Copper-catalyzed monoselective C–H amination of ferrocenes with alkylamines

• Zhen-Sheng Jia,
• Qiang Yue,
• Ya Li,
• Xue-Tao Xu,
• Kun Zhang and
• Bing-Feng Shi

Beilstein J. Org. Chem. 2021, 17, 2488–2495, doi:10.3762/bjoc.17.165

• Fukuzawa and Kanemoto [50]. Notably, our method proceeded under silver-free conditions at relatively lower temperature and in shorter time, providing a complementary alternative to the work of Fukuzawa and Kanemoto. Results and Discussion We initiated our study by investigating the C–H amination of

Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

• Yi Liu,
• Puying Luo,
• Yang Fu,
• Tianxin Hao,
• Xuan Liu,
• Qiuping Ding and
• Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

• -annulation of (E)-2-en-4-ynyl azides 1 was considered to involve 6-endo-dig cyclization to give a corresponding N-N2-substituted 1,2-dihydropyridine silver salt 5. This was protonated by TFA and the following species neutralized by base to provide a final 3,6-disubstituted pyridine product 2 (Scheme 2

• yield. Aliphatic amines were also tolerated, providing the desired products in only moderate yield. The plausible mechanism involves a tandem base-promoted aza-Michael addition, 1,2-iodocyclization, and iodine-mediated oxidative aromatization. In 2017, Zhang and co-workers reported a silver-catalyzed

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• vinylmercury intermediate (Scheme 55). For the synthesis of stereoselective tetrahydropyran derivatives 184, Hg(II)-catalyzed cyclization proved to be more effective than silver(I)-salt-mediated cyclization. It showed that methyl-substituted allenes undergo efficient cyclization to form polycyclic ethers under

Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• often requires relatively high catalyst loadings, directing groups, high reaction temperatures (100–160 °C), stoichiometric additives, or oxidants such as peroxide or silver salts that can be undesirable for large scale synthesis. Recently, photoredox dual catalysis has witnessed significant

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• -workers reported a one-pot synthesis of substituted anthracenes 37 from o-tolualdehyde 34 and aryl iodides 35 via a palladium-catalyzed C–H arylation with a silver oxidant (Scheme 8) [42]. During optimization studies, the authors noted that steric and electronic effects strongly affected the cyclization

Asymmetric organocatalyzed synthesis of coumarin derivatives

• Natália M. Moreira,
• Lorena S. R. Martelli and
• Arlene G. Corrêa

Beilstein J. Org. Chem. 2021, 17, 1952–1980, doi:10.3762/bjoc.17.128

• stereoselective one-pot procedure for the synthesis of five-membered annulated coumarins 28 was described by the group of Enders [40]. Using dual catalysis, with a cinchona primary amine derivative 22 and silver carbonate, a series of functionalized coumarin derivatives 28 were obtained in good yields (up to 91

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• further demonstrated by the hydroalkylation of the anti-inflammatory drug phenylbutazone (7j). Gold(I)/gold(III) and silver(I) catalysis in olefin hydroalkylation The early limitations associated with Pd catalysis in olefin hydroalkylation reactions prompted the search for alternative metals for olefin

• changing the previously optimized mild reaction conditions (Scheme 6). Only traces of 10 were observed in the absence of one of the metal salts; this excluded the participation of the silver salt in the olefin activation but highlighted its usual role in the activation of the gold catalyst, namely halide

• abstraction, to form a gold complex with a less coordinating ligand that serves as the active catalyst [39]. Following their initial work, the Li group investigated the use of silver triflate as the sole catalyst in the olefin hydroalkylation [40]. In their previous work, they had reported that neither the

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• -up report of the Miyaura group in 2007 provided an experimental protocol that allowed the addition of arylboronic acids instead of aryltrifluoroborates [34]. The previously used catalysts PdL1a,b were combined with additional silver salts (AgBF4 or AgSbF6) that greatly accelerated the transmetalation

• ][65][66][67]. Flowchart for the selection of the proper catalytic system. First example of asymmetric addition of organoboron reagents to cyclic enones [32][33]. Addition of arylboronic acids to enones accelerated by silver salts [34][35]. Synthesis of chromenes by the 1,4-addition of boronic acids to

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• the synthesized products by changing the classical recovery using silver oxide to simple alkali treatment. A number of different biguanides have been synthesized using this methodology with cleaner conversion and higher satisfactory yields (Scheme 5). Despite high temperature and sometimes long

