Glyco-gold nanoparticles: synthesis and applications

• Federica Compostella,
• Olimpia Pitirollo,
• Alessandro Silvestri and
• Laura Polito

Beilstein J. Org. Chem. 2017, 13, 1008–1021, doi:10.3762/bjoc.13.100

• metal-based anticancer drugs need to be developed. Recently, it has been reported the interesting synthesis of AuNPs coated with glyco-polymers and functionalized with gold(I) triphenylphosphine (Figure 7) [88]. This work showed the potentiality of these structures as novel cancer therapeutic drugs. The

First total synthesis of kipukasin A

• Chuang Li,
• Haixin Ding,
• Zhizhong Ruan,
• Yirong Zhou and
• Qiang Xiao

Beilstein J. Org. Chem. 2017, 13, 855–862, doi:10.3762/bjoc.13.86

• , ester protection is preferred for Vorbrüggen glycosylations in nucleoside syntheses. Very recently, ortho-alkynylbenzoate was successfully developed by our group as neighboring participation group to synthesize 2’-modified nucleosides [24], which could be removed smoothly in the presence of gold(I

From betaines to anionic N-heterocyclic carbenes. Borane, gold, rhodium, and nickel complexes starting from an imidazoliumphenolate and its carbene tautomer

• Ming Liu,
• Jan C. Namyslo,
• Martin Nieger,
• Mika Polamo and
• Andreas Schmidt

Beilstein J. Org. Chem. 2016, 12, 2673–2681, doi:10.3762/bjoc.12.264

• .12.264 Abstract The mesomeric betaine imidazolium-1-ylphenolate forms a borane adduct with tris(pentafluorophenyl)borane by coordination with the phenolate oxygen, whereas its NHC tautomer 1-(2-phenol)imidazol-2-ylidene reacts with (triphenylphosphine)gold(I) chloride to give the cationic NHC complex [Au

• on reaction with (triphenylphosphine)gold(I) chloride in boiling anhydrous THF under a nitrogen atmosphere, under which conditions the colorless gold complex [Au(6B)2][Cl] (9) is formed in 60% yield (Scheme 1). The protons of the OH resonate at δ = 10.34 ppm in DMSO-d6, and the 13C NMR chemical shift

• -butyl-1-(2-hydroxyphenyl)-1H-imidazolium-2-yl)gold monochloride (9): A solution of 0.43 g (0.20 mmol) of 2-(3-butyl-1H-imidazolium-1-yl)phenolate in 5 mL of anhydrous THF was treated with 0.05 g (0.10 mmol) of (triphenylphosphine)gold(I) chloride and stirred under an inert atmosphere overnight at reflux

Enduracididine, a rare amino acid component of peptide antibiotics: Natural products and synthesis

• Darcy J. Atkinson,
• Briar J. Naysmith,
• Daniel P. Furkert and
• Margaret A. Brimble

Beilstein J. Org. Chem. 2016, 12, 2325–2342, doi:10.3762/bjoc.12.226

• reaction site and poor compatibility of the cyclic guanidine motif with Lewis acids. Initial attempts to glycosylate cyclic guanidine 91 using an array of donors under Lewis acidic or basic conditions failed to provide access to N-mannosylguanidine 92 (Scheme 18). However, gold(I) mediated [71] N

Gold-catalyzed direct alkynylation of tryptophan in peptides using TIPS-EBX

• Gergely L. Tolnai,
• Jonathan P. Brand and
• Jerome Waser

Beilstein J. Org. Chem. 2016, 12, 745–749, doi:10.3762/bjoc.12.74

• mixture was stirred at 40 °C for 2 min. Gold(I) chloride (2.3 mg, 10 µmol, 0.05 equiv) was added in one portion. The reaction tube was sealed and stirring was continued for 24 h at 40 °C. Afterwards, the mixture was diluted with EtOAc (50 mL), and the organic layer was washed with a mixture of water (2.5

From steroids to aqueous supramolecular chemistry: an autobiographical career review

• Bruce C. Gibb

Beilstein J. Org. Chem. 2016, 12, 684–701, doi:10.3762/bjoc.12.69

• departments in the US carry out faculty searches, I now appreciate that I had struck gold. I never saw the letters that John, Jim and Neville wrote, but they must have said some nice things. And so I went through the interview process at the University of New Orleans and did well enough to get an offer. I had

Pyridylidene ligand facilitates gold-catalyzed oxidative C–H arylation of heterocycles

