the respective imidazolium salts that correlates with the higher s-character in the C–H bond). Therefore, we expected the average CO stretching frequencies to lie about 15 cm−1 higher at around 2050 cm−1 for complexes 2a and 2b

Methylpalladium complexes with pyrimidine-functionalized N-heterocyclic carbene ligands

• Dirk Meyer and
• Thomas Strassner

Beilstein J. Org. Chem. 2016, 12, 1557–1565, doi:10.3762/bjoc.12.150

• reported the synthesis of the imidazolium salts 1–4 and their corresponding silver complexes 5–8. The reaction with dichloro(cyclooctadiene)-palladium(II) [(COD)PdIICl2] allowed for the isolation and characterization of the [((pym)^(NHC-R))PdIICl2]-complexes [34]. For the synthesis of the corresponding

• decompose in DMSO-d6 by reductive cis-elimination [40] leading to imidazolium salts with the methyl group on the former carbene carbon atom and palladium black. The weaker coordination is most probably caused by the stronger trans effect of the methyl group. The decomposition is significantly slower in

• ), [(tmeda)Pd(CH3)2], an approach which is frequently used to synthesize dimethyl Pd complexes [50][51][52][53]. Deprotonation of the imidazolium salt 3 and subsequent conversion of the free carbene with [(tmeda)Pd(CH3)2] gave the desired dimethylpalladium(II) complex 15 (Scheme 5) in 47% yield. Conclusion

Artificial Diels–Alderase based on the transmembrane protein FhuA

• Hassan Osseili,
• Daniel F. Sauer,
• Klaus Beckerle,
• Marcus Arlt,
• Tomoki Himiyama,
• Tino Polen,
• Akira Onoda,
• Ulrich Schwaneberg,
• Takashi Hayashi and
• Jun Okuda

Beilstein J. Org. Chem. 2016, 12, 1314–1321, doi:10.3762/bjoc.12.124

• contains a cysteine residue at position 545 for conjugation [31], an NHC ligand containing a maleimide function was prepared (Scheme 1). The imidazolium salt 3 was synthesized by nucleophilic substitution of mesityl imidazol 1 with maleimide derivative 2. These salts were used to generate the Cu(I) NHC

• precipitate was filtered, washed with toluene (3 × 15 mL) and dried under vacuum to afford analytically pure imidazolium salt 1 (2.58 g, 6.40 mmol, 83%) as colorless powder. 1H NMR (400 MHz, CD2Cl2) δ 10.32 (s, 1H, NCHN), 8.07 (s, 1H, CH=CH), 7.28 (s, 1H, CH=CH), 7.05 (s, 2H, aryl CH), 6.73 (s, 2H, CH=CH

• ), 21.4 (p-Me), 18.0 (o-Me); ESIMS (+) m/z (%): calcd for (C19H22N3O2)+, 324.171; found, 324.170 (100). Synthesis and characterization of NHC-Cu(I)I complex 4 The Imidazolium salt 3 (200 mg, 0.495 mmol, 1.00 equiv), K2CO3 (280 mg, 2.02 mmol, 4.00 equiv) and CuI (95 mg, 0.495 mmol, 1.00 equiv) was stirred

Bi- and trinuclear copper(I) complexes of 1,2,3-triazole-tethered NHC ligands: synthesis, structure, and catalytic properties

• Shaojin Gu,
• Jiehao Du,
• Jingjing Huang,
• Huan Xia,
• Ling Yang,
• Weilin Xu and
• Chunxin Lu

Beilstein J. Org. Chem. 2016, 12, 863–873, doi:10.3762/bjoc.12.85

• Republic of China 10.3762/bjoc.12.85 Abstract A series of copper complexes (3–6) stabilized by 1,2,3-triazole-tethered N-heterocyclic carbene ligands have been prepared via simple reaction of imidazolium salts with copper powder in good yields. The structures of bi- and trinuclear copper complexes were