• except for one single use of silver dicyanamide [65]. Further investigations in this direction might help to soften the conditions and improve the yields. An interesting reactivity was reported with subsequent SEAr cyclization or 1,2,4-oxadiazole formation. However, these applications seem sparse with

Beyond ribose and phosphate: Selected nucleic acid modifications for structure–function investigations and therapeutic applications

• Christopher Liczner,
• Kieran Duke,
• Gabrielle Juneau,
• Martin Egli and
• Christopher J. Wilds

Beilstein J. Org. Chem. 2021, 17, 908–931, doi:10.3762/bjoc.17.76

• ) (TIPDS) protected uridine, protection of N3 was needed in order to prevent methylation at this position (Scheme 4). The N3-benzoylated derivative could then be treated with methyl iodide in the presence of silver oxide in order to methylate the 2'-OH. A similar strategy was employed to synthesize 3',5'-O

• iodide and silver oxide. The protected adenine base was regenerated by treatment with ammonia followed by benzoylation. Once the methyl group was incorporated into these ribonucleosides, the TIPDS group was selectively removed by tetrabutylammonium fluoride (TBAF) or hydrochloric acid treatment, followed

Synthesis and properties of oligonucleotides modified with an N-methylguanidine-bridged nucleic acid (GuNA[Me]) bearing adenine, guanine, or 5-methylcytosine nucleobases

• Naohiro Horie,
• Takao Yamaguchi,
• Shinji Kumagai and
• Satoshi Obika

Beilstein J. Org. Chem. 2021, 17, 622–629, doi:10.3762/bjoc.17.54

• '-dimethylisothiourea (271 mg, 1.84 mmol), anhydrous THF (12 mL) was added and the mixture placed in an ice bath under stirring. Subsequently, N,N-diisopropylethylamine (0.35 mL, 2.0 mmol) and silver triflate (507 mg, 1.97 mmol) were added, and the mixture was stirred at room temperature overnight. Upon completion of

• an ice bath under stirring. Subsequently, N,N-diisopropylethylamine (0.57 mL, 3.3 mmol) and silver triflate (835 mg, 3.25 mmol) were added, and the mixture was stirred at room temperature for 2 h. Upon completion of the reaction, the mixture was diluted with ethyl acetate and washed with sat. aq

• the mixture placed in an ice bath under stirring. Subsequently, N,N-diisopropylethylamine (0.28 mL, 1.6 mmol) and silver triflate (411 mg, 1.60 mmol) were added, and the mixture was stirred at room temperature for 1 h. Upon completion of the reaction, the mixture was diluted with ethyl acetate, after

Synthesis of N-perfluoroalkyl-3,4-disubstituted pyrroles by rhodium-catalyzed transannulation of N-fluoroalkyl-1,2,3-triazoles with terminal alkynes

• Olga Bakhanovich,
• Viktor Khutorianskyi,
• Vladimir Motornov and
• Petr Beier

Beilstein J. Org. Chem. 2021, 17, 504–510, doi:10.3762/bjoc.17.44

• phenylacetylene leads to a mixture of 3,4-diphenylpyrrole 2a and 2,4-diphenylpyrrole 2a’. However, repeating the experiment without the silver catalyst afforded the same results showing that the silver catalyst was not necessary in our case and that the product regioselectivity was not dependent on the silver

• of the rhodium-catalyzed transannulation to pyrroles has recently been investigated computationally with N-sulfonyltriazoles [31]. It seems that the formed rhodium carbenoid B reacts with the alkyne in a concerted process and even in the presence of Ag+ salts, a nucleophilic addition of silver

• regioselectivities (87:13 to 98:2). This is the first report of a transannulation leading to 3,4-disubstituted pyrroles. Additionally, the method did not require the use of a silver(I) co-catalyst. The scope for aliphatic alkynes is reasonably wide and the isolated yields were moderate to good. A one-pot

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• -Trimethylsiloxy-2,2-difluorocyclopropanes 158 underwent a silver-promoted ring opening by the nucleophilic heteroaromatic 1,2-dimethylindole (159) to give aryl-substituted 2-fluoroalkenyl compounds 160a,b (Scheme 68) [118]. An initial fluoride abstraction by Ag+ triggered the distal C–C bond cleavage to form an

• different types of catalysts have proved effective in facilitating the ring opening of difluorocyclopropane derivatives. Lewis acids (e.g., group 13 halides and silver ions) can polarize carbonyl substituents and assist the loss of halide ions, leading to the formation of carbocation intermediates. Low

