Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• reaction of internal alkynes with a difluorodiazoethane reagent, offering efficient access to a broad range of enantioenriched difluoromethylated cyclopropenes with almost quantitative yields and up to 97% ee [82]. This asymmetric carbene transfer reaction was performed using chiral RhII complexes, more

Cyclopropanation–ring expansion of 3-chloroindoles with α-halodiazoacetates: novel synthesis of 4-quinolone-3-carboxylic acid and norfloxacin

• Sara Peeters,
• Linn Neerbye Berntsen,
• Pål Rongved and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2019, 15, 2156–2160, doi:10.3762/bjoc.15.212

• decomposition of diazo compounds, are particularly versatile intermediates in organic synthesis, as they partake in cyclopropanation and C–H insertion reactions with high levels of selectivity [2]. This transition-metal-catalyzed carbene transfer has emerged as a mild and attractive route to indole

• carbene transfer reaction typically give N–H, C–H (at C3) and double N–H/C–H insertion products. The presence of electron-withdrawing groups on the indole nitrogen makes it possible to cyclopropanate the indole C2–C3 double bond and isolate indoline cyclopropanes. We recently discovered that Rh carbenes

Reusable and highly enantioselective water-soluble Ru(II)-Amm-Pheox catalyst for intramolecular cyclopropanation of diazo compounds

• Hamada S. A. Mandour,
• Yoko Nakagawa,
• Masaya Tone,
• Hayato Inoue,
• Nansalmaa Otog,
• Ikuhide Fujisawa,
• Soda Chanthamath and
• Seiji Iwasa

Beilstein J. Org. Chem. 2019, 15, 357–363, doi:10.3762/bjoc.15.31

• crucial for the intramolecular cyclopropanation reaction in a water/ether biphasic medium. The water-soluble catalyst could be reused at least six times with little loss in yield and enantioselectivity. Keywords: asymmetric synthesis; carbene transfer; cyclopropanation; diazoester; intramolecular

Gold-catalyzed ethylene cyclopropanation

• Silvia G. Rull,
• Andrea Olmos and
• Pedro J. Pérez

Beilstein J. Org. Chem. 2019, 15, 67–71, doi:10.3762/bjoc.15.7

• transfer; cyclopropane; cyclopropylcarboxylate; ethylene cyclopropanation; ethyl diazoacetate; gold catalysis; Introduction Nowadays the olefin cyclopropanation through metal-catalyzed carbene transfer starting from diazo compounds to give olefins constitutes a well-developed tool (Scheme 1a), with an

• given our experience with group 11 metal-based catalysts for carbene-transfer reactions from diazoacetates [15][16], we have investigated this transformation and found that the gold complex IPrAuCl (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene) along with one equivalent of NaBArF4 (BArF4

• carbene-transfer reactions [22][23]. Neutral IPrAuCl was not effective (Table 1, entry 4), assessing the need of a cationic, halide-free gold species toward that end. The choice of the halide scavenger is not innocent: on the other hand, it is key for the success of this search. Thus, addition of one

On the mechanism of imine elimination from Fischer tungsten carbene complexes

• Philipp Veit,
• Christoph Förster and
• Katja Heinze

Beilstein J. Org. Chem. 2016, 12, 1322–1333, doi:10.3762/bjoc.12.125

• pentacarbonyl metal fragments (M = Cr, Mo, W) have further proven to be effective carbene transfer agents to late transition metals in transmetalation reactions [9][10][11][12][13][14][15]. The manifold synthetic access routes to carbene complexes even allows the assembly of multicarbene and multimetal carbene

Recent advances in C(sp³)–H bond functionalization via metal–carbene insertions

• Bo Wang,
• Di Qiu,
• Yan Zhang and
• Jianbo Wang

Beilstein J. Org. Chem. 2016, 12, 796–804, doi:10.3762/bjoc.12.78

• (Figure 1). Compared to Rh(II) catalysts, these coinage metal-based catalysts are generally less efficient in carbene-transfer reactions, thus requiring a high catalyst loading in general. However, this drawback is compensated by much lower cost of these metals than rhodium. In 2008, Pérez, Díaz-Requejo

