Inter- and intramolecular enantioselective carbolithiation reactions

• Asier Gómez-SanJuan,
• Nuria Sotomayor and
• Esther Lete

Beilstein J. Org. Chem. 2013, 9, 313–322, doi:10.3762/bjoc.9.36

• , the internally coordinated organolithium would have two additional sites available for coordination with a chiral bidentate ligand. Thus, enantioselective versions of intramolecular carbolithiation reactions can also be carried out under the influence of a chiral ligand for lithium (Scheme 9). However

• attractive approach for the construction of carbon–carbon bonds. However, the applicability of this method is not yet general. Among the different types of ligands used, chiral bidentate diamines, and especially (−)-sparteine, are the most generally employed. However, the structural requirements of the

Palladium-catalyzed C–N and C–O bond formation of N-substituted 4-bromo-7-azaindoles with amides, amines, amino acid esters and phenols

• Rajendra Surasani,
• Dipak Kalita,
• A. V. Dhanunjaya Rao and
• K. B. Chandrasekhar

Beilstein J. Org. Chem. 2012, 8, 2004–2018, doi:10.3762/bjoc.8.227

• , entry 2). Other available ligands, e.g., SPhos (L2) and XPhos (L3) provided lower yields when Pd2(dba)3 was used as a catalyst, even after longer reaction time (Table 1, entries 3 and 4). By using Pd(OAc)2 as a catalyst and SPhos (L2) and XPhos (L3) as a bidentate ligand, low to moderate yields were

• (Table 5, entry 1). Other bidentate aryl phosphine ligands L2 and L3 did not result in any product formation (Table 5, entries 2 and 3). The tertiary phosphine ligand PCy3 (L4) was ineffective in the arylation of N-methyl-4-bromo-7-azaindole (1c) with D-alanine (6a) (Table 5, entry 4). It is believed

Design and synthesis of quasi-diastereomeric molecules with unchanging central, regenerating axial and switchable helical chirality via cleavage and formation of Ni(II)–O and Ni(II)–N coordination bonds

• Vadim A. Soloshonok,
• José Luis Aceña,
• Hisanori Ueki and
• Jianlin Han

Beilstein J. Org. Chem. 2012, 8, 1920–1928, doi:10.3762/bjoc.8.223

• spectra of compounds 14 and 15, resonances of aromatic and aliphatic hydrogens and carbons appear as sharp peaks indicating that the extra bidentate moiety in complexes 14 and 15 acts merely as a substituent and does not compete for coordination with Ni(II). Complexes 14 are red-colored, 15 is yellow, and

• derivatives of type 18, without the pendant side chain, undergo further stabilization through dimerization, giving rise to the corresponding binuclear complexes [48]. In this case, the presence of the bidentate substituent allows for a different, intramolecular stabilization mechanism leading to the formation

C2-Alkylation of N-pyrimidylindole with vinylsilane via cobalt-catalyzed C–H bond activation

• Zhenhua Ding and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2012, 8, 1536–1542, doi:10.3762/bjoc.8.174

• phenanthroline and bipyridine-type ligands (Table 1, entries 2–5) revealed that 2,9-dimethyl-1,10-phenanthroline (neocuproine) and 2,9-dimethyl-4,7-diphenylphenanthroline (bathocuproine) improved the yield of 3aa, while the byproduct 4 could not be suppressed (Table 1, entries 3 and 4). The P,N-bidentate ligand

Palladium-catalyzed substitution of (coumarinyl)methyl acetates with C-, N-, and S-nucleophiles

• Kalicharan Chattopadhyay,
• Erik Fenster,
• Alexander J. Grenning and
• Jon A. Tunge

Beilstein J. Org. Chem. 2012, 8, 1200–1207, doi:10.3762/bjoc.8.133

• the enolate proceeds in highest yield in acetonitrile (2a, Table 1, entry 3). Bidentate ligated palladium complexes gave mixed results: the Pd/dppf complex (Table 1,entry 4) catalyzed the reaction smoothly, while little product was seen on using the Pd/BINAP complex (Table 1,entry 5). Under the best

Synthesis of new pyrrole–pyridine-based ligands using an in situ Suzuki coupling method

• Matthias Böttger,
• Björn Wiegmann,
• Steffen Schaumburg,
• Peter G. Jones,
• Wolfgang Kowalsky and
• Hans-Hermann Johannes

Beilstein J. Org. Chem. 2012, 8, 1037–1047, doi:10.3762/bjoc.8.116

• of negatively charged β-diketonates with a “neutral ligand”, which is often bidentate or tridentate (Scheme 1, left). The coordination sphere and the positive charge of the rare-earth metal cation are thus saturated and neutralized, respectively. In a recent development, the Bünzli group has

Synthesis and anion recognition properties of shape-persistent binaphthyl-containing chiral macrocyclic amides

• Marco Caricato,
• Nerea Jordana Leza,
• Claudia Gargiulli,
• Giuseppe Gattuso,
• Daniele Dondi and
• Dario Pasini