• Kazuhiro Hata,
• Hideto Ito,
• Yasutomo Segawa and
• Kenichiro Itami

Beilstein J. Org. Chem. 2015, 11, 2737–2746, doi:10.3762/bjoc.11.295

• as a DFT study, indicated unusual stability of gold(III) species stabilized by strong electron donation from the 2-pyridylidene ligand. Thus, the gold(I)-to-gold(III) oxidation process is thought to be facilitated by the highly electron-donating 2-pyridylidene ligand. Keywords: carbene ligand; C–H

• represented by oxidative coupling that is expected to proceed through a gold(I)/gold(III) catalytic cycle [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81]. In particular, the

• elegant works of Lloyd-Jones and Russell on gold-catalyzed oxidative C–H arylation of simple arenes with arylsilanes have led the way to novel gold-catalyzed reactions that could not be achieved with other transition metals [68][69]. In these reactions, the oxidation of gold(I) to gold(III) is thought to

Evidencing an inner-sphere mechanism for NHC-Au(I)-catalyzed carbene-transfer reactions from ethyl diazoacetate

• Manuel R. Fructos,
• Juan Urbano,
• M. Mar Díaz-Requejo and
• Pedro J. Pérez

Beilstein J. Org. Chem. 2015, 11, 2254–2260, doi:10.3762/bjoc.11.245

• functionalization; olefin cyclopropanation; Introduction The discovery of the catalytic capabilities of soluble gold(I) species toward the hydration of alkynes by Teles and co-workers [1] is considered as the rising of the golden era for the use of this metal in homogeneous catalysis [2][3]. A number of

• of a gold(I) source and a diazo compound. It was not until 2005 that the first example of this transformation was reported by our group [15][16], when the complex IPrAuCl (1) (IPr = 1,3-bis(diisopropylphenyl)imidazole-2-ylidene), in the presence of NaBArF4 (BArF4− = tetrakis(3,5-bis(trifluoromethyl

Synthesis of constrained analogues of tryptophan

• Elisabetta Rossi,
• Valentina Pirovano,
• Marco Negrato,
• Giorgio Abbiati and
• Monica Dell’Acqua

Beilstein J. Org. Chem. 2015, 11, 1997–2006, doi:10.3762/bjoc.11.216

• only using copper(II) triflate as catalyst (Table 1, entry 5). Unsatisfactory results were obtained also in the presence of gold(III) and gold(I) catalysts (Table 1, entries 8 and 9). Only in the presence of a cationic gold(I) complex the diastereoisomeric cycloadducts 3a and 3'a were isolated in 20

Novel carbocationic rearrangements of 1-styrylpropargyl alcohols

• Christine Basmadjian,
• Fan Zhang and
• Laurent Désaubry

Beilstein J. Org. Chem. 2015, 11, 1017–1022, doi:10.3762/bjoc.11.114

• molybdenum(VI)-catalyzed etherification of allylic alcohol with a gold(I)-catalyzed intramolecular cyclization process [5][6]. During the optimization process of this synthesis, we examined several catalysts to transform allylic alcohol 1 into ether 2, including Re2O7, which is described to efficiently

Gold-catalyzed formation of pyrrolo- and indolo-oxazin-1-one derivatives: The key structure of some marine natural products

• Sultan Taskaya,
• Nurettin Menges and
• Metin Balci

Beilstein J. Org. Chem. 2015, 11, 897–905, doi:10.3762/bjoc.11.101

• acids has been reported in the literature to give the corresponding lactones [33][34][35][36][37][38][39][40]. For example, gold(I)-catalyzed reaction of 2-(phenylethynyl)benzoic acid (8) yielded the exo- and endo-dig cyclization products, lactones 9 and 10 in 62% yield in a ratio of 6:1 (Scheme 1) [41

• addition of a carboxy group to the alkyne functionality to give methylene-oxazin-1-one derivative 7 (or 18) (Scheme 6). In the next step, the double bond is activated by π-coordination of the gold(I) catalyst. This enables a nucleophilic attack by the alcohol oxygen, which affords hemiacetal 47. In case of

• reactions. Structures of some marine natural products 1–4. Structures 5–7. Geometry optimized structures of 6, 7, 30 and 31. Intramolecular gold(I)-catalyzed cyclization reaction of 8 to give 9 and 10. Synthesis of 13 and its reaction with AuCl3. Synthesis of 6. Reaction of 15 with Au(I)/AgOTf in the