• imidazolium backbone and N substituents. The copper–NHC complexes tested are highly active for the Cu-catalyzed azide–alkyne cycloaddition (CuAAC) reaction in an air atmosphere at room temperature in a CH3CN solution. Complex 4 is the most efficient catalyst among these polynuclear complexes in an air

• , structural characterization, and catalytic properties of a few copper-1,2,3-triazole-tethered NHC complexes is reported. Results and Discussion Synthesis and spectroscopic characterization The imidazolium salts (1a–e) were prepared according to the reported procedure in 61–90% yields [27]. These imidazolium

Muraymycin nucleoside-peptide antibiotics: uridine-derived natural products as lead structures for the development of novel antibacterial agents

• Daniel Wiegmann,
• Stefan Koppermann,
• Marius Wirth,
• Giuliana Niro,
• Kristin Leyerer and
• Christian Ducho

Beilstein J. Org. Chem. 2016, 12, 769–795, doi:10.3762/bjoc.12.77

• . Acetylation of the thus formed primary alcohol resulted in compound 38. This was followed by benzyl and Cbz deprotection and the subsequent urea formation with the imidazolium salt 39 to furnish tripeptide 40. After Boc deprotection, the resultant amine was guanidinylated using isothiourea 41. The thus

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

• imidazolium-derived ylides also catalysed benzoin reactions. In most of the cases, the NHC-catalysed formation of benzoin from aldehydes is reversible in nature. In the following sections, detailed discussions on various types of benzoin reactions catalysed by NHCs are presented. In general, thiazolium salt

• may be regarded as the first report of an NHC-catalysed benzoin reaction on a synthetically useful scale [9]. Much later, in 2005, Xu and Xia used N-alkyl-substituted imidazolium carbene 6 to efficiently promote benzoin reactions. Although a high catalyst loading (50 mol %) was required, the reactions

• heteroaromatic aldehydes (Scheme 3) [11]. Subsequently, the same group disclosed the application of bis(benzimidazolium) precursor 8 as a more efficient catalyst for the benzoin condensation in aqueous medium. Here, the NHC precatalyst incorporated a long aliphatic bridge between the two imidazolium entities

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

• ][10][11]. This is because NHC complexes are easily obtained by deprotonating imidazolium or benzimidazolium salts and most are relatively stable in air and moisture. They are weak π-acceptors and strong σ-donors and can form strong M–C bonds with transition metal ions compared to trivalent phosphine

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

• convenient to carry out the synthesis of imidazolinium salts in parallel to their imidazolium counterparts via the reduction of the diimines into diammonium salts. The critical assembly of the C2 precarbenic unit was best achieved with paraformaldehyde and chlorotrimethylsilane in the case of imidazolium

• ), 1,3-dimesitylimidazolium tetrafluoroborate (IMes·HBF4), 1,3-dimesitylimidazolinium chloride (SIMes·HCl), 1,3-bis(2,6-diisopropylphenyl)imidazolium chloride (IDip·HCl or IPr·HCl), 1,3-bis(2,6-diisopropylphenyl)imidazolinium chloride (SIDip·HCl or SIPr·HCl), and 1,3-bis(2,6-bis(diphenylmethyl)-4

• -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

Convenient preparation of high molecular weight poly(dimethylsiloxane) using thermally latent NHC-catalysis: a structure-activity correlation

• Stefan Naumann,
• Johannes Klein,
• Dongren Wang and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2015, 11, 2261–2266, doi:10.3762/bjoc.11.246

• prepare poly(dimethylsiloxane) (PDMS), using three different imidazolium-based free NHCs in combination with benzyl alcohol or methanol as initiator [24]. There, polymerizations were conducted at 80 °C for 16 h to achieve conversions of about 85% (1.5 < ÐM < 1.7, 0.1% catalyst loading). Notably, it was

