Coupling of α,α-difluoro-substituted organozinc reagents with 1-bromoalkynes

• Artem A. Zemtsov,
• Alexander D. Volodin,
• Vitalij V. Levin,
• Marina I. Struchkova and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2015, 11, 2145–2149, doi:10.3762/bjoc.11.231

• dimethylformamide under ligand-free conditions. Keywords: 1-bromoalkynes; cross-coupling; organofluorine compounds; organozinc reagents; Introduction gem-Difluorinated organic compounds have attracted increasing attention nowadays due to their applicability in medicinal chemistry [1][2] and other fields. Indeed

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

• reaction. Ghosh, Dhara et al. also reported a synthesis of substituted phenanthridines based on palladium-mediated Suzuki coupling (Scheme 14) [34][35]. Aerobic ligand-free domino Suzuki coupling–Michael addition reaction in the presence of Pd(OAc)2 and K3PO4 as a catalytic system in H2O was catalysed by

Exploration of C–H and N–H-bond functionalization towards 1-(1,2-diarylindol-3-yl)tetrahydroisoquinolines

• Michael Ghobrial,
• Marko D. Mihovilovic and
• Michael Schnürch

Beilstein J. Org. Chem. 2014, 10, 2186–2199, doi:10.3762/bjoc.10.226

• bulky THIQ residue. The group of Sames reported a ligand-free palladium-catalyzed protocol for C2-arylation of 3-substituted indoles [35]. However, this method did not give any conversion to C2-arylated products on our substrates. Yang et al. reported a mild palladium-catalyzed C2-arylation at room

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• review on organosilver compounds by Pouwer and Williams exhaustively highlights all these aspects of silver chemistry [100]. For example, functionalized propiolic acids can be selectively prepared by an AgI catalyzed carboxylation of terminal alkynes with CO2 under ligand free conditions with the

Advancements in the mechanistic understanding of the copper-catalyzed azide–alkyne cycloaddition

• Regina Berg and
• Bernd F. Straub

Beilstein J. Org. Chem. 2013, 9, 2715–2750, doi:10.3762/bjoc.9.308

• surface is sufficient to start the catalysis [14]. The group of Rothenberg introduced nanometric copper clusters for ligand-free CuAAC [44]. These copper nanoclusters are prepared by reduction of cuprous chloride. Compared to other catalytic systems such as copper powder, copper shavings or copper(II

• favourable to the reaction as well. Although these conditions are termed “ligand-free” it is obvious that solvent molecules such as acetonitrile as well as the nitrogen base will coordinate to the copper(I) ions. These coordinating additives ameliorate the catalytic performance by preventing oxidation and

• consequence, they suggested two copper centres to be required for catalytic turnover. Mechanistic studies for the “ligand-free” CuAAC followed [160]. The reaction of benzyl azide with phenylacetylene in dimethyl sulfoxide/water in the presence of copper(II) sulfate pentahydrate and an excess of sodium

An easy direct arylation of 5-pyrazolones

• Hao Gong,
• Yiwen Yang,
• Zechao Wang and
• Chunxiang Kuang

Beilstein J. Org. Chem. 2013, 9, 2033–2039, doi:10.3762/bjoc.9.240

• Education, Shanghai 200092, China 10.3762/bjoc.9.240 Abstract A mild, efficient and catalytic ligand-free method for the direct arylation of 5-pyrazolones by Pd-catalyzed C–H bond activation is reported. The process smoothly proceeds and yields are moderate to excellent. Keywords: arylation; aryl halide

• have been described [15]. In this paper, we report a convenient and catalytic ligand-free synthesis of a series of 4-aryl-5-pyrazolones 3 from 5-pyrazolones 1 and aryl halides 2 (Scheme 1). The direct arylation of 5-pyrazolones by Pd-catalyzed C–H bond activation was utilized. Results and Discussion We

Palladium(II)-catalyzed Heck reaction of aryl halides and arylboronic acids with olefins under mild conditions

• Tanveer Mahamadali Shaikh and
• Fung-E Hong

Beilstein J. Org. Chem. 2013, 9, 1578–1588, doi:10.3762/bjoc.9.180

• different reaction conditions employing base-free, ligand-free conditions or by using conventional oxidants such as oxygen, benzoquinone, Cu salts, etc. [48][49][50][51][52][53]. In this article we report two new protocols for Heck cross-coupling reactions: (i) a stable SPO ligated palladium complex 6

