Transition-metal-catalyzed synthesis of phenols and aryl thiols

• Yajun Liu,
• Shasha Liu and
• Yan Xiao

Beilstein J. Org. Chem. 2017, 13, 589–611, doi:10.3762/bjoc.13.58

• only suitable for activated halides having an ortho-nitro substituent; lower yields were observed in the case of unactivated aryl halides, such as 2-isopropylbromobenzene and 2,5-dimethylchlorobenzene. Inspired by a huge effect of the phosphine ligand on the reaction performance, the Beller group

Protonated paramagnetic redox forms of di-o-quinone bridged with p-phenylene-extended TTF: A EPR spectroscopy study

• Nikolay O. Chalkov,
• Vladimir K. Cherkasov,
• Gleb A. Abakumov,
• Andrey G. Starikov and
• Viacheslav A. Kuropatov

Beilstein J. Org. Chem. 2016, 12, 2450–2456, doi:10.3762/bjoc.12.238

• , should have opposite signs. Considering this, it becomes evident that the averaged value of the coupling constants in (1·)H3 (|0.74−2.28|/2 = 0.77) is in good agreement with the value 0.69 G, which was measured for quintet constant in (1·−)H2. The nature of the phosphine ligand is also important in the

Experimental and theoretical investigations on the high-electron donor character of pyrido-annelated N-heterocyclic carbenes

• Michael Nonnenmacher,
• Dominik M. Buck and
• Doris Kunz

Beilstein J. Org. Chem. 2016, 12, 1884–1896, doi:10.3762/bjoc.12.178

• shown to occur by an associative mechanism via a trigonal bipyramidal intermediate [66][67], which was also crystallographically characterized in the case of a cationic Rh complex bearing a bidentate phosphine ligand [68]. Our DFT-calculations for the tricarbonyl complex 3a bearing the dipiy ligand show

Flow carbonylation of sterically hindered ortho-substituted iodoarenes

• Carl J. Mallia,
• Gary C. Walter and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2016, 12, 1503–1511, doi:10.3762/bjoc.12.147

• fixed 5 mol % of Pd(OAc)2 and 10 mol % of the phosphine ligand was investigated. It was noted that the catalyst level could be reduced [34], but this amount allowed for an efficient catalytic process with short reaction times in the region of two hours, a good match for the flow system assembly [8

Stereodynamic tetrahydrobiisoindole “NU-BIPHEP(O)”s: functionalization, rotational barriers and non-covalent interactions

• Golo Storch,
• Sebastian Pallmann,
• Frank Rominger and
• Oliver Trapp

Beilstein J. Org. Chem. 2016, 12, 1453–1458, doi:10.3762/bjoc.12.141

• preparation of tailor-made functionalized stereodynamic ligands possible and give an outline for possible applications in enantioselective catalysis. Keywords: atropisomer; enantioselective DHPLC; ligand design; non-covalent interactions; Okamoto phases; phosphine ligand; stereodynamic ligands; Introduction

Chiral cyclopentadienylruthenium sulfoxide catalysts for asymmetric redox bicycloisomerization

• Barry M. Trost,
• Michael C. Ryan and
• Meera Rao

Beilstein J. Org. Chem. 2016, 12, 1136–1152, doi:10.3762/bjoc.12.110

• [41] (Figure 1a). The proposed mechanism of this fascinating reaction involves chloride abstraction of the ruthenium catalyst by indium(III) triflate and phosphine ligand dissociation. The propargyl alcohol then coordinates to the now coordinatively unsaturated cyclopentadienylruthenium (CpRu

• phosphine ligand before catalysis can occur (vide supra). In other words, ruthenium must have two open coordination sites in order to bind the substrate. To test if there is a similar requirement for 1, we decided to add one catalyst equivalent of an auxiliary ligand to test its impact on reaction rate

Regioselective palladium-catalyzed ring-opening reactions of C1-substituted oxabicyclo[2,2,1]hepta-2,5-diene-2,3-dicarboxylates

• Michael Edmunds,
• Mohammed Abdul Raheem,
• Rebecca Boutin,
• Katrina Tait and
• William Tam