Beilstein J. Org. Chem. 2012, 8, 967–976, doi:10.3762/bjoc.8.109

• of these strategies, resulting in the synthesis and characterization of three novel binaphthyl-based macrocycles, and the evaluation of their potential as supramolecular receptors for aliphatic bidentate carboxylate anions. Results and Discussion Design, synthesis and spectroscopic characterization

• suggest that the binding mode involves two NH groups linked to the same binaphthyl unit, rather than a complexation mode in which the bidentate guests are extended across the cavities of the macrocycles. These findings also explain why, in the presence of bulkier acetoxy groups on the binaphthyl units

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

• -oxazoline bidentate ligands with an axially chiral N-naphthyl framework were synthesized, and their coordination manners with AuCl·SMe2 were investigated. Diastereomeric NHC precursors 7, (Sa,S)-7 and (Ra,S)-7, gave the corresponding axially chiral NHC–Au complexes bearing a noncoordinated oxazoline group

Self-assembly of Ru₄ and Ru₈ assemblies by coordination using organometallic Ru(II)₂ precursors: Synthesis, characterization and properties

• Sankarasekaran Shanmugaraju,
• Dipak Samanta and
• Partha Sarathi Mukherjee

Beilstein J. Org. Chem. 2012, 8, 313–322, doi:10.3762/bjoc.8.34

• cm−1 (2a) and 1602 cm−1 (2b) corresponding to the symmetrical stretching frequencies (νCO) of the carbonyl groups of the coordinated bis-bidentate oxalato (2a) or N,N'-diphenyloxamidato (2b) ligands. These bands, due to symmetrical stretching (νCO) in the complexes, are slightly shifted to a higher

• bis-bidentate quinonato ligand, and this symmetric stretching frequency (νCO) in the isolated macrocycle is slightly shifted to the higher energy region compared to that of the starting acceptor (1c, νCO = 1515.8 cm−1) due to the ligand-to-metal coordination. The 1H NMR spectra of the macrocycle 2c

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

• bidentate ligands for metals such as iron or gallium that require an octahedral geometry. Katoh coupled N-hydroxypyrazinone substituents to cone-14a in order to prepare 23 (Scheme 13). Binding Ga3+ with remote lower-rim groups induced the cooperative binding of alkyl ammonium cations by the macrocycle [38

Thermodynamic and kinetic stabilization of divanadate in the monovanadate/divanadate equilibrium using a Zn-cyclene derivative: Towards a simple ATP synthase model

• Hanno Sell,
• Anika Gehl,
• Frank D. Sönnichsen and
• Rainer Herges

Beilstein J. Org. Chem. 2012, 8, 81–89, doi:10.3762/bjoc.8.8

• coordination bond to the Zn2+ ion and two hydrogen bonds to the NH groups of the cyclene ring (Figure 2). The formation of a bidentate complex (two vanadate oxygens coordinating with Zn2+) is considerably less favorable. This is also in agreement with X-ray structures of Zn-cyclene phosphate complexes [15

Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series

• Cécile Verrier,
• Pierrik Lassalas,
• Laure Théveau,
• Guy Quéguiner,
• François Trécourt,
• Francis Marsais and
• Christophe Hoarau

Beilstein J. Org. Chem. 2011, 7, 1584–1601, doi:10.3762/bjoc.7.187

• ). Thus, C2 selectivity was only attained by using the highly steric P(t-Bu)3/PivOH pair, whereas the less electron-donating tri(alkyl)arylphosphines as well as bidentate ligands were prompted to form an aryl-palladium complex possessing a highly electrophilic character, leading to C5-arylation. Catalytic

• trioxazoles [51]. Preparation of DPO- and POPOP-analogues [53]. Pd(0)-catalyzed direct arylation of benzoxazole with aryl chlorides [54]. Pd(0)-catalyzed direct C2-selective arylation of (benz)oxazoles with bromides and chlorides using bidentate ligands [55][56]. Palladium-catalyzed direct arylation of

Impact of the level of complexity in self-sorting: Fabrication of a supramolecular scalene triangle

• Kingsuk Mahata and
• Michael Schmittel

Beilstein J. Org. Chem. 2011, 7, 1555–1561, doi:10.3762/bjoc.7.183

• groups available for coordination in addition to its two bisimine nitrogens. Thus, unit 1 may either act as a strong bidentate, tridentate or tetradentate binding site for zinc(II) ions, and there is no large thermodynamic difference between a [Zn(16)(27)]+-type connection and a [Zn(16)(47)]+-type link

Synthesis and oxidation of some azole-containing thioethers

• Andrei S. Potapov,
• Nina P. Chernova,
• Vladimir D. Ogorodnikov,
• Tatiana V. Petrenko and
• Andrei I. Khlebnikov

Beilstein J. Org. Chem. 2011, 7, 1526–1532, doi:10.3762/bjoc.7.179

• . Selenium dioxide-catalyzed oxidation of benzotriazole thioether by H2O2, however, proceeds selectively and yields sulfoxide only. Keywords: azole; oxidation; sulfone; sulfoxide; thioether; Introduction Compounds comprising two pyrazole moieties linked by an aliphatic spacer act as bidentate chelating

