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

• ]. Five different phosphine ligands were subsequently tested, three of which were monodentate with a variable cone angle (6–8; 145–256°) [35][36] and the other two bidendate phosphine ligands namely 1,4-bis(diphenylphosphino)butane (DPPB, 9; βn = 98°) and Xantphos (10; 104 and 133°) with differing bite

• of X-ray structure; C) ball and stick representation of X-ray structure showing the tolyl group only; D) topside view of X-ray structure [18]. Reverse “tube-in-tube” reactor. Phosphine ligands used for the ortho-carbonylation reaction. X-ray structure of substrate 33. Comparison of plug flow reactor

Microwave-assisted synthesis of (aminomethylene)bisphosphine oxides and (aminomethylene)bisphosphonates by a three-component condensation

• Erika Bálint,
• Ádám Tajti,
• Anna Dzielak,
• Gerhard Hägele and
• György Keglevich

Beilstein J. Org. Chem. 2016, 12, 1493–1502, doi:10.3762/bjoc.12.146

• (aminomethylene)bisphosphonates, but in the latter case a secondary phosphine oxide is the P-reagent [33][39]. In addition, (aminomethylene)bisphosphine oxides can be synthesized by the reaction of two molecules of (dialkylamino)(diphenylphosphinoyl)chloromethane (Scheme 4a) [40][41], or by the addition of

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

Ring-whizzing in polyene-PtL₂ complexes revisited

• Oluwakemi A. Oloba-Whenu,
• Thomas A. Albright and
• Chirine Soubra-Ghaoui

Beilstein J. Org. Chem. 2016, 12, 1410–1420, doi:10.3762/bjoc.12.135

• is Pt and a phosphine. The second method employs the use of a bidentate phosphine. In this regard we have chosen diphosphinylethane (dpe). This idea here is that the P–Pt–P angle is around 100° in polyene–ML2 complexes. Upon dissociation the 14 electron PtL2 complex strongly prefers to be linear [22

• haptotropic rearrangement of 48 to 53. Notice that passage through the η2 intermediate causes the phosphines to become equivalent. Benn and co-workers [74] in fact observe phosphine equivalence with a barrier of approximately 13 kcal/mol for the naphthalene–Ni(PR3)2 compounds. Our calculations put 54 to be

Conjugate addition–enantioselective protonation reactions

• James P. Phelan and
• Jonathan A. Ellman

Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116

• enatiofacial selectivity, the use of a cyclic imide ensured exclusive formation of the Z-enolate. During optimization, it was found that an N-aryl group containing 2,6-disubstitution was crucial for obtaining high levels of enantioselectivity. Addition of a variety of bis-aryl secondary phosphine oxides

• nitroalkene [67]. α,β-Unsaturated phosphonates and phosphine oxides Transition metal catalysts In 2006, Hayashi and co-workers reported the first conjugate addition–enantioselective protonation of allenes 165 bearing a phosphine oxide (Scheme 39) [68]. Incorporation of the phosphine oxide allowed for

• enantioselective Friedel–Crafts addition of pyrroles to imides 84. Kobayashi’s enantioselective addition of malonates to α-substituted N-acryloyloxazolidinones. Chen and Wu’s enantioselective addition of thiophenol to N-methacryloyl benzamide. Tan’s enantioselective addition of secondary phosphine oxides and

NeoPHOX – a structurally tunable ligand system for asymmetric catalysis

• Jaroslav Padevět,
• Marcus G. Schrems,
• Robin Scheil and
• Andreas Pfaltz

Beilstein J. Org. Chem. 2016, 12, 1185–1195, doi:10.3762/bjoc.12.114

• difficult, literature precedence indicated that the introduction of the phosphine group might be possible by the reaction of a diarylphosphide anion with chloroalkyloxazoline 2. Ashby et al. [20] investigated the reactivity of neopentyl halide systems with various metal diphenylphosphides and found that the