Beilstein J. Org. Chem. 2016, 12, 239–244, doi:10.3762/bjoc.12.25

• on their oxidation state and the presence or absence of phosphine ligands (Table 1, entries 1–4). The catalyst lacking a phosphine ligand gave a low yield and the reaction proceeded very slowly (9%, 65 h, Table 1, entry 1). The addition of phosphine exogenously greatly increased the speed and the

Copper-catalyzed asymmetric conjugate addition of organometallic reagents to extended Michael acceptors

• Thibault E. Schmid,
• Sammy Drissi-Amraoui,
• Christophe Crévisy,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2015, 11, 2418–2434, doi:10.3762/bjoc.11.263

• synthesis of the antimicobacterial agent erogorgiaene (Scheme 12) [31]. One of the key steps of this synthesis involved the conversion of the bicyclic extended Michael acceptor 44 to 45 through a 1,4-selective copper-catalyzed ACA. Copper(I) triflate and chiral phosphine ligand L10 enabled this

Evidencing an inner-sphere mechanism for NHC-Au(I)-catalyzed carbene-transfer reactions from ethyl diazoacetate

• Manuel R. Fructos,
• Juan Urbano,
• M. Mar Díaz-Requejo and
• Pedro J. Pérez

Beilstein J. Org. Chem. 2015, 11, 2254–2260, doi:10.3762/bjoc.11.245

• )]SbF6 (L = tertiary phosphine ligand) abstracted the carbene group :CHPh from a tropilium derivative, and further transferred the gold-bonded carbene group to an olefin [17][18]. This contribution constituted a breakthrough in gold-mediated carbene-transfer reactions since the carbene source lacks of

New aryloxybenzylidene ruthenium chelates – synthesis, reactivity and catalytic performance in ROMP

• Patrycja Żak,
• Szymon Rogalski,
• Mariusz Majchrzak,
• Maciej Kubicki and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2015, 11, 1910–1916, doi:10.3762/bjoc.11.206

• isolated yields of 90% (complex 13) and 92% (complex 14). Catalytic activity The obtained complexes were tested in the ring opening metathesis polymerisation (ROMP) of cyclooctadiene. First, the impact of a phosphine ligand on the catalytic activity was investigated. Preliminary tests performed showed, as

• presence of 2 equiv of HCl as an activator. The chart illustrates an insignificant effect of the properties of the phosphine ligand on the catalytic activity of the complexes. The order of increasing activities of the activated species, i.e., 8 (PPh3) < 10 P(C6H4Me-4)3 < 1a (PCy3) < 9 P(C6H4CF3-4)3 does

• phosphine ligand. More basic phosphine more readily reacted with the activator (HCl) leading to a faster increase in the concentration of the phosphine-free form of the catalyst (Figure 4). The influence of electronic properties of substituents placed in the aromatic ring of the chelating ligand, in para

Stereochemistry of ring-opening/cross metathesis reactions of exo- and endo-7-oxabicyclo[2.2.1]hept-5-ene-2-carbonitriles with allyl alcohol and allyl acetate

• Piotr Wałejko,
• Michał Dąbrowski,
• Lech Szczepaniak,
• Jacek W. Morzycki and
• Stanisław Witkowski

Beilstein J. Org. Chem. 2015, 11, 1893–1901, doi:10.3762/bjoc.11.204

• -tolyl substituted NHC ligand in [Ru]5 exerts a smaller steric effect than the -PCy3 residue in [Ru]1–4. Furthermore, the bulky phosphine ligand (PCy3) expands away from the transition metal center (coordination sphere), while the N,N’-o-tolyl substituent attached to the central imidazole ring penetrates

Latent ruthenium–indenylidene catalysts bearing a N-heterocyclic carbene and a bidentate picolinate ligand

• Thibault E. Schmid,
• Florian Modicom,
• Adrien Dumas,
• Etienne Borré,
• Loic Toupet,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2015, 11, 1541–1546, doi:10.3762/bjoc.11.169

• of cocatalyst. While first examples of latent catalysts were based on phosphine-containing ruthenium complexes bearing a Schiff base ligand (O–N) [9] replacement of the phosphine ligand by sterically demanding and strongly σ-donor N-heterocyclic carbenes (NHC) afforded catalysts with improved

