Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

• phosphane ligands is crucial for the selectivity in this reaction. Suzuki coupling can also serve for the functionalization of iodochromones 55, which, as α,β-unsaturated ketones, undergo ring opening under the reaction conditions, followed by Michael addition–cyclocondensation. Xie et al. devised a method

• aliphatic alkynes, copper iodide is necessitated as a co-catalyst [141]. In addition to classic Sonogashira catalysts, phosphane-free palladium [Pd(NN)] chelate complexes can also be used, which promote excellent regioselectivity [142]. A variation of the reaction is possible with Mo(CO)6 as a carbon

Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• (Scheme 16). Within the framework of these domino reactions, we have mainly employed ferrocenyl phosphane ligands such as Taniaphos or Josiphos. In collaboration with Prof. Schmalz from Cologne University, we have also tested phosphite-phosphine ligands (e.g., L15) from their lab. The advantage of these

• ring, while flavylium triflate and 2,4,6-triphenylpyrylium tetrafluoroborate were not compatible with our reaction conditions. Heterodonor ferrocenyl phosphane–carbene ligands efficiently promote the conjugate addition of Grignard reagents to α,β-unsaturated lactones [58]. Building on this knowledge

Formal total synthesis of macarpine via a Au(I)-catalyzed 6-endo-dig cycloisomerization strategy

• Jiayue Fu,
• Bingbing Li,
• Zefang Zhou,
• Maosheng Cheng,
• Lu Yang and
• Yongxiang Liu

Beilstein J. Org. Chem. 2022, 18, 1589–1595, doi:10.3762/bjoc.18.169

• , including triphenylphosphane (Ph3P), [1,1'-biphenyl]-2-yl-di-tert-butylphosphane (JohnPhos) dicyclohexyl(2',4'-diisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl)phosphane (BrettPhos) (Table 1, entries 4–6) revealed that 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) was still the best one (Table 1

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• dienedioates. Interestingly, tricyclohexylphosphonium tetrafluoroborate (L18), along with CuCN, resulted in the 1,4-addition as the major pathway (Scheme 32, left). By contrast, the use of the bulkier tris(2,6-dimethoxyphenyl)phosphane (L19) led to the formation of 1,6-adducts (Scheme 32, right). The Oestreich

1,5-Phosphonium betaines from N-triflylpropiolamides, triphenylphosphane, and active methylene compounds

• Vito A. Fiore,
• Chiara Freisler and
• Gerhard Maas

Beilstein J. Org. Chem. 2019, 15, 2603–2611, doi:10.3762/bjoc.15.253

• (PR3 = alkyl-substituted phosphane, but not PPh3) have been obtained from isonicotinaldehyde [15], and betaines IV from aryl tosylimines [16]. For the stability of betaines III, the nature of the aryl substituent is critical; with the combination Ph3P/DMAD/EWG-substituted benzaldehydes, cyclization

Synthesis, dynamic NMR characterization and XRD studies of novel N,N’-substituted piperazines for bioorthogonal labeling

• Constantin Mamat,
• Marc Pretze,
• Matthew Gott and
• Martin Köckerling

Beilstein J. Org. Chem. 2016, 12, 2478–2489, doi:10.3762/bjoc.12.242

• connection to the label (e.g., fluorescence dye, radionuclide) and the second is used for the introduction of a (bioorthogonal) functional group (e.g., azide, alkyne, phosphane, tetrazine) to later connect to the biomolecule via bioorthogonal ligation. Our aim was the development of novel, N,N

On the mechanism of imine elimination from Fischer tungsten carbene complexes

• Philipp Veit,
• Christoph Förster and
• Katja Heinze

Beilstein J. Org. Chem. 2016, 12, 1322–1333, doi:10.3762/bjoc.12.125

• aminocarbenes, experiments on the synthesis and decomposition of carbene(tetracarbonyl)(phosphane) complexes of chromium and tungsten revealed the exclusive formation of cis-M(CO)4(PR3)(carbene) (R = n-Bu, Ph) [83][84][85]. M(CO)5(PR3) and trans-M(CO)4(PR3)2 (M = Cr, W) have been detected as side-products [83

• exhibit significantly smaller 1JWP coupling constants [85]. A 31P NMR resonance of a toluene-d8 solution of W(CO)5(E-2) with one equivalent PPh3 heated to 100 °C for 1 h was observed at δ = 27.3 ppm with 183W satellites (1JWP = 238 Hz) fitting to the carbene tetracarbonyl phosphane complex cis-W(CO)4(PPh3

