Pyridine-promoted dediazoniation of aryldiazonium tetrafluoroborates: Application to the synthesis of SF₅-substituted phenylboronic esters and iodobenzenes

• George Iakobson,
• Junyi Du,
• Alexandra M. Z. Slawin and
• Petr Beier

Beilstein J. Org. Chem. 2015, 11, 1494–1502, doi:10.3762/bjoc.11.162

• tetrafluoroborates and suggested the formation of diazopyridinium salts which homolytically decompose to aryl radicals, nitrogen and a pyridinium tetrafluoroborate radical [79][80]. Tanaka and co-workers have used the combination of PhN2+BF4− and pyridine for arylations of silylenol ethers [81]. They have observed

• aryldiazopyridinium 4 which decomposes to an aryl radical, a pyridinium tetrafluoroborate radical and nitrogen. The aryl radical reacts with B2pin2 to form the borylated product 2 and the Bpin radical (likely to be stabilized by pyridine) [82]. The byproducts pyridine·BF3 and F-Bpin are formed by the reaction of the

• pyridinium tetrafluoroborate radical and the Bpin radical. Subjecting the diazonium salt 3i to the borylation conditions gave further indirect evidence for the formation of aryl radicals (Scheme 3). Full conversion of 3i was observed affording a mixture of products 2i, 2i’, 5i (two isomers of unknown

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• treated with LAH to generate diol 266 (72–92%). The dehydration of diol 266 with pyridinium p-toluenesulfonate in benzene gave diolefin 267. [2 + 2] Photocycloaddition of diolefin 267 was carried out by irradiation with a 400 W high-pressure Hg lamp (Pyrex filter) in benzene for 26–92 h. After evaporation

Indolizines and pyrrolo[1,2-c]pyrimidines decorated with a pyrimidine and a pyridine unit respectively

• Marcel Mirel Popa,
• Emilian Georgescu,
• Mino R. Caira,
• Florentina Georgescu,
• Constantin Draghici,
• Raluca Stan,
• Calin Deleanu and
• Florea Dumitrascu

Beilstein J. Org. Chem. 2015, 11, 1079–1088, doi:10.3762/bjoc.11.121

• corresponding cycloimmonium bromides. In the case of 4-(3-pyridyl)pyrimidine and 4-(4-pyridyl)pyrimidine the quaternization reactions occur as expected at the pyridine nitrogen atom leading to pyridinium bromides and consequently to new indolizines via the corresponding pyridinium N-ylides. However, in the case

• bromide salts was performed and will be discussed in each case. In the case of pyridinium ylides generated from 4-(3-pyridyl)pyrimidine (7), new indolizines 14a–f decorated with a pyrimidine moiety were obtained (Scheme 2). The reaction appears to be selective towards the indolizines 14. In some cases the

• group induces a shielding effect on the C-1 atom from 115 ppm in the case of 14a, to 104.8–108.1 ppm for 14b–f. Similarly, in the case of pyridinium N-ylides generated from 8, the new indolizines 16 were synthesized (Scheme 3) and structurally characterized. Again, in the case of some compounds, the

Synthesis of multivalent carbohydrate mimetics with aminopolyol end groups and their evaluation as L-selectin inhibitors

• Joana Salta,
• Jens Dernedde and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2015, 11, 638–646, doi:10.3762/bjoc.11.72

• selected HATU (1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium-3-oxide hexafluorophosphate), a coupling reagent frequently used in peptide synthesis [34]. We applied standard conditions for the preparation of one divalent and two trivalent amides (Scheme 4). To our pleasure divalent

Novel stereocontrolled syntheses of tashiromine and epitashiromine

• Loránd Kiss,
• Enikő Forró and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2015, 11, 596–603, doi:10.3762/bjoc.11.66

• the indolizidine framework; access to tashiromine in racemic form can be achieved through the alkylation of succinimide, followed by ring closure via acyliminium intermediates [23][24], the reduction of cyclized pyridinium salts [25], iminium cascade cyclization [26], alkyne-mediated hydroformylation

The reactions of 2-ethoxymethylidene-3-oxo esters and their analogues with 5-aminotetrazole as a way to novel azaheterocycles

• Marina V. Goryaeva,
• Yanina V. Burgart,
• Marina A. Ezhikova,
• Mikhail I. Kodess and
• Viktor I. Saloutin

Beilstein J. Org. Chem. 2015, 11, 385–391, doi:10.3762/bjoc.11.44

• substitution. The use of diethyl 2-ethoxymethylidenemalonate in this reaction resulted in ethyl 7-hydroxytetrazolo[1,5-a]pyrimidine-6-carboxylate, while ethyl 2-ethoxymethylidenecyanoacetate yielded 5-[2,6-diamino-3,5-bis(ethoxycarbonyl)pyridinium-1-yl]tetrazol-1-ide through an alternative pathway. Ethyl 2

• to conclude that the molecule of compound 11 is symmetric and bears one methine proton, two amino groups and two ethoxycarbonyl substituents. The final structure of compound 11 as 5-[2,6-diamino-3,5-bis(ethoxycarbonyl)pyridinium-1-yl]tetrazol-1-ide was confirmed by X-ray diffraction (Figure 2). The

Properties of cationic monosubstituted tetraalkylammonium cyclodextrin derivatives – their stability, complexation ability in solution or when deposited on solid anionic surface

• Martin Popr,
• Sergey K. Filippov,
• Nikolai Matushkin,
• Juraj Dian and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2015, 11, 192–199, doi:10.3762/bjoc.11.20

• CD polymers, where the CD units are randomly crosslinked by suitable reagents. Systems for separation of gases, composed of cationic CD pyridinium polymer and a Nafion® membrane were reported by Grossi and coworkers [24]. The Kusumocahyo group studied separation abilities of cationic CD copolymers

Synthesis of dinucleoside acylphosphonites by phosphonodiamidite chemistry and investigation of phosphorus epimerization

• William H. Hersh

Beilstein J. Org. Chem. 2015, 11, 184–191, doi:10.3762/bjoc.11.19

• triflate as the activator to give the monoamidites 3′-O-(P(N(iPr)2)C(O)R)-5′-O-DMTr-thymidine, and further coupling with 3′-O-(tert-butyldimethylsilyl)thymidine was carried out with activation by pyridinium trifluoroacetate/N-methylimidazole. The new dinucleoside acylphosphonites could be further oxidized

• both 10 and 11 in the 1H and 13C NMR spectra. Since this was not relevant to phosphorus epimerization, it was not further investigated. Dinucleoside coupling was carried out using the 2:1 pyridinium trifluoroacetate/N-methylimidazole (PTFA/NMI) activator developed at Isis to combine phosphonamidites 10

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