Electrochemical selenium- and iodonium-initiated cyclisation of hydroxy-functionalised 1,4-dienes

• Philipp Röse,
• Steffen Emge,
• Jun-ichi Yoshida and
• Gerhard Hilt

Beilstein J. Org. Chem. 2015, 11, 174–183, doi:10.3762/bjoc.11.18

• organic trihalide salts [30], N-bromosuccinimide or N-iodosuccinimide and its derivatives [31][32][33][34][35][36], or more specialised reagents such as bis(pyridinium)iodonium(I) tetrafluoroborate [37][38][39]. Next to those, the in situ oxidation of halogenide ions with strong oxidants such as oxone, Pb

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

• radical mechanisms were proposed, the common feature is the generation of alkene via the radical dehydrogenation of alkane. 2.6 Other oxidative systems Esters were synthesized from aldehydes and methanol (6 equiv excess relative to aldehyde) using pyridinium dichromate in DMF [170]. Methyl esters were

Synthesis of divalent ligands of β-thio- and β-N-galactopyranosides and related lactosides and their evaluation as substrates and inhibitors of Trypanosoma cruzi trans-sialidase

• María Emilia Cano,
• Rosalía Agusti,
• Alejandro J. Cagnoni,
• María Florencia Tesoriero,
• José Kovensky,
• María Laura Uhrig and
• Rosa M. de Lederkremer

Beilstein J. Org. Chem. 2014, 10, 3073–3086, doi:10.3762/bjoc.10.324

• concentration of the SL used as donor (Scheme 4). The reaction mixture, containing unreacted 18 and sialyl derivatives 25 and 26, was purified using an AG1X2 (acetate form) resin column. After elution of neutral compounds with water, acidic derivatives were eluted with different concentrations of pyridinium

• passing through an anion exchange resin (AG1X2, acetate form, BioRad, 1.2 × 15 cm). Neutral compounds, namely 18 and lactose, were eluted with H2O and sialylated compounds with a stepped gradient from 50 mM to 500 mM pyridinium acetate buffer pH 5.4. Fractions (1.5 mL) were collected and analyzed by HPAEC

• . Compound 25, the product of sialylation of 18, was eluted with 100 mM pyridinium acetate while the remaining sialyllactose was eluted with 200 mM pyridinium acetate buffer. Further elution with 500 mM buffer afforded the disialylated compound 26 (2 mg). The pooled fractions were concentrated by

Molecular recognition of AT-DNA sequences by the induced CD pattern of dibenzotetraaza[14]annulene (DBTAA)–adenine derivatives

• Marijana Radić Stojković,
• Marko Škugor,
• Łukasz Dudek,
• Jarosław Grolik,
• Julita Eilmes and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2175–2185, doi:10.3762/bjoc.10.225

• importance of AT tracts and the selectivity of cyanine dyes. On this basis, we were inspired to prepare the novel binders AP5 with a DBTAA–adenine linker length between AP3 (oligo dT specific) and AP6 (oligo-dT inert) and AP3am, in which pyridinium is exchanged by a permethylated amine, with the aim of

• determining the importance of aromatic stacking interactions. The results were compared with the reference APH (lacking adenine) and previously studied DP77 [12] (Scheme 1), which, having pyridinium instead of adenine, can also be regarded as a reference structure. Double-stranded DNA/RNA targets chosen for

• contrast, the previously studied analogue DP77 exhibited strong bathochromic shifts of (Δλ346 nm = 4–13 nm; pyridinium instead of adenine) [12]. The observation of a hypochromic and not a bathochromic effect for the AP series suggested a different type of aromatic stacking interaction compared to DP77 (DNA

Reaction of selected carbohydrate aldehydes with benzylmagnesium halides: benzyl versus o-tolyl rearrangement

• Maroš Bella,
• Bohumil Steiner,
• Vratislav Langer and
• Miroslav Koóš

Beilstein J. Org. Chem. 2014, 10, 1942–1950, doi:10.3762/bjoc.10.202

• mixture of alcohols 4–7 (1.47 g, 5.0 mmol) in CH2Cl2 (25 mL) was added dropwise to a magnetically stirred solution of pyridinium dichromate (PDC, 2.45 g, 6.5 mmol) and acetic anhydride (1.3 mL) in CH2Cl2 (25 mL) under cooling in an ice-water bath followed by heating under reflux for 3 h. The greater part

C–H-Functionalization logic guides the synthesis of a carbacyclopamine analog

• Sebastian Rabe,
• Johann Moschner,
• Marina Bantzi,
• Philipp Heretsch and
• Athanassios Giannis

