Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

• guests such as trinitrofluorene (TNF) and tetracyanoquinodimethane (TCNQ) are complexed in the closed state [32]. Terpyridine-based switches have also been described with metalloporphyrin arms bearing metal ions such as Zn(II) and Au(III) [35]. Terpyridine bisporphyrin tweezers have been synthesized as

Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• [75]. However, the major drawback with using these catalysts in A3 reactions was the loss of the catalyst at the end of the reaction. Furthermore, on using Au(I), Ag(I), and Cu(I) in ionic liquids, as well as supported Au(III), Ag(I), CuI, and CuCl to catalyze A3 coupling reactions under heterogeneous

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

• –59%) by a final optimized hydride reduction. Both the open tetraamine intermediates and the cyclam derivatives successfully coordinated with AuCl3 to give moderate to excellent yields (50–96%) of the corresponding novel tetra-coordinated N,N,N,N-Au(III) complexes with alternating five- and six

• -membered chelate rings. The testing of the catalytic ability of the cyclam-based N,N,N,N-Au(III) complexes demonstrated high catalytic activity of some complexes in selected test reactions (full conversion in 1–24 h, 62–97% product yields). Keywords: Au(III); carboalkoxylation; coordination studies

• ]. In contrast, gold(III) catalysis was for a long time mostly based on inorganic salts, such as AuCl3, AuBr3, or pyridine–AuCl3 and Pic–AuCl2. However, Au(III) complexes with various coordinated ligands are about to become more explored. Different from the linear coordination mode of gold(I), gold(III

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

• -forming reaction under oxidant-free conditions, while the use of the gold catalyst gives promise of accessing highly site-selective transformations. Indeed, electrophilic Au(III) species were able to site-selectively activate C–H bonds of activated electron-rich arenes thus generating Au(III)–Ar species

• ) catalyst, followed by SET oxidation to provide an Ar–Au(III) intermediate (Figure 43). This Lewis-acidic Au species promotes the regioselective C–H auration of the electron-rich substrate, delivering a cationic intermediate that under deprotonation and subsequent reductive elimination furnishes the

• expected biaryl product. In parallel, the photocatalytic cycle warrants the mild generation of the Ar• radical as well as the key Au(II)/Au(III) oxidation. More recently, an alternative strategy for the straight, non-directed arylation of (hetero)arenes was reported by Ackermann (Figure 44) [105

Fluorohydration of alkynes via I(I)/I(III) catalysis

• Jessica Neufeld,
• Constantin G. Daniliuc and
• Ryan Gilmour

Beilstein J. Org. Chem. 2020, 16, 1627–1635, doi:10.3762/bjoc.16.135

• fluorinating reagents [44][45]. Developments by Hammond and Xu validated N-pyridine oxides as terminal oxidants to substitute Selectfluor® for the cationic Au(I)/Au(III) cycle, thereby enabling high functional group tolerance [46][47][48][49]. Inspired by these and other selected advances [50][51], in metal

AuBr₃-catalyzed azidation of per-O-acetylated and per-O-benzoylated sugars

• Jayashree Rajput,
• Srinivas Hotha and
• Madhuri Vangala

Beilstein J. Org. Chem. 2018, 14, 682–687, doi:10.3762/bjoc.14.56

• -glycosylation albeit in low yields, thus indicating the possible utility of the oxophilic character of Au(III) towards the acetylated sugars. Among the N-glycosides, anomeric azido glycosides are important intermediates due to various applications in the synthesis of various glycosyl amides [28][29

• the ability of Au(III) in catalyzing the azidation of deactivated sugars was shown. The reaction proceeds in the absence of molecular sieves without forming lactols as byproducts. This operationally simple protocol enables the synthesis of various N-glycoconjugates offering a wide range of

Strategies toward protecting group-free glycosylation through selective activation of the anomeric center

