Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

• and Epred = −2.10 V vs SCE for CF3Br) [93]. As a further application of conPET to atom transfer processes, the Wärnmark group recently disclosed an alternative protocol for the ATRA reaction of perfluoroalkyl iodides using the iron-based NHC complex [FeIII(btz)3](PF6)3 (btz = (3,3’-dimethyl-1,1’-bis(p

Pyridine C(sp²)–H bond functionalization under transition-metal and rare earth metal catalysis

• Haritha Sindhe,
• Malladi Mounika Reddy,
• Karthikeyan Rajkumar,
• Akshay Kamble,
• Amardeep Singh,
• Anand Kumar and
• Satyasheel Sharma

Beilstein J. Org. Chem. 2023, 19, 820–863, doi:10.3762/bjoc.19.62

• nickel Lewis acid catalyst with amino pendant linked NHC complex (Scheme 21). In addition, the authors were able to isolate the bimetallic intermediate structure η2,η1-pyridine–Ni(0)–Al(III) complex 112, as a support for their mechanism for the para-C–H functionalization. They further investigated the

Mechanochemical solid state synthesis of copper(I)/NHC complexes with K₃PO₄

• Ina Remy-Speckmann,
• Birte M. Zimmermann,
• Mahadeb Gorai,
• Martin Lerch and
• Johannes F. Teichert

Beilstein J. Org. Chem. 2023, 19, 440–447, doi:10.3762/bjoc.19.34

• “built-in base” route relies on the use of Cu2O which can be directly reacted with a suitable NHC precursor 1 (Scheme 1c) [28]. In any case, the most common approach hinges upon the use of the preliminary preparation of an intermediate silver(I)/NHC complex followed by facile transmetallation to copper(I

• ball mill was discovered (Scheme 1e) [44]. The possibility of synthesizing copper(I)/NHC complexes in the ball mill is promising due to the avoidance of organic solvents. Direct approaches from the NHC-precursor to the copper(I)/NHC complex not undergoing the transmetallation step have been disclosed

• an ester reduction with H2 as terminal reducing agent utilizing bifunctional copper(I)/NHC complex 5 bearing a guanidine moiety as additional catalytic unit [48]. This catalyst acts by employing the copper(I)/NHC complex for H2 activation on the one hand and by using the guanidine subunit for

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• phenylboronic acid to 2-cyclohexenone catalysed by L4/Pd2(dba)3·CHCl3 [41]. Plausible catalytic cycle of the addition of phenylboronic acid to 2-cyclohexenone catalysed by palladacycle PdL6 [43]. Proposed catalytic cycle for the addition of phenylboronic acids to 2-cyclohexenone catalysed by Pd-NHC complex

Synergy between supported ionic liquid-like phases and immobilized palladium N-heterocyclic carbene–phosphine complexes for the Negishi reaction under flow conditions

• Edgar Peris,
• Raúl Porcar,
• María Macia,
• Jesús Alcázar,
• Eduardo García-Verdugo and
• Santiago V. Luis

Beilstein J. Org. Chem. 2020, 16, 1924–1935, doi:10.3762/bjoc.16.159

• cross-coupling; NHC complex; palladium; supported ionic liquid; Introduction N-heterocyclic carbenes (NHCs) are known as efficient coordination ligands for different types of metals. The main feature of NHC complexes is their structural tunability [1]. Thus, their catalytic efficiency can be easily

• palladium species as calculated by ICP–MS of the respective solutions (>15 ppm of Pd). The elemental analysis of the catalyst after its use was also consistent with this Pd loss from the NHC complex. Additionally, the catalyst 8a was also tested under continuous flow conditions. Although, this time a

• combination of a classical molecular mode of operation and a cocktail-type mode of operation can also be involved in the Negishi reaction. Two different palladium species released from the NHC complex can act as catalyst for the Negishi reaction: i) soluble Pd(II) species or ii) palladium nanoparticles (PdNPs

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• merging C–H activation and photocatalysis while using a single metal catalyst. In this case, an original Rh–NHC complex was used for the ortho-directed C–H borylation of phenylpyridine substrates (Figure 40) [102]. As previously, the irradiation with visible light allowed performing this challenging

