Synthesis and characterization of S,N-heterotetracenes

• Astrid Vogt,
• Florian Henne,
• Christoph Wetzel,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2020, 16, 2636–2644, doi:10.3762/bjoc.16.214

• derivatives by Cadogan reaction of nitro-substituted precursors. Another possibility for the preparation of fused pyrrole rings is established by the Cadogan reaction [40]. Well-known examples are the reductive cyclization of 2-nitro-1,1’-biphenyls with triethyl phosphite or phosphanes as reducing agent to

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

• their isolation and structural characterization are still less common. A very convenient access to such betaines is provided by the nucleophilic addition of tertiary phosphanes to electron-deficient alkenes, alkynes and allenes (phospha-Michael addition), which generates the betaines as reactive

• intermediates that can be transformed intra- or intermolecularly into a wide array of acyclic, carbocyclic and heterocyclic structures. In these processes, the tertiary phosphanes can act as nucleophilic organocatalysts (for reviews, see [1][2][3][4] or be incorporated in the (pre-)final products, typically as

• leading to butenolides occurs easily [17]. In contrast to acetylenic esters and ketones, acetylenic carboxamides have rarely been exposed to nucleophilic phosphanes in organocatalytic or stoichiometric reactions. Recently, we have reported on the synthesis and reactivity of N-triflylpropiolamides 1

N-Heterocyclic carbenes

• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 2474–2475, doi:10.3762/bjoc.11.268

• seminal work of Bertrand [1] and Arduengo [2] (and mostly post-1994–1995) the field has underwent fantastic advances. Carbenes such as 1,3-dimesityl-1,3-dihydro-2H-imidazol-2-ylidene (IMes) and the 2,6-diisopropylphenyl analogue (IPr) have become commonplace, replacing tertiary phosphanes as modifying

Highly selective palladium–benzothiazole carbene-catalyzed allylation of active methylene compounds under neutral conditions

• Antonio Monopoli,
• Pietro Cotugno,
• Carlo G. Zambonin,
• Francesco Ciminale and
• Angelo Nacci

Beilstein J. Org. Chem. 2015, 11, 994–999, doi:10.3762/bjoc.11.111

• from Pd2dba3 and 3-methylbenzothiazolium salt V as precursors. A comparison of the performance of benzothiazole carbene with phosphanes and an analogous imidazolium carbene ligand is also proposed. Keywords: active methylene compounds; allylic carbonates; Pd–benzothiazol-2-ylidene complex; Tsuji–Trost

• overreactions giving the diallylated compounds [23][24], the need for catalysts that are tedious to prepare [18][19], and the use of toxic or expensive ligands such as phosphanes or phosphites [3][25]. Therefore, the careful selection of a suitable ligand capable for replacing phosphines and improving palladium

• activity is still mandatory in these kind of reactions. Among various ligands, N-heterocyclic carbenes (NHCs) have gained greater importance in organometallic chemistry. Unlike phosphanes, NHCs are not toxic and insensitive to air, heat and moisture. Moreover, the introduction of substituents onto the

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

• CNRS 3517, 33 rue St Leu, 80039 Amiens, France 10.3762/bjoc.10.276 Abstract New cyclodextrin (CD)-grafted polymers functionalized with water-soluble phosphanes were synthesized in three steps starting from polyNAS. Once characterized by NMR spectroscopy and size-exclusion chromatography, they were

• supercritical CO2, ionic liquids or fluorous phases have been used to immobilize the organometallic catalyst [3][4][5]. Co-solvents, surfactants, amphiphilic phosphanes, molecular receptors, polymers or dispersed particles have also been investigated to favour contacts between the aqueous and the organic

• 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

Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

Staudinger ligation towards cyclodextrin dimers in aqueous/organic media. Synthesis, conformations and guest-encapsulation ability

• Malamatenia D. Manouilidou,
• Yannis G. Lazarou,
• Irene M. Mavridis and
• Konstantina Yannakopoulou

Beilstein J. Org. Chem. 2014, 10, 774–783, doi:10.3762/bjoc.10.73

• side as well as intramolecularly from the narrow side. Such self-inclusion has been observed and taken advantage for selective catalysis in recently published cyclodextrin-phosphanes [35][36][37]. Moreover, some of the observed interactions could arise from the proximity of the phenyl and β-CD moieties

