Efficient synthetic protocols for the preparation of common N-heterocyclic carbene precursors

• Morgan Hans,
• Jan Lorkowski,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2015, 11, 2318–2325, doi:10.3762/bjoc.11.252

• of labile imidazolidine adducts (Scheme 1, path C) [36][37][38], or the recourse to Ag(I)–NHC complexes as NHC delivery agents (Scheme 1, path D) [39][40]. In many cases, however, these NHC surrogates are obtained from azolium intermediates. Hence, imidazolium and imidazolinium salts are the most

Weakly nucleophilic potassium aryltrifluoroborates in palladium-catalyzed Suzuki–Miyaura reactions: relative reactivity of K[4-RC₆F₄BF₃] and the role of silver-assistance in acceleration of transmetallation

• Vadim V. Bardin,
• Anton Yu. Shabalin and
• Nicolay Yu. Adonin

Beilstein J. Org. Chem. 2015, 11, 608–616, doi:10.3762/bjoc.11.68

• consumption of K[4-RC6F4BF3] and SEP of the respective 4-RC6F4 group does not show certain correlation. Conclusion 1. The relative reactivities of K[4-RC6F4BF3] in the Ag(I)-assisted Pd-catalyzed cross-coupling reactions with 3-IC6H4F, 4-IC6H4F, 4-IC6H4CH3 or 4-BrC6H4CH3 in the presence of P(t-Bu)3 or PPh3

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

• equivalent amount of alcohol. 2.2 Oxidative systems based on noble metals and oxygen The oxidative coupling of benzyl alcohols with aliphatic alcohols in the presence of Pd(II) salt/Ag(I) salt/base/oxygen system was proposed [96][97]. In the study [97], phosphine ligands were additionally employed. It is

A new approach for the synthesis of bisindoles through AgOTf as catalyst

• Jorge Beltrá,
• M. Concepción Gimeno and
• Raquel P. Herrera

Beilstein J. Org. Chem. 2014, 10, 2206–2214, doi:10.3762/bjoc.10.228

• approach for this interesting and appealing reaction. Keywords: Ag(I); aldehydes; bisindole; catalysis; indole; Introduction Indole is an interesting structural motif present in more than 3000 isolated natural products and embedded in many biological systems [1][2][3]. Although this field has attracted a

• preparing BIMs from aldehydes and simple Ag(I) species (Scheme 1). In order to test the viability of this idea, the investigation was started by exploring the efficiency of four easily accessible Ag(I) species in two reaction models (Scheme 1), and following the course of the process by TLC until no

• could be in agreement with the higher coordination capacity of the tested counterions, while OTf is considered to be low-coordinating with some cations, thus favouring the Lewis acid character of Ag(I) [41][42]. Bearing this promising result in mind, the ensuing screening was performed using AgOTf as

Second generation silver(I)-mediated imidazole base pairs

• Susanne Hensel,
• Nicole Megger,
• Kristina Schweizer and
• Jens Müller

Beilstein J. Org. Chem. 2014, 10, 2139–2144, doi:10.3762/bjoc.10.221

• Susanne Hensel Nicole Megger Kristina Schweizer Jens Muller Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstr. 28/30, 48149 Münster, Germany 10.3762/bjoc.10.221 Abstract The imidazole–Ag(I)–imidazole base pair is one of the best-investigated

• artificial metal-mediated base pairs. We show here that its stability can be further improved by formally replacing the imidazole moiety by a 2-methylimidazole or 4-methylimidazole moiety. A comparison of the thermal stability of several double helices shows that the addition of one equivalent of Ag(I) leads

• necessarily require the presence of artificial ligands. In contrast, natural nucleobases have also been successfully applied in the generation of metal-mediated base pairs such as thyminate–Hg(II)–thyminate or cytosine–Ag(I)–cytosine [23][24][25]. It has even been shown that polymerases are capable of

Synthesis of zearalenone-16-β,D-glucoside and zearalenone-16-sulfate: A tale of protecting resorcylic acid lactones for regiocontrolled conjugation

• Hannes Mikula,
• Julia Weber,
• Dennis Svatunek,
• Philipp Skrinjar,
• Gerhard Adam,
• Rudolf Krska,
• Christian Hametner and
• Johannes Fröhlich

Beilstein J. Org. Chem. 2014, 10, 1129–1134, doi:10.3762/bjoc.10.112

• glucosylation; no conversion of 10, partially rearrangement of 11 to glucosyl acetamide 12. (C) Königs–Knorr glucosylation; Ag(I): Ag2CO3 or Ag2O, CH2Cl2 or MeCN; PTG: phase transfer glucosylation, NaOH, tetrabutylammonium bromide, pH 10–11, CHCl3/H2O. Regioselective acetylation of ZEN (1) affording 14-O