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• required if CuCN is used as the catalyst. Under such conditions, the desired product could be obtained faster than when the NHC was used. However, aldehydes containing reactive functional groups, as in 85–87, gave none of the desired product with either CuCN or the Cu–NHC complex 74. On the other hand

Formal preparation of regioregular and alternating thiophene–thiophene copolymers bearing different substituents

• Atsunori Mori,
• Keisuke Fujita,
• Chihiro Kubota,
• Toyoko Suzuki,
• Kentaro Okano,
• Takuya Matsumoto,
• Takashi Nishino and
• Masaki Horie

Beilstein J. Org. Chem. 2020, 16, 317–324, doi:10.3762/bjoc.16.31

• by polymerization catalyzed by a nickel complex, leading to the regioregular HT polythiophene (Scheme 1) [8][9]. An additional feature of the deprotonative protocol for polythiophene is the possibility to use chlorothiophene 3, in which the use of a nickel N-heterocyclic carbene (NHC) complex was

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• considerably lower activity than the other tested catalysts. The replacement of the mesityl group by a 2,6-diisopropylphenyl group as in complexes 24a and 33 led preferentially to bis(NHC)-coordinated complexes, which showed metathesis activity only at elevated temperatures [23]. However, the mono(NHC) complex

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

• Mizoroki–Heck cross-coupling reactions [64][65]. These electron-donating groups could provide a flexible environment for the Pd center and thus favoring the complexation and the migratory insertion of an alkene. Cavell reported that a pyridine functionalized Pd–NHC complex showed outstanding catalytic

• NMR spectrum, which is similar to the reported 13C NMR analysis for Pd–NHC species [66]. It is strongly suggested that a Pd–NHC complex was formed from deprotonation of L1 under the reaction conditions. However, the exact structure of this complex is not clear yet. With the preliminary reaction

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

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

• , entries 3 and 4). CuI NHC complex 4 showed the same activity and selectivity as CuI (Table 1, entry 6). By using the bioconjugate 13, the conversion with 62% is comparable with the protein-free catalysts or CuI itself, but the selectivity significantly changed the endo product preferred (Table 1, entry 7

• in THF (5 mL) for 24 h at 23 °C. The solvent was evaporated under vacuum and the residue was dissolved in dichloromethane (4 mL). After filtering over Celite® the solvent was evaporated under vacuum and the residue dried under vacuum to afford CuI NHC complex 6 (150 mg, 0.292 mmol, 59%) as orange

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

• pyrimidyl-imidazole complex [32]. However, a red binuclear Cu(I) complex 3 was obtained in 57% yield when we reacted pyrimidyl benzimidazolium salt 1b with copper powder. Furtherly, we got a yellow Cu(I)–NHC complex 4 in about 70% yield from pyridine imidazolium salt 1c and copper powder (Scheme 1). In

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

• –NHC complex as catalyst resulted in low yields and conversions (Table 3, entries 9–12). The usage of the morpholinoethyl substituted benzimidazolium compound 4 with Pd(OAc)2 resulted in higher yields of 2-(4-nitrophenyl)benzo[b]thiophene compared to the usage of compounds 1–3. Generally, the PEPPSI Pd

• –NHC complexes showed similar catalytic activity with in situ formed Pd–NHC complexes under the same experiment conditions (Table 3 and Table 4). The 2-morpholinoethyl substituted Pd–NHC complex 8, on the other hand, displayed very low activity compared to the other three complexes for the coupling of

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

• might be a mono- or bis-NHC complex. We therefore decided to prepare and test [NiCl(Cp)(ICy)] (3) (closely related to [NiCl(Cp)(IDD)] (4)) in some model catalytic reactions, to discover whether the favourable properties of ICy in cross-coupling catalysis could be combined with the ease of synthesis and

• conversions (ca. 15% with [NiCl(Cp)(ICy)] (3)). This may be due to the thermal sensitivity of these complexes, or may suggest that the active species in Chatani’s work is in fact a bis(NHC) complex. Further work is underway in our laboratory to understand the effect of NHC structure on cross-coupling

