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

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

A novel three-component reaction between isocyanides, alcohols or thiols and elemental sulfur: a mild, catalyst-free approach towards O-thiocarbamates and dithiocarbamates

• András György Németh,
• György Miklós Keserű and
• Péter Ábrányi-Balogh

Beilstein J. Org. Chem. 2019, 15, 1523–1533, doi:10.3762/bjoc.15.155

• as enzyme inhibitors [26] or antitumor agents [27]. These species are also used as valuable synthetic intermediates [28] and chemosensors for mercury and silver [29][30]. The general methods for the synthesis of O-thiocarbamates and dithiocarbamates traditionally rely on substitution reactions of the

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• Heck cyclization reaction between the substituted alkyne and aryl bromide in 133 takes place to form a cyclic palladium intermediate 134 with E-configuration, resulting from a syn-addition mechanism of this step. The addition of a silver salt reduces the probability of isomerization of the double bond

Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors

• Kirill B. Polyanskii,
• Kseniia A. Alekseeva,
• Pavel V. Raspertov,
• Pavel A. Kumandin,
• Eugeniya V. Nikitina,
• Atash V. Gurbanov and
• Fedor I. Zubkov

Beilstein J. Org. Chem. 2019, 15, 769–779, doi:10.3762/bjoc.15.73

• methods have been reported for the synthesis of 2-(N,N-dialkylaminomethyl)styrenes [39][40][41][42][43][44][45][46] relying on different approaches: i) from o-vinylbenzyl chloride [43], ii) by the Hofmann cleavage of quaternary tetrahydroisoquinoline salts under the action of silver oxide [39][42] and iii

Synthesis of 2H-furo[2,3-c]pyrazole ring systems through silver(I) ion-mediated ring-closure reaction

• Vaida Milišiūnaitė,
• Rūta Paulavičiūtė,
• Eglė Arbačiauskienė,
• Vytas Martynaitis,
• Wolfgang Holzer and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2019, 15, 679–684, doi:10.3762/bjoc.15.62

• and efficient procedure to access the 2H-furo[2,3-c]pyrazole ring system was developed by employing the silver(I) ion-mediated ring-closure reaction of 4-alkynyl-3-hydroxy-1-phenyl-1H-pyrazoles as a key step. The required intermediate hydroxyalkynyl substrates for this reaction were prepared by a Pd

• -catalyzed coupling of 4-iodo-1-phenyl-1H-pyrazol-3-ol with ethyne derivatives. The structures of the obtained target compounds were unequivocally confirmed by detailed 1H, 13C and 15N NMR spectroscopic experiments, HRMS and a single-crystal X-ray diffraction analyses. This silver(I)-mediated 5-endo-dig

• cyclization of readily available 4-alkynyl-3-hydroxy-1H-pyrazoles can be used as an efficient method to access many novel 2,5-disubstituted 2H-furo[2,3-c]pyrazoles. Keywords: 5-endo-dig cyclization; 2H-furo[2,3-c]pyrazole; pyrazole; silver(I) catalyst; Sonogashira coupling; Introduction Heterocyclic ring

The LANCA three-component reaction to highly substituted β-ketoenamides – versatile intermediates for the synthesis of functionalized pyridine, pyrimidine, oxazole and quinoxaline derivatives

• Tilman Lechel,
• Roopender Kumar,
• Mrinal K. Bera,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2019, 15, 655–678, doi:10.3762/bjoc.15.61

• , who treated pivalonitrile (1) with lithiated methoxyallene 2 and isolated the expected primary addition product 3 [21]. This intermediate was subjected to different cyclization conditions (Scheme 1) and the desired pyrrole derivative 4 was produced under specific conditions employing silver nitrate as

Low-budget 3D-printed equipment for continuous flow reactions

• Jochen M. Neumaier,
• Amiera Madani,
• Thomas Klein and
• Thomas Ziegler

Beilstein J. Org. Chem. 2019, 15, 558–566, doi:10.3762/bjoc.15.50

• preparing acetobromo glycoses. In order to show the suitability of our flow system for the preparation of simple glycosides, we first tested Koenigs–Knorr glycosylation conditions with silver triflate as activator. Thus, silver triflate (2 equiv) was mixed with molecular sieves (4 Å) and placed in a packed