Phosphinate-containing heterocycles: A mini-review

• Olivier Berger and
• Jean-Luc Montchamp

Beilstein J. Org. Chem. 2014, 10, 732–740, doi:10.3762/bjoc.10.67

• ]. Miura et al. simultaneously reported the same reaction but with 4 equivalents of AgOAc instead, delivering the heterocycle 17 in 53% yield (Scheme 8) [22]. Both reactions used 4 equivalents of Ag(I) as well as an excess of H-phosphinate. 1,3-Oxaphospholes Cristau and coworkers have achieved the direct

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• to be overcome in the near future. The first example of Ag(I)-catalyzed A3-coupling was reported by Li and co-workers in 2003 [5]. In this pioneering work, a simple silver(I) salt demonstrated to be able to catalyze the coupling between aliphatic/aromatic aldehydes, cyclic secondary amines and

• recently, silver–NHC complexes were found to be valuable catalysts for this MCR. Their first application was reported by Wang and co-workers in 2008 [12], who developed a polystyrene-supported NHC–Ag(I) complex as an efficient catalyst for the A3-coupling under solvent-free conditions, at room temperature

• secondary amines, as well as aryl and alkyl-substituted alkynes (Scheme 2). It is noteworthy that the approach tolerated challenging substrates such as formaldehyde, o-substituted benzaldehydes, and secondary aromatic amines. Moreover, the PS–NHC–Ag(I) catalyst was proven to be reusable at least 12 times

New developments in gold-catalyzed manipulation of inactivated alkenes

• Michel Chiarucci and
• Marco Bandini

Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294

• with simple ketones. Proposed reaction mechanism for the intramolecular [Au(I)]-catalyzed hydroalkylation of alkenes with ketones. Tandem Michael addition/hydroalkylation catalyzed by [Au(I)] and [Ag(I)] salts. Intramolecular [Au(I)]-catalyzed tandem migration/[2 + 2] cycloaddition of 1,7-enyne

Gold-catalyzed intermolecular coupling of sulfonylacetylene with allyl ethers: [3,3]- and [1,3]-rearrangements

• Jungho Jun,
• Hyu-Suk Yeom,
• Jun-Hyun An and
• Seunghoon Shin

Beilstein J. Org. Chem. 2013, 9, 1724–1729, doi:10.3762/bjoc.9.198

• undergo intermolecular alkoxylation-[3,3]-sigmatropic rearrangement under Ag(I) or Au(I) catalysis [7][8], allyl ethers that are less nucleophilic due to steric reasons react more slowly and have not been known to undergo similar reactions until recently. In our previous work [9], it was shown that ester

Palladium-catalyzed dual C–H or N–H functionalization of unfunctionalized indole derivatives with alkenes and arenes

• Gianluigi Broggini,
• Egle M. Beccalli,
• Andrea Fasana and
• Silvia Gazzola

Beilstein J. Org. Chem. 2012, 8, 1730–1746, doi:10.3762/bjoc.8.198

• reoxidized with the Ag(I) and Cu(II) salts. Intermolecular reactions involving arenes The formation of homo-coupling products is one of the most common drawbacks in intermolecular reactions between arenes without preactivation of the substrates. In 2006, Lu and co-workers reported one of the first articles

Fluorescent hexaaryl- and hexa-heteroaryl[3]radialenes: Synthesis, structures, and properties

• Antonio Avellaneda,
• Courtney A. Hollis,
• Xin He and
• Christopher J. Sumby

Beilstein J. Org. Chem. 2012, 8, 71–80, doi:10.3762/bjoc.8.7

• limited extent [18][19][20][21]. Three coordination modes were observed for hexa(2-pyridyl)[3]radialene with Ag(I): A discrete M6L2 cage, a 1-D coordination polymer composed of M3L2 cages bridged by linear silver atoms, and a second 1-D coordination polymer where the radialene ligand acts as a

Efficient gold(I)/silver(I)-cocatalyzed cascade intermolecular N-Michael addition/intramolecular hydroalkylation of unactivated alkenes with α-ketones

• Ya-Ping Xiao,
• Xin-Yuan Liu and
• Chi-Ming Che

Beilstein J. Org. Chem. 2011, 7, 1100–1107, doi:10.3762/bjoc.7.126

• system at 90 °C in toluene for 20 h gave the product 3a in 76% yield. With the optimal reaction conditions, we next explored the substrate scope with the protocol for the Au(I)/Ag(I)-cocatalytic system (Table 3). For example, treatment of substrate 1b, which has an electron-donating para-methoxy group on

Chiral gold(I) vs chiral silver complexes as catalysts for the enantioselective synthesis of the second generation GSK-hepatitis C virus inhibitor

• María Martín-Rodríguez,
• Carmen Nájera,
• José M. Sansano,
• Abel de Cózar and
• Fernando P. Cossío

