Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

• rhodium-based catalysts and 5% of [Rh(CO)2Cl]2 were found to be the best catalyst loading (28% yield). The addition of a silver additive, to make the reaction quicker and to remove a CO ligand, appeared to be useless in this case, with no reaction, and the use of 50% dppp as ligand allowed the formation

Germacrene B – a central intermediate in sesquiterpene biosynthesis

• Houchao Xu and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2023, 19, 186–203, doi:10.3762/bjoc.19.18

• -workers [19], through a sequence of reduction to the alcohol, acetylation and reduction with lithium in ammonia (Scheme 3A) [20], and its structure was unambiguously assigned by X-ray crystallography of a silver nitrate adduct [21]. From natural sources, the compound was first obtained from Humulus

Catalytic aza-Nazarov cyclization reactions to access α-methylene-γ-lactam heterocycles

• Bilge Banu Yagci,
• Selin Ezgi Donmez,
• Onur Şahin and
• Yunus Emre Türkmen

Beilstein J. Org. Chem. 2023, 19, 66–77, doi:10.3762/bjoc.19.6

• the synthesis of tricyclic α-methylene-γ-lactams 7 as single diastereomers and in good to high yields through the use of a catalytic amount of AgOTf (silver trifluoromethanesulfonate) as an anion-exchange agent (Scheme 1d) [35]. In this transformation, treatment of 3,4-dihydroisoquinolines 5 with acyl

Formal total synthesis of macarpine via a Au(I)-catalyzed 6-endo-dig cycloisomerization strategy

• Jiayue Fu,
• Bingbing Li,
• Zefang Zhou,
• Maosheng Cheng,
• Lu Yang and
• Yongxiang Liu

Beilstein J. Org. Chem. 2022, 18, 1589–1595, doi:10.3762/bjoc.18.169

• ) itself failed to catalyze the cycloisomerization (Table 1, entry 1). Evaluation of a number of silver salts illustrated that silver hexafluoroantimonate (AgSbF6) was the optimal additive to activate the gold catalyst (Table 1, entries 2, 3, and 7). Screening of the other ligands of Au(I) catalysts

• ). The Au(I)-catalyzed cycloisomerization reaction of substrate 10 occurred under the catalysis of 5 mol % [1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]gold(I) chloride (IPrAuCl) and 5 mol % silver hexafluoroantimonate (AgSbF6) [25][26] in anhydrous DCM at room temperature for 2 h forming a benzene

Design, synthesis, and evaluation of chiral thiophosphorus acids as organocatalysts

• Karen R. Winters and
• Jean-Luc Montchamp

Beilstein J. Org. Chem. 2022, 18, 1471–1478, doi:10.3762/bjoc.18.154

• based on silver either gave a complex mixture or unreacted starting material. Phosphonate 8 was converted into the corresponding thiophosphonate 9 in moderate yield using Lawesson's reagent. Cleavage of the methyl ester was easily accomplished in quantitative yield, producing racemic tryptophol CPA 1

• -catalyzed hydrophosphinylation [45]. The key heterocyclization of 11 into 12 was accomplished using silver-promoted homolytic aromatic substitution [46], which was superior to our own manganese methodology (43% yield) [36]. Copper-catalyzed arylation [34] of 12 with iodobenzene and 4-nitroiodobenzene gave

Preparation of an advanced intermediate for the synthesis of leustroducsins and phoslactomycins by heterocycloaddition

• Anaïs Rousseau,
• Guillaume Vincent and
• Cyrille Kouklovsky

Beilstein J. Org. Chem. 2022, 18, 1385–1395, doi:10.3762/bjoc.18.143

• groups. Several conditions were tested: silver oxide on celite [33] failed to give any conversion. PCC with sodium acetate [34] gave only traces of the target lactone 25. However, the use of the Jones’ reagent gave reproducible yields of 25, together with the deprotected alcohol 26. Under optimized

Enantioselective total synthesis of putative dihydrorosefuran, a monoterpene with an unique 2,5-dihydrofuran structure

• Irene Torres-García,
• Josefa L. López-Martínez,
• Rocío López-Domene,
• Manuel Muñoz-Dorado,
• Ignacio Rodríguez-García and
• Miriam Álvarez-Corral

