Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

• Mikhail V. Makarov and
• Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

• chloride to yield the triacetylated chloride salt or with 2,3,5-tri-O-benzoyl-D-ribofuranosyl chloride to yield the tribenzoylated chloride salt. The halosugars were obtained from 1,2,3,5-tetra-O-acetyl-D-β-ribofuranose (2a) or 1-O-acetyl-2,3,5-tri-O-benzoyl-D-β-ribofuranose (2b) [21]. Both pyridinium

• conjugates of NR+. Modifications which include protection of 2′- and 3′-hydroxy goups and reduction of the pyridinium core are used when direct modifications at the 5′-position are not possible due to the cleavage of the glycosidic bond under the required conditions, or are troublesome due to the low

• results in the in situ generation of pyridinium hydroxide, resulting in further NR+ hydrolysis. This unfavorable reactivity of the C-1′ position was briefly addressed in the earlier sections of this review, as evidenced by the needs of anhydrous conditions and low temperatures in the deprotection steps to

Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• (2S,3R)-2 via Sharpless epoxidation. Reagents and conditions: a) TBHP, D-(−)-DIPT, Ti(OiPr)4, MS, CH2Cl2; b) t-BuMe2SiCl, imidazole, DMAP, DMF; c) NaIO4, RuO2, AcOEt/H2O. Synthesis of (2S,3S)-2 from the imide 51. Reagents and conditions: a) NaBH4, MeOH/CH2Cl2; b) Ac2O, pyridinium perchlorate; c) furan

Mn-mediated sequential three-component domino Knoevenagel/cyclization/Michael addition/oxidative cyclization reaction towards annulated imidazo[1,2-a]pyridines

• Olga A. Storozhenko,
• Alexey A. Festa,
• Delphine R. Bella Ndoutoume,
• Alexander V. Aksenov,
• Alexey V. Varlamov and
• Leonid G. Voskressensky

Beilstein J. Org. Chem. 2018, 14, 3078–3087, doi:10.3762/bjoc.14.287

• Chemistry, North Caucasus Federal University, Pushkin st. 1a, 355009 Stavropol, Russian Federation 10.3762/bjoc.14.287 Abstract The sequential three-component reaction between o-hydroxybenzaldehydes, N-(cyanomethyl)pyridinium salts and a nucleophile towards substituted chromenoimidazopyridines under

• , complicated by the need of an oxidant to fulfil the final aromatization. Following our interest in domino [42][43] and MCR chemistry [44][45] and taking an advantage of 2-iminochromene reactivity, herein we report a sequential three-component domino reaction of salicylaldehydes 2 and N-(cyanomethyl)pyridinium

• salts 1 with a broad scope of nucleophiles to produce diversely substituted valuable chromenoimidazopyridines under oxidative conditions (Scheme 1, reaction 2). Results and Discussion To prove the designed concept, the reaction between salicylaldehyde (2a), N-(cyanomethyl)pyridinium chloride (1) and

The influence of the cationic carbenes on the initiation kinetics of ruthenium-based metathesis catalysts; a DFT study

• Magdalena Jawiczuk,
• Angelika Janaszkiewicz and
• Bartosz Trzaskowski

Beilstein J. Org. Chem. 2018, 14, 2872–2880, doi:10.3762/bjoc.14.266

• recently and examples of their transition metal complexes are scarce. In 2013 Ganter described a cationic NHC with a fused pyridinium moiety and the formal +1 charge just one bond away from the imidazole core [27]. In 2017 César synthesized a cationic imidazolylidene NHC with an ammonium tag attached

Oxidative and reductive cyclization in stiff dithienylethenes

• Michael Kleinwächter,
• Ellen Teichmann,
• Lutz Grubert,
• Martin Herder and
• Stefan Hecht

Beilstein J. Org. Chem. 2018, 14, 2812–2821, doi:10.3762/bjoc.14.259

• reached within the redox window determined by the electrolyte. Thus, a strongly electron-deficient substituent such as pyridinium is necessary to shift the reduction potential to accessible values. However, not every electron-withdrawing group appears to be suited to induce cathodic cyclization [40][42

An overview on recent advances in the synthesis of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials and their catalytic applications in chemical processes

• Hashem Sharghi,
• Pezhman Shiri and
• Mahdi Aberi

Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253

• ) composite materials such as poly(1-vinyl-3-sulfo-1H-imidazolium chloride) grafted on MWCNT 100, poly(4-styrenesulfonic acid) grafted on MWCNT 101, and poly(4-vinyl-1-sulfo-pyridinium chloride) grafted on MWCNT 102 (CNT-PVSAIC, CNT-PSSA, and CNT-PVSAPC, respectively) was prepared (Scheme 18). Obtained

