Iridium-catalyzed intramolecular [4 + 2] cycloadditions of alkynyl halides

• Andrew Tigchelaar and
• William Tam

Beilstein J. Org. Chem. 2012, 8, 1765–1770, doi:10.3762/bjoc.8.201

• halides were investigated by using [IrCl(cod)]2 as catalyst, and dppe was found to be the most suitable phosphine ligand for the reaction. No oxidative insertion of the iridium into the carbon–halide bond was observed, and the reactions proceeded to provide the halogenated cycloadducts in good yield (75

Synthesis of axially chiral oxazoline–carbene ligands with an N-naphthyl framework and a study of their coordination with AuCl·SMe₂

• Feijun Wang,
• Shengke Li,
• Mingliang Qu,
• Mei-Xin Zhao,
• Lian-Jun Liu and
• Min Shi

Beilstein J. Org. Chem. 2012, 8, 726–731, doi:10.3762/bjoc.8.81

• design and synthesis of chiral gold complexes has received wide attention. Compared with the more commonly used air-sensitive phosphine ligand, N-heterocyclic carbenes (NHCs), with intrinsic characteristics such as strong δ-donor but poor π-acceptor abilities, ease of preparation, air and thermal

Double N-arylation reaction of polyhalogenated 4,4’-bipyridines. Expedious synthesis of functionalized 2,7-diazacarbazoles

• Mohamed Abboud,
• Emmanuel Aubert and
• Victor Mamane

Beilstein J. Org. Chem. 2012, 8, 253–258, doi:10.3762/bjoc.8.26

• yield of 61% achieved with XPhos [38]. The bulk of the phosphine ligand enhances the stability and the activity of the catalytic system [39] thus allowing the use of an elevated temperature (120 °C) necessary for the double N-arylation reaction [20]. Encouraged by these results, we further explored the

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• results for this Pd-catalyzed tandem Sonogashira/double C–N coupling reaction were obtained when Pd(OAc)2 was used as the catalyst along with a bulky bidentate phosphine ligand such as Xantphos in the presence of Cs2CO3 as base. Most likely, the reaction proceeds through a Pd-catalyzed Sonogashira

• followed by reductive elimination furnishes N-aryl-2-benzylpyrrolidine derivatives 71. In this process, both reactions are catalyzed by zerovalent palladium and the choice of the phosphine ligand for the N-arylation of amines and the carboamination reactions is of great significance and an in situ

• modification of the catalyst by phosphine ligand exchange was necessary to achieve the selective diarylation in good yields (Scheme 30). A three-component reaction involving a palladium-catalyzed double N-arylation in combination with a S-arylation in a single operation was developed for the preparation of

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

• )oxiranyl ketones 13 [50]. The method provides heterobicyclic products of type 14 in a highly diastereoselective fashion. In these reactions, the gold complex Au3, derived from the bulky biaryl phosphine ligand RuPhos, provided the best reaction yields (Scheme 8). From a mechanistic point of view, the

• , formally resulting from an internal (2 + 2) cycloaddition [87]. However, in 2009, Toste demonstrated that, when a gold catalyst such as Au1/AgSbF6, with a more readily donating phosphine ligand is employed, the alternative (3 + 2) cycloaddition leading to bicyclo[4.3.0]nonanes 58 is favored (Scheme 30) [99

Intramolecular hydroamination of alkynic sulfonamides catalyzed by a gold–triethynylphosphine complex: Construction of azepine frameworks by 7-exo-dig cyclization

• Hideto Ito,
• Tomoya Harada,
• Hirohisa Ohmiya and
• Masaya Sawamura

Beilstein J. Org. Chem. 2011, 7, 951–959, doi:10.3762/bjoc.7.106

• reaction proceeded slowly, even with a conventional phosphine ligand PPh3, such that the starting material was not fully consumed even after 24 h and the yield was as low as 26% (Table 1, entry 10). Increasing the catalyst loading of [Au(NTf2)(PPh3)] to 5.0 mol % caused full consumption of 4a, but the