Reactions of nitroxides 15. Cinnamates bearing a nitroxyl moiety synthesized using a Mizoroki–Heck cross-coupling reaction

• Jerzy Zakrzewski and
• Bogumiła Huras

Beilstein J. Org. Chem. 2015, 11, 1155–1162, doi:10.3762/bjoc.11.130

• Mizoroki–Heck cross-coupling reaction between 4-acryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl and iodobenzene derivatives in the presence of palladium(II) acetate coordinated with a tri(o-tolyl)phosphine ligand immobilized in a polyurea matrix. Keywords: 4-acryloyloxy-2,2,6,6-tetramethylpiperidine-1

• –i) were obtained using the coupling of 4-acryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (3) with a series of iodobenzene derivatives (4a–i) in the presence of palladium(II) acetate coordinated with tri(o-tolyl)phosphine ligand immobilized in a polyurea matrix (commercially available as

Hydrogenation of unactivated enamines to tertiary amines: rhodium complexes of fluorinated phosphines give marked improvements in catalytic activity

• Sergey Tin,
• Tamara Fanjul and
• Matthew L. Clarke

Beilstein J. Org. Chem. 2015, 11, 622–627, doi:10.3762/bjoc.11.70

• donating phosphine ligand for this process. For enamines 1g, 1h and 1i, experiments with much lower catalyst loadings were performed in order to prove that the rate of hydrogenation is faster when 8 is used instead of 4. Of particular note is the hydrogenation of the deactivated enamines 1b and 1c. It is

Weakly nucleophilic potassium aryltrifluoroborates in palladium-catalyzed Suzuki–Miyaura reactions: relative reactivity of K[4-RC₆F₄BF₃] and the role of silver-assistance in acceleration of transmetallation

• Vadim V. Bardin,
• Anton Yu. Shabalin and
• Nicolay Yu. Adonin

Beilstein J. Org. Chem. 2015, 11, 608–616, doi:10.3762/bjoc.11.68

• [C6F5BF3] retards toward K2CO3 [39] as well as K2CO3 in a mixture with catalytic amounts of Pd(OAc)2 in refluxing MeOH [19]. Resistance of K[C6F5BF3] (1a) towards K2CO3 and Ag2O in toluene (without palladium catalyst and phosphine ligand) is confirmed by stirring the corresponding suspensions at 100 °C for

Phosphinocyclodextrins as confining units for catalytic metal centres. Applications to carbon–carbon bond forming reactions

• Matthieu Jouffroy,
• Rafael Gramage-Doria,
• David Sémeril,
• Dominique Armspach,
• Dominique Matt,
• Werner Oberhauser and
• Loïc Toupet

Beilstein J. Org. Chem. 2014, 10, 2388–2405, doi:10.3762/bjoc.10.249

• to enantioselectivity, only one chiral mono-P(III) ligand [30][31][32] has so far shown some potential in the notoriously challenging, but industrially relevant asymmetric hydroformylation [33][34][35][36][37]. Recently, we have synthesised a new type of chiral phosphine ligand (HUGPHOS-1 [38] and

• yield (46.5%) was obtained when operating with 1 mol-% catalyst and one equivalent of HUGPHOS-2 per palladium (Table 3, entry 5). Higher phosphine:Pd ratios did not improve the catalytic outcome (Table 3, entry 4). These results clearly indicate that a single phosphine ligand is sufficient to stabilise

Palladium-catalysed cyclisation of alkenols: Synthesis of oxaheterocycles as core intermediates of natural compounds

• Miroslav Palík,
• Jozef Kožíšek,
• Peter Koóš and
• Tibor Gracza

Beilstein J. Org. Chem. 2014, 10, 2077–2086, doi:10.3762/bjoc.10.216

• carboetherification [45][46][47][48][49] under strong basic conditions in the presence of a phosphine ligand. In order to enhance the ligand affinity of the hydroxy group in the formation of σ-palladiumII-complex D (Scheme 6), we have decided to adopt the described conditions and to examine the transformation of

P(O)R₂-directed Pd-catalyzed C–H functionalization of biaryl derivatives to synthesize chiral phosphorous ligands

