An integrated photocatalytic/enzymatic system for the reduction of CO₂ to methanol in bioglycerol–water

• Michele Aresta,
• Angela Dibenedetto,
• Tomasz Baran,
• Antonella Angelini,
• Przemysław Łabuz and
• Wojciech Macyk

Beilstein J. Org. Chem. 2014, 10, 2556–2565, doi:10.3762/bjoc.10.267

• ] [Cp*Rh(bpy)(H2O)]Cl2 [aquo(2,2’-bipyridine)(pentamethylcyclopentadienyl)]rhodium(III), where Cp* = pentamethylcyclopentadienyl. For comparison we have also used its iridium analog, with phenantroline as a bidentate N-ligand replacing bpy. Iridium showed interesting activity, comparable to that of Rh

Preparation of phosphines through C–P bond formation

• Iris Wauters,
• Wouter Debrouwer and
• Christian V. Stevens

Beilstein J. Org. Chem. 2014, 10, 1064–1096, doi:10.3762/bjoc.10.106

• –phosphido intermediate was beneficial for the alkylation. The scope of the reaction was investigated using diverse benzylic bromides 22b and secondary phosphines 36b. Bidentate ligands 40 and 41 were also synthesized [61][62]. This procedure was also restricted to benzylic halides. High enantiomeric

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

• chiral phosphine ligands and AgOAc via bidentate chelation of a properly substituted aldimine. Chiral phosphine–silver(I) complexes are emerging as a valuable tool for carbon–carbon bond forming reactions. These catalysts are effective in promoting enantioselective allylations, aldol reactions, Mannich

• bidentate chelation (Scheme 36). The substrate is bound anti to the bulky amino acid substituent (R) and reacts with the siloxyfuran via endo-type addition. Intramolecular silyl transfer, iPrOH mediated desilylation of the amide terminus, and protonation of the N–Ag bond delivers the final product and the

New hydrogen-bonding organocatalysts: Chiral cyclophosphazanes and phosphorus amides as catalysts for asymmetric Michael additions

• Helge Klare,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2014, 10, 224–236, doi:10.3762/bjoc.10.18

• . DFT computations reveal high hydrogen-bonding strengths of cyclodiphosphazane PV-amides compared to urea-based catalysts. Experimental results and computations on the enantiodetermining step with cis-cyclodiphosphazane 14a suggest a strong bidentate H-bond activation of the nitrostyrene substrate by

• incorporation of a chiral amido-scaffold into bis(amido)cyclodiphosphazanes (cis-[R'NHP(S)(μ-NR)]2), bulky and conformationally constrained bidentate HB catalysts with an improved H-acidity should be accessible. HB interaction with donor substrates of the different structural motifs I–IV is expected to be

• hydrogen bonding. Mechanistic considerations We anticipated cyclodiphosphazane catalyst 14a to act as a bidentate bifunctional H-bond-donor catalyst. Therefore a conformation of the catalyst similar to the crystal structure but with an (exo/exo)-conformation is reasonable as otherwise a bidentate H-bonding

Garner’s aldehyde as a versatile intermediate in the synthesis of enantiopure natural products

• Mikko Passiniemi and
• Ari M.P. Koskinen

Beilstein J. Org. Chem. 2013, 9, 2641–2659, doi:10.3762/bjoc.9.300

• syn-selectivities were achieved with vinylZnCl in Et2O (1:6 anti/syn). Coleman also noticed that the addition of excess ZnCl2 did not increase the syn-selectivity at all. They attributed this to the mono-coordination of the metal to the carbamate instead of the usual “bidentate” chelation control

• metal-acetylide with terminal alkynes, such as 40. The phosphine ligand had to be monodentate; bidentate ligands gave a lot lower yields. Their catalyst system worked very efficiently with many carbonyl electrophiles, also with Garner’s aldehyde (R)-1. The reaction of 1 with 40 gave 41 with high

Gold-catalyzed regioselective oxidation of propargylic carboxylates: a reliable access to α-carboxy-α,β-unsaturated ketones/aldehydes

• Kegong Ji,
• Jonathan Nelson and
• Liming Zhang

Beilstein J. Org. Chem. 2013, 9, 1925–1930, doi:10.3762/bjoc.9.227

• the use of a P,S-bidentate ligand, which is proposed to enable the formation of tris-coordinated and hence less electrophilic gold carbene species. α-Carboxy α,β-unsaturated ketones/aldehydes can be obtained with fair to excellent yields. Keywords: enone; gold catalysis; oxidation; propargyl

• could reach >200:1 by using the gold(I) catalyst derived from our previously developed bulky P,S-bidentate ligand L1 (Figure 1) [11]. A similarly high selectivity was also achieved by using the P,N-bidentate ligand Mor-DalPhos [36][37]. However, the Z/E ratios of 5a-OAc in the former case is ~13:1