• developed the Heck reaction of arylboronic acids with various alkenes employing N-bromosuccinimide as an additive and catalyzed by Pd(OAc)2, under base- and ligand-free conditions at 25 °C. The yields of the coupled products are moderate to good. Heck reaction of olefins with aryl halides and arylboronic

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

• = cinnamyl) species are known for their ease of activation through the reduction of the metal centre from Pd(II) to Pd(0) [17]. Therefore, we have investigated the use of such precatalysts in the direct arylation of heteroaromatic compounds in order to compare them to ligand-free or phosphine-bearing

Synthesis of fluorinated maltose derivatives for monitoring protein interaction by ¹⁹F NMR

• Michaela Braitsch,
• Hanspeter Kählig,
• Georg Kontaxis,
• Michael Fischer,
• Toshinari Kawada,
• Robert Konrat and
• Walther Schmid

Beilstein J. Org. Chem. 2012, 8, 448–455, doi:10.3762/bjoc.8.51

• between the two domains. MBP exists in two different conformations: The ligand-free “open” form, exposing the binding site, and in the presence of a ligand, the “closed” form, trapping the ligand to provide contacts from both domains [17][18][19]. The number of protein–sugar hydrogen bonds associated with

Nano copper oxide catalyzed synthesis of symmetrical diaryl sulfides under ligand free conditions

• K. Harsha Vardhan Reddy,
• V. Prakash Reddy,
• A. Ashwan Kumar,
• G. Kranthi and
• Y.V.D. Nageswar

Beilstein J. Org. Chem. 2011, 7, 886–891, doi:10.3762/bjoc.7.101

• reactions mediated by recyclable copper oxide nanoparticles under ligand free conditions. This protocol avoids foul smelling thiols, for the synthesis of a variety of symmetrical diaryl sulfides, via the cross-coupling of different aryl halides with potassium thiocyanate, affording corresponding products in

• moderate to excellent yields. Keywords: aryl halides; aryl sulfides; copper oxide; cross-coupling; ligand free; potassium thiocyanate; recyclable; Introduction After the discovery of copper-promoted Ullmann reaction [1][2][3] for the construction of carbon-hetero atom bonds, several protocols have been

• , especially under ligand-free conditions, for the synthesis of such highly useful organic compounds. In the past few years, considerable efforts have been made in the area of heterogeneous catalysis for various organic transformations. In general, heterogeneous catalysts offer higher surface area and lower

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

• arylboronic acids. The reaction gave excellent yields (70–98%) under ligand free conditions in a 1:1 DMF/H2O solvent mixture, in short reaction times (10–60 min). The catalyst could be recovered easily by applying an external magnetic field. The polyaryls were similarly synthesized. Keywords: heterogeneous

• halides and the limited scope of the Suzuki reaction under ligand free conditions in the absence of additives thus faced with these limitations requires a fresh approach to carry out the Suzuki reaction. Recently, the use of Pd supported on surface-modified nano NiFe2O4 catalyst for the Heck and Suzuki

• the successful exploitation of the magnetically recoverable Pd supported on NiFe2O4 catalyst for the Suzuki reaction with various substrates and the optimization of reaction conditions under ligand free heterogeneous conditions in an aqueous phase. Moreover, to the best of our knowledge, this is the

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

• , reaction temperatures (90–115 °C) and reaction times (48 h) are comparable to the palladium-catalysed processes. Ligand-free and ligand-assisted reaction conditions have been applied in the synthesis of biologically active compounds. DMEDA, proline and phenanthroline are the most commonly used ligands. In

C-Arylation reactions catalyzed by CuO-nanoparticles under ligand free conditions

• Mazaahir Kidwai,
• Saurav Bhardwaj and
• Roona Poddar

Beilstein J. Org. Chem. 2010, 6, No. 35, doi:10.3762/bjoc.6.35

Chemoselective reduction of aldehydes by ruthenium trichloride and resin- bound formates

• Basudeb Basu,
• Bablee Mandal,
• Sajal Das,
• Pralay Das and
• Ashis K. Nanda

Beilstein J. Org. Chem. 2008, 4, No. 53, doi:10.3762/bjoc.4.53

• of aryl aldehydes and 1,2-diketones to aryl alcohols and α-hydroxy ketones respectively under mild, base-free and phosphine- or any ligand-free conditions. It is observed that aryl ketones and several other potentially reducible functionalities remain unchanged under the reaction conditions. The