Synthesis of 1,2-divinylcyclopropanes by metal-catalyzed cyclopropanation of 1,3-dienes with cyclopropenes as vinyl carbene precursors

• Jesús González,
• Alba de la Fuente,
• María J. González,
• Laura Díez de Tejada,
• Luis A. López and
• Rubén Vicente

Beilstein J. Org. Chem. 2019, 15, 285–290, doi:10.3762/bjoc.15.25

• –vinyl carbenes generated from vinyldiazoacetates (Scheme 1b) [14][15][16]. This reaction has been fruitfully exploited, although it is inherently limited by the restricted availability of potentially explosive diazo compounds. Consequently, the use of alternative vinyl carbene precursors is highly

• desirable to expand the accessibility to 1,2-divinylcyclopropanes [17][18][19]. In this regard, cyclopropenes have demonstrated to be suitable precursors of metal–vinyl carbenes [20][21], which can be easily trapped with alkenes [22][23][24][25]. Our recent studies showed that simple ZnCl2 could be used to

• good yield (77%) in a stereoctive manner (Scheme 4). Finally, we were curious to study the reactivity of metal–vinyl carbenes generated from 3,3-disubstituted cyclopropenes with some particular dienes (Scheme 5). Interestingly, we found that the reaction of cyclopropenes 1a,b with furan (6) using ZnCl2

Olefin metathesis in multiblock copolymer synthesis

• Maria L. Gringolts,
• Yulia I. Denisova,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2019, 15, 218–235, doi:10.3762/bjoc.15.21

• transformations and ex situ NMR monitoring of the dyad composition evolution [90]. It was found that Gr1 first interacts with PCOE so that all Ru-carbenes become bound to those macromolecules approximately within one hour (Scheme 9, reaction 1 and Figure 7). Recall that the addition of Gr1 to a mixture of NB and

• [Ru]=PCOE carbenes and C=C bonds in PNB chains (Scheme 9, reaction 2). Its low rate is consistent with the bulky structure of NB units. During the cross metathesis, the concentration of [Ru]=PNB carbenes is very low but they are necessary for the cross reaction to proceed (Scheme 9, reaction 3). An

Catalysis of linear alkene metathesis by Grubbs-type ruthenium alkylidene complexes containing hemilabile α,α-diphenyl-(monosubstituted-pyridin-2-yl)methanolato ligands

• Tegene T. Tole,
• Johan H. L. Jordaan and
• Hermanus C. M. Vosloo

Beilstein J. Org. Chem. 2019, 15, 194–209, doi:10.3762/bjoc.15.19

• in organic and polymer chemistry [1][2]. The development of metal alkylidene precatalysts based on ruthenium, starting with the so-called Grubbs 1 (1) and 2 (2) metal carbenes, played a major role to extend the versatility of the reaction including the application of these in industrial processes

• (Figure 1). Of course, the role of the so-called Schrock metal carbenes based on tungsten and molybdenum should not be ignored in the success story of the alkene metathesis reaction but it is not the focus of this article. The large number of ruthenium alkylidene precatalysts that has been developed is

• Grubbs 2-type (5) metal carbenes with pyridinyl alcoholato ligands for the 1-octene metathesis reaction (Figure 3) [10][11][12][13][14]. The incorporation of pyridinyl-alcoholato ligands in the Grubbs-type precatalysts has shown an increase in the thermal stability, activity and lifetime of the

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

• to the current state of research are discussed. Keywords: ligand design; olefin metathesis; ruthenium catalysts; selectivity; unsymmetrical N-heterocyclic carbenes; Introduction The transition metal-catalyzed olefin metathesis reaction is an indispensable synthetic tool for the construction of new

• heteroatoms, such as thiazol-2-ylidene ligands [10], or those containing one nitrogen substituent, such as the series of cyclic (alkyl) (amino) carbenes (CAACs) introduced by Bertrand et al. [11], are not included in this survey. Review Ruthenium catalysts coordinated with N-aryl, N’-aryl NHCs The first

MoO₃ on zeolites MCM-22, MCM-56 and 2D-MFI as catalysts for 1-octene metathesis

• Hynek Balcar,
• Martin Kubů,
• Naděžda Žilková and
• Mariya Shamzhy

Beilstein J. Org. Chem. 2018, 14, 2931–2939, doi:10.3762/bjoc.14.272

• carbenes as real catalytically active species has been suggested [6][7]. The replacement of ordinary silicas for mesoporous molecular sieves SBA-15 or MCM-41 increased the catalyst activity substantially, which allowed performing the metathesis of long chain olefins under mild reaction conditions [8][9][10