Effective ascorbate-free and photolatent click reactions in water using a photoreducible copper(II)-ethylenediamine precatalyst

• Redouane Beniazza,
• Natalia Bayo,
• Florian Molton,
• Carole Duboc,
• Stéphane Massip,
• Nathan McClenaghan,
• Dominique Lastécouères and
• Jean-Marc Vincent

Beilstein J. Org. Chem. 2015, 11, 1950–1959, doi:10.3762/bjoc.11.211

• Gautier and coworkers based on a water-soluble Cu(I)–NHC complex, which could be used under ascorbate-free and open air conditions for the CuAAC ligation of oxidation-sensitive peptides in buffered aqueous media [10]. Recently, we developed the photoreducible copper(II) complexes 2 and 3 incorporating a

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

• phenanthrolin-functionalized Ru(II)–NHC complexes containing acetonitrile ligands [33][34]. The most notable example is the acetonitrile-coordinated dinuclear Ru(II)–NHC complex derived from 3,6-bis(N-(pyridylmethyl)imidazolylidenyl)pyridazine, which is a very efficient catalyst for the oxidation of alkenes [35

• complexes show good catalytic activity in the transfer hydrogenation of ketones. The reaction of acetonitrile-coordinated Ru–NHC complex 2 with other donors such as triphenylphosphine and 1,10-phenanthroline was also studied. Results and Discussion Synthesis and characterization of [Ru(L1)2(CH3CN)2](PF6)2

• nickel afforded the nickel–NHC complexes which were not isolated [30]. The subsequent reaction of the generated nickel–NHC complexes with a quarter equivalent of [Ru(p-cymene)Cl2]2 in refluxing acetonitrile solution afforded bis-NHC complex [Ru(L1)2(CH3CN)2](PF6)2 (1) in a yield of 76% (Scheme 1). When a

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

• ] and many papers were published recently [15][16][17][18][19][20][21][22]. The 4–6 triads could particularly be interesting as new ligands for the preparation of mixed complexes: a chelate complex with the carboxypyrrole part and a monodentate NHC complex. Not so much is known about metal chelate

Gold-catalyzed formation of pyrrolo- and indolo-oxazin-1-one derivatives: The key structure of some marine natural products

• Sultan Taskaya,
• Nurettin Menges and
• Metin Balci

Beilstein J. Org. Chem. 2015, 11, 897–905, doi:10.3762/bjoc.11.101

• carbene (NHC) complex of Au(I) in chloroform (Table 1, entry 5). Reactions with InCl3 and PtCl2(PPh3)3 as catalysts gave very poor yields of exo-dig cyclization product 7 after 24 h (entries 3 and 4). AgOTf and AuCl3 were also screened and AuCl3 was identified as the optimal choice due to the shorter

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

• involving a well-defined [Pd(NHC)] complex has been described. However, it is noteworthy that variously substituted benzothiophene cores have been extensively studied in the direct arylation process [4][31][32][33][34][35][36][37]. Initial screening of precatalysts 1–4 was performed with a 2 mol % loading

The role of silver additives in gold-mediated C–H functionalisation

• Scott R. Patrick,
• Ine I. F. Boogaerts,
• Sylvain Gaillard,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2011, 7, 892–896, doi:10.3762/bjoc.7.102

• stoichiometric reaction between Ag2O and the substrate displayed substitution of one of the protons. However, deuterium incorporation experiments were unsuccessful and mass spectrometry on the product was inconclusive. The reaction depicted in Scheme 2 was performed using a neutral gold(I)-NHC complex. The

Suzuki–Miyaura cross-coupling reaction of 1-aryltriazenes with arylboronic acids catalyzed by a recyclable polymer-supported N-heterocyclic carbene–palladium complex catalyst

• Guangming Nan,
• Fang Ren and
• Meiming Luo

Beilstein J. Org. Chem. 2010, 6, No. 70, doi:10.3762/bjoc.6.70

• Suzuki–Miyaura cross-coupling reaction of 1-aryltriazenes with arylboronic acids catalyzed by a recyclable polymer-supported Pd–NHC complex catalyst has been realized for the first time. The polymer-supported catalyst can be re-used several times still retaining high activity for this transformation