Beilstein J. Org. Chem. 2014, 10, 1564–1569, doi:10.3762/bjoc.10.161

• tetrahydropyranyl ether (3,4-dihydro-2H-pyran, cat. pyridinium para-toluenesulfonate, CH2Cl2, 25 °C, quantiative, inconsequential mixture of diastereoisomers), and the C17 carbonyl group was transformed into its 2-picolylimine (2-picolylamine, cat. para-toluenesulfonic acid, toluene, 111 °C, 92% yield). Subjecting

Amino acid motifs in natural products: synthesis of O-acylated derivatives of (2S,3S)-3-hydroxyleucine

• Oliver Ries,
• Martin Büschleb,
• Markus Granitzka,
• Dietmar Stalke and
• Christian Ducho

Beilstein J. Org. Chem. 2014, 10, 1135–1142, doi:10.3762/bjoc.10.113

• catalyst to pyridinium p-toluenesulfonate (PPTS) only led to small amounts of the product after prolonged reaction times and could not suppress the formation of the O,O-acetal (Table 1, entries 2 and 3). The use of racemic camphorsulfonic acid (CSA) in toluene and acetone, respectively, resulted in the

Addition of H-phosphonates to quinine-derived carbonyl compounds. An unexpected C9 phosphonate–phosphate rearrangement and tandem intramolecular piperidine elimination

• Łukasz Górecki,
• Artur Mucha and
• Paweł Kafarski

Beilstein J. Org. Chem. 2014, 10, 883–889, doi:10.3762/bjoc.10.85

• the BH3·THF complex and then oxidized with pyridinium chlorochromate (recommended PCC on SiO2 [26]) a complicated mixture of products (50% of conversion) was obtained. The mixture contained the target aldehyde 6 (minority, Scheme 2) and the corresponding alcohol (majority, ratio 1:5), both in their

Cyclic phosphonium ionic liquids

• Sharon I. Lall-Ramnarine,
• Joshua A. Mukhlall,
• James F. Wishart,
• Robert R. Engel,
• Alicia R. Romeo,
• Masao Gohdo,
• Sharon Ramati,
• Marc Berman and
• Sophia N. Suarez

Beilstein J. Org. Chem. 2014, 10, 271–275, doi:10.3762/bjoc.10.22

• ) are composed primarily of nitrogen-centered (particularly imidazolium, pyridinium, pyrrolidinium, and related quaternary ammonium) cations with a wide range of anions [1]. While a number of these ILs have been applied successfully to commercial processes [1], efforts are continually underway to

The total synthesis of D-chalcose and its C-3 epimer

• Jun Sun,
• Song Fan,
• Zhan Wang,
• Guoning Zhang,
• Kai Bao and
• Weige Zhang

Beilstein J. Org. Chem. 2013, 9, 2620–2624, doi:10.3762/bjoc.9.296

• ,THF, rt, 96%; (b) AD-mix-β, t-BuOH/H2O, 0 °C, 80%; (c) TEMPO, NaClO, CH2Cl2, −5 °C. AD = asymmetric dihydroxylation, TEMPO = 2,2,6,6-tetramethyl-1-piperidinyloxy, free radical. Reagents and conditions: (a) PhCH(OCH3)2, PPTS, CH2Cl2, rt; (b) DIBAL-H, CH2Cl2, 0 °C, 76% in two steps. PPTS = pyridinium p

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

• metabolism via oxidation or methylation pathways forming the corresponding pyridinium ions [9][10]. Although many of these metabolites are potentially highly toxic to humans they are conveniently and quickly excreted from the body via the kidneys. With a good understanding of the pharmacokinetics and

• , mono:di) using a buffered solution of pyridinium perbromide in methylene chloride/pyridine at low temperature. After purification of the resulting intermediate by flash column chromatography the direct displacement of the newly installed bromide by an azidoethanol moiety yields the desymmetrised

The preparation of several 1,2,3,4,5-functionalized cyclopentane derivatives

• André S. Kelch,
• Peter G. Jones,
• Ina Dix and
• Henning Hopf

Beilstein J. Org. Chem. 2013, 9, 1705–1712, doi:10.3762/bjoc.9.195

• acetylenedicarboxylate (22) with dimethyl malonate (23) under the catalytic influence of pyridinium acetate, the fully substituted cycloheptadienes 24 and 25 (Scheme 5) were produced; both authors also proposed reaction mechanisms for this complex transformation that can be considered as reasonable even today; for the

Synthesis of the calcilytic ligand NPS 2143

• Henrik Johansson,
• Thomas Cailly,
• Alex Rojas Bie Thomsen,
• Hans Bräuner-Osborne and
• Daniel Sejer Pedersen