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

• CHCO2Et to the substrate (styrene or methanol) takes place in the coordination sphere of Au(I) by means of an inner-sphere mechanism, in contrast to the generally accepted proposal of outer-sphere mechanisms for Au(I)-catalyzed reactions. Keywords: carbene transfer; inner sphere; gold catalysis; O–H

• )]SbF6 (L = tertiary phosphine ligand) abstracted the carbene group :CHPh from a tropilium derivative, and further transferred the gold-bonded carbene group to an olefin [17][18]. This contribution constituted a breakthrough in gold-mediated carbene-transfer reactions since the carbene source lacks of

• mechanism). Those intermediates are quite reactive, in contrast to similar but low reactive gold–carbene complexes recently and independently described by the groups of Fürstner [19] and Straub [20]. Scheme 4a shows a generally accepted mechanism for the metal-catalyzed carbene transfer from diazo compounds

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

• 176.42°. The rest coordination nitrogen atoms of acetonitrile and phenanthroline lie on the axial positions with the N(7)–Ru(1)–N(5) angle of 173.74°. Conclusion In summary, Ru–NHC complexes bearing pyrimidine- and pyridine-functionalized NHC ligands have been prepared through a carbene transfer reaction

Gold(I)-catalyzed enantioselective cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2013, 9, 2250–2264, doi:10.3762/bjoc.9.264

• eleven, gold has also demonstrated to be an efficient promoter of intermolecular carbene transfer reactions from diazo compounds to unsaturated systems such as alkenes or alkynes, resulting in cyclopropanation processes [44][45]. The development of an enantioselective variant of this type of reactions

Gold-catalyzed naphthalene functionalization

• Pedro J. Pérez,
• M. Mar Díaz-Requejo and
• Iván Rivilla

Beilstein J. Org. Chem. 2011, 7, 653–657, doi:10.3762/bjoc.7.77

• cyclopropanation, ring opening and the formal insertion of CHCO2Et into the aromatic C–H bonds were observed, with 2a being by far the major product (Scheme 2). In the course of our research, focussed on the development of group 11 metal-based catalysts for carbene transfer reactions from diazo compounds [10], we

Sequential Au(I)-catalyzed reaction of water with o-acetylenyl-substituted phenyldiazoacetates

• Lei Zhou,
• Yizhou Liu,
• Yan Zhang and
• Jianbo Wang

Beilstein J. Org. Chem. 2011, 7, 631–637, doi:10.3762/bjoc.7.74

• transfer a carbene unit to saturated or unsaturated organic substrates [3]. However, compared to the other group 11 metals, i.e., copper and silver, there are only a few reports on gold-catalyzed carbene transfer reactions of diazo compounds [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. In 2005

• , Díaz-Requejo, Nolan, Pérez and co-workers reported the first example of carbene transfer from ethyl diazoacetate (EDA) using (IPr)AuCl. The subsequent generation of a gold carbene was followed by insertion into a phenyl C–H bond, an O–H bond, or an N–H bond [6]. Similar reactions were also reported by

• Dias and co-workers with a gold(I) ethylene complex [7]. Although the scope of those studies was limited to ethyl diazoacetate, the examples therein demonstrated that gold complexes can be used as efficient catalysts in carbene transfer reactions with diazo compounds. On the other hand, the development

Synthesis of chiral mono(N-heterocyclic carbene) palladium and gold complexes with a 1,1'-biphenyl scaffold and their applications in catalysis

• Lian-jun Liu,
• Feijun Wang,
• Wenfeng Wang,
• Mei-xin Zhao and
• Min Shi

Beilstein J. Org. Chem. 2011, 7, 555–564, doi:10.3762/bjoc.7.64

• allylic acetates [75][76], carbene-transfer reactions from ethyl diazoacetate [77], formation of conjugated enones and enals [78], regio- and stereoselective synthesis of fluoroalkenes [79], and so on [80][81][82][83][84][85]. However, reports on NHC–Au catalyzed asymmetric reactions are rare [86]. The