Crystal design using multipolar electrostatic interactions: A concept study for organic electronics

• Peer Kirsch,
• Qiong Tong and
• Harald Untenecker

Beilstein J. Org. Chem. 2013, 9, 2367–2373, doi:10.3762/bjoc.9.272

• fluorinated arenes, without expanding the geometry too much. Arene–perfluoroarene interactions are well known to stabilize molecular crystals [11][12][13] through multipolar electrostatic interactions, and there are a few examples for their use in organic electronics [10][14]. Another point to consider are

Synthesis of axially chiral gold complexes and their applications in asymmetric catalyses

• Yin-wei Sun,
• Qin Xu and
• Min Shi

Beilstein J. Org. Chem. 2013, 9, 2224–2232, doi:10.3762/bjoc.9.261

• catalysts based on the binaphthyl skeleton. Very recently, Echavarren’s group has reported a very important gold–arene interaction in dialkylbiarylphosphane gold complexes, which is very useful in gold catalysis [54]. It has been disclosed that there was a weak gold-π interaction between the gold atom and

• the aromatic ring in catalysts 1 [46]. On the basis of this finding, we envisaged that if an aryl group is introduced near the ligated gold atom, the gold–arene interaction may affect the catalytic efficiency in gold catalysis (Figure 1). Results and Discussion Synthesis of the carbene–Au(I) complexes

• indicated that no reaction occurred in the absence of a Au catalyst (Table 1, entry 14). Conclusion Axially chiral Au(I) complexes exhibiting a binaphthalene scaffold with NHC or phosphine gold complexes on one side and an arene moiety on another side were prepared starting from axially chiral BINOL. A weak

Gold(I)-catalyzed hydroarylation reaction of aryl (3-iodoprop-2-yn-1-yl) ethers: synthesis of 3-iodo-2H-chromene derivatives

• Pablo Morán-Poladura,
• Eduardo Rubio and
• José M. González

Beilstein J. Org. Chem. 2013, 9, 2120–2128, doi:10.3762/bjoc.9.249

• a variety of functional groups and, interestingly, it is compatible with the presence of strong electron-withdrawing groups attached to the arene. The overall transformation can be termed as a new example of a migratory cycloisomerization and, formally, it involves well-blended 1,2-iodine shift and

• , the influence of the ancillary ligand and the arene over the cyclization products was recognized [43]. The catalyst based on the N-heterocyclic carbene ligand IPr [49] (IPr: 1,3-bis(2,6-diisopropyl)phenylimidazol-2-ylidene), was identified as suitable controller to favor the formation of the product

The chemistry of isoindole natural products

• Klaus Speck and
• Thomas Magauer

Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243

• installation of the isoindolinone, a seven-step sequence similar to the one described for stachyflin (156) was used (Scheme 23). The arene appendage was desymmetrized via monobromination and cross coupling with copper cyanide provided a nitrile. Hydrogenation and lactam formation under basic conditions

The chemistry of amine radical cations produced by visible light photoredox catalysis

• Jie Hu,
• Jiang Wang,
• Theresa H. Nguyen and
• Nan Zheng

Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234

• Michael adduct 106. Alternatively, the radical is added onto arene to form a cyclohexadienyl radical 107. This step is reversible in the absence of oxygen. However, in the presence of oxygen, superoxide is formed via one-electron reduction of oxygen by Ir(II). The cyclohexadienyl radical 107 is converted

Computational study of the rate constants and free energies of intramolecular radical addition to substituted anilines

• Andreas Gansäuer,
• Meriam Seddiqzai,
• Tobias Dahmen,
• Rebecca Sure and
• Stefan Grimme

Beilstein J. Org. Chem. 2013, 9, 1620–1629, doi:10.3762/bjoc.9.185

• the molecules is important and that a combination of electrophilic radicals with preferably nucleophilic arenes results in the highest rate constants. This is opposite to the Minisci reaction where the radical acts as nucleophile and the arene as electrophile. The substitution at the N-atom of the