Beilstein J. Org. Chem. 2013, 9, 1383–1387, doi:10.3762/bjoc.9.154

• (Scheme 2). Reduction of 7 was easily achieved on multigram scale by using LiAlH4 to provide amine 8 in excellent yield and purity after work-up. According to the method of Katritzky et al. [16] amine 8 was activated as the corresponding pyridinium salt 10 upon treatment with triphenylpyrylium salt 9 in

• ethanol under reflux. Subsequently, the crude pyridinium salt 10 was exposed to the sodium salt of 2-nitropropane (11) to give nitro compound 12. Reduction of the nitro group in 12 by catalytic hydrogenation at atmospheric pressure to produce amine 6 has previously been described by Kamal and Chouhan [17

Efficient regio- and stereoselective access to novel fluorinated β-aminocyclohexanecarboxylates

• Loránd Kiss,
• Melinda Nonn,
• Reijo Sillanpää,
• Santos Fustero and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2013, 9, 1164–1169, doi:10.3762/bjoc.9.130

• position 4 was efficiently synthesized. Oxidation of the hydroxy group of amino ester 5 with pyridinium chlorochromate (PCC) in CH2Cl2 yielded the corresponding oxo-group-containing amino ester 8, which was then converted with Deoxo-Fluor in CH2Cl2 at 0 °C to the corresponding geminal difluoro amino ester

Tandem dinucleophilic cyclization of cyclohexane-1,3-diones with pyridinium salts

• Mostafa Kiamehr,
• Firouz Matloubi Moghaddam,
• Satenik Mkrtchyan,
• Volodymyr Semeniuchenko,
• Linda Supe,
• Alexander Villinger,
• Peter Langer and
• Viktor O. Iaroshenko

Beilstein J. Org. Chem. 2013, 9, 1119–1126, doi:10.3762/bjoc.9.124

• Katalyse e.V. an der Universität Rostock, Albert-Einstein-Straße 29a, D-18059 Rostock, Germany 10.3762/bjoc.9.124 Abstract The cyclization of cyclohexane-1,3-diones with various substituted pyridinium salts afforded functionalized 8-oxa-10-aza-tricyclo[7.3.1.02,7]trideca-2(7),11-dienes. The reaction

• proceeds by regioselective attack of the central carbon atom of the 1,3-dicarbonyl unit to 4-position of the pyridinium salt and subsequent cyclization by base-assisted proton migration and nucleophilic addition of the oxygen atom to the 2-position, as was elucidated by DFT computations. Fairly extensive

• screening of bases and additives revealed that the presence of potassium cations is essential for formation of the product. Keywords: cyclization; density functional calculations; heterocycles; nucleophilic addition; pyridinium salt; Introduction The nucleophilic addition to pyridinium salts has recently

Synthesis of guanidinium–sulfonimide ion pairs: towards novel ionic liquid crystals

• Martin Butschies,
• Manuel M. Neidhardt,
• Markus Mansueto,
• Sabine Laschat and
• Stefan Tussetschläger

Beilstein J. Org. Chem. 2013, 9, 1093–1101, doi:10.3762/bjoc.9.121

• ]. Although Heintz was the pioneer, who observed in 1854 melting and clearing transitions upon heating of magnesium myristate [9][10], he did not recognize this as liquid-crystalline behavior. The first regular pyridinium ILCs were reported in 1938 by Knight and Shaw [11][12], followed by seminal findings by

Facile synthesis of functionalized spiro[indoline-3,2'-oxiran]-2-ones by Darzens reaction

• Qin Fu and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2013, 9, 918–924, doi:10.3762/bjoc.9.105

• phenacyl bromides and report the facile synthesis of versatile spiro[indoline-3,2'-oxiran]-2-ones. Results and Discussion In recent years we have found that pyridinium salts react with versatile reactive methylene compounds to give different kinds of products, including functionalized cyclopropanes, 2,3

• -dihydrofurans, polysubstituted pyridines, pyrido[1,2-a]benzimidazoles and charge-separated zwitterionic salts [26][27][28][29][30][31]. We envisaged that in situ generated pyridinium ylide might react with the reactive carbonyl group of isatins to afford spiro epoxyoxindoles (Scheme 1). To test this feasibility

• , the reactions of various substituted isatins with pyridinium salt in the presence of base were examined under different conditions. We were disappointed that the reactions produced much complicated mixtures and no acceptable results were obtained. Thus, our attention was turned toward the development

Reductions of aldehydes and ketones with a readily available N-heterocyclic carbene borane and acetic acid

• Vladimir Lamm,
• Xiangcheng Pan,
• Tsuyoshi Taniguchi and
• Dennis P. Curran

Beilstein J. Org. Chem. 2013, 9, 675–680, doi:10.3762/bjoc.9.76

• ethyl acetate (EtOAc) was complete in 30 min and gave 3-phenylpropanol (3) in 86% yield after evaporation and flash chromatography (Scheme 2). Other acids including pyridinium p-toluenesulfonate, benzohydroxamic acid, and 2,2-dimethyl-1,3-dioxane-4,6-dione (Meldrum’s acid) also promoted this reduction