Au(I)/Au(III)-catalyzed Sonogashira-type reactions of functionalized terminal alkynes with arylboronic acids under mild conditions

• Deyun Qian and
• Junliang Zhang

Beilstein J. Org. Chem. 2011, 7, 808–812, doi:10.3762/bjoc.7.92

• , entry 2). Moreover, a control experiment was carried out to determine whether AgOTf by itself could catalyze this transformation. However, no 2a was produced in the absence of Ph3PAuCl (Table 1, entry 3). Without the phosphine ligand, both AuCl/AgOTf or AuCl3/AgOTf could catalyze this reaction, but the

Synthesis of Ru alkylidene complexes

• Renat Kadyrov and
• Anna Rosiak

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

• from the phosphine ligand (see Scheme 4). At low temperature both isomers of 1e are visible in the NMR spectrum due to comparable concentrations (obtained enthalpy difference ΔH = 1.3 kcal/mol, see Supporting Information File 1). A number of NOE experiments at −40 °C allowed the assignment of 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

• -arylation of 25 was carried out under standard conditions using 24, and the best yield of 26 was achieved with the dicyclohexyl(2',4',6'-triisopropylbiphenyl-2-yl)phosphine ligand 27 (59%, Scheme 7) compared to the ligands, 28 and 29 [57]. The synthesis of vitamin E amines 35, possessing anti-proliferative

The allylic chalcogen effect in olefin metathesis

• Yuya A. Lin and
• Benjamin G. Davis

Beilstein J. Org. Chem. 2010, 6, 1219–1228, doi:10.3762/bjoc.6.140

• exchange of the alcohol for a phosphine ligand exchange to generate 6. The anionic complex 7 could also promote the reaction (Figure 2). Hydrogen bonding between the allylic hydroxy group on the substrate and the chloride ligand on the catalyst could also be another reason that favors subsequent metathesis

A convenient catalyst system for microwave accelerated cross- coupling of a range of aryl boronic acids with aryl chlorides

• Matthew L. Clarke,
• Marcia B. France,
• Jose A. Fuentes,
• Edward J. Milton and
• Geoffrey J. Roff

Beilstein J. Org. Chem. 2007, 3, No. 18, doi:10.1186/1860-5397-3-18

• strategies are required. In summary, a readily prepared, air stable Pd pre-catalyst derived from the amine-phosphine ligand, dcpmp has been found to promote Suzuki coupling between activated aryl chlorides and a range of boronic acids under microwave heating conditions. High yields of the desired biaryls can

• for aryl chloride activation, including diphosphine-Pd catalysts,[7] mono-phosphine Pd catalysts, [8][9] cyclometallated Pd precursors,[10] and potentially hemi-labile bidentate ligands. [11][12][13][14][15] Some years ago, we demonstrated that the palladium complexes formed from the amine-phosphine

• ligand, dcpmp, 1 gave very active catalysts for this reaction[13]. At the time this system was one of the few catalysts capable of cross-coupling unactivated aryl chlorides below 100°C. Reaction times were typically 12 hours or slightly less. More recently, advances in chemical microwave technology have

Conformational rigidity of silicon- stereogenic silanes in asymmetric catalysis: A comparative study

• Sebastian Rendler and
• Martin Oestreich

Beilstein J. Org. Chem. 2007, 3, No. 9, doi:10.1186/1860-5397-3-9

• ) Coordination of pyridyl alcohol rac-4 accompanied by liberation of dihydrogen (12 → 10), (ii) rate-limiting dissociation of one phosphine ligand to generate a free coordination site, [18] (iii) coordination of the weakly donating chiral silane (10 → 11), followed by (iv) an exothermic and irreversible σ-bond

• metathesis [19] establishing the silicon-oxygen linkage in 5 and regenerating copper hydride 12 after coordination of another phosphine ligand (11 → 12). With steps (ii) and (iii) being reversible and chelate 10 being capable of alkoxide exchange, that is exchange of the optical antipodes of 4, one