The influence of the cationic carbenes on the initiation kinetics of ruthenium-based metathesis catalysts; a DFT study

• Magdalena Jawiczuk,
• Angelika Janaszkiewicz and
• Bartosz Trzaskowski

Beilstein J. Org. Chem. 2018, 14, 2872–2880, doi:10.3762/bjoc.14.266

• Magdalena Jawiczuk Angelika Janaszkiewicz Bartosz Trzaskowski Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097 Warszawa, Poland 10.3762/bjoc.14.266 Abstract Cationic carbenes are a relatively new and rare group of ancillary ligands, which have shown their superior activity in

• a number of challenging catalytic reactions. In ruthenium-based metathesis catalysis they are often used as ammonium tags, to provide water-soluble, environment-friendly catalysts. In this work we performed computational studies on three cationic carbenes with the formal positive charge located at

• different distances from the carbene carbon. We show that the predicted initiation rates of Grubbs, indenylidene, and Hoveyda–Grubbs-like complexes incorporating these carbenes show little variance and are similar to initiation rates of standard Grubbs, indenylidene, and Hoveyda–Grubbs catalysts. In all

Olefin metathesis catalysts embedded in β-barrel proteins: creating artificial metalloproteins for olefin metathesis

• Daniel F. Sauer,
• Johannes Schiffels,
• Takashi Hayashi,
• Ulrich Schwaneberg and
• Jun Okuda

Beilstein J. Org. Chem. 2018, 14, 2861–2871, doi:10.3762/bjoc.14.265

• ]. According to the Chauvin mechanism, the catalytically active species are Schrock-type carbenes or alkylidenes [2]. Olefin metathesis greatly profited from the isolation of structurally well-defined metal alkylidene complexes [3][4]. The best studied and most commonly employed catalysts are based on Mo, W

Novel photochemical reactions of carbocyclic diazodiketones without elimination of nitrogen – a suitable way to N-hydrazonation of C–H-bonds

• Liudmila L. Rodina,
• Xenia V. Azarova,
• Jury J. Medvedev,
• Dmitrij V. Semenok and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2018, 14, 2250–2258, doi:10.3762/bjoc.14.200

• ][3][4][5]. A direct irradiation of diazo compounds by UV light usually gives rise to nitrogen elimination and generation of carbenes [6][7][8][9][10] or ketenes [11][12][13][14][15][16][17][18] and their ensuing transformations. On the other hand, photochemical reactions of diazocarbonyl compounds

Diazirine-functionalized mannosides for photoaffinity labeling: trouble with FimH

• Femke Beiroth,
• Tomas Koudelka,
• Thorsten Overath,
• Stefan D. Knight,
• Andreas Tholey and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2018, 14, 1890–1900, doi:10.3762/bjoc.14.163

• insert into OH, NH, or CH groups of a protein in a fast reaction [5][6]. Further advantages of the diazirine group are its robustness at different pH values and its stability against nucleophiles. However, besides desired insertion reactions, carbenes can undergo unwanted side reactions, in particular

Thiocarbonyl-enabled ferrocene C–H nitrogenation by cobalt(III) catalysis: thermal and mechanochemical

• Santhivardhana Reddy Yetra,
• Zhigao Shen,
• Hui Wang and
• Lutz Ackermann

Beilstein J. Org. Chem. 2018, 14, 1546–1553, doi:10.3762/bjoc.14.131

• and Discussion We initiated our studies by probing various reaction conditions for the envisioned C–H amidation of ferrocene 1a (Table 1). Among a variety of ligands, N-heterocyclic carbenes and phosphines provided unsatisfactory results (Table 1, entries 1–3), while the product 3aa was formed when

Recent advances in phosphorescent platinum complexes for organic light-emitting diodes

• Cristina Cebrián and
• Matteo Mauro

Beilstein J. Org. Chem. 2018, 14, 1459–1481, doi:10.3762/bjoc.14.124

• shorter exciton lifetime that contributes to reduce detrimental nonradiative processes such as triplet–triplet annihilation (TTA) and triplet–polaron annihilation (TPA). On the other hand, strong σ-donor NHC carbenes ligands could be regarded as the neutral variant of phenylate-like counterparts [28][29