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

The synthesis of functionalized bridged polycycles via C–H bond insertion

• Jiun-Le Shih,
• Po-An Chen and
• Jeremy A. May

Beilstein J. Org. Chem. 2016, 12, 985–999, doi:10.3762/bjoc.12.97

• oxide oxidant. Notably, a hindered ligand was again necessary for bridged-bicycle formation – in this case the diadamantyl phosphine 106. The Thorpe–Ingold effect was also found to be highly beneficial for the reaction. An interesting mechanistic study using a less selective substrate showed that the

A cross-metathesis approach to novel pantothenamide derivatives

• Jinming Guan,
• Matthew Hachey,
• Lekha Puri,
• Vanessa Howieson,
• Kevin J. Saliba and
• Karine Auclair

Beilstein J. Org. Chem. 2016, 12, 963–968, doi:10.3762/bjoc.12.95

• after dissociation from the metal complex, phosphine ligands can attack the carbine [23]. Thus a phosphine-free catalyst was desirable, and the Hoveyda–Grubbs’ 2nd generation catalyst (4) was chosen. As predicted, the yields increased (Table 1) when catalyst 4 was used for the reaction of 9 with

1H-Imidazol-4(5H)-ones and thiazol-4(5H)-ones as emerging pronucleophiles in asymmetric catalysis

• Antonia Mielgo and
• Claudio Palomo

Beilstein J. Org. Chem. 2016, 12, 918–936, doi:10.3762/bjoc.12.90

• of thiazol-4(5H)-ones as pronucleophiles in asymmetric catalytic reactions has been investigated in the Michael addition reaction to nitroalkenes and α-silyloxyenones, phosphine-catalyzed γ-addition to allenoates and alkynoates, α-amination reactions and iridium-catalyzed allylic substitution

• interaction. In addition, adducts 76 and 77 were easily transformed into the corresponding carboxylic acids 79 and 80 by treatment with periodic acid (Scheme 14) and thiolactone 81 by simple ring opening of the latter under mild acidic conditions. Phosphine-catalyzed γ-addition to allenoates and alkynoates

• . Chiral phosphine-mediated nucleophilic catalysis has attracted considerable attention in the recent years [98][99][100][101]. However, few examples of phosphine-mediated γ-addition reactions have been reported. Pioneering studies on γ-additions of pronucleophiles to allenoates or alkynoates were first

A modular approach to neutral P,N-ligands: synthesis and coordination chemistry

• Vladislav Vasilenko,
• Torsten Roth,
• Clemens K. Blasius,
• Sebastian N. Intorp,
• Hubert Wadepohl and
• Lutz H. Gade

Beilstein J. Org. Chem. 2016, 12, 846–853, doi:10.3762/bjoc.12.83

• neutral κ2-P,N-ligands comprising an imine and a phosphine binding site. These ligands were reacted with rhodium, iridium and palladium metal precursors and the structures of the resulting complexes were elucidated by means of X-ray crystallography. We observed that subtle changes of the ligand backbone

• have a significant influence on the binding geometry und coordination properties of these bidentate P,N-donors. Keywords: P,N-ligands; phosphanylformamidines; phosphine imines; transition metal complexes; Introduction P,N-ligands have been applied in a wide variety of chemical reactions ranging from

• . In addition, the resulting ligand families should provide nitrogen and phosphorus donors with varying donor strength (amidine vs imine, phosphine vs heteroatom-bound phosphorus) and different bite angles (five- vs six-membered chelate rings). Results and Discussion Ligand synthesis We based the

A convenient route to symmetrically and unsymmetrically substituted 3,5-diaryl-2,4,6-trimethylpyridines via Suzuki–Miyaura cross-coupling reaction

• Dariusz Błachut,
• Joanna Szawkało and
• Zbigniew Czarnocki

Beilstein J. Org. Chem. 2016, 12, 835–845, doi:10.3762/bjoc.12.82

• . The screening was then continued with Pd(OAc)2 and tri-(o-tolyl)phosphine (P(o-tol)3) used as a catalyst in the mixture toluene/water/ethanol as solvent system and with sodium carbonate as a base. In order to control the progress of the process, the mixture was regularly sampled and the components