Au(III) complexes with tetradentate-cyclam-based ligands

• Ann Christin Reiersølmoen,
• Thomas N. Solvi and
• Anne Fiksdahl

Beilstein J. Org. Chem. 2021, 17, 186–192, doi:10.3762/bjoc.17.18

• showed no interaction with Au(III), as expected. A similar resistance to coordinate was observed for the open diamides 1c–e. The phosphorus containing ligand 1c did undergo phosphorus oxidation instead of Au(III) coordination. No effect was obtained by refluxing or by adding additives, such as silver

• and 12 hours for complex 6a-Au(III) (Table 1, entries 2 and 5), where the ligand seems to stabilize and deactivate the Au(III) during the reaction. Attempts to improve the 6b-Au(III) complex stability by anion exchange with less coordinating anions failed, as addition of different standard silver

Silver-catalyzed synthesis of β-fluorovinylphosphonates by phosphonofluorination of aromatic alkynes

• Yajing Zhang,
• Qingshan Tian,
• Guozhu Zhang and
• Dayong Zhang

Beilstein J. Org. Chem. 2020, 16, 3086–3092, doi:10.3762/bjoc.16.258

• 200032, P. R. China 10.3762/bjoc.16.258 Abstract A silver-catalyzed three-component reaction involving alkynes, Selectfluor®, and diethyl phosphite was employed for the one-pot formation of C(sp2)–F and C(sp2)–P bonds to provide an efficient access to β-fluorovinylphosphonates in a highly regio- and

• subsequent fluorine atom transfer. Keywords: β-fluorovinylphosphonates; fluorine atom transfer; P-centered radical; silver catalysis; three-component reaction; Introduction As one of the most important topics in organic chemistry, the introduction of fluorine and phosphorus atoms into double bonds is an

• others concerning the silver-catalyzed phosphonofluorination of alkenes [24][25][26], we herein present a general silver-catalyzed regio- and stereoselective phosphonofluorination of alkynes using Selectfluor® and phosphonates as reactants (Scheme 1). This new silver-catalyzed approach to fluorinated

Pentannulation of N-heterocycles by a tandem gold-catalyzed [3,3]-rearrangement/Nazarov reaction of propargyl ester derivatives: a computational study on the crucial role of the nitrogen atom

• Giovanna Zanella,
• Martina Petrović,
• Dina Scarpi,
• Ernesto G. Occhiato and
• Enrique Gómez-Bengoa

Beilstein J. Org. Chem. 2020, 16, 3059–3068, doi:10.3762/bjoc.16.255

• on the proton abstraction pathway. Several possible bases exist in the reaction medium, such as the counterion in the gold(I) salt, the anion participating in the silver salt coadditives, or water. In analogy to our previous work [16], we initially modelled the deprotonation step with the triflate

• AgOTf as the silver salt). Under both conditions, the reaction of 14 led to the formation of the cyclopentenone 15 in a lower yield (51% and 66%, respectively), and in comparison to the gold(I)-catalyzed reaction of the enynyl acetates 1, it was much slower with both catalytic systems (6–16 h vs 1.5–2 h

Controlled decomposition of SF₆ by electrochemical reduction

• Sébastien Bouvet,
• Bruce Pégot,
• Stéphane Sengmany,
• Erwan Le Gall,
• Eric Léonel,
• Anne-Marie Goncalves and
• Emmanuel Magnier

Beilstein J. Org. Chem. 2020, 16, 2948–2953, doi:10.3762/bjoc.16.244

• reactions were carried out in a single compartment with a conventional three-electrode arrangement: two platinum electrodes and one silver reference electrode, SRE (Figure 3). The electrolysis is performed at constant potential (−2.3 V vs Fc+/Fc) with a continuous supply of SF6 placed in a rubber balloon

• . All potentials were measured against a pseudo silver reference electrode (SRE). The addition of ferrocene in the electrolyte gives access to an internal reference [33]. In order to improve the current detection level of SF6, platinum disk electrodes were used as working electrode (Pt

• electrode (silver wire), 4: counter-electrode (platinum), 5: working electrode (platinum). Electrolysis of SF6 at −2.3 V vs Fc+/Fc in acetonitrile freshly distilled after addition of TBAClO4 (0.1 M) at room temperature under slight argon stream. (a) Exponential decrease of the cathodic current according to