• . In accordance with intuition, all transition states are ‘later’ than that of the 5-exo cyclization as indicated by the shorter distances between the radical center and the C-atom attacked for 1–3 (2.15–2.17 Å vs 2.30 in the 5-exo cyclization). Moreover, the trajectory of attack on the arene is very

• . In order to ensure comparability the examples were chosen with phenyl substitution at N. They are shown in Scheme 5 and the results are summarized in Table 4. The notion that the radical acts as an electrophile and the arene as nucleophile is further corroborated by the highest rate constant for the

Mechanistic studies on the CAN-mediated intramolecular cyclization of δ-aryl-β-dicarbonyl compounds

• Brian M. Casey,
• Dhandapani V. Sadasivam and
• Robert A. Flowers II

Beilstein J. Org. Chem. 2013, 9, 1472–1479, doi:10.3762/bjoc.9.167

• obtain a better understanding of the impact of arene substitution on the intramolecular cyclization, DFT calculations were performed at UB3LYP/6-31G(d) level by using Gaussian 03/09 [28]. Previous research from our group has shown that the oxidation of the enol tautomer of a diketone initially forms a

• ’. The stability of the cyclized radical is reflected in the activation barrier, and rotational transition structure TS1g’ has a barrier of 2.5 kcal/mol. For the electron-withdrawing chloro-substituted arene 1h’, the energy barrier for the cyclization on the aromatic ring is 16.9 kcal/mol, nearly 5 kcal

• m-chloro substituent has the highest barrier among the systems studied and leads to the least stable cyclohexadienyl radical. For the unsubstituted arene substrate, the energy barrier to cyclization as well as the energy of the cyclohexadienyl radical intermediate falls between the calculated values

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

Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes

• Roy T. McBurney and
• John C. Walton

Beilstein J. Org. Chem. 2013, 9, 1083–1092, doi:10.3762/bjoc.9.120

• spectroscopy. Iminyls with suitably placed arene or heteroarene acceptors underwent cyclisations yielding phenanthridine-type products from ortho-additions. For benzofuran and benzothiophene acceptors, spiro-cyclisation predominated at low temperatures, but thermodynamic control ensured ortho-products

• affecting this are weighed up. Results and Discussion The arene and heteroarene-based oxime carbonates 1 and 2 were prepared as described previously by reaction of the corresponding aromatic ethanone oximes with ethyl chloroformate [26]. Precursors 3 and 4 were made in a similar way from the oximes of 2

• iminyls compared with alkyls seems established for both alkene- and arene-type acceptors. QM Computations To shed further light on the spiro versus ortho alternatives we computed the activation parameters [ΔE‡298] and reaction enthalpies [ΔH298], corrected to 298 K for thermal effects, for the spiro- and

Study on the total synthesis of velbanamine: Chemoselective dioxygenation of alkenes with PIFA via a stop-and-flow strategy

• Huili Liu,
• Kuan Zheng,
• Xiang Lu,
• Xiaoxia Wang and
• Ran Hong

Beilstein J. Org. Chem. 2013, 9, 983–990, doi:10.3762/bjoc.9.113

• particularly striking to us that the arene unprecedentedly stabilizes the primary carbon cation through a neighboring participation in the mechanism proposed by Tellitu et al. To resolve the confusion, we synthesized the corresponding pyrrolidine through an alternative approach (Scheme 4). The amination of

Simple synthesis of pyrrolo[3,2-e]indole-1-carbonitriles

• Adam Trawczyński,
• Robert Bujok,
• Zbigniew Wróbel and
• Krzysztof Wojciechowski

Beilstein J. Org. Chem. 2013, 9, 934–941, doi:10.3762/bjoc.9.107

• position 2 with electron-withdrawing groups. Keywords: alkylation; ketones; nitriles; pyrroloindole; reduction; trimethylchlorosilane; Introduction Indole and its analogues bearing condensed arene and heteroarene rings are privileged structures amongst biologically active compounds. The 1,2

Synthesis of phenanthridines via palladium-catalyzed picolinamide-directed sequential C–H functionalization