• )3)4 clearly confirms that the later compound is more active in the cross-coupling reaction [46]. The results of the cross coupling depend on electronic and steric properties of the ligands coordinated to the metal atom. In the case of phosphine-based ligands, the structure of the aryl and alkyl

Asymmetric α-amination of 3-substituted oxindoles using chiral bifunctional phosphine catalysts

• Qiao-Wen Jin,
• Zhuo Chai,
• You-Ming Huang,
• Gang Zou and
• Gang Zhao

Beilstein J. Org. Chem. 2016, 12, 725–731, doi:10.3762/bjoc.12.72

• , Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, People’s Republic of China 10.3762/bjoc.12.72 Abstract A highly enantioselective α-amination of 3-substituted oxindoles with azodicarboxylates catalyzed by amino acids-derived chiral phosphine

• catalysts is reported. The corresponding products containing a tetrasubstituted carbon center attached to a nitrogen atom at the C-3 position of the oxindole were obtained in high yields and with up to 98% ee. Keywords: 3-aminooxindoles; asymmetric catalysis; phosphine catalyst; tetrasubstituted

• novel amino acid-derived chiral bifunctional organophosphine catalysts, which have successfully applied to catalyze various asymmetric reactions [40][41]. As a general concept, a tertiary phosphine adds to an electrophilic reactant to form a zwitterion which serves as either a nucleophile or a Bronsted

Diradical reaction mechanisms in [3 + 2]-cycloadditions of hetaryl thioketones with alkyl- or trimethylsilyl-substituted diazomethanes

• Grzegorz Mlostoń,
• Paulina Pipiak and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2016, 12, 716–724, doi:10.3762/bjoc.12.71

• the reaction mixture with tris(diethylamino)phosphine, and the respective ethenes 9 were isolated as the final products. It is worth mentioning that in the case of the non-symmetrical aryl/hetaryl thioketones 1c, 1f–h and 2-diazopropane (7a), the formed 1,3-dithiolanes 10 were isolated as mixtures of

• tris(dimethylamino)phosphine desulfurization leading to the ethane derivative was carried out. Reaction of thioketones 1d–e with (trimethylsilyl)diazomethane (7c) – General procedure: The corresponding thioketones 1d–e (1 mmol) were dissolved in freshly distilled THF (2.5 mL) and the solution was

Copper-mediated arylation with arylboronic acids: Facile and modular synthesis of triarylmethanes

• H. Surya Prakash Rao and
• A. Veera Bhadra Rao

Beilstein J. Org. Chem. 2016, 12, 496–504, doi:10.3762/bjoc.12.49

• report a copper(II) triflate-catalyzed modular synthesis of triarylmethanes by employing diarylmethanols 9 and arylboronic acids 10. It is advantageous to employ a base metal catalyst such as copper(II) triflate instead of palladium [55][56] or nickel (Ni) [57] catalysts and to avoid the use of phosphine

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• ion intermediate through a stabilizing cation–π-interaction. They came to this conclusion, after an extensive catalyst screening. In 2014, Shi and co-workers presented the synthesis of products 243, utilizing substrates 244 and α,β-unsaturated aldehyde 245. Chiral phosphine organocatalyst 246 was

Enantioselective [3 + 2] annulation of α-substituted allenoates with β,γ-unsaturated N-sulfonylimines catalyzed by a bifunctional dipeptide phosphine

• Huanzhen Ni,
• Weijun Yao and
• Yixin Lu

Beilstein J. Org. Chem. 2016, 12, 343–348, doi:10.3762/bjoc.12.37

• of a dipeptide phosphine catalyst, a wide range of highly functionalized cyclopentenes bearing an all-carbon quaternary center were obtained in moderate to good yields and with good to excellent enantioselectivities. Keywords: [3 + 2] annulation; α-substituted allenoate; dipeptide phosphine

• ; enantioselective; Introduction Over the past decade, chiral phosphine catalysts have been utilized extensively for the construction of a broad range of synthetically useful molecular structures [1][2][3][4][5][6][7][8][9][10][11][12][13]. Since the initial discovery of phosphine-catalyzed [3 + 2] annulation of