Beilstein J. Org. Chem. 2011, 7, 988–996, doi:10.3762/bjoc.7.111

• , generated from chiral phosphoramidites or BINAP as ligands, in order to prepare antiviral agent 2a. Results and Discussion The efficiency of the chiral phosphoramidite/silver(I) salts [25][26][29] and BINAP/Ag(I) salts [30][31] in 1,3-DC, following the general pattern shown in Scheme 1, has been

Gold-catalyzed propargylic substitutions: Scope and synthetic developments

• Olivier Debleds,
• Eric Gayon,
• Emmanuel Vrancken and
• Jean-Marc Campagne

Beilstein J. Org. Chem. 2011, 7, 866–877, doi:10.3762/bjoc.7.99

• obtained on a multi-gram scale, by our recently described allenylcuprate chemistry [71][72][73]. In the meantime, Aponick [77] and Akai [78] described very similar results using Au(I)/Ag(I) catalysts. Some of our gold(III)-catalyzed reactions are illustrated in Scheme 19. Interestingly, when the

Design and synthesis of a cyclitol-derived scaffold with axial pyridyl appendages and its encapsulation of the silver(I) cation

• Pierre-Marc Léo,
• Christophe Morin and
• Christian Philouze

Beilstein J. Org. Chem. 2010, 6, 1022–1024, doi:10.3762/bjoc.6.115

• -inositol the three axial hydroxy groups can be used to link substituents in a pre-organized manner [8][9][10]. Thus the introduction of pyridine groups (known to bind Ag(I) efficiently [11][12][13][14]) on a scyllo-inositol orthoester was considered, which led to the design of scaffold 1 (Figure 1). Indeed

• Information File 1). However, in the absence of characteristic signals for Ag(I)-complex (even at low temperature: −50 °C) NMR methods cannot be used for the determination of the complex stability constant. The electrospray mass spectrum (from the very solution contained in the NMR tube) revealed a 1:1

• described Ag(I) complex in a N3O3 environment [13]. Study of the molecular structure of the complex was made possible as a single crystal could be grown by slow evaporation of a methanol/ethanol solution of stoichiometric amounts of 1 and silver trifluoromethanesulfonate. The complex crystallises in the

A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis

• Magnus Rueping and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2010, 6, No. 6, doi:10.3762/bjoc.6.6

• and Brønsted acids, including Au(III), Ag(I), In(III), Zn(II), Cu(II) salts or sulfonic acids. AuCl3 was the most reactive and was subsequently used for further studies. With 5 mol% of catalyst and performing the reaction at room temperature, the desired allylated arenes and heteroarenes 66 were

• , intramolecular FC-type allylations are of great importance. One of the first intramolecular FC-type transformations using allyl alcohols was developed by Nishizawa et al. using Hg(OTf)2 as Lewis acid [89]. Since Hg(II) is not an environmentally friendly transition metal, Bandini et al. developed a “greener” Ag(I

• leading to 1,1-diarylalkane 38 from the linear precursor citral (37). Bi(III)-catalyzed hydroarylation of styrenes with arenes and heteroarenes. BiCl3-catalyzed ene/FC alkylation reaction cascade – A fast access to highly arylated dihydroindenes. Au(I)/Ag(I)-catalyzed hydroarylation of indoles with

Sordarin, an antifungal agent with a unique mode of action

• Huan Liang

Beilstein J. Org. Chem. 2008, 4, No. 31, doi:10.3762/bjoc.4.31

• persulfate-pyridine system [32]. The ensuing Ag(I) catalyzed oxidative radical cyclization proceeded in 85% yield. Racemic ketone 43 underwent regio- and stereoselective allylation under Corey-Enders conditions to provide olefin 44, which was subjected to Lemieux-Johnson cleavage to corresponding aldehyde

The vicinal difluoro motif: The synthesis and conformation of erythro- and threo- diastereoisomers of 1,2-difluorodiphenylethanes, 2,3-difluorosuccinic acids and their derivatives

• David O'Hagan,
• Henry S. Rzepa,
• Martin Schüler and
• Alexandra M. Z. Slawin

Beilstein J. Org. Chem. 2006, 2, No. 19, doi:10.1186/1860-5397-2-19

• , rather than compound 16 which would have a trans relationship and a much larger 3JHF coupling constant (~30 Hz), and reinforces the stereochemical assignment made to 14 as illustrated in Scheme 5 [21]. Substitution of the bromine in anti-14 with fluorine was accomplished by treatment with Ag(I)F in

• pot process with NBS, PPHF and Ag(I)F again proceeded smoothly however it also gave erythro-13 as the major product of the reaction, although with a reduced diastereoisomeric ratio (47% de) more suitable for threo- 13 isolation. The bias towards erythro- 13 in this case is clearly a result of internal