• selectivity can be much enhanced by the use of our previously developed P,S-bidentate ligand, which enables the generation of tri-coordinated and less electrophilic gold carbene species. α-Acyloxy α,β-unsaturated ketones/aldehydes can be obtained with fair to excellent yields. The impact of ligands on the

The first example of the Fischer–Hepp type rearrangement in pyrimidines

• Inga Cikotiene,
• Mantas Jonusis and
• Virginija Jakubkiene

Beilstein J. Org. Chem. 2013, 9, 1819–1825, doi:10.3762/bjoc.9.212

• preparation of condensed pyrimidine derivatives [27][28], have an interesting crystal structures [29][30][31], can be useful as bidentate ligands [32][33][34], and represent a class of biologically active compounds [35][36][37][38][39]. Results and Discussion The starting compounds 1 were prepared by the

A scalable synthesis of the (S)-4-(tert-butyl)-2-(pyridin-2-yl)-4,5-dihydrooxazole ((S)-t-BuPyOx) ligand

• Hideki Shimizu,
• Jeffrey C. Holder and
• Brian M. Stoltz

Beilstein J. Org. Chem. 2013, 9, 1637–1642, doi:10.3762/bjoc.9.187

• multi-gram scale synthesis and provides the target ligand in 64% overall yield. Keywords: asymmetric catalysis; diamine ligands; optimization; synthesis; Introduction Pyridinooxazoline (PyOx) ligands represent a growing class of bidentate dinitrogen ligands used in asymmetric catalysis [1][2][3][4][5

True and masked three-coordinate T-shaped platinum(II) intermediates

• Manuel A. Ortuño,
• Salvador Conejero and
• Agustí Lledós

Beilstein J. Org. Chem. 2013, 9, 1352–1382, doi:10.3762/bjoc.9.153

• the synthesis of cationic [Pt(norbornyl)(P–P)]+ complexes A1a–e (P–P = bidentate phosphine ligand) [34][35]. Further studies involved other alkyl ligands such as ethyl (A2b–c), 3,3-dimethylbutyl (A3b–c) and 2,3,3-trimethylbutyl (A4) [36][37][38]. NMR spectroscopic data and X-ray structures of A1a [34

• bidentate phosphine ligands to yield complexes S4 in which one THF molecule is coordinated to the metal center [59][60]. Romeo’s group was actively working on solvento Pt(II) complexes S5. For instance, they employed an extended series of phosphine ligands to obtain cis and trans-solvento complexes

• ) and solvent (S17) forms [53]. Energetically accessible T-shaped species can also be intermediates in the site exchange of bidentate ligands of square-planar complexes. Fluxional motions of the 2,9-dimethyl-1,10-phenanthroline ligand (dmphen) have been observed in cationic complexes as [Pt(Me)(NN)(L

Homolytic substitution at phosphorus for C–P bond formation in organic synthesis

• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 1269–1277, doi:10.3762/bjoc.9.143

•  2) [29][30]. The reactions favor the formation of Z isomers, which results from photoinduced isomerization of initially formed E isomers. Ogawa’s diphosphination is thus potentially useful for the synthesis of (Z)-1,2-diphosphanyl-1-alkenes, which can serve as bidentate ligands. Morse developed

• photoinduced addition of tetrafluorodiphosphine to alkenes and alkynes in the gas phase (Table 3) [31][32][33][34]. The addition provides a series of intriguing bidentate phosphine ligands. The addition to alkynes yields 1:1 mixtures of E/Z isomers. Due to the high reactivity of a difluorophosphanyl radical

• phosphorus always culminates in difunctionalization of a multiple bond. Therefore this methodology will find application in the synthesis of complex phosphines including bidentate ones. Radical substitution of halogen in organic halide with phosphorus will be an alternative to classical ionic substitution

Palladium-catalyzed synthesis of N-arylated carbazoles using anilines and cyclic diaryliodonium salts

• Stefan Riedmüller and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2013, 9, 1202–1209, doi:10.3762/bjoc.9.136

• isolated in 35% yield (Table 1, entry 3). Next, we varied the phosphine ligands (Table 1, entries 4–9). Xantphos was the most efficient bidentate ligand yielding 3a in 46% yield (Table 1, entry 6). Xylenes as the solvent, for example p-xylene, were also suitable for the reaction; in contrast to DME, where

• angle of the phosphines 99° and 93°, respectively) (Table 1, entry 5 and 7). When using bidentate ligands with bite angles higher than 100° (DPEphos 104°, Xantphos 108°) the reaction is more efficient and the yield increases significantly. Next, we asked ourselves, whether other palladium salts could be

Spin state switching in iron coordination compounds

• Philipp Gütlich,
• Ana B. Gaspar and
• Yann Garcia

Beilstein J. Org. Chem. 2013, 9, 342–391, doi:10.3762/bjoc.9.39

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