Reaction of allene esters with Selectfluor/TMSX (X = I, Br, Cl) and Selectfluor/NH₄SCN: Competing oxidative/electrophilic dihalogenation and nucleophilic/conjugate addition

• A. Srinivas Reddy and
• Kenneth K. Laali

Beilstein J. Org. Chem. 2015, 11, 1641–1648, doi:10.3762/bjoc.11.180

• presence of phosphane catalysts an umpolung addition takes place, whereby the nucleophilic addition occurs inversely at the beta-gamma double bond [22][23]. Vinyl azides have been prepared by hydroazidation of allenyl esters through a Michael-type addition with high regio- and stereoselectivity [24

New palladium–oxazoline complexes: Synthesis and evaluation of the optical properties and the catalytic power during the oxidation of textile dyes

• Rym Hassani,
• Mahjoub Jabli,
• Yakdhane Kacem,
• Jérôme Marrot,
• Damien Prim and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2015, 11, 1175–1186, doi:10.3762/bjoc.11.132

• which NMR analysis shows the presence of two dimeric forms. For better elucidation of their structures, dimeric complexes 4 were transformed into their mononuclear phosphane derivatives 5a and 5b using PPh3 in toluene. According to 1HNMR data, the mixture contains 5a and 5b in the ratio of 4:1. Essays

Diastereoselective and enantioselective conjugate addition reactions utilizing α,β-unsaturated amides and lactams

• Katherine M. Byrd

Beilstein J. Org. Chem. 2015, 11, 530–562, doi:10.3762/bjoc.11.60

• -unsaturated N- alkenoyloxazolidinones [88]. The authors employed a chiral triamide phosphane in order to induce stereoselectivity, which is quite different from other chiral ligands that have been used in ECA reactions. The Hoveyda group has utilized amino acid-based ligands, which were rapidly identified

Articulated rods – a novel class of molecular rods based on oligospiroketals (OSK)

• Pablo Wessig,
• Roswitha Merkel and
• Peter Müller

Beilstein J. Org. Chem. 2015, 11, 74–84, doi:10.3762/bjoc.11.11

• give 36 (Scheme 8). Besides the widely used CuAAC ligation the Staudinger ligation [22] is also an important tool for coupling molecules. To verify that the diazide 34 is also suitable for this reaction we first prepared the cinnamoyl substituted phosphane 38 from (2-hydroxyphenyl)diphenylphosphane (37

Cyclodextrin-grafted polymers functionalized with phosphanes: a new tool for aqueous organometallic catalysis

• Jonathan Potier,
• Stéphane Menuel,
• David Mathiron,
• Véronique Bonnet,
• Frédéric Hapiot and
• Eric Monflier

Beilstein J. Org. Chem. 2014, 10, 2642–2648, doi:10.3762/bjoc.10.276

• ; phosphane; polymer; Introduction Although aqueous organometallic catalysis has been developed long before P. T. Anastas and J. C. Warner set out the foundations of Green Chemistry [1], the very essence of this concept relies on several of the twelve fundamental principles. As such, the use of effective

• were added separately in the aqueous catalytic solution in our previous study, we synthesized a CD-substituted polymer functionalized with water-soluble phosphanes. The idea was to increase the local concentration of interfacial additive and phosphane-coordinated Rh catalyst at the aqueous/oganic

• ][15][16][17][18]. To access the expected CD-substituted polymer functionalized with water-soluble phosphanes, a sulfonation step of a commercially available phosphane was first required. 2-(Diphenylphosphino)ethanamine was sulfonated in an oleum/H2SO4 mixture at room temperature over a period of 15

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

• -coupling reaction (Scheme 24) [166]. The enol phosphates 88 were prepared from the corresponding amides. The phosphane function was introduced in the α-position of the nitrogen. Several chiral and achiral secondary phosphine borane complexes 13 were used. The coupling was achieved under mild conditions

A novel family of (1-aminoalkyl)(trifluoromethyl)- and -(difluoromethyl)phosphinic acids – analogues of α-amino acids

• Natalia V. Pavlenko,
• Tatiana I. Oos,
• Yurii L. Yagupolskii,
• Igor I. Gerus,
• Uwe Doeller and
• Lothar Willms

Beilstein J. Org. Chem. 2014, 10, 722–731, doi:10.3762/bjoc.10.66

• , contain a labile P–H bond and synthetic problems underly their preparation. Emeléus and Haszeldine were the first [26] to prepare CF3P(III) compounds via the interaction of red phosphorus and CF3I in an autoclave. This gave mixtures of CF3-containing phosphanes and phosphane iodides but in poor yields

