The biomimetic synthesis of balsaminone A and ellagic acid via oxidative dimerization

• Sharna-kay Daley and
• Nadale Downer-Riley

Beilstein J. Org. Chem. 2020, 16, 2026–2031, doi:10.3762/bjoc.16.169

• previous synthesis of balsaminone A (4) [22] (Scheme 3), silver oxide was used as the oxidative dimerizing agent for the formation of the binaphthoquinone intermediate 13. This was followed by photolytic cyclisation and ortho-formylation to give carbaldehyde 14. Conversion to balsaminone A (4) could then

Syntheses of spliceostatins and thailanstatins: a review

• William A. Donaldson

Beilstein J. Org. Chem. 2020, 16, 1991–2006, doi:10.3762/bjoc.16.166

• epoxidation [37] of 5-methyl-2-methylene-4-penten-1-ol gave the epoxyalcohol 92 in 94% ee, which was oxidized to the aldehyde 93. While the addition of the lithium salt of methyl propynoate proceeded in a nondiastereoselective fashion, the use of a zirconium/silver-mediated alkynylation gave the alcohol 94

Metal-free synthesis of phosphinoylchroman-4-ones via a radical phosphinoylation–cyclization cascade mediated by K₂S₂O₈

• Qiang Liu,
• Weibang Lu,
• Guanqun Xie and
• Xiaoxia Wang

Beilstein J. Org. Chem. 2020, 16, 1974–1982, doi:10.3762/bjoc.16.164

•  1a). Besides, in 2016 Li’s group [28] reported a silver-catalyzed straightforward approach for the synthesis of phosphonate-functionalized chroman-4-ones via a phosphoryl radical-initiated cascade cyclization of 2-(allyloxy)arylaldehydes using K2S2O8 as an oxidant, however, diphenylphosphine oxide

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• concerned the development of “classical” C–H activation reactions, while a photoredox cycle was implemented to reoxidize the metal catalyst, thus obviating the need for a stoichiometric amount of metal-based oxidants, such as silver or copper salts. In parallel, dual synergistic catalysis has emerged. In

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• experimental parameters such as solvent, concentration, temperature, catalyst and silver salt. Under standard reaction conditions, no reaction was observed in the absence of a silver salt, and the best results were obtained in the presence of AgOTf (20 mol %), giving the corresponding gem-difluorinated

Five-component, one-pot synthesis of an electroactive rotaxane comprising a bisferrocene macrocycle

• Natalie Lagesse,
• Luca Pisciottani,
• Maxime Douarre,
• Pascale Godard,
• Brice Kauffmann,
• Vicente Martí-Centelles and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2020, 16, 1564–1571, doi:10.3762/bjoc.16.128

• -containing rotaxane 1a was studied by cyclic voltammetry in CH2Cl2/CH3CN 1:5 (v/v) using a three-electrode cell, with a glassy carbon working electrode, a silver wire counter electrode and an Ag/AgCl (3 M KCl) reference electrode. Tetrabutylammonium hexafluorophosphate was used as the supporting electrolyte

• -electrode cell, with a glassy carbon working electrode, a silver wire counter electrode, and an Ag/AgCl (3 M KCl) reference electrode. The rotaxane 1a (4.0 mg) was dissolved in dry dichloromethane (0.8 mL), sonicated for 5 min then diluted in acetonitrile (4 mL) to give a final concentration of 0.67 mM

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

• radical that did not undergo decomposition and dimerization in the solution for a time sufficient to use it as a reagent was the di-tert-butyliminoxyl radical (8) [45][59]. It was obtained by oxidation of di-tert-butyl ketoxime (1f) with silver(I) oxide (Ag2O) in benzene at 25 °C (Scheme 2). This radical

• intermediate 83 proceeds in the presence of a base (Scheme 31). Oxidation of 83 with silver(I) affords the iminoxyl radical 84, which undergoes cyclization to form 85. Subsequent oxidation leads to intermediate 86, which is deprotonated to form the final product 82. A convenient method for the synthesis of

Synthesis and properties of quinazoline-based versatile exciplex-forming compounds