• A. Michael Downey and
• Michal Hocek

Beilstein J. Org. Chem. 2017, 13, 1239–1279, doi:10.3762/bjoc.13.123

• this section we highlight some very elegant examples of transition metal-catalyzed glycosylation strategies that have been successful even in the presence of other unprotected hydroxy groups in the molecules. 3.4.1 Au(III)–alkynyl complexation: The Finn group [62] developed a protecting-group-free Au

• (III)-catalyzed strategy to access both simple aliphatic glycosides and disaccharides in good yields using either a propargyl or 2-butynyl glycosyl donor. They argued that since Au(III) is not too oxophilic and is also working in aprotic solvents, this metal would be suitable for anomeric activation of

N-Propargylamines: versatile building blocks in the construction of thiazole cores

• S. Arshadi,
• E. Vessally,
• L. Edjlali,
• R. Hosseinzadeh-Khanmiri and
• E. Ghorbani-Kalhor

Beilstein J. Org. Chem. 2017, 13, 625–638, doi:10.3762/bjoc.13.61

• in this reaction [99]. 4 Miscellaneous Recently, Stevens and co-workers reported a robust protocol towards dihydrothiazoles through an Au(III)-catalyzed intramolecular cyclization of the corresponding dithiocarboimidates. Thus, the corresponding 5-alkylidene-dihydrothiazoles 58 were synthesized in

• dihydrothiazol-2-ylamides 54. (b) Possible reaction pathway for the generation of product 54. Proposed mechanism for the generation of the iodine-substituted 4H-1,3-thiazines 56 and 4,5-dihydrothiazoles 57. Au(III)-catalyzed synthesis of 5-alkylidenedihydrothiazoles 58 developed by Stevens. Microwave-assisted

Recent advances in metathesis-derived polymers containing transition metals in the side chain

• Ileana Dragutan,
• Valerian Dragutan,
• Bogdan C. Simionescu,
• Albert Demonceau and
• Helmut Fischer

Beilstein J. Org. Chem. 2015, 11, 2747–2762, doi:10.3762/bjoc.11.296

• 4 with ferricenium hexafluorophosphate led to a stable biferrocenium polymer while oxidation with Au(III) or Ag(I) allowed the formation of networks with nanosnake morphology, consisting of mixed-valent Fe(II)–Fe(III) polymers that encapsulate metal (Au or Ag) nanoparticles (NPs). These polymers

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

• carbophilic Lewis acids even if their use as σ-activators has been rarely reported. Recently, transformations involving Au(I)/Au(III)-redox catalytic systems have been reported in the literature. In this review we highlight all these aspects of silver and gold-mediated processes and their application in

• tertiary propargylamines from aldehydes, secondary amines and alkynes was reported by Li and co-workers [19], a bare three months before the work on silver cited above [5]. Both Au(I) and Au(III) salts demonstrated to be effective with low catalyst loading (1 mol %). Surprisingly, water was the solvent of

• silver-catalyzed approach, involving the activation of the C–H bond of alkyne by an Au(I) species. For the AuBr3-catalyzed reaction, the authors argued that Au(I) could be generated in situ by a reduction of Au(III) from the alkyne. Starting from this seminal work, many other gold catalysts, including

Aminofluorination of 2-alkynylanilines: a Au-catalyzed entry to fluorinated indoles

• Antonio Arcadi,
• Emanuela Pietropaolo,
• Antonello Alvino and
• Véronique Michelet

Beilstein J. Org. Chem. 2014, 10, 449–458, doi:10.3762/bjoc.10.42

• in the presence of the Au(I) cationic catalyst or the Au(III) catalyst (Table 2, conditions A and B). The anilines 1b–1f were subjected to conditions A and B at room temperature or refluxing ethanol. Under conditions A, the NaAuCl4·2H2O catalyst operated smoothly and Selectfluor (3 equiv) was added

• when full conversion of the gold(III)-catalyzed cyclization of 1 was observed. The use of the cationic PPh3AuNTf2 complex allowed in situ addition of Selectfluor. Both catalytic systems were efficient and depending on the substrate higher yields were obtained either in the presence of the Au(III) or Au