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

• yields (Scheme 7). When enantiomerically pure prolinol was used as amine the process took place with excellent diastereoselectivity (dr 99:1, determined by 1H NMR). A series of new imidazole-based phosphane ligands were prepared by the research group of Kunz [35]. The corresponding Au(I) NP complexes

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

• (I) phosphane complexes with dialkylbiarylphosphane ligands (Figure 1) by using AgSbF6 as an additive and toluene as a solvent. No reaction occurred when gold(I) phosphane complexes 8–10 (Figure 1) were used as catalysts under identical conditions (Table 2, entries 2–4). Furthermore, the usage of

• gold(I) phosphane complexes 7, 11, 13 and 14 (Figure 1) as catalysts gave 3a in 10–29% yields (Table 2, entries 1, 5, 7 and 8). Gold complex 12 (Figure 1) with an electron-rich biphenylphosphine ligand was identified as the best catalyst, giving 3a in 67% yield (Table 2, entry 6). We attempted to

Synthesis and structure of trans-bis(1,4-dimesityl-3-methyl-1,2,3-triazol-5-ylidene)palladium(II) dichloride and diacetate. Suzuki–Miyaura coupling of polybromoarenes with high catalytic turnover efficiencies

• Jeelani Basha Shaik,
• Venkatachalam Ramkumar,
• Babu Varghese and
• Sethuraman Sankararaman

Beilstein J. Org. Chem. 2013, 9, 698–704, doi:10.3762/bjoc.9.79

• -metal and lanthanide metal chemistry [1][10][11]. Over the past few years they have gradually replaced the conventional phosphane ligands. The transition-metal complexes of these versatile ligands have been shown to be excellent catalysts for various organic transformations [9][10][11][12][13][14

Rh(III)-catalyzed directed C–H bond amidation of ferrocenes with isocyanates

• Satoshi Takebayashi,
• Tsubasa Shizuno,
• Takashi Otani and
• Takanori Shibata

Beilstein J. Org. Chem. 2012, 8, 1844–1848, doi:10.3762/bjoc.8.212

• structures. For instance, a 1,2-disubstituted ferrocenyl ligand, Xyliphos ((R)-1-[(S)-2-(diphenylphosphanyl)ferrocenyl]ethyl bis(3,5-dimethylphenyl)phosphane) is used for iridium-catalyzed enantioselective hydrogenation to produce the herbicide (S)-metolachlor on a scale of more than 10000 tons/year [5

Cyclization of ortho-hydroxycinnamates to coumarins under mild conditions: A nucleophilic organocatalysis approach

• Florian Boeck,
• Max Blazejak,
• Markus R. Anneser and
• Lukas Hintermann

Beilstein J. Org. Chem. 2012, 8, 1630–1636, doi:10.3762/bjoc.8.186

• -hydroxycinnamates, followed by the phosphane catalyzed cyclization. Keywords: catalysis; coumarins; heterocycles; mechanisms; organocatalysis; phosphanes; Introduction Coumarins are important structural motifs in natural products and bioactive compounds, in which they exhibit broad biological activity, e.g., as

• temperature of 60 °C (Table 2). Conversion to the product in toluene was now considerably reduced (Table 2, entry 1). The broad solvent screening implied that some protic solvents, in particular methanol (Table 2, entry 7), were superior to toluene or polar aprotic solvents. The alternative phosphane PCy3 was

• the catalyst n-Bu3P present will be converted to a water-soluble phosphonium salt, which is easier to separate from the coumarin product than the neutral phosphane is. Second, the yields of coumarins were higher when the quenching procedure was used. This implies that part of the coumarin product may

Impact of cyclodextrins on the behavior of amphiphilic ligands in aqueous organometallic catalysis

• Hervé Bricout,
• Estelle Léonard,
• Christophe Len,
• David Landy,
• Frédéric Hapiot and
• Eric Monflier

Beilstein J. Org. Chem. 2012, 8, 1479–1484, doi:10.3762/bjoc.8.167

• that the addition of randomly modified β-cyclodextrin (RAME-β-CD) in aqueous medium could have a beneficial impact on the catalytic performances of phosphane-based aggregates in the Pd-catalyzed cleavage of allyl carbonates (Tsuji–Trost reaction). The RAME-β-CD/phosphane supramolecular interactions

• helped explain the catalytic results. The presence of RAME-β-CD in the aqueous compartment improved the phosphane-based aggregate dynamics. The exchanges between the hydrophobic substrate-containing aggregate core and the catalyst-containing aqueous phase were then greatly favored, resulting in an

• carbonates (Tsuji–Trost reaction) and four amphiphilic phosphanes as aggregate-building blocks. The RAME-β-CD/phosphane interaction and its consequence on the catalytic results are discussed. Results and Discussion To expand the scope of the CD/amphiphilic phosphane combination in aqueous-phase