• Rasa Keruckiene,
• Simona Vekteryte,
• Ervinas Urbonas,
• Matas Guzauskas,
• Eigirdas Skuodis,
• Dmytro Volyniuk and
• Juozas V. Grazulevicius

Beilstein J. Org. Chem. 2020, 16, 1142–1153, doi:10.3762/bjoc.16.101

• carried out for the solutions in dry dichloromethane containing 0.1 M tetrabutylammonium hexafluorophosphate at 25 °C; the scan rate was 50 mV/s while the sample concentration was 10−3 M. The potentials were measured against silver as a reference electrode. A platinum wire was used as a counter electrode

Synthesis of novel multifunctional carbazole-based molecules and their thermal, electrochemical and optical properties

• Nuray Altinolcek,
• Ahmet Battal,
• Mustafa Tavasli,
• William J. Peveler,
• Holly A. Yu and
• Peter J. Skabara

Beilstein J. Org. Chem. 2020, 16, 1066–1074, doi:10.3762/bjoc.16.93

• tetrabutylammonium hexafluorophosphate as the electrolyte (Figure 2). A platinum disk was used as a working electrode, silver wire as the reference electrode and platinum wire as the counter electrode. The ferrocene-ferrocenium redox couple was used as an internal reference. At positive potentials, compounds 7a and

Aryl-substituted acridanes as hosts for TADF-based OLEDs

• Naveen Masimukku,
• Dalius Gudeika,
• Oleksandr Bezvikonnyi,
• Ihor Syvorotka,
• Rasa Keruckiene,
• Dmytro Volyniuk and
• Juozas V. Grazulevicius

Beilstein J. Org. Chem. 2020, 16, 989–1000, doi:10.3762/bjoc.16.88

• -electrode cell consisting of a platinum coil as counter electrode, a glassy carbon working electrode, and a silver wire as reference electrode was used; sweep rate – 100 mV/s, 0.1 M solution of tetrabutylammonium hexafluorophosphate (n-Bu4NPF6)) and b) photoelectron emission spectra of the layers of

Cation-induced ring-opening and oxidation reaction of photoreluctant spirooxazine–quinolizinium conjugates

• Phil M. Pithan,
• Sören Steup and
• Heiko Ihmels

Beilstein J. Org. Chem. 2020, 16, 904–916, doi:10.3762/bjoc.16.82

• silver(I) or gold(III) ions, the spironaphthoxazine 1aSO or the corresponding 5-chloro-substituted analog underwent thermal–oxidative degradation even under an inert gas atmosphere in the dark [74][75]. Based on the formation of silver or gold nanoparticles during the reaction, the authors proposed a two

Bipyrrole boomerangs via Pd-mediated tandem cyclization–oxygenation. Controlling reaction selectivity and electronic properties

• Liliia Moshniaha,
• Marika Żyła-Karwowska,
• Joanna Cybińska,
• Piotr J. Chmielewski,
• Ludovic Favereau and
• Marcin Stępień

Beilstein J. Org. Chem. 2020, 16, 895–903, doi:10.3762/bjoc.16.81

• (NDA) and naphthalenemonoimide (NMI) moieties. The double C–H bond activation initially used palladium(II) acetate in acetic acid as the coupling system. The subsequent screening revealed, however, that a catalytic coupling could be also achieved in the presence of silver(I) carbonate as the

• that the coupling and α-oxygenation can also be achieved with 1 equiv of Pd(OAc)2 in the presence of 2 equiv of silver carbonate. Nevertheless, Ag2CO3 oxidation provided lower yields and the efficiency of this variant was dramatically diminished when the loading of palladium(II) acetate was decreased

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• plastics [26][27][28][29][30][31] represent some practical examples. Nevertheless, cyanines have held a long history regarding their practical use, which started to use such materials as sensitizers in silver halide photography [32][33][34] until the point when electronic media took their place in imaging

• sciences to save pictures. Many fundamental knowledge was grown up in this period as shown for example by several reviews [35][36][37][38][39][40]. Particularly, the use of model systems and the knowledge obtained by exploration systems in silver halide photography [32][33][34][41][42][43][44][45] also