• , the five-membered imidazolium derivative 5-Mes was determined to have a pKa-value of only 20.8 (which compares to 15–19 for typical alcohols; in turn, silanols are even more acidic than the corresponding alcohols) [28][29][30][31][32]. At the same time, 5Me-Me-CO2 successfully catalyzed PDMS-formation

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

• metathesis Formation of pyridinium/imidazolium salt prior to metathesis Most of the examples of RCM involving substrates that possess a pyridine ring relied on the pre-requisite formation of a pyridinium salt. In 2004, Vaquero et al. reported the synthesis of dihydroquinolizium cations through RCM of dienic

Synthesis and structures of ruthenium–NHC complexes and their catalysis in hydrogen transfer reaction

• Chao Chen,
• Chunxin Lu,
• Qing Zheng,
• Shengliang Ni,
• Min Zhang and
• Wanzhi Chen

Beilstein J. Org. Chem. 2015, 11, 1786–1795, doi:10.3762/bjoc.11.194

• (1), [RuL1(CH3CN)4](PF6)2 (2) and [RuL2(CH3CN)3](PF6)2 (3) The ruthenium–NHC complexes 1 and 2 were synthesized by using the corresponding nickel–NHC complexes as the carbene transfer agent [36]. The reaction of imidazolium salt HL1(PF6) (L1 = 3-methyl-1-(pyrimidine-2-yl)imidazolylidene) with Raney

• analysis and X-ray diffraction. In the 1H NMR spectra of complexes 1 and 2, disappearance of the resonances assigned to the imidazolium acidic CH and p-cymene protons were observed. The acetonitrile protons of complex 1 were found at 2.41 ppm as a singlet. However, the protons of acetonitrile ligands of

• imidazolium salt HL2(PF6) (L2 = 1,3-bis(pyridin-2-ylmethyl)benzimidazolylidene) with a half equivalent of [Ru(p-cymene)Cl2]2 and an excess of NH4PF6 in a refluxing acetonitrile solution afforded the tri-acetonitrile coordinated Ru(II)–NHC complex [RuL2(CH3CN)3](PF6)2 (3) in a yield of 61% (Scheme 2). The

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

• -imidazoles based on the formation of a pyrrole ring via the reaction of 2H-azirines with 1-alkyl-3-phenacyl-1H-imidazolium bromides [29], in which one example of the synthesis of ethyl 4-imidazolylpyrrole-2-carboxylate from ethyl 3-methyl-2H-azirine-2-carboxylate was described. Earlier it was found that

• -dicarbonyl compounds under relay catalysis [31]. Taking into account the facts discussed above, we envisioned that the synthesis of 5-alkoxycarbonylpyrrol-3-ylimidazolium salts 1 could be carried out starting from easily available 5-alkoxyisoxazoles 7 [32][33] and 1-alkyl-3-phenacyl-1H-imidazolium bromides 9

• by Et3N; 3: activation of azirine 8 with Et3HN+Br−; 4: reaction of the activated azirine 11 with the imidazolium ylide 10) as a domino reaction under relay catalysis [35][36]. A simple procedure, consisting of stirring a mixture of isoxazole 7, phenacylimidazolium salt 9, FeCl2·4H2O and Et3N in MeCN

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

• increased in addition the steric congestion [20]. It is important to recognize that synthetically the stable forms for handling of imidazole carbenes are imidazolium salts. In imidazolium-based NHC chemistry two synthetic aspects are important: 1) there are several fundamental synthetic routes available

• are designed to bear bulky aromatic moieties as N1,N2-substituents. As mentioned before the synthetic pre-stages of NHCs are always imidazolium salts, but benzimidazolium salts, which possess two aromatic N1,N2-substituents are rare. More common are benzimidazolium salts having different N1,N2

• of nucleophilic aromatic substitutions (SNAr) of benzene-1,2-diamine at 2-chloropyridine (Scheme 1). Once all the different N1,N2-diarylbenzene-1,2-diamines were prepared a method had to be developed to build up the imidazolium salts by ring closure. 3-Cl and 4-Cl could principally be obtained from