• the dopant was also shown by Strassner and co-workers [36][37][38]. Compared with previously reported imidazolylidene and triazolylidene acetylacetonate (acac) platinum(II) complexes, complexes 12 bearing 1,3-thiazol-2-ylidene carbenes outperformed the former when evaluating the photophysical

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

Enhanced quantum yields by sterically demanding aryl-substituted β-diketonate ancillary ligands

• Rebecca Pittkowski and
• Thomas Strassner

Beilstein J. Org. Chem. 2018, 14, 664–671, doi:10.3762/bjoc.14.54

• demonstrated. Phenyl-substituted N-heterocyclic carbenes (NHCs) as C^C* cyclometalating ligands shift the emission color towards higher energy, due to the strong donor character of NHCs compared to C^N cyclometalating ligands [33][34]. Recently, it was shown that the introduction of sterically demanding aryl

Heterogeneous Pd catalysts as emulsifiers in Pickering emulsions for integrated multistep synthesis in flow chemistry

• Katharina Hiebler,
• Georg J. Lichtenegger,
• Manuel C. Maier,
• Eun Sung Park,
• Renie Gonzales-Groom,
• Bernard P. Binks and
• Heidrun Gruber-Woelfler

Beilstein J. Org. Chem. 2018, 14, 648–658, doi:10.3762/bjoc.14.52

• are utilised. The employment of a variety of different ligands such as phosphines, amines and carbenes allows precise tuning of the properties of homogeneous Pd catalysts, which led to significant improvements in turn over number (TON), reaction rates, enantioselectivity as well as catalyst robustness

Recent progress in the racemic and enantioselective synthesis of monofluoroalkene-based dipeptide isosteres

• Myriam Drouin and
• Jean-François Paquin

Beilstein J. Org. Chem. 2017, 13, 2637–2658, doi:10.3762/bjoc.13.262

• -heterocyclic carbenes (NHCs, Scheme 11) [40]. The reaction was first performed on the γ,γ-difluoro-α,β-enal 52 which was synthesized via a Wittig olefination of 50. The resulting monofluoroalkene Boc-Val-ψ[(Z)-CF=CH]-Gly-OEt was obtained in good yield. Afterwards, the γ,γ-difluoro-α,β-enoylsilane 55, obtained

Rh(II)-mediated domino [4 + 1]-annulation of α-cyanothioacetamides using diazoesters: A new entry for the synthesis of multisubstituted thiophenes

• Jury J. Medvedev,
• Ilya V. Efimov,
• Yuri M. Shafran,
• Vitaliy V. Suslonov,
• Vasiliy A. Bakulev and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2017, 13, 2569–2576, doi:10.3762/bjoc.13.253

• reactions; thiophenes; Introduction In recent years the diversified reactivity of metal carbenes, catalytically generated from diazocarbonyl compounds, has found wide application in organic synthesis [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. A particular interest was attracted recently to

• groups [23][27][28], C=C double [24][25][26], or C≡C triple [29][30][31][32] bonds in the structure of the initial molecule (Scheme 1). Intermolecular reaction of metal carbenes with thioamides usually generates thiocarbonyl ylides which leads for example to enaminones [14][33][34][35] or, in the

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

• Grzegorz Mlostoń and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221

• comparison of the methods for the synthesis of E- and Z-1 shows that the most convenient protocol is the treatment of the corresponding alkyl cyanoacetate with SOCl2 and subsequent photoisomerization of the obtained E-1 into the Z-isomer. Applications in organic synthesis Reactions with carbenes

NHC-catalyzed cleavage of vicinal diketones and triketones followed by insertion of enones and ynones

• Ken Takaki,
• Makoto Hino,
• Akira Ohno,
• Kimihiro Komeyama,
• Hiroto Yoshida and
• Hiroshi Fukuoka

Beilstein J. Org. Chem. 2017, 13, 1816–1822, doi:10.3762/bjoc.13.176

• ; N-heterocyclic carbene; ring enlargement; Stetter reaction; vicinal polyketone; Introduction N-Heterocyclic carbenes (NHCs) have been indispensable catalysts for organic synthesis, particularly for umpolung of various functional groups [1][2][3][4][5][6][7][8][9]. In the Stetter reaction, NHCs