Room-temperature Pd/Ag direct arylation enabled by a radical pathway

• Amy L. Mayhugh and
• Christine K. Luscombe

Beilstein J. Org. Chem. 2020, 16, 384–390, doi:10.3762/bjoc.16.36

• incorporations of nitrobenzene into the polymer chains. The 2-nitrobenzoic acid used to form a silver carboxylate in the reaction system is the origin of the nitrophenyl group. Three different types of chains are represented, corresponding to incorporation of I/nitrophenyl, H/nitrophenyl, and two nitrophenyl end

• reported for decarboxylative coupling between indole and 2-nitrobenzoic acids at 110 °C [18]. Under such conditions, silver carboxylates decompose to produce carbonyl and phenyl radicals, which could explain the origin of nitrobenzene incorporation [19][20]. When the radical trapping agent BHT was added to

• to form hybrid palladium-radical intermediate 5. This carbon-centered radical can then add to the indole. From here, three different pathways to rearomatize 7 are possible, eventually affording the arylated product 10. Pd(0) can be regenerated by a base; in this case, the silver carboxylate. This

Copper-promoted/copper-catalyzed trifluoromethylselenolation reactions

• Clément Ghiazza and
• Anis Tlili

Beilstein J. Org. Chem. 2020, 16, 305–316, doi:10.3762/bjoc.16.30

• tandem formation of C–Se and Se–fluoroalkyl bonds have emerged in the last five years. In 2014, Hor and Weng reported the trifluoromethylselenolation of (hetero)aryl iodides and alkyl bromides with the Ruppert–Prakash reagent, TMSCF3, elemental selenium, potassium fluoride, and silver carbonate under

• copper catalysis (Scheme 15, conditions I) [39]. Mechanistically, the authors proposed the formation of a silver(I)–SeCF3 adduct, followed by a transmetallation step, yielding the active CuSeCF3 species. Good to very good yields were obtained on a broad scope, including amide-, ester-, and heterocycle

Halogen-bonding-induced diverse aggregation of 4,5-diiodo-1,2,3-triazolium salts with different anions

• Xingyu Xu,
• Shiqing Huang,
• Zengyu Zhang,
• Lei Cao and
• Xiaoyu Yan

Beilstein J. Org. Chem. 2020, 16, 78–87, doi:10.3762/bjoc.16.10

• and the solution stirred in a glove box in the dark for 6 h. Then AgI was removed by filtration and the solution was washed with water (10 mL) to remove the excess of silver. The pure product was obtained by evaporation of dichloromethane solution (176 mg, 92%). 1H NMR (400 MHz, CDCl3) δ 7.00 (s, 4H

• (5 mL) to remove the excess of silver. The pure product was obtained by evaporation of the dichloromethane solution (125 mg, 53%). 1H NMR (400 MHz, CDCl3) δ 7.08 (s, 4H), 2.40 (s, 6H), 2.00 (s, 12H); 13C NMR (100 MHz, CDCl3) δ 161.0 (q, J = 35.0 Hz), 143.3, 134.2, 131.9, 130.2, 116.5 (q, J = 297.2 Hz

Iodine-mediated hydration of alkynes on keto-functionalized scaffolds: mechanistic insight and the regiospecific hydration of internal alkynes

• Zachary Lee,
• Brandon R. Jones,
• Nyochembeng Nkengbeza,
• Michael Phillips,
• Kayla Valentine,
• Alexis Stewart,
• Brandon Sellers,
• Nicholas Shuber and
• Karelle S. Aiken

Beilstein J. Org. Chem. 2019, 15, 2747–2752, doi:10.3762/bjoc.15.265

• (II) [7], silver(I) [8], and gold(I)/(III) [9][10][11][12]. While less toxic than mercury, such catalysts are still environmental hazards and tend to be costlier [13][14]. The iodine-mediated hydration described herein is a viable solution to these issues [15][16]. This metal-free method produces