Reaction of allene esters with Selectfluor/TMSX (X = I, Br, Cl) and Selectfluor/NH₄SCN: Competing oxidative/electrophilic dihalogenation and nucleophilic/conjugate addition

• A. Srinivas Reddy and
• Kenneth K. Laali

Beilstein J. Org. Chem. 2015, 11, 1641–1648, doi:10.3762/bjoc.11.180

• A. Srinivas Reddy Kenneth K. Laali Department of Chemistry, University of North Florida, 1 UNF Drive, Jacksonville, Florida 32224, USA 10.3762/bjoc.11.180 Abstract Reaction of benzyl and ethyl allenoates with TMSX (X = I, Br, Cl) and with NH4SCN were investigated in MeCN, DMF, and in imidazolium

• “X+” or “SCN+” at the central carbon of the allenyl moiety to form incipient allyl cations which on subsequent quenching with X− or SCN− furnished the 2,3-adducts as major products. The 1,2-addition products were only observed with TMSCl. The reactions were carried out in MeCN and in imidazolium

• in the absence of Selectfluor 1c became the predominant product, and minor amounts of the isomeric 1d was also isolated (Scheme 1). Switching to imidazolium ILs as solvent (Scheme 2), from the reaction of 1 with TMSBr/Selectfluor in [BMIM][NTf2] the dibromoalkenoate 1a and the hydrobromination

Grubbs–Hoveyda type catalysts bearing a dicationic N-heterocyclic carbene for biphasic olefin metathesis reactions in ionic liquids

• Maximilian Koy,
• Hagen J. Altmann,
• Benjamin Autenrieth,
• Wolfgang Frey and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2015, 11, 1632–1638, doi:10.3762/bjoc.11.178

• the IL used is of utmost importance, the more since imidazolium-based ILs can contain substantial amounts of free base [25], which in turn can negatively affect catalyst performance. As can be seen, M1–M6 can be polymerized via ROMP under biphasic conditions in good yields, except for M6. This low

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

• from Pd2dba3 and 3-methylbenzothiazolium salt V as precursors. A comparison of the performance of benzothiazole carbene with phosphanes and an analogous imidazolium carbene ligand is also proposed. Keywords: active methylene compounds; allylic carbonates; Pd–benzothiazol-2-ylidene complex; Tsuji–Trost

IR and electrochemical synthesis and characterization of thin films of PEDOT grown on platinum single crystal electrodes in [EMMIM]Tf₂N ionic liquid

• Andrea P. Sandoval,
• Marco F. Suárez-Herrera and
• Juan M. Feliu

Beilstein J. Org. Chem. 2015, 11, 348–357, doi:10.3762/bjoc.11.40

• recording the behavior of the electrode surface. Also, it is important to recognize that there are no water bands, which means that the IL is practically dry. The bands at 3186 and 3151 cm−1 in the p-polarized and ATR spectra, are related to the imidazolium cation. However, the intensity of these bands is

A new charge-tagged proline-based organocatalyst for mechanistic studies using electrospray mass spectrometry

• J. Alexander Willms,
• Rita Beel,
• Martin L. Schmidt,
• Christian Mundt and
• Marianne Engeser

Beilstein J. Org. Chem. 2014, 10, 2027–2037, doi:10.3762/bjoc.10.211

• now [43][53]. They consist of an imidazolium salt attached to hydroxyproline via an ester group at the end of a flexible alkyl spacer. Interestingly, such charge tags can cause an enhancement of the catalytic performance through electrosteric activation [53], but backfolding can also alter and disturb

• not present in the unlabeled reference system have not been observed. There are no indications for an interference of the charge tag with the catalysis, in contrast to the findings with the flexible imidazolium-labeled proline derivatives reported previously [43]. The mere detection of ions at m/z