• examples make use of allenoates without an α-substitution. As demonstrated by Yu, Kwon and their co-workers [34][35][36], this is due to the requirement of a hydrogen atom at the α-position for a proton shift during the reaction cycle. Instead, α-substituted allenoates were shown to interact with phosphine

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

Simple activation by acid of latent Ru-NHC-based metathesis initiators bearing 8-quinolinolate co-ligands

• Julia Wappel,
• Roland C. Fischer,
• Luigi Cavallo,
• Christian Slugovc and
• Albert Poater

Beilstein J. Org. Chem. 2016, 12, 154–165, doi:10.3762/bjoc.12.17

• behavior in ROMP and especially for their use in the synthesis of poly(dicyclopentadiene) (pDCPD). Bearing either the common phosphine leaving ligand in the first and second Grubbs olefin metathesis catalysts, or the Ru–O bond cleavage for the next Hoveyda-type catalysts, this work is a step forward

• ][59]. Thus this study opens a door to find out new families of olefin metathesis catalysts [60], overcoming the issue of bearing a phosphine or to break a Ru–O bond in the precatalysts [55][61]. The initiators exhibit an excellent stability in the solid state as well as in solution and an outstanding

Versatile deprotonated NHC: C,N-bridged dinuclear iridium and rhodium complexes

• Albert Poater

Beilstein J. Org. Chem. 2016, 12, 117–124, doi:10.3762/bjoc.12.13

• bond [7][8], which favored the synthesis of new NHCs and to their use as ligands in transition metal complexes. The latter complexes were usually obtained by an easy replacement of a phosphine by the new NHC ligand, displaying a very high stability under many catalytic conditions. Furthermore, NHCs

N-Methylphthalimide-substituted benzimidazolium salts and PEPPSI Pd–NHC complexes: synthesis, characterization and catalytic activity in carbon–carbon bond-forming reactions

• Senem Akkoç,
• Yetkin Gök,
• İlhan Özer İlhan and
• Veysel Kayser

Beilstein J. Org. Chem. 2016, 12, 81–88, doi:10.3762/bjoc.12.9

• ][10][11]. This is because NHC complexes are easily obtained by deprotonating imidazolium or benzimidazolium salts and most are relatively stable in air and moisture. They are weak π-acceptors and strong σ-donors and can form strong M–C bonds with transition metal ions compared to trivalent phosphine

Effective immobilisation of a metathesis catalyst bearing an ammonium-tagged NHC ligand on various solid supports

• Krzysztof Skowerski,
• Jacek Białecki,
• Stefan J. Czarnocki,
• Karolina Żukowska and
• Karol Grela

Beilstein J. Org. Chem. 2016, 12, 5–15, doi:10.3762/bjoc.12.2

• metathesis catalysts has been the cardinal factor to distribute olefin metathesis in the synthesis of many important compounds [1][2][3][4]. Commercially available homogeneous complexes, including phosphine-containing Gru-II, Ind-II or phosphine-free Hov-II and Gre-II are usually employed in such cases

• backbone is a much better approach than the previously used ones (e.g., via phosphine or benzylidene ligands). An early example of a non-covalent attachment is complex 4, an activated catalyst deposited on glass polymer Raschig rings, which was tested in various metathesis reactions carried out in batch

Comparison of the catalytic activity for the Suzuki–Miyaura reaction of (η⁵-Cp)Pd(IPr)Cl with (η³-cinnamyl)Pd(IPr)(Cl) and (η³-1-t-Bu-indenyl)Pd(IPr)(Cl)

• Patrick R. Melvin,
• Nilay Hazari,
• Hannah M. C. Lant,
• Ian L. Peczak and
• Hemali P. Shah

Beilstein J. Org. Chem. 2015, 11, 2476–2486, doi:10.3762/bjoc.11.269

• and feature strongly electron-donating and sterically bulky phosphine or N-heterocyclic carbene (NHC) ancillary ligands [6][7]. In particular, precatalysts of the type (η3-allyl)Pd(NHC)(Cl) have shown excellent activity for the Suzuki–Miyaura reaction, with systems incorporating an η3-cinnamyl moiety

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