Incorporation of a metal-mediated base pair into an ATP aptamer – using silver(I) ions to modulate aptamer function

• Marius H. Heddinga and
• Jens Müller

Beilstein J. Org. Chem. 2020, 16, 2870–2879, doi:10.3762/bjoc.16.236

• towards ATP is restored again. The silver(I)-mediated base-pair formation was particularly suitable to modulate the aptamer function when the Im:Im mispairs (and hence the resulting metal-mediated base pairs) were located close to the ATP-binding pocket of the aptamer. Being able to trigger the aptamer

Using multiple self-sorting for switching functions in discrete multicomponent systems

• Amit Ghosh and
• Michael Schmittel

Beilstein J. Org. Chem. 2020, 16, 2831–2853, doi:10.3762/bjoc.16.233

• innovative catch–release system with multiple functions combined the ON/OFF-adjustment of silver(I) catalysis and fluorescence monitoring [59]. Actually, the ratiometric luminescence response allowed the exact monitoring of the catalytic activity. In the initial incomplete self-sorting (state SelfSORT-I

• ), the silver(I) ions were tightly captured within the cavity of the triangular nanoswitch 35 (“catch”) while the luminophore 36 was left uncoordinated exhibiting emission at 554 nm (Figure 13). Due to the firm complexation of the silver(I) ions in [Ag(35)]+ any catalysis was switched OFF. Upon the

• addition of zinc(II), the silver(I) ions were translocated as a second messenger from the nanoswitch [Ag(35)]+ to the anthracene-appended crown ether 36 in a 2-fold completive self-sorting, i.e., furnishing [Zn(35)]2+ and [Ag(36)]+ (state SelfSORT-II). In this state, SelfSORT-II, the emission emerged at

Thermodynamic and electrochemical study of tailor-made crown ethers for redox-switchable (pseudo)rotaxanes

• Henrik Hupatz,
• Marius Gaedke,
• Hendrik V. Schröder,
• Julia Beerhues,
• Arto Valkonen,
• Fabian Klautzsch,
• Sebastian Müller,
• Felix Witte,
• Kari Rissanen,
• Biprajit Sarkar and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2020, 16, 2576–2588, doi:10.3762/bjoc.16.209

• spectroelectrochemical measurements (0.1 M n-Bu4PF6, CH2Cl2/CH3CN 1:1, 298 K) of a) NDIC7 (0.5 mM), b) NDIC8 (0.5 mM), and c) NDIRot (1 mM). Potentials are referenced against a silver wire pseudo-reference electrode. Schematic representation of synthetic routes towards TTFC7, exTTFC7, NDIC7, and NDIC8. Thermodynamic

Water-soluble host–guest complexes between fullerenes and a sugar-functionalized tribenzotriquinacene assembling to microspheres

• Si-Yuan Liu,
• Xin-Rui Wang,
• Man-Ping Li,
• Wen-Rong Xu and
• Dietmar Kuck

Beilstein J. Org. Chem. 2020, 16, 2551–2561, doi:10.3762/bjoc.16.207

• , white: H for TBTQ-(OG)6; silver grey: C for C60). SEM images of (a) C60; (b) TBTQ-(OG)6; (c) and (d) TBTQ-(OG)6 C60 (C60: 1.4 mM; TBTQ-(OG)6: 1.4 mM in water, samples were freeze-dried and gold-sputtered before imaging). Synthetic route to TBTQ-(OG)6. Supporting Information Supporting Information File

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• explained via the migration of the bromide ion followed by the aromatization of bromodienone compound 71 to the stable o-bromohydroxysumanene 72. Having compound 71 in hand, next it was treated with silver acetate in H2O/THF (1:1) to furnish compound 74. On the other hand, alcoholysis of the same compound

Efficient [(NHC)Au(NTf₂)]-catalyzed hydrohydrazidation of terminal and internal alkynes

• Maximillian Heidrich and
• Herbert Plenio

Beilstein J. Org. Chem. 2020, 16, 2080–2086, doi:10.3762/bjoc.16.175

• chromatography system. Synthesis of gold complex 1. To a solution of the (NHC)AuCl complex 1a (60 mg, 0.043 mmol, 1 equiv) in DCM (5 mL) silver bis(trifluoromethanesulfonyl)amide (18 mg, 0.043 mmol, 1 equiv) was added and the mixture was stirred at rt for 30 min. The formed suspension was filtered through a plug