Gold(I)-catalysed synthesis of a furan analogue of thiamine pyrophosphate

• Amjid Iqbal,
• El-Habib Sahraoui and
• Finian J. Leeper

Beilstein J. Org. Chem. 2014, 10, 2580–2585, doi:10.3762/bjoc.10.270

• , involving gold(I)-catalysed cyclisation of an alkynyl alcohol to form the furan ring. The furan analogue of thiamine diphosphate (ThDP) was also made and tested for binding to and inhibition of pyruvate decarboxylase (PDC) from Zymomonas mobilis (overexpressed in E. coli with a N-terminal His-tag). It is a

• dehydrative cyclisation reaction of alkynyl alcohols catalysed by simple gold(I) salts [31]. The reaction proceeds rapidly under mild, open flask conditions to provide aromatic heterocycles such as furans, pyrroles and thiophenes in high yield with low catalyst loadings (Scheme 2). Following this synthetic

• . Dehydrative cyclization catalysed by gold(I) and its presumed mechanism [31]. Synthesis of furan 12. Reagents and conditions: (i) TBDMS-Cl, N-methylimidazole. (ii) n-BuLi, −78 °C, then 9 and to rt, 55% (iii) TBAF, THF, 79%. (iv) AuCl, THF, 85%. Synthesis of the furan analogue 17 of ThDP. Reagents and

Preparation of phosphines through C–P bond formation

• Iris Wauters,
• Wouter Debrouwer and
• Christian V. Stevens

Beilstein J. Org. Chem. 2014, 10, 1064–1096, doi:10.3762/bjoc.10.106

• catalysis (Table 16) [244]. Besides copper(I) iodide several other copper salts effectuated the reaction albeit in lower yields as did silver(I) iodide, palladium(II) chloride and platinum(II) chloride. Other transition metal catalysts such as gold(I) chloride, nickel(II) chloride and cobalt(II) chloride

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

• lifetimes of gold(III) chloride catalysts in A3-MCRs by the addition of inexpensive and commercially available reagents such as CuCl2 and TEMPO [36]. The proposed rationale seems simple and elegant: the reduction of gold(I) (real active species) to colloidal Au(0) was responsible for the deactivation of the

• multicomponent reactions In gold(I) and gold(III)-catalyzed reactions the metal acts as a carbophilic Lewis acid, facilitating nucleophilic addition to unsaturated systems. Moreover, also the oxophilic character of gold species has been highlighted by several authors. More recently, gold-promoted transformations

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

• and alkynyl phenylhydrazones, respectively. Propargyl amidines were converted into 5-fluoromethylimidazoles in the presence of Selectfluor under gold(I) catalysis [34][35][36] through a cascade cyclization/fluorination process [37]. Following our previous work on gold catalysts (Scheme 1) [38], we

• [39]. When the same reaction was performed in the presence of [bis(trifluoromethanesulfonyl)imidate](triphenylphosphine)gold(I) catalyst [40] (5 mol %), the formation of the difluorinated 3H-indole 2a was observed although in low overall yield (Table 1, entry 2). No traces of C–C bond formation, a

• in 75% yield (Table 1, entry 9). The addition of NaHCO3 [20][33] as a base to the reaction mixture failed to give 2a, whereas it was successful for the preparation of fluorinated pyrazole, via the gold(I)-catalyzed tandem aminofluorination of 1-phenyl-2-(4-phenylbut-3-yn-2-ylidene)hydrazine. Other

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• wise mechanism and involves charged intermediates. Nevado and coworkers [206] applied a closely related reaction to propargylic acetate 262 using a cationic gold(I) catalyst, which was used to selectively cyclopropanate the less hindered double bond of dienes like 263. Spontaneous DVCPR provided

• 278) could be accessed. The selective formation of annulated bicycle 278 in preference of the possible bridged variant underlined the prefered reactivity of their enyne system. Gagosz and coworkers [211] recently showed that the cycloisomerization of enynes can be catalyzed by gold(I) catalysts. In a

Gold(I)-catalyzed domino cyclization for the synthesis of polyaromatic heterocycles

• Mathieu Morin,
• Patrick Levesque and
• Louis Barriault

Beilstein J. Org. Chem. 2013, 9, 2625–2628, doi:10.3762/bjoc.9.297

• Mathieu Morin Patrick Levesque Louis Barriault Center for Catalysis Research and Innovation, Department of Chemistry, University of Ottawa, Ottawa, Canada K1T 1B5 10.3762/bjoc.9.297 Abstract Gold(I) complexes have emerged as powerful and useful catalysts for the formation of new C–C, C–O and C–N

• ; cyclization; gold(I); gold catalysis; heterocycles; regioselectivity; Introduction In the last decade, phosphino and NHC–gold complexes have become prominent catalysts for the addition of nucleophiles to alkenes, alkynes and allenes [1][2][3][4][5][6][7][8][9][10][11]. Owing to the high affinity of gold(I