Asymmetric Diels–Alder reaction with >C=P– functionality of the 2-phosphaindolizine-η¹-P-aluminium(O-menthoxy) dichloride complex: experimental and theoretical results

• Rajendra K. Jangid,
• Nidhi Sogani,
• Neelima Gupta,
• Raj K. Bansal,
• Moritz von Hopffgarten and
• Gernot Frenking

Beilstein J. Org. Chem. 2013, 9, 392–400, doi:10.3762/bjoc.9.40

• theoretically as well as experimentally [16]. In this context, we found that 1,3-bis(alkoxycarbonyl)-2-phosphaindolizines (1a, Z = CO2R1) prepared through 1,5-electrocyclization of in situ generated bis(pyridinium ylidyl)phosphenium chlorides [17] lead to successful DA reaction [18][19], but 3-alkoxycarbonyl-2

Glycosylation efficiencies on different solid supports using a hydrogenolysis-labile linker

• Mayeul Collot,
• Steffen Eller,
• Markus Weishaupt and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2013, 9, 97–105, doi:10.3762/bjoc.9.13

• resins, an additional Zemplén cleavage site for fast LC–MS analysis is introduced. Synthesis of linker 1. Reactions and conditions: (a) NEt3, DCM, rt, 84%; (b) DHP, pyridinium p-toluenesulfonate, DCM, rt, quant.; (c) 2 M aq NaOH, THF, rt, 91%; (d) DSC, NEt3, CH3CN, 0 °C to rt; (e) NEt3, DCM, rt, 80% over

Supramolecular hydrogels formed from poly(viologen) cross-linked with cyclodextrin dimers and their physical properties

• Yoshinori Takashima,
• Yang Yuting,
• Miyuki Otsubo,
• Hiroyasu Yamaguchi and
• Akira Harada

Beilstein J. Org. Chem. 2012, 8, 1594–1600, doi:10.3762/bjoc.8.182

• range of the 1H NMR time scale due to the slow equilibrium [19][20]. Cationic groups, such as pyridinium and pyridylpyridinium terminal groups, inhibit the decomposition of polyrotaxane and stabilize the complexes between α-CD and cationic alkanediyl compounds [21][22][23]. Herein, to study the

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

• -position are significantly more effective than aryl substituents in stabilizing the pyridinium ions formed through acetyl cation addition. Photo-switchable 3,4-diaminopyridines including a diazo moiety are potentially useful as special-purpose catalysts. The azobenzene substituent itself is electron

Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part I: Dihydronepetalactones

• Nicole Zimmermann,
• Robert Hilgraf,
• Lutz Lehmann,
• Daniel Ibarra and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1246–1255, doi:10.3762/bjoc.8.140

• intermediate 16 was transformed to the aldehyde 23. In the course of this short sequence, the free hydroxy group of 16 was protected as the TBDMS ether to yield 21 which afforded the mono-protected diol 22 after treatment with KOH in methanol. Subsequently, 22 was oxidized with pyridinium dichromate to give

Control over molecular motion using the cis–trans photoisomerization of the azo group

• Estíbaliz Merino and
• María Ribagorda

Beilstein J. Org. Chem. 2012, 8, 1071–1090, doi:10.3762/bjoc.8.119

• fluorescence emitted by the pyridinium salt free cyclophane. The azobenzene trans-10 is conveniently replaced with electron donor units, so that when it is associated, as azo-10∙11, the fluorescence is completely inhibited by charge-transfer interactions. The photoexcitation carried out by irradiation with

Recent advances towards azobenzene-based light-driven real-time information-transmitting materials

• Jaume García-Amorós and
• Dolores Velasco

Beilstein J. Org. Chem. 2012, 8, 1003–1017, doi:10.3762/bjoc.8.113

• -azobenzene derivatives. This notable red-shift of the absorption wavelength arises from the strong charge transfer from the alkoxy group to the positively-charged nitrogen atom of the pyridinium salt. Figure 8 shows the transient absorption generated upon pulsed laser irradiation of ethanol solutions of azo

• electron transfer from the alkoxy group to the pyridinium salt produces a partial breaking of the double N–N bond of the azo moiety, thereby facilitating the rotation around this bond to recover the more stable initial trans configuration in a quick fashion [56]. Type-II azoderivatives: photochromic

• azoderivatives [63]. This section collects different families of azoderivatives that combine the two strategies aforementioned: the presence of powerful electron-withdrawing groups, like nitro or pyridinium salts, and the existence of a phenol function in the convenient positions (2’ and 4’) of the azobenzene