• ]. Unfortunately, the synthetic steps for the glycoside preparation could not be combined in a multistep reaction, due to clogging of the packed bed reactor, most likely due to the formation of silver bromide during the Koenigs–Knorr reaction. No such clogging was observed when the column was packed with Fetizon’s

• synthesis of acetobromo-α-D-glucose 2. b) Photograph of a typical setting for continuous flow reaction. Preparation of acetobromo-α-D-glucose 2. Flow Koenigs–Knorr reaction to methyl glycoside 3 with silver triflate. Preparation of glycosyl donor 5. Two-step glycosylation reactions starting from pyranose 3

Tandem copper and photoredox catalysis in photocatalytic alkene difunctionalization reactions

• Nicholas L. Reed,
• Madeline I. Herman,
• Vladimir P. Miltchev and
• Tehshik P. Yoon

Beilstein J. Org. Chem. 2019, 15, 351–356, doi:10.3762/bjoc.15.30

• of the oxidants screened, silver(I) salts were found to be uniquely effective at mediating turnover of the copper(II) catalyst [34][35][36]. After screening commercially available silver(I) salts, Ag2CO3 was found to be the optimal terminal oxidant (Table 1, entry 5). There is a competitive silver

• -mediated photodecomposition process that consumes the starting alkene unproductively, and thus the copper(II)/silver(I) ratio was tuned to optimize the efficiency of the desired oxyamination process (Table 1, entries 5–7). Optimal conditions were found to be 2.5 mol % TPPT, 30 mol % Cu(TFA)2, and 1 equiv

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• indole moiety to afford the target product 64 along with the regenerated Rh(III) catalyst. A silver-catalyzed intramolecular cascade amination/ring-opening/cyclization of a variety of substituted MCPs 69 was proposed by Fan and co-workers, which provided a simple and efficient way for the building of

• . Notably, this finding was the first example for silver-catalyzed regioselective C2-alkylation of heterorarenes with primary alkyl radicals, generated from cyclopropanols through a radical ring-opening process. Lopp’s group also reported an efficient approach for copper-catalyzed ring-opening and

• scope under mild conditions. Surprisingly, four- and five-membered cycloalkanols were suitable in this system. In 2015, Zhu’s group developed the silver-catalyzed ring-opening of cycloalkanols 91 with NCS 118 for the synthesis of distally chlorinated ketones 119 (Scheme 28) [108]. The reaction was

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

• give dimethyl ester 98 (Scheme 25). Silver oxide-promoted methylation introduces a MeO-C4 unit. Regioselective aziridine ring opening in 99 was then carried out in the known way with benzyl alcohol or methanol to produce substituted dimethyl L-glutamates 100 and 101. To ensure clean deprotection in the

Gold-catalyzed ethylene cyclopropanation

• Silvia G. Rull,
• Andrea Olmos and
• Pedro J. Pérez

Beilstein J. Org. Chem. 2019, 15, 67–71, doi:10.3762/bjoc.15.7

• development of a catalytic route for cyclopropane 1, we have not invested efforts in the characterization of such materials. The silver complex Tp(CF3)2,BrAg(thf) [19] (Table 1, entry 3) was not effective toward the aforementioned target, since only 5% of 1 was formed. In this case, the product derived from

• the insertion of the carbene CHCO2Et group into the C–Cl of the solvent was the major one, accordingly with previous work from this and other laboratories using silver-based catalysts [20][21]. Therefore, we moved onto gold-based catalysts that had already been validated for EDA decomposition and

• the solvent (4) constituted the main transformation. This is probably the effect of the silver in the reaction medium, since simple silver salts promote such reaction. The use of NaBArF4 delivered ethyl cyclopropanecarboxylate (1) in 62% yield, with only 2% of olefins 2 as byproducts, the remaining 36

Gold-catalyzed post-Ugi alkyne hydroarylation for the synthesis of 2-quinolones

• Xiaochen Du,
• Jianjun Huang,
• Anton A. Nechaev,
• Ruwei Yao,
• Jing Gong,
• Erik V. Van der Eycken,
• Olga P. Pereshivko and
• Vsevolod A. Peshkov

Beilstein J. Org. Chem. 2018, 14, 2572–2579, doi:10.3762/bjoc.14.234

• ). Conducting the AuPPh3Cl/AgOTf-catalyzed reaction in trifluoroethanol (TFE) led to improved results producing 8a in up to 97% yield (Table 1, entry 6). Thus, this greener alternative [63] to chlorinated solvents was selected as the solvent of choice for the further exploration. Changing the silver counterpart