• ) complexes to C–C π-systems in the presence of other functional groups combined by its predictable reactivity pattern, the gold(I)-catalyzed reaction provides tremendous opportunities for the discovery of new and useful reactions [12]. Recently, we [13] and other groups [14][15][16][17] reported that

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

• would also concur to a better optimization/rationalization of optical outcomes deriving from stereoselective transformations. Despite the apparent interchangeability between cationic gold(I) species and [H+] sources, a major breakthrough introduced by [Au(I)] complexes in the nucleophilic manipulation

• )]-catalyzed hydroamination of alkenes with carbamates. [Au(I)]-catalyzed inter- as well as intramolecular addition of sulfonamides to isolated alkenes. Intramolecular hydroamination of N-alkenylureas catalyzed by gold(I) carbene complex. Enantioselective hydroamination of alkenyl ureas with biphenyl tropos

• carbolactonization of terminal alkenes with arylboronic acids. Synthesis of tricyclic indolines via gold-catalyzed formal [3 + 2] cycloaddition. Gold(I) catalyzed aminoarylation of terminal alkenes in presence of Selectfluor [dppm = bis(diphenylphosphino)methane]. Mechanistic investigation on the aminoarylation of

Stereodivergent synthesis of jaspine B and its isomers using a carbohydrate-derived alkoxyallene as C₃-building block

• Volker M. Schmiedel,
• Stefano Stefani and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2013, 9, 2564–2569, doi:10.3762/bjoc.9.291

• cyclization of 7 gave a higher yield than the attempted gold(I) catalysis (39% overall yield), which might be due to the deactivation of the gold catalyst by impurities still present in the crude allenyl alcohol 7. Next, several methods for the introduction of the amino group were examined. We were very

• employing gold(I) catalysis [44], which after purification and separation afforded the expected products in 41% and 31% yields, respectively. The dihydrofurans 14 and 15 are more stable than the allenyl alcohols 12 and 13 and therefore allowed smooth separation by HPLC. At this point, the assignment of the

Ambient gold-catalyzed O-vinylation of cyclic 1,3-diketone: A vinyl ether synthesis

• Yumeng Xi,
• Boliang Dong and
• Xiaodong Shi

Beilstein J. Org. Chem. 2013, 9, 2537–2543, doi:10.3762/bjoc.9.288

• ether; Introduction The past decade has witnessed the fast growth of homogeneous gold catalysis as one of the important branches in transition-metal chemistry [1][2][3][4][5][6][7][8][9]. The utility of cationic gold(I) complexes as π-carbophilic acids toward alkyne and allene activation renders them

• cross-coupling reactions [18]. Based on the π-carbophilicity of gold(I), the addition of alcohol to alkyne should provide direct access to the corresponding vinyl ether. However, most of the reported gold-catalyzed O-nucleophile additions to alkynes are intramolecular reactions. No general protocol for

• vinyl ether synthesis using gold has been reported to date [17]. Nevertheless, there have been examples regarding the intermolecular addition of carboxylic acids [19][20], phenols [21][22] as well as phosphoric acids [23][24][25] to alkynes. In this context, we report a gold(I)-catalyzed O-vinylation of

Synthetic scope and DFT analysis of the chiral binap–gold(I) complex-catalyzed 1,3-dipolar cycloaddition of azlactones with alkenes

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

Beilstein J. Org. Chem. 2013, 9, 2422–2433, doi:10.3762/bjoc.9.280

• electrophilic alkenes using the bis-gold(I) complex 3 (where the gold atom:ligand ratio is 1:1, Figure 1) [25][26][27] inspired us to test it in this azlactone involved cycloaddition. Previous experience in the 1,3-DC between imino esters and electrophilic alkenes revealed that the dimeric chiral gold complex 3

• order to clarify the enantio- and anomalous regioselectivity. Results and Discussion Initially, the synthesis of oxazolones 5 was accomplished under mild reaction conditions by mixing N-acyl-α-amino acid derivatives in the presence of dehydrating agents such as carbodiimides [2][3][4][5]. Gold(I

• silver(I) salt. These complexes were used immediately after filtration through a celite path. Particularly, complexes 3 and 4 (X = TFA) could be isolated in 96 and 89% yield, respectively, but other gold(I) complexes (see Table 1) with different anions were generated in situ and used as catalysts in the

Gold(I)-catalyzed enantioselective cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2013, 9, 2250–2264, doi:10.3762/bjoc.9.264