• adsorption showed some peaks at 1646, 1626, 1549 and 1476 cm−1. The peaks at 1646, 1626, and 1549 cm−1 could be due to the vibration of pyridinium (PyH+) species, corresponding to the existence of Brønsted acid sites on the s-MWCNTs 137. The peak at 1476 cm−1 was also labeled to the coordination of electron

Synthesis of 3-aminocoumarin-N-benzylpyridinium conjugates with nanomolar inhibitory activity against acetylcholinesterase

• Nisachon Khunnawutmanotham,
• Cherdchai Laongthipparos,
• Patchreenart Saparpakorn,
• Nitirat Chimnoi and
• Supanna Techasakul

Beilstein J. Org. Chem. 2018, 14, 2545–2552, doi:10.3762/bjoc.14.231

• well as with benzylpyridinium moieties [12][13][14] have been reported as dual-binding site AChE inhibitors. Recently we have reported the AChE inhibitory activity of the coumarin derivative, scopoletin conjugated with a pyridinium side chain (Figure 1) [15] and a docking study revealed that the

• conversion to N-acyl-3-aminocoumarins 4, 5, 9, and 10 did not lead to any improvement (% inhibitions of all compounds were less than 10% at 1 μM). In order to screen the AChE inhibitory activities of the pyridinium salts, compounds 4, 5, 9, and 10 were treated with benzyl bromide to provide the corresponding

• findings, the coumarin isonicotinamides 4 or 9 were selected as appropriate precursors for the preparation of the subsequent pyridinium salts. The presence of methoxy groups in the 6 and 7 positions of the coumarin ring remarkably enhanced the inhibitory activity against AChE as observed from the

Synergistic approach to polycycles through Suzuki–Miyaura cross coupling and metathesis as key steps

• Sambasivarao Kotha,
• Milind Meshram and
• Chandravathi Chakkapalli

Beilstein J. Org. Chem. 2018, 14, 2468–2481, doi:10.3762/bjoc.14.223

• cyclization with the aid of HCl followed by pyridinium dichromate (PDC) oxidation (Scheme 8). Schmidt and co-workers [39] described an efficient route involving RCM and SM coupling towards the synthesis of 8-aryl-substituted coumarin 64, a natural product isolated from the plant Galipea panamensis. To this

• . Then, the cyclized product was subjected to the oxidation sequence with pyridinium chlorochromate (PCC) to generate cylophane derivative 115 in 75% yield (Scheme 17). Similarly, treatment of dialdehyde 113 with a freshly prepared Grignard reagent derived from 4-bromobut-1-ene (116) afforded dialkenyl

Synthesis of eunicellane-type bicycles embedding a 1,3-cyclohexadiene moiety

• Alex Frichert,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2018, 14, 2461–2467, doi:10.3762/bjoc.14.222

• to the formation of pyridinium triflinate. It has also been reported that the triflinate anion can be generated from 2,6-lutidine/Tf2O [28] or Et3N/Tf2O [29]. Allenyl triflone 34 could be formed by attack of triflinate as S-nucleophile [30] at the chain carbon of propargyl cation 33. An alternative

A pyridinium/anilinium [2]catenane that operates as an acid–base driven optical switch

• Sarah J. Vella and
• Stephen J. Loeb

Beilstein J. Org. Chem. 2018, 14, 1908–1916, doi:10.3762/bjoc.14.165

• Sarah J. Vella Stephen J. Loeb Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario N9B 3P4, Canada 10.3762/bjoc.14.165 Abstract A two-station [2]catenane containing a large macrocycle with two different recognition sites, one bis(pyridinium)ethane and one

• bis(pyridinium)ethane site, while addition of acid forms a charged benzylanilinium site. The DB24C8 then shuttles between the two charged recognition sites with occupancy favoring the bis(pyridinium)ethane site by a ratio of 4:1. The unprotonated [2]catenane has a deep yellow/orange color when the

• DB24C8 ring resides solely at the bis(pyridinium)ethane site and changes to colorless when the crown ether is shuttling (i.e., circumrotating) back and forth between the two recognition sites thus optically signalling the onset of the shuttling dynamics. Keywords: catenane; mechanically interlocked

Synthesis of 9-arylalkynyl- and 9-aryl-substituted benzo[b]quinolizinium derivatives by Palladium-mediated cross-coupling reactions

• Siva Sankar Murthy Bandaru,
• Darinka Dzubiel,
• Heiko Ihmels,
• Mohebodin Karbasiyoun,
• Mohamed M. A. Mahmoud and
• Carola Schulzke

Beilstein J. Org. Chem. 2018, 14, 1871–1884, doi:10.3762/bjoc.14.161

• positively charged nitrogen atoms and π···π donor–acceptor attractions between the phenyl and pyridinium moieties. In our case, the situation is somehow more complex as the novel compounds bear aromatic substituents (via alkyne spacer) in the benzo[b]quinolizinium 9 position. These aromatic substituents now