Cation affinity numbers of Lewis bases

• Christoph Lindner,
• Raman Tandon,
• Boris Maryasin,
• Evgeny Larionov and
• Hendrik Zipse

Beilstein J. Org. Chem. 2012, 8, 1406–1442, doi:10.3762/bjoc.8.163

• of the MCA values that can again be derived as given in equation 4 (Scheme 4). This is shown together with the respective data points in Figure 3. On the basis of equation 4 it is possible to predict the MCA value for a phosphane Me2PR with one infinitively long alkyl substituent (MCA = 618.3 kJ/mol

• ) and for a phosphane PR3 with three infinitively long alkyl substituents (MCA = 646.5 kJ/mol). Phosphanes with branched alkyl substituents show systematically larger MCA values as compared to unbranched systems of otherwise comparable structure. An α-branched substituent leads to a higher MCA value

• particularly interesting, because they contain an n-butyl substituent decorated with additional methyl groups in varying positions (Figure 5). With two methyl groups in α-position the MCA value is increased by 7 kJ/mol compared to the phosphane without methyl groups. In contrast, the positive inductive

Valence isomerization of cyclohepta-1,3,5-triene and its heteroelement analogues

• Helen Jansen,
• J. Chris Slootweg and
• Koop Lammertsma

Beilstein J. Org. Chem. 2011, 7, 1713–1721, doi:10.3762/bjoc.7.201

• biological importance (Scheme 1) [3][4]. The phosphane analogues 9 and 10 received far less attention, with their applicability as a phosphinidene (R–P) precursor being the most notable use [5][6][7][8][9]. Reviewing the influence of the heteroatom on the cycloheptatriene–norcaradiene valence isomerization

• [98]. 1H-Phosphepine – benzene phosphane Although the parent 1H-phosphepine (9) and its 2.5 kcal·mol−1 more-stable valence isomer benzene phosphane (10) have never been isolated [45], there is evidence for the existence of the parent phosphatropylium ion (29; Figure 4), which was generated in the gas

Efficient synthesis of 1,3-diaryl-4-halo-1H-pyrazoles from 3-arylsydnones and 2-aryl-1,1-dihalo-1-alkenes

• Yiwen Yang,
• Chunxiang Kuang,
• Hui Jin,
• Qing Yang and
• Zhongkui Zhang

Beilstein J. Org. Chem. 2011, 7, 1656–1662, doi:10.3762/bjoc.7.195

• ], alkenyl arenes [19], 1,3-dienes [20][21], α,β-unsaturated esters [19][22] and nitriles [23], phosphane oxides [24] or with alkynyl silanes [18], stannanes [18][25][26], arenes [27][28], esters [29][30][31][32][33], boronic esters [34][35]. However, the cycloaddition of sydnones with 1,1-dihaloalkenes is

Solvent- and ligand-induced switch of selectivity in gold(I)-catalyzed tandem reactions of 3-propargylindoles

• Estela Álvarez,
• Delia Miguel,
• Patricia García-García,
• Manuel A. Fernández-Rodríguez,
• Félix Rodríguez and
• Roberto Sanz

Beilstein J. Org. Chem. 2011, 7, 786–793, doi:10.3762/bjoc.7.89

• cyclization [28][29]. The use of cationic gold complexes bearing different types of phosphane ligands always provided the iso-Nazarov product 3a as the major isomer, with a small increase in the competing Nazarov product 4a on switching the ligand to SPhos (Table 1, entries 1–4). The use of complexes bearing

Light-induced olefin metathesis

• Yuval Vidavsky and
• N. Gabriel Lemcoff

Beilstein J. Org. Chem. 2010, 6, 1106–1119, doi:10.3762/bjoc.6.127

• ) by adding a bulky phosphane ligand to the complex. Thus, a more active and soluble neutral species with the anionic ligands bound to the metal could be obtained. The same concept of arene displacement by UV radiation was used for the release of a p-cymene ligand to produce a more reactive catalytic

• species. Osmium precatalysts 11a–f did not polymerise norbornene under standard conditions. However, 5 min irradiation of a toluene solution of the complex with a 200 W Hg lamp led to active catalysts. The more active catalysts were those possessing more sterically hindered phosphane ligands. Thus

• respective yields and the required reaction times. In line with the development of ruthenium benzylidene initiators [66][67], the phosphane ligand was replaced by an N-heterocyclic carbene (NHCs) in the photoactivated precatalysts. Accordingly, Noels et al. [68][69] synthesised a range of NHC substituted