Beilstein J. Org. Chem. 2022, 18, 1264–1269, doi:10.3762/bjoc.18.132

• , 3H) ppm; 13C{1H} NMR (75 MHz, CDCl3, DEPT) δ 206.0 (C), 177.0 (C), 98.0 (C), 80.4 (CH), 77.5 (CH2), 28.5 (CH2), 26.1 (CH2), 15.0 (CH3) ppm; HRMS–ESI (Q-TOF, m/z): [M + H]+ calcd for C8H11O2,139.0759; found, 139.0782. Silver(I)-promoted cyclization of ethyl 4-hydroxy-5-methylhepta-5,6-dienoate (3) A

Scope of tetrazolo[1,5-a]quinoxalines in CuAAC reactions for the synthesis of triazoloquinoxalines, imidazoloquinoxalines, and rhenium complexes thereof

• Laura Holzhauer,
• Chloé Liagre,
• Olaf Fuhr,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2022, 18, 1088–1099, doi:10.3762/bjoc.18.111

• ). Improving this route provides an alternative to the literature-known method [11] that requires both a special porphyrin complex and glovebox conditions. Using neither silver(I) triflate nor copper(I) iodide yielded the imidazole product, indicating that the use of copper(I) triflate is crucial for the

First example of organocatalysis by cathodic N-heterocyclic carbene generation and accumulation using a divided electrochemical flow cell

• Daniele Rocco,
• Ana A. Folgueiras-Amador,
• Richard C. D. Brown and
• Marta Feroci

Beilstein J. Org. Chem. 2022, 18, 979–990, doi:10.3762/bjoc.18.98

• (Table 1, entry 4). However, using a silver electrode the corresponding thione was not observed (Table 1, entry 3) [37]. In view of the acidic character of the perfluorosulfonic acid Nafion® membrane, and possible NHC protonation to form the imidazolium cation, the Nafion® membrane was pretreated with an

Complementarity of solution and solid state mechanochemical reaction conditions demonstrated by 1,2-debromination of tricyclic imides

• Petar Štrbac and
• Davor Margetić

Beilstein J. Org. Chem. 2022, 18, 746–753, doi:10.3762/bjoc.18.75

• , a synthetic methodology for the preparation of 1–3 was developed by Warrener and co-workers by a Zn/Ag couple debromination [13][14][15]. However, this methodology has some disadvantages, such as tedious preparation of the catalyst, the use of dry solvent and expensive silver acetate as well as side

• usual procedure from Zn and silver acetate. Several simplifications of the Zn/Ag couple preparation were tested and showed that simple milling with Zn dust and Ag dust or wire can be also applied (Table 1, entries 5–8) [21]. Further improvement in the procedure was the replacement of the Ag dust with Cu

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

• useful alkylation approach is the Kochi–Anderson method [76] (or also known as Jacobsen–Torssell method [77][78]), via oxidative decarboxylation, where the quinone reacts with a carboxylic acid in the presence of silver(I) nitrate and ammonium or potassium peroxydisulfate. Nucleophilic free radicals are

• -workers [79]. 1,4-Naphthoquinone (1) was treated with acetic acid in the presence of ammonium persulfate, as oxidizing agent, and silver(I) catalysis for only 1 hour, furnishing menadione (10) in 47% yield (Scheme 1). After this pioneering work, some adaptations were reported. As an example, Liu and co

• -dimethoxyarenes is another valid synthetic approach to achieve 1,4-quinones, with the oxidative demethylation of 2-methyl-1,4-dimethoxynaphthalene (19) can be used to synthesize menadione (10). The oxidizing agents most commonly used in oxidative demethylation are cerium(IV) ammonium nitrate (CAN), and silver(II

Synthesis of piperidine and pyrrolidine derivatives by electroreductive cyclization of imine with terminal dihaloalkanes in a flow microreactor

• Yuki Naito,
• Naoki Shida and
• Mahito Atobe

Beilstein J. Org. Chem. 2022, 18, 350–359, doi:10.3762/bjoc.18.39

• of the cathode material on the yield of 3a using three different cathode materials: platinum (Pt), glassy carbon (GC), and silver (Ag). As shown in Table 1, the yield of 3a was higher using GC than that of the other cathode materials. The yield of the hydromonomeric product 4 was also highest when GC