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

Advances in synthetic approach to and antifungal activity of triazoles

• Kumari Shalini,
• Nitin Kumar,
• Sushma Drabu and
• Pramod Kumar Sharma

Beilstein J. Org. Chem. 2011, 7, 668–677, doi:10.3762/bjoc.7.79

• composition and structure of the inhibitor [70]. Novel heteroleptic iridium complexes containing the 1-substituted-4-phenyl-1H-1,2,3-triazole cyclometalating ligand were synthesized by the [3 + 2] Huisgen dipolar cycloaddition method which was utilized to prepare a class of bidentate ligands by adding

Synthesis of 5-(2-methoxy-1-naphthyl)- and 5-[2-(methoxymethyl)-1-naphthyl]-11H-benzo[b]fluorene as 2,2'-disubstituted 1,1'-binaphthyls via benzannulated enyne–allenes

• Yu-Hsuan Wang,
• Joshua F. Bailey,
• Jeffrey L. Petersen and
• Kung K. Wang

Beilstein J. Org. Chem. 2011, 7, 496–502, doi:10.3762/bjoc.7.58

• allow these compounds to serve as hetero-bidentate ligands for complex formation with transition metals [20]. We also investigated the possibility of using the benzannulated enediynes bearing a 1-naphthyl, a 2-methoxy-1-naphthyl, or a 2-(methoxymethyl)-1-naphthyl substituent at one of the alkynyl

The cross-metathesis of methyl oleate with cis-2-butene-1,4-diyl diacetate and the influence of protecting groups

• Arno Behr and
• Jessica Pérez Gomes

Beilstein J. Org. Chem. 2011, 7, 1–8, doi:10.3762/bjoc.7.1

• catalysts illustrate once more their higher metathesis activity and their higher tolerance towards functional groups [2]. Comparable or higher conversions of 1 and cross-metathesis yields of 3 and 4 (Table 1, entries 5–8) were obtained with ruthenium complexes [Ru]-5–[Ru]-8. Due to their bidentate Schiff

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

(Pseudo)amide-linked oligosaccharide mimetics: molecular recognition and supramolecular properties

• José L. Jiménez Blanco,
• Fernando Ortega-Caballero,
• Carmen Ortiz Mellet and
• José M. García Fernández

Beilstein J. Org. Chem. 2010, 6, No. 20, doi:10.3762/bjoc.6.20

• , thioureas can be easily transformed into carbodiimides and thus serve as key intermediate in the synthesis of other pseudoamide functionalities (urea, guanidine, etc.) [70][71][72][76][77][78][79]. Thirdly, thiourea bridges provide efficient anchoring points for bidentate hydrogen-bonding recognition, which

• bonding with the formation of a 7-membered ring (e.g. 40) [80]. This conformation changes to the Z,Z-conformation in aqueous solution [70] or in the presence of carboxylate ligands due to the formation of a bidentate hydrogen bond (Figure 16) [80]. Examples of thiourea-connected saccharides have been

• monosaccharide units in glycooligomers is particularly attractive with regard to molecular recognition processes. Like thioureas and ureas, guanidines can also form bidentate hydrogen bonds. In addition, because of their positively charged character, guanidines can exert strong electrostatic interactions with

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

• 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

A superior P-H phosphonite: Asymmetric allylic substitutions with fenchol- based palladium catalysts

• Bernd Goldfuss,
• Thomas Löschmann,
• Tina Kop-Weiershausen,
• Jörg Neudörfl and
• Frank Rominger

Beilstein J. Org. Chem. 2006, 2, No. 7, doi:10.1186/1860-5397-2-7

• Pamies et al. (Scheme 2) [7]. Besides bidentate P, N-ligands, monodentate ligands are useful, as was demonstrated successfully by Hayashi et al. with the MeO-MOP ligand, yielding 90% branched product with 87% ee for a C-methylated malonate nucleophile and the 4-methoxyphenylallyl substrate [8]. Van

• ). BIFOL based phosphanes (BIFOPs) are sterically highly hindered and were employed in copper-catalyzed 1,4-additions of diethylzinc to 2-cyclohexenone [26]. Here we use a selection of fenchol-based bidentate pyridine FENOP- and monodentate BIFOP-ligands in Pd-catalysts to study allylic substitutions of

• File 1 for full experimental data). All three P, N-bidentate FENOP ligands, FENOP, FENOP-Me and FENOP-NMe2, favor branched alkylation products (Table 1). This tendency towards formation of chiral, branched products is even apparent from X-ray crystal structure analyses of corresponding Pd-phenylallyl

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

• acquisition, simply mixing them pairwise in all possible permutational modes generates high catalyst diversity without the need to synthesize new ligands. Of course, once a hit has been identified in the form of MLaLb, structural and mechanistic considerations may help in designing the optimal bidentate

• 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