• Investigación en Química Biolóxica e Materiais Moleculares (CIQUS). Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain 10.3762/bjoc.9.264 Abstract In recent years there have been extraordinary developments of gold(I)-catalyzed enantioselective processes. This includes progress in the

• processes. Keywords: alkyne; allene; asymmetric catalysis; cycloaddition; enantioselective; gold; gold catalysis; Introduction In the past decade, there have been extraordinary advances in the development of novel stereoselective gold(I)-catalyzed transformations [1][2][3][4][5][6][7][8][9][10]. In this

• context, enantioselective gold catalysis has been identified as a particularly challenging goal because the linear two-coordination mode of gold(I) complexes and the out-sphere π-activation usually associated to carbophilic gold catalysts [11] places ligands far from the reacting centers, thus limiting

Gold(I)-catalyzed 6-endo hydroxycyclization of 7-substituted-1,6-enynes

• Ana M. Sanjuán,
• Alberto Martínez,
• Patricia García-García,
• Manuel A. Fernández-Rodríguez and
• Roberto Sanz

Beilstein J. Org. Chem. 2013, 9, 2242–2249, doi:10.3762/bjoc.9.263

• )-3-(methylbut-2-enyl)benzenes, 1,6-enynes having a condensed aromatic ring at C3–C4 positions, has been studied under the catalysis of cationic gold(I) complexes. The selective 6-endo-dig mode of cyclization observed for the 7-substituted substrates in the presence of water or methanol giving rise to

• presence of cationic gold(I) complexes instead of the usually more favoured 5-exo-dig pathway. So, we initially prepared a variety of these o-disubstituted benzene derivatives 1 by two approaches (see Supporting Information File 1) (Scheme 3). First, o-(bromo)-3-(methylbut-2-enyl)benzene was prepared by

• compound [D]-7b in 75% yield (>90% deuterium incorporation at C4). The generation of that compound could be explained by deuterodemetallation of the vinylgold species B generated by an attack of the nucleophile on intermediate 4b or 4b’ (Scheme 8). Conclusion We described an efficient gold(I)-catalyzed 6

Synthesis, characterization and luminescence studies of gold(I)–NHC amide complexes

• Adrián Gómez-Suárez,
• David J. Nelson,
• David G. Thompson,
• David B. Cordes,
• Duncan Graham,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2013, 9, 2216–2223, doi:10.3762/bjoc.9.260

• Nanometrology, University of Strathclyde, 295 Cathedral Street, Glasgow, G1 1XL, UK 10.3762/bjoc.9.260 Abstract A flexible, efficient and straightforward methodology for the synthesis of N-heterocyclic carbene gold(I)–amide complexes is reported. Reaction of the versatile building block [Au(OH)(IPr)] (1) (IPr

• (NHC) ligands [8][9][10]. Recently, we have been very active in the synthesis and characterization of new gold(I)–NHC complexes and the study of their reactivity, with a special focus on the development of straightforward methodologies [11][12]. As a result of our investigations, we have recently

• reported the synthesis of [AuX(NHC)] (X = Cl, Br, I) complexes, directly from imidazolium and imidazolidinium salts and a suitable gold source, such as [AuCl(SMe2)], using K2CO3 as a base [13]. Moreover, we have also reported the synthesis of the first mononuclear gold(I) hydroxide species, [Au(OH)(IPr

Gold(I)-catalyzed hydroarylation reaction of aryl (3-iodoprop-2-yn-1-yl) ethers: synthesis of 3-iodo-2H-chromene derivatives

• Pablo Morán-Poladura,
• Eduardo Rubio and
• José M. González

Beilstein J. Org. Chem. 2013, 9, 2120–2128, doi:10.3762/bjoc.9.249

• recognized as suitable catalysts to convert aryl propargyl ethers into chromenes. Nowadays, alternative gold(I)-based catalysts have been successfully exploited to further prepare substituted 2H-chromenes [34][35][36][37][38], as well as a wide variety of relevant heterocyclic compounds [39][40]. On the

• other hand, migratory cycloisomerization are important processes in contemporary catalysis [41]. In this context, our group is interested in C–H functionalization reactions of arenes involving propargylic derivatives [42]. Furthermore, the influence of different gold(I) catalysts over the outcome of the

• aryl (3-iodoprop-2-yn-1-yl) ethers relying on the power of gold(I) catalysis, as depicted in Scheme 1 entry d. Herein, we report a new strategy to carry out this transformation. Results and Discussion In a previous work on gold-catalyzed cyclization reactions of N-(3-iodoprop-2-ynyl)-N-tosylanilines