• -withdrawing groups on both the aniline and the aryl moiety under Au(III) conditions, the desired product 2h was accompanied by the hemiaminal difluoroadduct 3h, which was isolated in 56% yield. The isolated 3h spontaneously decomposed to give quantitatively 2h. A similar trend was observed in the case of

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

• molecular motifs. In this context, homogenous [Au(I)] and [Au(III)] catalysis continues to inspire developments within organic synthesis, providing reliable responses to this interrogative, by combining crucial aspects such as chemical selectivity/efficiency with mild reaction parameters. This review

• functionalization of alkenes rely on the use of “oxidative strategies” exploiting the [Au(I)/Au(III)] or [Au(I)Au(I)/Au(II)Au(II)] catalytic couples that can be accessed through the use of a suitable exogenous oxidant (Figure 2, path c) [9]. Last but not least, the potential role of Brønsted acid co-catalysis

• , carboxylic acids required a higher loading of catalyst (5 mol %), but an acceptable yield was obtained even when sterically demanding 2-methylpropionic acid was employed as the nucleophile (Scheme 1b). Li and co-workers exploited the [Au(III)]-catalyzed addition of phenols and naphthols to conjugated dienes

Gold-catalyzed intermolecular hydroamination of allenes with sulfonamides

• Chen Zhang,
• Shao-Qiao Zhang,
• Hua-Jun Cai and
• Dong-Mei Cui

Beilstein J. Org. Chem. 2013, 9, 1045–1050, doi:10.3762/bjoc.9.117

• [7][8][9][10][11][12][13][14][15]. More recently, Au(I), Au(III), Pt(II) and Rh(I) have been used for the intermolecular hydroamination of allenes with secondary alkylamines, ammonia, or carboxamide [7][16][17][18][19][20][21][22][23][24]. Although some of these advances have been efficiently made in

Synthesis of a novel chemotype via sequential metal-catalyzed cycloisomerizations

• Bo Leng,
• Stephanie Chichetti,
• Shun Su,
• Aaron B. Beeler and
• John A. Porco Jr.

Beilstein J. Org. Chem. 2012, 8, 1338–1343, doi:10.3762/bjoc.8.153

• processes and chemotypes [5]. For example, we have conducted multidimensional reaction screens using alkynyl o-benzaldehyde scaffolds, which revealed a number of reactions affording novel polycyclic scaffolds, including Au(III)-catalyzed addition of diethyl malonate to 1 to afford isochromene 2 (Scheme 1

Synthesis of fluoranthenes by hydroarylation of alkynes catalyzed by gold(I) or gallium trichloride

• Sergio Pascual,
• Christophe Bour,
• Paula de Mendoza and
• Antonio M. Echavarren

Beilstein J. Org. Chem. 2011, 7, 1520–1525, doi:10.3762/bjoc.7.178

• form 6–8-membered rings [29][30][31]. A similar reaction can also be carried out with GaCl3 [32] and Pt(II) [33] as catalysts. In contrast, alkynyl furans react with gold to give phenols by using Au(III), Au(I) [1][2][34][35][36][37], or Pt(II) as the catalyst [38][39]. In our efforts towards the

Access to pyrrolo-pyridines by gold-catalyzed hydroarylation of pyrroles tethered to terminal alkynes

• Elena Borsini,
• Gianluigi Broggini,
• Andrea Fasana,
• Chiara Baldassarri,
• Angelo M. Manzo and
• Alcide D. Perboni

Beilstein J. Org. Chem. 2011, 7, 1468–1474, doi:10.3762/bjoc.7.170

• should be noted that the 1-unsubstituted pyrrole derivative 1a did not undergo cyclization, under various conditions, based on both Au(III) and Au(I) catalysts (Table 1, entries 1–5). Otherwise, AuCl3 was able to promote the intramolecular reaction of the methyl-substituted substrate 1b giving two

Combination of gold catalysis and Selectfluor for the synthesis of fluorinated nitrogen heterocycles