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• mixture during the electroreduction of acetophenone on a mercury cathode induces optical activity in the product (alcohol 24a, Scheme 7) [29]. Additionally, pinacol (23) was also obtained via dimerization along with chiral alcohols. The same method was reinvestigated by Wang and Lu in 2013 using a silver

• following publication [36]. The same group, in 2014, published two concomitant reports on the synthesis of metallo-organic hybrid materials by means of entrapment of alkaloids within silver particles [37][38]. They further used this organically doped metal as cathode for the enantioselective

• asymmetric electrocarboxylation of 4-methylpropiophenone. Enantioselective hydrogenation of methyl benzoylformate using an alkaloid entrapped silver cathode. Alkaloid-induced enantioselective hydrogenation using a Cu nanoparticle cathode. Alkaloid-induced enantioselective hydrogenation of aromatic ketones

AgNTf₂-catalyzed formal [3 + 2] cycloaddition of ynamides with unprotected isoxazol-5-amines: efficient access to functionalized 5-amino-1H-pyrrole-3-carboxamide derivatives

• Ziping Cao,
• Jiekun Zhu,
• Li Liu,
• Yuanling Pang,
• Laijin Tian,
• Xuejun Sun and
• Xin Meng

Beilstein J. Org. Chem. 2019, 15, 2623–2630, doi:10.3762/bjoc.15.255

• derivatives can be obtained in up to 99% yield. The reaction mechanism might involve the generation of an unusual α-imino silver carbene intermediate (or a silver-stabilized carbocation) and subsequent cyclization/isomerization to build the significant pyrrole-3-carboxamide motif. The reaction features the

• use of an inexpensive catalyst, simple reaction conditions, simple work-up without column chromatographic purification for most of products and high yields. Keywords: [3 + 2] cycloaddition; isoxazole; pyrrole; silver catalysis; ynamide; Introduction Silver-catalyzed transformations of alkynes have

• attracted much attention over the past decade [1][2]. As a powerful π-activator, silver can promote various reactions of alkynes in high efficiencies [3][4][5][6][7][8]. Generally speaking, the proceeding of these reactions involves the activation of alkyne bond by coordination of [Ag] and then the

Formation of alkyne-bridged ferrocenophanes using ring-closing alkyne metathesis on 1,1’-diacetylenic ferrocenes

• Celine Bittner,
• Dirk Bockfeld and
• Matthias Tamm

Beilstein J. Org. Chem. 2019, 15, 2534–2543, doi:10.3762/bjoc.15.246

• with high yields whilst giving full conversion of the terminal alkynes. Furthermore, the solvent-dependant reactivity of 2a towards Ag(SbF6) is investigated, leading to oxidation and formation of the ferrocenium hexafluoroantimonate 4 in dichloromethane, whereas the silver(I) coordination polymer 5 was

• potentials recorded for the Ag+/Ag couple, which are strongly solvent dependent and vary from 0.04 V in acetonitrile to 0.65 V in DCM [98]. Therefore, oxidation should occur in the latter solvent, while silver(I) complexation could be expected in more coordinating solvents. Consequently, addition of a

• solution of Ag(SbF6) (1 equiv) in DCM to a solution of 2a in DCM resulted in an immediate colour change from orange to dark green alongside with precipitation of a black solid, indicating the formation of elemental silver. A dark solid was isolated after filtration and evaporation of the solvent

Experimental and computational electrochemistry of quinazolinespirohexadienone molecular switches – differential electrochromic vs photochromic behavior

• Eric W. Webb,
• Jonathan P. Moerdyk,
• Kyndra B. Sluiter,
• Benjamin J. Pollock,
• Amy L. Speelman,
• Eugene J. Lynch,
• William F. Polik and
• Jason G. Gillmore

Beilstein J. Org. Chem. 2019, 15, 2473–2485, doi:10.3762/bjoc.15.240

• nitrogen-purged MBraun MBS-SPS 07-299 solvent purification system) or highest anhydrous grade (used as received). Acetonitrile-d3 and acetone-d6 were used as received in 1 g ampules (Cambridge Isotope Labs). Ferrocene, tetrabutylammonioum hexafluorophosphate (TBAH), and silver nitrate were of