• study on the multicomponent reaction of thiazolium carbenes, benzils and water to yield 1,4-thiazin-3-ones [22]. Although the initial process producing the salt 12 was similar, the total mode of the two reactions was quite different, that is, stoichiometric vs catalytic reaction with respect to the

• thiazolium carbenes. In the Massi reaction, monoacylated Breslow intermediate C was readily hydrolyzed by hydroxide, whereas Stetter reaction took place exclusively in our reaction. The difference would be caused by the reaction conditions, particularly by the solvent system. Since the product 12 was

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

• –Pd bonds under aqueous reaction conditions often restricted the reuse of the catalyst and led to undesired residues. Therefore, in recent years, efforts have been turned to the development of water-soluble non-phosphine ligands [28][29][30][31][32][33][34]. In this context, N-heterocyclic carbenes

Construction of highly enantioenriched spirocyclopentaneoxindoles containing four consecutive stereocenters via thiourea-catalyzed asymmetric Michael–Henry cascade reactions

• Yonglei Du,
• Jian Li,
• Kerong Chen,
• Chenglin Wu,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2017, 13, 1342–1349, doi:10.3762/bjoc.13.131

• strategies with chiral transition metals [27][28][29][30][31][32][33], organocatalysts such as secondary amines [34][35][36], nucleophilic phosphines [26][37][38][39][40][41][42][43][44], tertiary amines [45], N-heterocyclic carbenes (NHCs) [46][47][48], and cinchona alkaloid derivatives [25][28][49][50

Phosphazene-catalyzed desymmetrization of cyclohexadienones by dithiane addition

• Matthew A. Horwitz,
• Elisabetta Massolo and
• Jeffrey S. Johnson

Beilstein J. Org. Chem. 2017, 13, 762–767, doi:10.3762/bjoc.13.75

• developed an acyl anion addition promoted by N-heterocyclic carbenes (NHC) that furnished bicyclic furanones via Stetter addition [21]; later, the You group developed an extension of this theme using the same catalytic manifold [22]. More recently, the Corey group has enabled the enantioselective conjugate

Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis

• Flavio Fanelli,
• Giovanna Parisi,
• Leonardo Degennaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2017, 13, 520–542, doi:10.3762/bjoc.13.51

• highly energetic reagents [79][80]. For this reason, the in situ generation of such reagents has been investigated under flow conditions. Moody and co-workers reported a new method for the in situ generation of diazo compounds as precursors of highly reactive metal carbenes (Scheme 16) [81]. As reported

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• to cis-trihydroxyindano[2,1-a]indan-5-ones 74 (Scheme 25). Another example of the 1-indanone synthesis using N-heterocyclic carbenes (NHC) has been described by Gravel et al. [50][51]. The benefit of the described reaction was a rapid construction of three new carbon–carbon bonds and a carbon

• obtained from the reaction of o-phthalaldehyde (86) with acetophenone 87 (Scheme 28). Iron(III) complexes of 88a–d turned out to be promising candidates for potential photovoltaic or luminescence applications. An intramolecular hydroacylation, catalyzed by nickel(0)/N-heterocyclic carbenes leading to the

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

• biological activities of NHC complexes [23][24]. In the last decade, attention has also been directed to anionic N-heterocyclic carbenes [25]. In this context, mesomeric betaines are interesting from two viewpoints. They are not only able to undergo tautomerisations to neutral NHCs and thus provide a safe

• been prepared from mesoionic compounds (Figure 1). The carbenes 3 [31] and 4 [32][33] originate from a conjugated ylide and a cross-conjugated mesomeric betaine, respectively. A review elucidates the interconversions of mesomeric betaines to different types of N-heterocyclic carbenes (NHC, aNHC, rNHC

• ), 6.72 ppm, and 5.81 ppm, respectively. Single crystals of [Rh(7)3] (11) were obtained by slow evaporation of a concentrated solution of 11 in a mixture of EtOAc and MeOH. The single crystal X-ray analysis proved that three anionic N-heterocyclic carbenes 7 serve as bidentate ligands, respectively

Correction: 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, 2124–2124, doi:10.3762/bjoc.12.201

• Interdisciplinary Science and Technology,Trivandrum 695 019, India.; Fax: +91 471 2491712; Tel: +91 471 2490406 10.3762/bjoc.12.201 Keywords: acyloin reaction; benzoin reaction; N-heterocyclic carbenes; organocatalysis; umpolung; On page 446, column 2, the sentence “Inoue and co-workers found that it promotes