• Ryan Pearson,
• Shuyu Zhang,
• Gang He,
• Nicola Edwards and
• Gong Chen

Beilstein J. Org. Chem. 2013, 9, 891–899, doi:10.3762/bjoc.9.102

• us to explore whether we could develop a new strategy for synthesizing phenanthridines. As outlined in Scheme 1B, we envisioned that ortho-arylated benzylamine picolinamides could undergo an intramolecular amination at the ortho ε-C–H position of the newly installed arene group to form cyclized

• . Extension of the cyclization–oxidation step to other arylated picolinamide substrates. The coupled cyclization–oxidation step detailed above was then used to synthesize phenanthridines from other arylated picolinamide substrates (Figure 2). In general, electron-rich arene motifs, installed by C–H arylation

Efficient Cu-catalyzed base-free C–S coupling under conventional and microwave heating. A simple access to S-heterocycles and sulfides

• Silvia M. Soria-Castro and
• Alicia B. Peñéñory

Beilstein J. Org. Chem. 2013, 9, 467–475, doi:10.3762/bjoc.9.50

• thiolate anion by the addition of 2 equiv of KOt-Bu. Different chemical transformations are possible from the arene thiolate ions formed; for example, oxidation to the diaryl disulfide, subsequent nucleophilic substitution reaction with alkyl halides to afford alkyl aryl sulfides, or a second copper

• , condensation, nucleophilic substitution, oxidation or a second copper cross-coupling of the arene thiolate anion intermediates from S-aryl thioacetate hydrolysis. These thioacetates are obtained by copper-catalyzed reaction of commercial potassium thioacetate with aryl iodides under microwave irradiation

Alkyne hydroarylation with Au N-heterocyclic carbene catalysts

• Cristina Tubaro,
• Marco Baron,
• Andrea Biffis and
• Marino Basato

Beilstein J. Org. Chem. 2013, 9, 246–253, doi:10.3762/bjoc.9.29

• ; gold; hydroarylation; N-heterocyclic carbenes; Introduction The hydroarylation of alkynes (Scheme 1) is arguably one of the most intensively studied reactions leading to aromatic C–H bond functionalization [1][2][3][4][5][6][7]. In this reaction, the C–H bond of an arene adds formally trans to the

• ]. In such reactions, often simply termed cyclisation reactions, the arene and the alkyne are linked through a tether, the nature of which can range from simple alkyl groups to ether, amino, ester or amido groups; depending on the nature and length of the tether, different kinds of unsaturated poly

• evaluated with other arene and alkyne substrates under the same reaction conditions and the results are reported in Table 1. The catalytic activity of the complexes remained high also with less substituted substrates, complex VI being systematically superior to complex VII. The selectivity of the reaction

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• (UVC) and are particularly suited to carbonyl and arene photochemistry as well as halogenation chemistry. These lamps are also available with a range of phosphor coatings to emit both UVB and UVA radiation. They have found commercial use in medical, tanning and insect-attraction applications. These

Palladium-catalyzed dual C–H or N–H functionalization of unfunctionalized indole derivatives with alkenes and arenes

• Gianluigi Broggini,
• Egle M. Beccalli,
• Andrea Fasana and
• Silvia Gazzola

Beilstein J. Org. Chem. 2012, 8, 1730–1746, doi:10.3762/bjoc.8.198

• the reactivity of some Ar-Pd(II) complexes with arenes (through a proton-transfer palladation mechanism), depending on the C–H acidity rather than the arene nucleophilicity. Synthetic procedures based on this strategy allowed the direct arylation at C-2 and C-3 positions of indoles 9 with a high

• ) intermediate XII. The subsequent selective coordination of the arene generates the complex XIII, which in turn undergoes reductive elimination providing the final product and a Pd(0) species. The reoxidation of the latter giving the active Pd(II) catalyst completes the catalytic cycle. In addition to the

• –deprotonation of the arene was hypothesized to explain the mechanism for C–H palladation. Intramolecular reactions involving alkenes The first example of intramolecular indole alkenylation was reported in 1978 by Trost, who applied reaction conditions based on stoichiometric amounts of PdCl2(MeCN)2 and silver