• inserted through a pinhole in the septum for an argon purge and vent. The setup used a CHI112 nonaqueous Ag/AgNO3 reference electrode. The auxiliary electrode was formed by removing the silver wire from a CHI112 nonaqueous reference electrode and replacing it with a rolled 7 × 70 mm piece of platinum mesh

Self-assembled coordination thioether silver(I) macrocyclic complexes for homogeneous catalysis

• Zhen Cao,
• Aline Lacoudre,
• Cybille Rossy and
• Brigitte Bibal

Beilstein J. Org. Chem. 2019, 15, 2465–2472, doi:10.3762/bjoc.15.239

• -atropisomer, as revealed by X-ray diffraction. This alkylaryl thioether ligand (L) formed different macrocyclic complexes by coordination with silver(I) salts depending on the nature of the anion: M2L2 for AgOTf and AgOTFA, M6L4 for AgNO3. A discrete M2L complex was obtained in the presence of bulky PPh3AgOTf

• . These silver(I) complexes adopted similar structures in solution and in the solid state. As each sulfur atom in the ligand is prochiral, macrocycles L2M2 were obtained as mixtures of diastereoisomers, depending on the configurations of the sulfur atoms coordinated to silver cations. The X-ray structures

• of the two L2·(AgOTf)2 stereoisomers highlighted their different geometry. The catalytic activity of all silver(I) complexes was effective under homogeneous conditions in two tandem addition/cycloisomerization of alkynes using 0.5–1 mol % of catalytic loading. Keywords: coordination macrocycle

Small anion-assisted electrochemical potential splitting in a new series of bistriarylamine derivatives: organic mixed valency across a urea bridge and zwitterionization

• Keishiro Tahara,
• Tetsufumi Nakakita,
• Alyona A. Starikova,
• Takashi Ikeda,
• Masaaki Abe and
• Jun-ichi Kikuchi

Beilstein J. Org. Chem. 2019, 15, 2277–2286, doi:10.3762/bjoc.15.220

• . Such N–H···F hydrogen-bond formation was also reported for other urea derivatives with PF6− as counteranion in the solid state [54][55]. The N···F distance of 2.85 Å in 1b+–PF6− is slightly longer than that observed in the crystal structure of a silver complex having a pyridyl urea ligand (2.67 and

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• different catalysts, such as palladium, copper, silver, iron, nickel, ruthenium, cobalt, etc. Palladium catalysis Palladium is a member of the nickel triad in the periodic table, and palladium complexes exist in three oxidation states, Pd(0), Pd(II), and Pd(IV). Straightforward interconversion between

• (III)–F species. Other catalysts Other transition metals, including Co, Ni, Fe, Ag, Ir, Mn, etc., have received more and more attention. Aliphatic and benzylic C–H fluorination and decarboxylative fluorination: In 2012, a silver-catalyzed radical decarboxylative fluorination of aliphatic carboxylic

• ) [138]. The process proceeded smoothly to give the trifluoromethylated alkenes in good to excellent yields via a radical mechanism. Additionally, Duan and co-workers [139] discovered a copper/silver-catalyzed decarboxylative trifluoromethylation of α,β-unsaturated carboxylic acids with CF3SO2Na. This

Attempted synthesis of a meta-metalated calix[4]arene

• Christopher D. Jurisch and
• Gareth E. Arnott

Beilstein J. Org. Chem. 2019, 15, 1996–2002, doi:10.3762/bjoc.15.195

• , followed by metalation of the triazolium salt 4 with silver oxide, which was immediately transmetalated with [RuCl2(p-cymene)]2. In our hands, purification using Albrecht’s trituration method was unsuccessful, however, neutral alumina column chromatography produced the desired model ruthenium metallocycle

• may create a far too sterically congested environment. Practically, we could observe the successful formation of the silver(I) intermediate via TLC analysis, and then also the putative ruthenacycle as well. After following Albrecht’s trituration method for purification, the 1H NMR spectrum revealed