Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• benzimidazolium salts 15 in the presence of CuI (Scheme 8). In a similar manner, Cu(I) complexes 18 of so-called “abnormal” carbenes [9] or mesoionic carbenes [8], such as 1,2,3-triazol-5-ylidenes have been prepared (Scheme 9). These NHC–Cu(I) complexes have been found to be highly efficient catalysts for the [3

• addition of Et2Zn to cyclohexenone employing NHC–Cu(I) complex as catalyst. After trying a number of copper salts and benzimidazolium salts, the combination of Cu(OTf)2 with the salt 120 (R1 = R2 = t-Bu) was found to give the best results with 96% yield and 63% ee (Scheme 45). Sakaguchi and co-workers [65

• -worker [22] synthesized [(NHC)Cu(μ-I)2Cu(NHC)] complexes 16 (Scheme 8) from CuI and benzimidazolium salts and 18 (Scheme 9) from 1,2,3-triazolium salts. Both types of complexes turned out to be highly efficient catalysts for the [3 + 2] cycloaddition of azides with alkynes. The reactions were complete in

Synthesis and reactivity of azole-based iodazinium salts

• Thomas J. Kuczmera,
• Annalena Dietz,
• Andreas Boelke and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2023, 19, 317–324, doi:10.3762/bjoc.19.27

• used to create dicationic iodonium salts. The N-Me and N-Ph-iodonium-benzimidazolium salts 5av and 5aw were obtained in 47% and 36% yield, respectively. The introduction of additional ortho-methyl groups resulted in the formation of the σ-hole-protected N-substituted salts 5ax–az in up to 97% yield

• the dicationic salts is a reactive site for oxidative transformations [44][45]. The reaction of the iodine-protected benzimidazolium salts 5ax–az and 12 with different oxygen sources revealed K2CO3 and NCS as the optimal system to form the benzimidazole-2-ones 13a–d in 18–48% yield, with the best

Tosylhydrazine-promoted self-conjugate reduction–Michael/aldol reaction of 3-phenacylideneoxindoles towards dispirocyclopentanebisoxindole derivatives

• Sayan Pramanik and
• Chhanda Mukhopadhyay

Beilstein J. Org. Chem. 2022, 18, 469–478, doi:10.3762/bjoc.18.49

• ][10][11][12][13][14]. Among the known synthetic methodologies, the domino cycloaddition reaction of benzimidazolium salts with two molecules of 2-(2-oxoindolin-3-ylidene)acetates provided as an important tool for the construction of dispirooxindoles [15]. In particular, most of the dispirooxindole

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

• , 44280 Malatya, Turkey 10.3762/bjoc.12.9 Abstract A series of novel benzimidazolium salts (1–4) and their pyridine enhanced precatalyst preparation stabilization and initiation (PEPPSI) themed palladium N-heterocyclic carbene complexes [PdCl2(NHC)(Py)] (5–8), where NHC = 1-(N-methylphthalimide)-3

• with 4-chlorotoluene. Keywords: arylation; benzimidazolium salts; catalysis; N-heterocyclic carbene; PEPPSI complex; Suzuki–Miyaura cross-coupling reaction; Introduction The use of N-heterocyclic carbenes (NHCs) as ligands was started by Wanzlick [1] and Öfele [2] almost fifty years ago. There have

• ][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

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

• leads to the formation of polycyclic isoquinoline derivatives [29] and the reaction of 3,5-di(tert-butyl)-1,2-benzoquinone with 1,2,3-trimethyl-benzimidazolium salts gives rise a spirocyclic derivative of sterically hindered pyrocatechol [30]. The structures of the prepared 2-hetaryl-1,3-tropolones have

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

• Gabriele Grieco Olivier Blacque Heinz Berke Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland, Fax: (+41)-1-635-6802 10.3762/bjoc.11.182 Abstract An atom-economic synthetic route to benzimidazolium salts is presented. The annulated polycyclic

• : 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

• 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

Synthesis of axially chiral gold complexes and their applications in asymmetric catalyses

• Yin-wei Sun,
• Qin Xu and
• Min Shi

Beilstein J. Org. Chem. 2013, 9, 2224–2232, doi:10.3762/bjoc.9.261

• yield (Scheme 3). With these NHC precursor salts (S)-13 and (S)-14 in hand, their coordination pattern with Au was examined. Benzimidazolium salts (S)-13 and (S)-14 were treated with AuCl·S(Me)2 in acetonitrile in the presence of NaOAc under reflux, giving the corresponding Au complexes (S)-15 [two

N-Heterocyclic carbene–palladium catalysts for the direct arylation of pyrrole derivatives with aryl chlorides

• Ismail Özdemir,
• Nevin Gürbüz,
• Nazan Kaloğlu,
• Öznur Doğan,
• Murat Kaloğlu,
• Christian Bruneau and
• Henri Doucet

Beilstein J. Org. Chem. 2013, 9, 303–312, doi:10.3762/bjoc.9.35

• benzimidazolium salts (10 mmol) in DMSO (5 mL) was added palladium(II) diacetate (5 mmol) under argon, and the resulting mixture was stirred at room temperature for 2 h, then at 60 °C for 4 h, at 80 °C for 2 h and finally at 110 °C for 2 h. Volatiles were removed in vacuo, and the residue was washed twice with

Synthesis of axially chiral oxazoline–carbene ligands with an N-naphthyl framework and a study of their coordination with AuCl·SMe₂

• Feijun Wang,
• Shengke Li,
• Mingliang Qu,
• Mei-Xin Zhao,
• Lian-Jun Liu and
• Min Shi

Beilstein J. Org. Chem. 2012, 8, 726–731, doi:10.3762/bjoc.8.81

• benzimidazolium salts 7, respectively. Coordination study with AuCl·SMe2 The coordination behavior of ligand 7 with Pd(OAc)2 has been disclosed in previous work. However, only (Sa,S)-7 could give the corresponding Pd-complex (Sa,S)-8, while the Pd(II)-complex with R-geometry of the chiral N-naphthyl axis could

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

• Jiří Kulhánek and
• Filip Bureš

Beilstein J. Org. Chem. 2012, 8, 25–49, doi:10.3762/bjoc.8.4

• [77]. Terphenyl-bridged bis(benzimidazolium) salts 71, soluble in water and common organic solvents, emit blue light with λmax,em at 420–441 nm in thin films [78]. This feature makes them potentially applicable as blue-light emitters in OLEDs. Benzimidazole-based push–pull systems were studied also