• Rong-Bin Hu,
• Hong-Li Wang,
• Hong-Yu Zhang,
• Heng Zhang,
• Yan-Na Ma and
• Shang-dong Yang

Beilstein J. Org. Chem. 2014, 10, 2071–2076, doi:10.3762/bjoc.10.215

• temperature and the corresponding functionalized products exhibited good enantioselectivities. We propose a unique seven-membered cyclopalladium transition state for this transformation and provide a new and efficient route to synthesize the substituted axially-chiral oxygen–phosphine or alkene–phosphine

• ligand analogues. Experimental See Supporting Information File 1. C–H functionalization of axially chiral phosphorus substrates. The yields are isolated yields and the ee values are determind by HPLC. aReaction conditions: substrate (0.3 mmol), ethyl acrylate (1.5 mmol), Pd(OAc)2 (10 mol %), Ac-Gly-OH

Continuous-flow Heck synthesis of 4-methoxybiphenyl and methyl 4-methoxycinnamate in supercritical carbon dioxide expanded solvent solutions

• Phei Li Lau,
• Ray W. K. Allen and
• Peter Styring

Beilstein J. Org. Chem. 2013, 9, 2886–2897, doi:10.3762/bjoc.9.325

• -donating group relative to Pd, thereby eliminating the requirement of the phosphine ligand. The catalyst can also aid the reaction without requiring an inert atmosphere. In this paper we report the Heck reaction between 4-iodoanisole and either styrene or methyl acrylate in a continuous flow reactor. 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

• one hour at room temperature). The effect of the phosphine ligand is generally attributed to an increase in the copper(I) salt’s solubility in organic media. Feringa et al. used copper(I) salts in combination with phosphoramidite ligands such as MonoPhos. With copper(I) chloride (1 mol %) and MonoPhos

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

• ]. Chisholm has been looking for milder catalytic metal-alkyne nucleophiles for carbonyl 1,2-addition reactions, which wouldn’t enolize the labile α-protons next to a carbonyl group (Scheme 17) [71]. They found that a Rh(I)-catalyst with a monodentate electron rich phosphine ligand 42 formed a nucleophilic

• 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 reaction of oxabicyclic alkenes with electron-deficient terminal alkynes to produce acrylate derivatives

• Yin-wei Sun,
• Qin Xu and
• Min Shi

Beilstein J. Org. Chem. 2013, 9, 1969–1976, doi:10.3762/bjoc.9.233

• phosphine ligand was used as a catalyst (Table 1, entry 7). In order to further improve the yield of 3a, we employed gold complex 6 (Figure 1) coordinated by a sterically bulky and electron-rich biaryl phosphine-type ligand as a catalyst, affording 3a in 40% yield (Table 1, entry 8). In the absence of

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

• -cyclometalated phosphine ligand. Subsequent hydrogenation generates the corresponding hydride complexes A6a–b. On the basis of NMR studies (1JPt,H values of ca. 2000 Hz, see next section), a weak interaction trans to the hydride ligand, typically an agostic contact, is supposed to exist. Carmona and co-workers

• , Carmona and co-workers have recently described that the hydrogenation of the 16-electron Pt(II) carbene 3 bearing a cyclometalated phosphine ligand (Scheme 4) resulted in the formation of the cyclometalated complex A5c, which can be further hydrogenated to give the Pt(II) hydride A6c [40], similar to

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

• systematically optimized the reaction conditions of a reaction between aniline and cyclic iodonium salt 1 (Table 1). Various reaction parameters, in particular the Pd catalyst, catalyst loading, the phosphine ligand, and the temperature had a significant influence on the outcome of this transformation. Starting

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

• provided average yields of 60 and 62%, respectively, in 6 h (Table 3, entries 3 and 4). However, the tertiary phosphine ligand PCy3 (L4) was ineffective in generating any product (Table 3, entries 5 and 12). Interestingly, Pd(OAc)2 results in poor yields of the product (Table 3, entries 6–12). Given this

• (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

• , no product formation was observed even after 24 h (Table 5, entry 18). The tertiary phosphine ligand PCy3 (L4) was found to be ineffective when treated with N-methyl-4-bromo-7-azaindole (1c) and D-alanine methyl ester (6b) (Table 5, entry 19). These results indicate that increasing the steric