Efficient CO₂ capture by tertiary amine-functionalized ionic liquids through Li⁺-stabilized zwitterionic adduct formation

• Zhen-Zhen Yang and
• Liang-Nian He

Beilstein J. Org. Chem. 2014, 10, 1959–1966, doi:10.3762/bjoc.10.204

• were developed for efficient CO2 chemisorption [23][25][26][27][28][29][30]. Binary absorbents derived from superbases together with various non-volatile weak proton donors such as hydroxy-functionalized ILs, imidazolium ILs, fluorinated alcohol, imidazole and phenol, were also found to be efficient

• ligands/LiNTf2 (Table 1, entries 5–7 and 10–13). This is much higher than for the conventional IL 1-hexyl-3-methylimidazolium hexafluorophosphate (0.0881 wt %) [43], and comparable to amino-functionalized imidazolium-based IL (7.4 wt %) [23] and ILs derived from amino acids [24]. Hence, our IL system has

Relay cross metathesis reactions of vinylphosphonates

• Raj K. Malla,
• Jeremy N. Ridenour and
• Christopher D. Spilling

Beilstein J. Org. Chem. 2014, 10, 1933–1941, doi:10.3762/bjoc.10.201

• ethylimidazole would reacted with dimethyl methylphosphonate to give ethylimidazolium methylphosphonate in quantitative yield [32]. We were pleased to observe [31P NMR] that dimethyl vinylphosphonate 12b reacted with neat methylimidazole at 100 °C to give the imidazolium salt 37 (Scheme 13). Treatment of the

Synthesis of zearalenone-16-β,D-glucoside and zearalenone-16-sulfate: A tale of protecting resorcylic acid lactones for regiocontrolled conjugation

• Hannes Mikula,
• Julia Weber,
• Dennis Svatunek,
• Philipp Skrinjar,
• Gerhard Adam,
• Rudolf Krska,
• Christian Hametner and
• Johannes Fröhlich

Beilstein J. Org. Chem. 2014, 10, 1129–1134, doi:10.3762/bjoc.10.112

• protection was applied for the synthesis of ZEN-16-sulfate (8) using a procedure that was successfully applied for the synthesis of ZEN-14-sulfate (6) as described recently [20]. Reaction of 22 with the 2,2,2-trichloroethyl (TCE) protected sulfuryl imidazolium salt 23 [36][37] gave the protected sulfate 24

• successfully used as intermediates for the preparation of corresponding glucosides and sulfates applying the Königs–Knorr glucosylation and chemical sulfation using TCE-protected sulfuryl imidazolium salt 23, respectively. These methods were used for the first chemical synthesis of the ZEN-16-conjugates 7 and

• , >99% for 21 and 22; b: 13, Ag2O, MeCN, 96 h, rt; c: TBAF, AcOH, THF, 24 h; d: KOH, THF/H2O, 4 h, rt, 41% for 17, 34% for 7 (3 steps). Chemical sulfation using the 2,2,2-trichloroethyl (TCE)-protected sulfuryl imidazolium salt 23 yielding ZEN-16-sulfate (8) as tetrabutylammonium salt; a: 23, 1,2

Preparation of phosphines through C–P bond formation

• Iris Wauters,
• Wouter Debrouwer and
• Christian V. Stevens

Beilstein J. Org. Chem. 2014, 10, 1064–1096, doi:10.3762/bjoc.10.106

• obtained was 45%. The same group has shown that imidazolium based ionic liquids can be used as a medium to perform the C–P cross-coupling reactions. This method allows an easy separation of the product from the catalyst and the recycling of the palladium catalyst [176]. Stelzer and co-workers have

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• developed a new saturated 1,3-bis(2,6-diisopropylphenyl)imidazolium (SIPr) silver complex, characterized by the presence of a less bulky acetoxy anion [15]. The new NHC–Ag(I) complex displayed a broad scope in A3-coupling reactions, tolerating alkyl and arylaldehydes (also unactivated ones), cyclic and