Practical tetrafluoroethylene fragment installation through a coupling reaction of (1,1,2,2-tetrafluorobut-3-en-1-yl)zinc bromide with various electrophiles

• Ken Tamamoto,
• Shigeyuki Yamada and
• Tsutomu Konno

Beilstein J. Org. Chem. 2018, 14, 2375–2383, doi:10.3762/bjoc.14.213

• Ken Tamamoto Shigeyuki Yamada Tsutomu Konno Faculty of Molecular Chemistry and Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan 10.3762/bjoc.14.213 Abstract (1,1,2,2-Tetrafluorobut-3-en-1-yl)zinc bromide was prepared by insertion of the zinc–silver couple

• quantitatively recovered (Table 1, entry 1). Interestingly, when a zinc–silver couple Zn(Ag) [34] was employed instead of zinc powder, the desired zinc insertion took place very smoothly to form the desired (1,1,2,2-tetrafluorobut-3-en-1-yl)zinc bromide (2-Zn) in 86% NMR yield, along with a small amount of a

Coordination-driven self-assembly of discrete Ru₆–Pt₆ prismatic cages

• Aderonke Ajibola Adeyemo and
• Partha Sarathi Mukherjee

Beilstein J. Org. Chem. 2018, 14, 2242–2249, doi:10.3762/bjoc.14.199

• silver nitrate in methanol at room temperature for 3 hours gave the dinuclear arene–ruthenium(II) clips 1a,1b(NO3)2. As represented in Scheme 1, the self-assembly reactions of methanolic solutions of 1a,1b(NO3)2 and methanolic solution of the triplatinum metalloligand 2 at room temperature yielded the

Cobalt-catalyzed peri-selective alkoxylation of 1-naphthylamine derivatives

• Jiao-Na Han,
• Cong Du,
• Xinju Zhu,
• Zheng-Long Wang,
• Yue Zhu,
• Zhao-Yang Chu,
• Jun-Long Niu and
• Mao-Ping Song

Beilstein J. Org. Chem. 2018, 14, 2090–2097, doi:10.3762/bjoc.14.183

• previous literature [30][31][46][47], a plausible reaction mechanism for cobalt-catalyzed alkoxylation was proposed. As shown in Scheme 4, initially, CoIIX2 could be oxidized to CoIIIX2OR in the presence of a silver salt and an alcohol. Based on the experiments and the density functional theory

Preparation and X-ray structure of 2-iodoxybenzenesulfonic acid (IBS) – a powerful hypervalent iodine(V) oxidant

• Irina A. Mironova,
• Pavel S. Postnikov,
• Rosa Y. Yusubova,
• Akira Yoshimura,
• Thomas Wirth,
• Viktor V. Zhdankin,
• Victor N. Nemykin and
• Mekhman S. Yusubov

Beilstein J. Org. Chem. 2018, 14, 1854–1858, doi:10.3762/bjoc.14.159

• selectively affords the respective iodine(V) product after heating at 60 °C for 16 h with almost quantitative conversion. The aqueous solution containing IBS-Na (as sodium salt) and inorganic products resulting from the reduction of NaIO4 was treated with silver nitrate to precipitate I– and IO3– anions. The

• precipitate of silver salts was filtered off, and the mother liquor was concentrated using blowing air to about half of the initial volume. The concentrated aqueous solution was left for several days resulting in the formation of a microcrystalline precipitate of IBS-Na isolated in 61% yield. 1H and 13C NMR

Investigations of alkynylbenziodoxole derivatives for radical alkynylations in photoredox catalysis

• Yue Pan,
• Kunfang Jia,
• Yali Chen and
• Yiyun Chen

Beilstein J. Org. Chem. 2018, 14, 1215–1221, doi:10.3762/bjoc.14.103

• group first used alkynylbenziodoxoles for decarboxylative radical alkynylation under silver salt and persulfate conditions [19]. In 2014, the Chen group discovered that alkynylbenziodoxoles (BI-alkyne) readily participated in photoredox catalysis as the radical alkynylation reagent [20], after which

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

• method for the synthesis of 2-bromobenzotropone 26 starting from dihydronaphthalene (322) was also realized by Balci’s group (Scheme 54) [188]. After addition of dibromocarbene to 322, the obtained dibromocyclopropane 323 was submitted to silver ion-catalyzed ring expansion/hydrolysis in aqueous acetone