Organocatalytic asymmetric nitroso aldol reaction of α-substituted malonamates

• Ekta Gupta,
• Narendra Kumar Vaishanv,
• Sandeep Kumar,
• Raja Krishnan Purshottam,
• Ruchir Kant and
• Kishor Mohanan

Beilstein J. Org. Chem. 2022, 18, 217–224, doi:10.3762/bjoc.18.25

• using a silver-BINAP catalyst combination [25]. Later, the same group could successfully tune the catalytic system to control the regioselectivity in the addition of metal enolate to nitrosoarenes to achieve an α-hydroxyamination [26]. Since then, several groups have shown the use of metal-catalyzed

Study on the interactions between melamine-cored Schiff bases with cucurbit[n]urils of different sizes and its application in detecting silver ions

• Jun-Xian Gou,
• Yang Luo,
• Xi-Nan Yang,
• Wei Zhang,
• Ji-Hong Lu,
• Zhu Tao and
• Xin Xiao

Beilstein J. Org. Chem. 2021, 17, 2950–2958, doi:10.3762/bjoc.17.204

• host–guest interactions. Among them, Q[7]-TBT is selected as a UV detector for the detection of silver ions (Ag+). This work makes full use of the characteristics of each cucurbituril and melamine-cored Schiff base to construct a series of complexes and these are applied to metal detection. Keywords

• : cucurbiturils; melamine; Schiff base; silver ion; Introduction Schiff bases [1] are usually synthesized by the condensation of amines and active carbonyl compounds, endowing them both nitrogen and oxygen donor atoms [2][3][4][5]. Schiff bases are not only easy to coordinate with various transition metal ions

• supermolecule polymer with TBT due to its larger cavity. Since Q[7] and TBT form a host–guest complex, the carboxyl group at the end of TBT and the carbonyl group of the Q[7] still have a strong ability to coordinate with metals. Therefore, Q[7]-TBT is selected for the detection of silver ions (Ag+) [32][33

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

Host–guest interaction and properties of cucurbit[8]uril with chloramphenicol

• Lin Zhang,
• Jun Zheng,
• Guangyan Luo,
• Xiaoyue Li,
• Yunqian Zhang,
• Zhu Tao and
• Qianjun Zhang

Beilstein J. Org. Chem. 2021, 17, 2832–2839, doi:10.3762/bjoc.17.194

• in water and has a bitter taste. Upon forming an inclusion complex with cyclodextrin, the solubility and bitter taste of CPE can be improved [4][5]. Ramesh Gannimani et al. [6] reported that the inclusion complex of cyclodextrin and CPE loaded silver nanoparticles possessed stronger antibacterial

Selective sulfonylation and isonitrilation of para-quinone methides employing TosMIC as a source of sulfonyl group or isonitrile group

• Chuanhua Qu,
• Run Huang,
• Yong Li,
• Tong Liu,
• Yuan Chen and
• Guiting Song

Beilstein J. Org. Chem. 2021, 17, 2822–2831, doi:10.3762/bjoc.17.193

• reaction without adding bases, and unexpectedly found Ag salts could catalyze the 1,6-conjugate addition of TosMIC (2a) and p-QM 1a to provide aryl(phenol)methane isonitrile 4a under base-free conditions (Table 1, entries 6–8). When the silver salt was removed from the reaction conditions, the reaction did

Synthesis of highly substituted fluorenones via metal-free TBHP-promoted oxidative cyclization of 2-(aminomethyl)biphenyls. Application to the total synthesis of nobilone

• Ilya A. P. Jourjine,
• Lukas Zeisel,
• Jürgen Krauß and
• Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2668–2679, doi:10.3762/bjoc.17.181

• . Benzylamines and derivatives thereof have been described in literature to be susceptible to oxidation by diverse reagents (tritylium ion [40], silver [38] and cerium salts [41], peroxides [42][43][44] and persulfates [45], nitroxyls [46], hypervalent iodine compounds [39][47], or tetrahalomethanes [48]) to

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