• engage in π···π donor–acceptor attractions with the pyridinium moiety (outer most ring of the tricyclic moiety) and the two positively charged nitrogen atoms are per se much further apart due to the larger intramolecular separation between the intermolecularly interacting π-systems. In addition, the

• significant here and the preference for the anti-ht arrangement must be dominated by the π···π attractions. Centroid distances between the aromatic 9-substituent and the pyridinium moiety are 3.619 Å for 2a (C16 → C21; C5 → C9, N1) and 3.676 Å for 2b (C16 → C21; C1 → C5, N1), respectively (Figure S1

Mild and selective reduction of aldehydes utilising sodium dithionite under flow conditions

• Nicole C. Neyt and
• Darren L. Riley

Beilstein J. Org. Chem. 2018, 14, 1529–1536, doi:10.3762/bjoc.14.129

• ]. Sodium dithionite can act as a powerful reducing agent [16], is mild, easy to use, and it is compatible with protic solvents like water and isopropanol. It has previously been used to reduce a range of different organic functional groups including aldehydes and ketones [17][18], pyridinium ions to afford

Design and biological characterization of novel cell-penetrating peptides preferentially targeting cell nuclei and subnuclear regions

• Anja Gronewold,
• Mareike Horn and
• Ines Neundorf

Beilstein J. Org. Chem. 2018, 14, 1378–1388, doi:10.3762/bjoc.14.116

• (Marktredwitz, Germany). Other chemicals and consumables including 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (HATU), N,N-diisopropylethylamine (DIPEA), acetonitrile (ACN), and trifluoroacetic acid (TFA), dimethylformamide (DMF), N-methylpyrrolidine (NMP

Development of novel cyclic NGR peptide–daunomycin conjugates with dual targeting property

• Andrea Angelo Pierluigi Tripodi,
• Szilárd Tóth,
• Kata Nóra Enyedi,
• Gitta Schlosser,
• Gergely Szakács and
• Gábor Mező

Beilstein J. Org. Chem. 2018, 14, 911–918, doi:10.3762/bjoc.14.78

• . The lyophilized compound was then purified by RP-HPLC prior to the cyclization. Cyclization Prior to the head-to-side chain cyclization a salt exchange needs to be performed using 10 equiv of pyridinium hydrochloride in 5 mL MeOH. After 20 min volatiles were removed under reduced pressure, the

Enzyme-free genetic copying of DNA and RNA sequences

• Marilyne Sosson and
• Clemens Richert

Beilstein J. Org. Chem. 2018, 14, 603–617, doi:10.3762/bjoc.14.47

• small heterocycles, such as pyridine, can increase the rate of the reaction [60]. Most probably, this effect was organocatalytic in nature, being caused by a pyridinium species that forms in the reaction medium, an effect known from the acceleration of DCC-induced acylation reactions with

Preparation of trinucleotide phosphoramidites as synthons for the synthesis of gene libraries

• Ruth Suchsland,
• Bettina Appel and
• Sabine Müller

Beilstein J. Org. Chem. 2018, 14, 397–406, doi:10.3762/bjoc.14.28

• advantages of solution chemistry and solid-phase methods. Thus, solid-supported acyl chloride or pyridinium tosylate as the activator of nucleoside-3'-O-H-phosphonates/phosphoramidites, and polystyrene-bound trimethylammonium periodate as oxidation reagent have been demonstrated to be superior for dimer and

Transition-metal-free [3 + 3] annulation of indol-2-ylmethyl carbanions to nitroarenes. A novel synthesis of indolo[3,2-b]quinolines (quindolines)

• Michał Nowacki and
• Krzysztof Wojciechowski

Beilstein J. Org. Chem. 2018, 14, 194–202, doi:10.3762/bjoc.14.14

• ]. Several methods use prerequisite quinoline derivatives for the construction of the pyrrole ring of quindoline. 2-(2-Aminophenyl)-3-bromoquinoline cyclized to quindoline by reacting with pyridinium hydrochloride (d) [14]. Insertion of nitrene generated from 2-(2-nitrophenyl)quinoline by triethylphosphite

Aminosugar-based immunomodulator lipid A: synthetic approaches

• Alla Zamyatina

Beilstein J. Org. Chem. 2018, 14, 25–53, doi:10.3762/bjoc.14.3

Acid-catalyzed ring-opening reactions of a cyclopropanated 3-aza-2-oxabicyclo[2.2.1]hept-5-ene with alcohols

• Katrina Tait,
• Alysia Horvath,
• Nicolas Blanchard and
• William Tam

Beilstein J. Org. Chem. 2017, 13, 2888–2894, doi:10.3762/bjoc.13.281

• represent the first examples of ring-openings of cyclopropanated 3-aza-2-oxabicyclo[2.2.1]alkenes that lead to the cleavage of the C–O bond instead of the N–O bond. Different acid catalysts were tested and it was found that pyridinium toluenesulfonate in methanol gave the best yields in the ring-opening