• Antoine Simonneau,
• Pierre Garcia,
• Jean-Philippe Goddard,
• Virginie Mouriès-Mansuy,
• Max Malacria and
• Louis Fensterbank

Beilstein J. Org. Chem. 2011, 7, 1379–1386, doi:10.3762/bjoc.7.162

• isolated in 43% yield (Scheme 3). Our mechanistic proposal for the formation of fluorinated pyrrolidines is outlined in Scheme 4. Oxidation of the Au(I) complex by Selectfluor should give the active cationic Au(III) species A. Formation of A is consistent with 19F NMR experiments analogous to those

• previously described in the literature [12][27]. Thus, upon addition of Selectfluor to PPh3AuCl, a new peak at −181.6 ppm in CD3CN was observed that is characteristic of Au(III) species A [28]. Coordination of 1a to A would lead to complex B in which the coordinated triple bond is activated towards a

• nucleophilic attack by the NH moiety. The resulting σ-vinyl Au(III) intermediate C could undergo a reductive elimination of its σ-vinyl and F ligands to give 2a, or a protodeauration leading to pyrrolidine 6, which would also rapidly isomerize into 7. Both 6 and 7 under the given reaction conditions would

Gold(I)-catalyzed synthesis of γ-vinylbutyrolactones by intramolecular oxaallylic alkylation with alcohols

• Michel Chiarucci,
• Mirko Locritani,
• Gianpiero Cera and
• Marco Bandini

Beilstein J. Org. Chem. 2011, 7, 1198–1204, doi:10.3762/bjoc.7.139

• . With the less bulky triphenylphosphine ligand, the corresponding cationic gold(I) complex (i.e., PPh3AuNTf2) led to an increase in the isolated yield up to 52%, although the diastereoselection remained elusive (≈ 1:1, entry 3). After demonstrating that the Au(III) catalysis promoted the cyclization in

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• alkenes. Examples of these cycloadditions, originally reported under tungsten catalysis [51], have been recently reported by Iwasawa with Au(III) and Pt(II) catalysts [52], allowing the assembly of interesting tricyclic indole skeletons 16 in good yields (Scheme 9). In 2008, Shin and coworkers reported an

• ethers and alkenes (MOM = methoxymethyl, Scheme 25) [90]. The activation of these allenes by the dichloro(pyridine-2-carboxylato)Au(III) complex Au7 generates an oxocarbenium intermediate XXVII, which undergoes the (3 + 2) annulation with the alkene. The resulting bicyclo[3.1.0] species XXVIII, related

Triazole–Au(I) complex as chemoselective catalyst in promoting propargyl ester rearrangements

• Dawei Wang,
• Yanwei Zhang,
• Rong Cai and
• Xiaodong Shi

Beilstein J. Org. Chem. 2011, 7, 1014–1020, doi:10.3762/bjoc.7.115

• reactivity of gold catalysts greatly depends on the nature of the ligands coordinating with the metal cations [10][11][12][13][14][15]. Of the two typical oxidation states, Au(I) and Au(III), more studies have been focused on the former cation due to the easier preparation of the catalyst and better pre

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• homogeneous gold-catalyzed oxidative cross-coupling which leads to α-arylenones 190 from propargylic acetates 189 and arylboronic acids has been developed by Zhang’s group (Scheme 35) [86]. This cross-coupling reaction reveals the synthetic potential of Au(I)/Au(III) catalytic cycles. Kimber reported a facile

• . Gung and co-workers developed a 3,3-rearrangement/transannular [4 + 3] cycloaddition reaction (Scheme 40) in the presence of either a Au(I) or Au(III) catalyst [109]. In these reactions, the regiochemistry of the product 223 is controlled by the position of the acetoxy group in the starting material

• role of Au(I)/Au(III) catalysis. Toste’s group and Russell’s group subsequently reported the aminoarylation and oxyarylation of alkenes (352 and 355) following a similar protocol [168][169]. In the gold-catalyzed intramolecular aminoarylation of alkenes, ligand and halide effects played a dramatic role

