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

• coupling partners. The desired coupling products were obtained in moderate to good yields by using 1 mol % of these air-stable palladium complexes. This is an advantage compared to the procedures employing air-sensitive phosphines, which have been previously shown to promote the coupling of aryl chlorides

• ligands, which are electronically and sterically tunable, and which generally form thermally stable compounds with different metal ions, are strong σ-donors. These qualities have rendered N-heterocyclic carbene ligands as classical substitutes to phosphines in organometallic catalysis [10][11][12][13][14

Alkenes from β-lithiooxyphosphonium ylides generated by trapping α-lithiated terminal epoxides with triphenylphosphine

• David. M. Hodgson and
• Rosanne S. D. Persaud

Beilstein J. Org. Chem. 2012, 8, 1896–1900, doi:10.3762/bjoc.8.219

• way than the above approaches to β-lithiooxyphosphonium ylides 4 (R2 = H), we were attracted to the possibility of phosphines intercepting α-lithiated terminal epoxides 10 (Scheme 2) and report here the results of that study. Such carbenoids 10 are unstable, but they can be easily formed from terminal

A quantitative approach to nucleophilic organocatalysis

• Herbert Mayr,
• Sami Lakhdar,
• Biplab Maji and
• Armin R. Ofial

Beilstein J. Org. Chem. 2012, 8, 1458–1478, doi:10.3762/bjoc.8.166

• (Figure 3d) were linear, with their slopes giving the second-order rate constants k2 (M–1 s–1) [35][36]. For the investigations of reactions of the iminium ions on the micro- and nanosecond time scale, laser flash spectroscopy was employed [37]. As tertiary phosphines PR3 (10) are known to be excellent

• photonucleofuges [38][39][40][41], the stable iminium salts 3-PF6 were treated with tertiary phosphines 10 at room temperature to give the enamino-phosphonium ions 11 instantaneously (Figure 4a). Their irradiation with 7 ns laser pulses (266 nm) regenerated the iminium ions, the decay of which was monitored

Chiral multifunctional thiourea-phosphine catalyzed asymmetric [3 + 2] annulation of Morita–Baylis–Hillman carbonates with maleimides

• Hong-Ping Deng,
• De Wang,
• Yin Wei and
• Min Shi

Beilstein J. Org. Chem. 2012, 8, 1098–1104, doi:10.3762/bjoc.8.121

• work of Lu [11][12][13][14][15][16][17][18][19][20], all phosphine-mediated [3 + 2] annulations proceeded through an important intermediate “1,3-dipolar synthon”. The formation of a 1,3-dipolar synthon by using a catalytic amount of phosphines have been directed toward the following two paths

• : phosphines attack the middle carbon atom of allenes to produce the 1,3-dipolar synthon (Scheme 1, reaction 1), and phosphines add to the β-position of MBH carbonate to remove carbon dioxide and tert-butanol, affording the 1,3-dipolar synthon (Scheme 1, reaction 2). Concerning the asymmetric [3 + 2

• ] annulation catalyzed by chiral phosphines, Zhang and co-workers first reported the asymmetric [3 + 2] annulation of allenoates with acrylates catalyzed by a bicyclic chiral phosphine in 1997 [21]. Moreover, Fu [22][23][24], Marinetti [25][26][27][28], Lu [29][30][31] and other researchers [32][33][34][35][36

Fifty years of oxacalix[3]arenes: A review

• Kevin Cottet,
• Paula M. Marcos and
• Peter J. Cragg

Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22

• highly atypical but may be due to the templating effect of Na+. Separation by column chromatography afforded the cone conformer in 72% yield although the partial-cone was never obtained in a pure form. Reduction by phenylsilane (PhSiH3) gave the corresponding cone and partial-cone phosphines 26

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• the possibility of modulating the properties of the metal through modification of its ancillary ligands (e.g., phosphines, N-heterocyclic carbenes, etc.), which considerably widens the potential and versatility of these catalysts, and in particular of those consisting of cationic gold(I) complexes

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• was observed by employing alcohol substrates bearing coordination functionalities. In addition, the catalyst system with electron deficient phosphines was also found to catalyze the desired reaction effectively (Scheme 10). An efficient approach [36] for the preparation of unsymmetrical ethers from

When cyclopropenes meet gold catalysts

• Frédéric Miege,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2011, 7, 717–734, doi:10.3762/bjoc.7.82

• the desired cyclopropanation product 48, but the yield and the diastereoselectivity were highly dependent on the gold ligand. As anticipated from the structural studies, π-acidic phosphites that increase cation-like reactivity gave little or none of the cyclopropanation product 48. Phosphines gave