Synthesis of chiral sulfoximine-based thioureas and their application in asymmetric organocatalysis

• Marcus Frings,
• Isabelle Thomé and
• Carsten Bolm

Beilstein J. Org. Chem. 2012, 8, 1443–1451, doi:10.3762/bjoc.8.164

• leading to higher enantioselectivities. Perhaps, substituted arene backbones could be used for inducing enhanced positive effects on both units through electronic fine-tuning. The additional stereogenic centers in the ethylene linker as in (SS,SC)-18 and (RS,SC)-19 had none or at best only a minor impact

Organocatalytic C–H activation reactions

• Subhas Chandra Pan

Beilstein J. Org. Chem. 2012, 8, 1374–1384, doi:10.3762/bjoc.8.159

• and heteroaryl iodides as well as bromides, and poor to good yields (13–82%) for products 20 were obtained (Scheme 16) [35]. A variety of electron-donating and -withdrawing substituents were incorporated on the arene part and high ortho-selectivities were observed for the products 22. The authors also

Synthesis and structure of tricarbonyl(η⁶-arene)chromium complexes of phenyl and benzyl D-glycopyranosides

• Thomas Ziegler and
• Ulrich Heber

Beilstein J. Org. Chem. 2012, 8, 1059–1070, doi:10.3762/bjoc.8.118

• Thomas Ziegler Ulrich Heber Institute of Organic Chemistry, University of Tuebingen, Auf der Morgenstelle 18, 72076 Tuebingen, Germany 10.3762/bjoc.8.118 Abstract A series of 15 glycoside-derived tricarbonyl(η6-arene)chromium complexes were prepared in 19–87% yield by heating fully acetylated or

• hydrogen bonds. Keywords: aryl glycosides; carbohydrates; transition-metal complex; tricarbonyl(arene)chromium; Introduction In 1957, Fischer and Öfele published the preparation of tricarbonyl(η6-benzene)chromium, which was the first arene tricarbonylchromium complex [1]. Since then, a plethora of

• transition-metal complexes of arenes have been prepared, characterized and described in the literature. Among the multitude of transition-metal complexes of aromatic compounds, however, only tricarbonyl(η6-arene)chromium compounds are widely used for organic syntheses [2][3][4]. This is due to the fact that

Hybrid super electron donors – preparation and reactivity

• Jean Garnier,
• Douglas W. Thomson,
• Shengze Zhou,
• Phillip I. Jolly,
• Leonard E. A. Berlouis and
• John A. Murphy

Beilstein J. Org. Chem. 2012, 8, 994–1002, doi:10.3762/bjoc.8.112

• shown. This should then react with an iodoarene 37 to afford the dication salt 38 featuring an aryl anion and an iodide as counterions. In these circumstances, we suggest that the aryl anion can abstract a proton rapidly from the periphery of 38 to form reduced arene 39, consistent with our previous

Low-generation dendrimers with a calixarene core and based on a chiral C₂-symmetric pyrrolidine as iminosugar mimics

• Marco Marradi,
• Stefano Cicchi,
• Francesco Sansone,
• Alessandro Casnati and
• Andrea Goti

Beilstein J. Org. Chem. 2012, 8, 951–957, doi:10.3762/bjoc.8.107

• , Parco Area delle Scienze 17/A, I-43124 Parma, Italy 10.3762/bjoc.8.107 Abstract The preparation of low-generation dendrimers based on a simple calix[4]arene scaffold by insertion of the iminosugar-analogue C2-symmetric 3,4-dihydroxypyrrolidine is described. This methodology allows a rapid incorporation

• dendrimers, based on the C2-symmetric (3S,4S)-3,4-dihydoxypyrrolidine (1) unit, to a simple calix[4]arene scaffold (Figure 1). This allows a rapid increase of the valency of the iminosugar dendrimer in a reduced volume. The C2 symmetry of pyrrolidine 1, its ready accessibility from the “chiral pool” (L