The role of silver additives in gold-mediated C–H functionalisation

• Scott R. Patrick,
• Ine I. F. Boogaerts,
• Sylvain Gaillard,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2011, 7, 892–896, doi:10.3762/bjoc.7.102

• (Scheme 2) [16]. The observation of a high kinetic isotope effect is suggestive of a concerted metalation–deprotonation mechanism, as first suggested for Pd(II) complexes, in which a pivalate ligand behaves as a proton acceptor via a six-membered transition state [17]. However, addition via a transient Au

• (III) hydride would also be consistent with these observations. Results and Discussion We became interested in understanding the mechanistic details of this transformation by identifying the role of the individual components. Reactions were performed between individual reagents and the formation of

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

• , allylsilanes, aromatic compounds and nitrogen nucleophiles. Interestingly, these reactions were not limited to monosubstituted propargylic alcohols [19][20][21][22]. In 2005, we described the direct Au(III)-catalyzed substitution of propargylic alcohols in the presence of various nucleophiles (allylsilanes

• room temperature was investigated (Scheme 2, Table 1). Gratifyingly, the reaction proved to be efficient with various Au(III) reagents (at 5% catalyst loading) (Table 1, entries 1–4). The best results were observed with NaAuCl4·2H2O (Table 1, entry 1). In the presence of Au(I) catalysts (Table 1

• allylic and a propargylic alcohol, was submitted to the same reaction conditions. A 2:2:1 inseparable mixture of SN 2p and SN’ 2q and 2r products was obtained (Scheme 3). The Au(III)-catalyzed reaction was next investigated for diverse series of nucleophiles. A large number of nucleophiles are very

Au(I)/Au(III)-catalyzed Sonogashira-type reactions of functionalized terminal alkynes with arylboronic acids under mild conditions

• Deyun Qian and
• Junliang Zhang

Beilstein J. Org. Chem. 2011, 7, 808–812, doi:10.3762/bjoc.7.92

• , Chinese Academy of Sciences, Ling Ling Road 345 Shanghai 200032 (P. R. China) 10.3762/bjoc.7.92 Abstract A straightforward, efficient, and reliable redox catalyst system for the Au(I)/Au(III)-catalyzed Sonogashira cross-coupling reaction of functionalized terminal alkynes with arylboronic acids under

• , this transformation catalyzed by gold, involving Au(I)/Au(III) catalytic cycles has, as yet, been less explored [15][16][17][18][19][20][21][22]. In the few examples already documented some conditions, such as rather high reaction temperatures (130 °C), high catalysis loading or special reagents were

• required [23]. Herein, we report a straightforward, efficient and robust catalyst system for the Sonogashira-type cross-coupling, in which Au(I)/Au(III) catalyzed Csp2–Csp bond formation of terminal alkynes from arylboronic acids under mild conditions. By analogy with other d10 species, Au(I) has the same

Gold-catalyzed heterocyclizations in alkynyl- and allenyl-β-lactams

• Benito Alcaide and
• Pedro Almendros

Beilstein J. Org. Chem. 2011, 7, 622–630, doi:10.3762/bjoc.7.73

• five-membered oxacycle. A computational study (using density functional theory, DFT) of the above heterocyclization has been carried out [50]. The Au(III)-catalyzed cyclization of γ-allenol I (Figure 1) takes place regio- and stereoselectively through a 5-exo hydroalkoxylation because of a kinetic

• of Au(III)-catalyzed reaction is determined by the presence or absence of a methoxymethyl protecting group at the γ-allenol oxygen atom, thus allenols 8 gave 5-exo hydroalkoxylation whilst γ-allenol derivatives 14 exclusively underwent a 7-endo oxycyclization. Thus, it has been demonstrated that

• would then liberate the compound 15 with concomitant regeneration of the Au(III) species. Probably, the proton in the last step of the catalytic cycle arises from trace amounts of water present in the solvent or the catalyst. In the presence of the MOM group, 5-exo cyclization falters. As calculations