Studies on Pd/NiFe₂O₄ catalyzed ligand-free Suzuki reaction in aqueous phase: synthesis of biaryls, terphenyls and polyaryls

• Sanjay R. Borhade and
• Suresh B. Waghmode

Beilstein J. Org. Chem. 2011, 7, 310–319, doi:10.3762/bjoc.7.41

• of phosphorous ligands. Efforts have been made to enhance the catalytic activity by the use of various ligands containing nitrogen or sulfur, as well as phosphines, salen and N-heterocyclic carbenes in traditional organic solvents [12][13][14][15][16][17][18][19]. However, the problems associated

Synthesis of Ru alkylidene complexes

• Renat Kadyrov and
• Anna Rosiak

Beilstein J. Org. Chem. 2011, 7, 104–110, doi:10.3762/bjoc.7.14

• precursors for the “second generation” catalysts bearing NHC ligands are the alkylidene ruthenium complexes coordinated with two phosphines [1]. For recent reviews see [2][3][4]. There are several routes for accessing five-coordinated ruthenium(II) alkylidene complexes such as diazo-transfer [5] and the

Olefin metathesis in nano-sized systems

• Didier Astruc,
• Abdou K. Diallo,
• Sylvain Gatard,
• Liyuan Liang,
• Cátia Ornelas,
• Victor Martinez,
• Denise Méry and
• Jaime Ruiz

Beilstein J. Org. Chem. 2011, 7, 94–103, doi:10.3762/bjoc.7.13

• chelating phosphine ligands on the branch termini. The choice of chelating phosphines may seem counter-intuitive, because the activity of Grubbs catalysts involves the decoordination of a phosphine from these trans-bis-phosphine complexes [15]. However, studies by the groups of Hofmann [16][17][18], Fog [19

• ][20] and Leitner [20] had demonstrated the metathesis activity of cis-bis-phosphine ruthenium benzylidene catalysts. We therefore used Reetz’s bis-phosphines derived from the commercial polyamine DSM dendrimers [21]. These dendritic bis-phosphines are useful and versatile in metallodendritic catalysis

• and provided the first recyclable metallodendritic catalysts [21]. Moreover, dendritic bis-phosphines with two phenyl groups on each phosphorus atom very cleanly yielded the first dendrimers decorated with clusters at the periphery via an efficient electron-transfer-chain reaction using [Ru3(CO)12

Palladium- and copper-mediated N-aryl bond formation reactions for the synthesis of biological active compounds

• Carolin Fischer and
• Burkhard Koenig

Beilstein J. Org. Chem. 2011, 7, 59–74, doi:10.3762/bjoc.7.10

• -aryl bond formation, and many examples illustrate their wide application in organic synthesis. The chelating phosphines BINAP, DPPF [17] and DtBPF [18], commonly used for the Buchwald–Hartwig amination, were recently displaced by the biaryl-(dialkyl)phosphine or arylphosphinepyrrole ligands [18][19][20

Aromatic and heterocyclic perfluoroalkyl sulfides. Methods of preparation

• Vladimir N. Boiko

Beilstein J. Org. Chem. 2010, 6, 880–921, doi:10.3762/bjoc.6.88

Shelf-stable electrophilic trifluoromethylating reagents: A brief historical perspective

• Norio Shibata,
• Andrej Matsnev and
• Dominique Cahard

Beilstein J. Org. Chem. 2010, 6, No. 65, doi:10.3762/bjoc.6.65

• in situ (a carboxylate from 35 and an alcoholate from 37). P-Trifluoromethyl phosphines were formed in moderate to high yields from either diarylphosphines or P-trimethylsilylated derivatives under the same reaction conditions (Scheme 30). By contrast, the corresponding lithium and potassium

Pd-catalyzed decarboxylative Heck vinylation of 2-nitrobenzoates in the presence of CuF₂

• Lukas J. Gooßen,
• Bettina Zimmermann and
• Thomas Knauber

Beilstein J. Org. Chem. 2010, 6, No. 43, doi:10.3762/bjoc.6.43

• the catalyst system, and discovered that phosphines impede the decarboxylation step. In contrast, nitrogen-containing ligands had a beneficial effect (entries 16–18). In the presence of 1,4,5-triazanaphthalene, the Heck product was formed in 67% yield (entry 18). We subsequently tested several

Synthesis of bis(3-{[2-(allyloxy)ethoxy]methyl}-2,4,6-trimethylbenzoyl)(phenyl)phosphine oxide – a tailor-made photoinitiator for dental adhesives