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

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

• established catalysts in Morita–Baylis–Hillman type reactions, where they add to conjugated acceptor systems [39]. Tests with either nitrogen bases (Table 1, entries 2–5) or N-heterocyclic carbenes (Table 1, entry 6) were not rewarded with success. Finally, phosphanes were tested, and while triphenylphosphane

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

• increase in the catalytic performances. Keywords: amphiphilic phosphanes; biphasic system; cyclodextrins; micelles; Introduction Facing the need of developing a greener chemistry, chemists have recently focused their investigations on clean transformation processes to convert organic molecules into

• substrates constitutes a real challenge not completely solved so far. Recently, we showed that an association of cyclodextrins (CDs) and amphiphilic phosphanes could significantly improve the catalytic performances in an aqueous rhodium-catalyzed hydroformylation of higher olefins [6]. Herein we clearly

• demonstrate that the beneficial effect of CDs on a catalytic micellar system can be generalized to another reaction and other amphiphilic phosphanes. To this end, we undertook a study using the randomly methylated β-cyclodextrin (RAME-β-CD) as an additive in an aqueous Pd-catalyzed cleavage reaction of allyl

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

• MCA values for a large number of trialkylphosphanes and alkyldiphenylphosphanes. For organocatalytic processes especially the phosphanes 89, 98, 117, 120–124 are of note. Analysis of the results for unbranched trialkylphosphanes indicates that longer alkyl chains increase the MCA values in a

• ) 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

• than a β-branched substituent; this can be illustrated with the phosphanes 76 and 83. Both phosphanes are dimethyl(methylpropyl)phosphanes, but one in α-position (83, MCA = 617.3 kJ/mol) and one in β-position (76, MCA = 611.9 kJ/mol). Deviations from the regular behavior of the MCA values are due to

Backbone tuning in indenylidene–ruthenium complexes bearing an unsaturated N-heterocyclic carbene

• César A. Urbina-Blanco,
• Xavier Bantreil,
• Hervé Clavier,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2010, 6, 1120–1126, doi:10.3762/bjoc.6.128

• phosphanes, and more recently, has been used to study the electronic properties of NHCs [34]. However, the high toxicity of [Ni(CO)4] encouraged the search for analogous systems using different metals to determine the TEP. One of the most popular and suitable alternatives to nickel is a rhodium carbonyl

Synthesis of novel photochromic pyrans via palladium- mediated reactions

• Christoph Böttcher,
• Gehad Zeyat,
• Saleh A. Ahmed,
• Elisabeth Irran,
• Thorben Cordes,
• Cord Elsner,
• Wolfgang Zinth and
• Karola Rueck-Braun

Beilstein J. Org. Chem. 2009, 5, No. 25, doi:10.3762/bjoc.5.25

• for the fine chemical industry, a variety of methods have been developed recently for the efficient cyanation of aryl halides under mild conditions. By applying electron-rich phosphanes and either Zn(CN)2 or K4[Fe(CN)6], the transformation of chlorides to nitriles was successfully achieved under

Expedient syntheses of the N-heterocyclic carbene precursor imidazolium salts IPr·HCl, IMes·HCl and IXy·HCl

• Lukas Hintermann

Beilstein J. Org. Chem. 2007, 3, No. 22, doi:10.1186/1860-5397-3-22

• prominent members of the family of N-heterocyclic carbenes (NHC) are the sterically encumbered imidazolylidenes IPr and IMes (Figure 1), which can also be considered as analogues of bulky and electron-rich tertiary phosphanes. In contrast to the latter, their synthesis does not involve air-sensitive or

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

• ). 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

An exceptional P-H phosphonite: Biphenyl- 2,2'-bisfenchylchlorophosphite and derived ligands (BIFOPs) in enantioselective copper- catalyzed 1,4-additions

• T. Kop-Weiershausen,
• J. Lex,
• J.-M. Neudörfl and
• B. Goldfuss

Beilstein J. Org. Chem. 2005, 1, No. 6, doi:10.1186/1860-5397-1-6

• (X) side (FAA), the pyramidality of phosphorus measured as angle sum and the distance of phosphorus to the biaryl axis (C1-C1’). Biphenyl-2,2'-bisfenchol based phosphanes (BIFOPs) as chiral ligands in enantioselective Cu-catalyzed 1,4-additions. Anharmonic B3LYP/6-31G*(C,H,N,O,F,Cl,Br) /SDD(Cu) CO