• strategy. A convergent synthetic approach was chosen for the conjugation of pyrrolidine 4 and pyrrolidine-based dendron 5 (see Scheme 1) to the calix[4]arene core, via intermediate 11, in order to obtain iminosugar-based calixarene-dendrimers 2 and 3 (see Scheme 2). The starting calixarene used in this

Synthesis of functionalized macrocyclic derivatives of trioxabicyclo[3.3.0]nonadiene

• Sabine Leber,
• Gert Kollenz and
• Curt Wentrup

Beilstein J. Org. Chem. 2012, 8, 738–743, doi:10.3762/bjoc.8.83

• the sterically hindering tert-butyl groups make it an interesting spacer group, and it thus has been applied successfully in syntheses of several macrocyclic polyether and polymethyleneoxy rings containing one, two or three bisdioxine units, e.g., 4 and 5 (Scheme 1) [4][5]. Capping of a calix[6]arene

Enantioselective supramolecular devices in the gas phase. Resorcin[4]arene as a model system

• Caterina Fraschetti,
• Matthias C. Letzel,
• Antonello Filippi,
• Maurizio Speranza and
• Jochen Mattay

Beilstein J. Org. Chem. 2012, 8, 539–550, doi:10.3762/bjoc.8.62

• counterion effects. Keywords: diastereomeric complexes; gas phase enantioselectivity; kinetics; mass spectrometry; resorcin[4]arene receptor; Review Enzymes are macromolecular assemblies that make up the machinery whose structures and dynamics enable and support life functions. They are invariably

• , strongly dependent on the isomeric structure of the used guest [10]. Resorcin[4]arene molecules are characterized by three main contact regions [11]: (1) The down-region is the cavity of the receptor, which can be hydrophilic or lipophilic depending on the nature of the lateral chains; (2) The external

• the attention will be focussed on the most recent results obtained by our group with this particular kinetic method. Methodology The proton-bound [M∙H∙G]+ aggregates (M: chiral hosting resorcin[4]arene; G: guest biomolecule) were generated by electrospray ionization (ESI) of M/G methanolic mixtures

Discovery of practical production processes for arylsulfur pentafluorides and their higher homologues, bis- and tris(sulfur pentafluorides): Beginning of a new era of “super-trifluoromethyl” arene chemistry and its industry

• Teruo Umemoto,
• Lloyd M. Garrick and
• Norimichi Saito

Beilstein J. Org. Chem. 2012, 8, 461–471, doi:10.3762/bjoc.8.53

• economical production of various arylsulfur pentafluorides and their higher homologues, which could then open up a new era of “super-trifluoromethyl” arene chemistry and its applications in many areas. Keywords: arylsulfur chlorotetrafluoride; arylsulfur pentafluoride; pentafluorosulfanyl; sulfur

• pentafluorides. Thus, it is expected that this will lead to new and rapid advances in “super-trifluoromethyl” arene chemistry and associated industries in many areas. Preparation of ArSF4Cl 2. Preparation of Ar(SF4Cl)n from Ar(SH)n (n = 2, 3). Reaction mechanism for the formation of ArSF4Cl. Reaction mechanism

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

• ]. When one or more CH2 bridges are replaced by CH2OCH2 groups the macrocycles are known as homooxacalixarenes, or simply oxacalixarenes. The presence of the heteroatom is reflected in the name of the compound, for example, p-tert-butylcalix[4]arene (1) with a CH2OCH2 group instead of a CH2 bridge is p

• -tert-butyldihomooxacalix[4]arene (2) [5]. “Dihomo” implies two additional atoms in the bridge and “oxa” that one of them is oxygen. The remainder of the calixarene nomenclature denotes any substituents attached to the phenolic oxygens, known as the “lower rim”, and substituents found in the para

• -position of the phenols, also known as the “upper rim” (Figure 2). For the purposes of this review the term “oxacalix[n]arene” will be used as a generalization for this class of compounds. Although some aspects of homooxacalixarene chemistry have been reviewed [4][6][7][8], notably by Shokova and Kovalev