• Norbert Moszner,
• Iris Lamparth,
• Jörg Angermann,
• Urs Karl Fischer,
• Frank Zeuner,
• Thorsten Bock,
• Robert Liska and
• Volker Rheinberger

Beilstein J. Org. Chem. 2010, 6, No. 26, doi:10.3762/bjoc.6.26

• characterization of WBAPO The synthesis of bisacylphosphines and their oxides often start either from P,P-dichlorophenylphosphine (PhPCl2) [13] or free phenylphosphine [14]. We chose to use the PhPCl2-route since primary phosphines have an unpleasant smell, a high toxicity and are very air-sensitive. Furthermore

From discovery to production: Scale- out of continuous flow meso reactors

• Peter Styring and
• Ana I. R. Parracho

Beilstein J. Org. Chem. 2009, 5, No. 29, doi:10.3762/bjoc.5.29

• activating agents such as substituted phosphines, or else catalysts possessing ligands with complex and expensive motifs [1]. Often, the scale at which such reactions are performed is far greater than that required for initial characterisation and property screening [2][3]. Once a compound is identified for

• reaction. This makes catalyst recovery and re-cycling problematic if not impossible. It also leads to the possibility of metal contamination at trace levels in the final product. Furthermore, added phosphines and other activating agents tend to be expensive and also difficult to recover, adding both an

Asymmetric reactions in continuous flow

• Xiao Yin Mak,
• Paola Laurino and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2009, 5, No. 19, doi:10.3762/bjoc.5.19

• observed to be higher in the microreactor. A single-channel, falling film microreactor designed specifically for efficient gas-liquid phase contact was used to screen the asymmetric hydrogenation of (Z)-methyl acetamidocinnamate 4 and related substrates (Scheme 2) [13][14]. Seventeen chiral phosphines were

Efficient 1,4-addition of α-substituted fluoro(phenylsulfonyl)methane derivatives to α,β-unsaturated compounds

• G. K. Surya Prakash,
• Xiaoming Zhao,
• Sujith Chacko,
• Fang Wang,
• Habiba Vaghoo and
• George A. Olah

Beilstein J. Org. Chem. 2008, 4, No. 17, doi:10.3762/bjoc.4.17

• nucleophile to a variety of α,β-unsaturated compounds has been achieved under mild conditions using either phosphines or potassium carbonate at room temperature. α-Substituted fluoro(phenylsulfonyl)methane easily undergoes Michael addition to α,β-unsaturated ketones, esters, nitriles, sulfones, as well as

• -stabilizing abilities of the two strong electron-withdrawing groups are not sufficient to overcome the well-known carbanion destabilization by the adjacent fluorine [25]. With this in mind, we first opted to use phosphines as nucleophilic catalysts. Concerning applications of 3a–d, and 3f in constructing the

• in the course of above-mentioned Michael reactions, under the reaction conditions. We then screened various electronically and sterically different phosphines such as PPh3, Bu3P, (iPr)3P and PMe3. Initial experiments revealed that the catalytic activity of phosphines and phosphine loading (varying

Synthesis of coumarin or ferrocene labeled nucleosides via Staudinger ligation

• Ivana Kosiova,
• Andrea Janicova and
• Pavol Kois

Beilstein J. Org. Chem. 2006, 2, No. 23, doi:10.1186/1860-5397-2-23

• Ivana Kosiova Andrea Janicova Pavol Kois Comenius University, Faculty of Natural Sciences, Department of Organic Chemistry, Mlynska dolina, Pavilon CH2, SK-84215 Bratislava, Slovak Republic 10.1186/1860-5397-2-23 Abstract Background Reaction of azides with triaryl phosphines under mild conditions

• , boranes) and at N3 with nucleophiles, very frequently with phosphorous nucleophiles. Reaction of azides with triaryl phosphines under mild conditions gives iminophosphoranes without formation of any byproducts. [14] The intermediate which is formed almost quantitatively can be rapidly hydrolysed to the

Mixtures of monodentate P-ligands as a means to control the diastereoselectivity in Rh-catalyzed hydrogenation of chiral alkenes

• Manfred T. Reetz and
• Hongchao Guo

Beilstein J. Org. Chem. 2005, 1, No. 3, doi:10.1186/1860-5397-1-3

• extensive manner. For example, Brown reported the Rh-catalyzed hydrogenation of the racemic allylic alcohol 1 with formation of diastereomers 2 and 3, ketone 4 forming as a side product due to undesired isomerization.[29] From a small collection of mono-phosphines and bidentate diphosphines, diphos-4 led to