• -opened product at a yield of 38% (Table 1, entry 7) while using camphorsulfonic acid (CSA) increased the yield to 50% but took 46 hours to go to completion (Table 1, entry 8). The organic acid pyridinium p-toluenesulfonate (PPTS) produced the highest yield of ring-opened product with a 61% yield (Table 1

• examples of ring-openings of cyclopropanated 3-aza-2-oxabicyclo[2.2.1]alkenes that lead to the cleavage of the C–O bond instead of the N–O bond. Different acid catalysts were tested and it was found that pyridinium toluenesulfonate in methanol gave the best yields in the ring-opening reactions. The scope

The photodecarboxylative addition of carboxylates to phthalimides as a key-step in the synthesis of biologically active 3-arylmethylene-2,3-dihydro-1H-isoindolin-1-ones

• Ommid Anamimoghadam,
• Saira Mumtaz,
• Anke Nietsch,
• Gaetano Saya,
• Cherie A. Motti,
• Jun Wang,
• Peter C. Junk,
• Ashfaq Mahmood Qureshi and
• Michael Oelgemöller

Beilstein J. Org. Chem. 2017, 13, 2833–2841, doi:10.3762/bjoc.13.275

• 8a–y, possibly via an acylaminium cation intermediate (Scheme 9) [60]. The change in stability may be caused by a stabilizing ionic–π interaction for the Z-isomer during isomerization [61]. A similar thermal isomerization towards the more stable isomer induced by catalytic amounts of pyridinium p

Recent progress in the racemic and enantioselective synthesis of monofluoroalkene-based dipeptide isosteres

• Myriam Drouin and
• Jean-François Paquin

Beilstein J. Org. Chem. 2017, 13, 2637–2658, doi:10.3762/bjoc.13.262

• , oxidation of the secondary alcohol with pyridinium dichromate into the corresponding cyclopentanone derivative and subsequent olefination using CBr3F gave the monofluoroalkene 96 with a modest selectivity towards the (Z)-alkene. A Negishi coupling then gave alkene 98. Stereoselective reductive amination

Electron-deficient pyridinium salts/thiourea cooperative catalyzed O-glycosylation via activation of O-glycosyl trichloroacetimidate donors

• Mukta Shaw,
• Yogesh Kumar,
• Rima Thakur and
• Amit Kumar

Beilstein J. Org. Chem. 2017, 13, 2385–2395, doi:10.3762/bjoc.13.236

• trichloroacetimidate donors using a synergistic catalytic system of electron-deficient pyridinium salts/aryl thiourea derivatives at room temperature is demonstrated. The acidity of the adduct formed by the 1,2-addition of alcohol to the electron-deficient pyridinium salt is increased in the presence of an aryl

• , the optimized method is also utilized for the regioselective O-glycosylation by using a partially protected acceptor. Keywords: cooperative catalysis; electron-deficient pyridinium salts; O-glycoside; regioselectivity; thiourea; Introduction The glycosidic linkage is the principal bond present in a

• activation at room temperature [32][33][34][35][36]. It is known from the literature that pyridinium salts exhibit pKa values of about 5.2 [37]. Of late, Berkessel et al. disclosed an elegant method, where different electron deficient pyridinium salts (expected pKa values less than 5) were used as a catalyst

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• anions can control Pd-catalysed α-fluorinations [84]). Very interestingly, however, the authors clearly proved that the nature of the F-transfer reagent is crucial to obtain high selectivities. While NFSI or SelectfluorTM did not give reasonable enantioselectivities [81], the pyridinium salt 6 turned out

Block copolymers from ionic liquids for the preparation of thin carbonaceous shells

• Sadaf Hanif,
• Bernd Oschmann,
• Dmitri Spetter,
• Muhammad Nawaz Tahir,
• Wolfgang Tremel and
• Rudolf Zentel

Beilstein J. Org. Chem. 2017, 13, 1693–1701, doi:10.3762/bjoc.13.163

• organic asymmetric cations, like imidazolium, pyridinium or alkylammonium and inorganic anions, such as halides, mineral acid anions, or polyatomic inorganic anions (PF6−, BF4−) [3]. Because of the steric hindrance, they are not able to build a strong lattice like inorganic salts. Therefore, not much

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• MnO2. Selenium dioxide and potassium dichromate-mediated oxidative dehydrogenation of tetrahydro-β-carbolines [65][66]. Synthesis of substituted benzazoles in the presence of barium permanganate. Oxidative dehydrogenation with phenanthroline-based catalysts. PPTS = pyridinium p-toluenesulfonic acid