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

• acid to activate unsaturated C–C bonds towards nucleophilic attack [1][2][3][4][5][6][7][8][9][10] (for selected reviews on gold-catalyzed reactions see [1][2][3][4][5][6][7][8][9]). Based on this mode of activation, several methods for the gold-catalyzed inter- and intramolecular addition of oxygen

• - [11][12][13][14][15], nitrogen- [10][16][17][18] (for recent reviews on gold-catalyzed hydroamination see [16][17][18]), or carbon-nucleophiles [19][20][21][22][23][24] to unactivated alkenes [21][22][23][24][25] have been developed. On the other hand, in recent years, considerable efforts have been

• simple starting materials [41]. We initially envisioned that the gold(I)-catalyzed cascade process could be established starting from the intermolecular N-Michael reaction of α,β-unsaturated ketone 1 and substituted allylamine 2 to furnish an α-ketone intermediate I [42][43][44] (for gold-catalyzed

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

• al CSIC. Universidad de Santiago de Compostela, Avda. de las Ciencias, s/n, 15782, Santiago de Compostela, Spain, (+) 34 981563100 Fax: (+) 34 981595012 10.3762/bjoc.7.124 Abstract In the last years there have been extraordinary advances in the development of gold-catalyzed cycloaddition processes

• the most recent contributions, organized according to the type of unsaturated system that is initially activated by the electrophilic gold complex [12]. Related Pt-catalyzed cycloadditions will only be mentioned when required in the context of a particular gold-catalyzed process, or to highlight the

• start by addition of a π-carbon nucleophile instead of a heteronucleophile. For instance it has been shown that it is possible to achieve gold-catalyzed formal intramolecular (4 + 2) cycloadditions between alkynes and non-activated dienes such as 19 (e.g., Scheme 11) [55]. This type of cycloaddition has

Asymmetric Au-catalyzed cycloisomerization of 1,6-enynes: An entry to bicyclo[4.1.0]heptene

• Alexandre Pradal,
• Chung-Meng Chao,
• Patrick Y. Toullec and
• Véronique Michelet

Beilstein J. Org. Chem. 2011, 7, 1021–1029, doi:10.3762/bjoc.7.116

• gold-catalyzed cycloisomerization reaction of heteroatom tethered 1,6-enynes is described. The cycloisomerization reactions were conducted in the presence of the chiral cationic Au(I) catalyst consisting of (R)-4-MeO-3,5-(t-Bu)2-MeOBIPHEP-(AuCl)2 complex and silver salts (AgOTf or AgNTf2) in toluene

• comprehensive study on gold-catalyzed enantioselective synthesis of bicyclo[4.1.0]heptenes, focusing on the scope and limitations of such systems. Results and Discussion Optimization of the catalytic system Based on our ongoing program on asymmetric gold catalysis [46][49][50][51][52], and on literature reports

• contributed to the development of an asymmetric gold-catalyzed cycloisomerization reaction allowing the formation of oxa- and aza-bicyclo[4.1.0]heptene derivatives. The combination of chiral Au(I) complex (R)-4-MeO-3,5-(t-Bu)2-MeOBIPHEP-(AuCl)2 associated to silver salts promotes the enantioselective

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

• also influenced the allene reactivity, probably through gold catalyzed allene activation. The fact that TA–Au gave the dominant (E)-isomers strongly suggests that these complexes may be applied as the chemoselective catalyst in alkyne activation over allene. The reactions of propargyl ester 1a with TA

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

• atoms of the catalyst both in the TS and the ylide complex is the explanation for the success of the gold-catalyzed cycloaddition, in constrast to the observed TS involving methyl benzylideneiminoleucinate. Experimental General. All reactions were carried out in the absence of light. Anhydrous solvents

Intramolecular hydroamination of alkynic sulfonamides catalyzed by a gold–triethynylphosphine complex: Construction of azepine frameworks by 7-exo-dig cyclization

• Hideto Ito,
• Tomoya Harada,
• Hirohisa Ohmiya and
• Masaya Sawamura

Beilstein J. Org. Chem. 2011, 7, 951–959, doi:10.3762/bjoc.7.106

• Hideto Ito Tomoya Harada Hirohisa Ohmiya Masaya Sawamura Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan 10.3762/bjoc.7.106 Abstract The gold-catalyzed, seven-membered ring forming, intramolecular hydroamination of alkynic sulfonamides has been

• for the construction of N-heterocyclic compounds, metal-catalyzed intramolecular hydroamination of unactivated C–C multiple bonds is particularly straightforward and efficient [17][18]. Specifically, gold-catalyzed intramolecular hydroaminations of alkynes, alkenes and allenes show remarkable

• efficiency [19][20][21][22][23][24][25][26][27][28]. Unfortunately, however, the application of these methodologies to the synthesis of the N-heterocyclic seven-membered ring compounds is hampered by the low efficiency of seven-membered ring formations. Despite extensive studies on the gold-catalyzed

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

• strategies to form these bonds in more convenient ways. In this review, we highlight recent advances in the gold-catalyzed chemistry of addition of X–H (X = O, N, C) bonds to C–C multiple bonds, tandem reactions, and asymmetric additions. This review covers gold-catalyzed organic reactions published from

• 2008 to the present. Keywords: asymmetric addition; catalysis; gold; C−C multiple bonds; tandem reaction; Review 1 Introduction Gold-catalyzed reactions have emerged as a powerful synthetic tool in modern organic synthesis. This past decade has been the boom time for homogeneous gold catalysis, which

• was rather limited in organic synthesis until the advantages of gold complexes as catalysts were discovered [1]. In comparison to other transition-metal catalysts, most gold-catalyzed reactions are atom-economic, remarkably mild with regard to reaction conditions, and most importantly, have a

Gold(I)-catalyzed formation of furans by a Claisen-type rearrangement of ynenyl allyl ethers

• Florin M. Istrate and
• Fabien Gagosz

Beilstein J. Org. Chem. 2011, 7, 878–885, doi:10.3762/bjoc.7.100

• of a new procedure for the synthesis of polysubstituted furans by a gold-catalyzed cycloisomerization of ynenyl allyl ethers [45][46][47][48]. In the course of our work on the development of new gold-catalyzed transformations [49][50][51], we recently found that a series of ynenyl allyl tosylamides 1

• -derivatives would therefore support our initial mechanistic proposal and would broaden the scope of this new gold-catalyzed Claisen-type rearrangement [55][56][57][58][59][60][61][62]. Moreover this synthetic approach to furans would be particularly interesting for several reasons: • The required ynenyl allyl

• with ethers 6r–s, which could not be completely converted into the corresponding furans 7r–s (entries 18–19). A mechanistic proposal for the formation of furans 7a–s is presented in Scheme 3. It is based on the results shown in entries 2–19 (Table 1), which support the involvement of a gold-catalyzed

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

• Olivier Debleds Eric Gayon Emmanuel Vrancken Jean-Marc Campagne Institut Charles Gerhardt, UMR 5253, Equipe AM2N, ENSCM 8 rue de l’Ecole Normale, 34296 Montpellier Cédex, France 10.3762/bjoc.7.99 Abstract This personal account summarizes our recent developments in gold-catalyzed direct

• domino reactions. Review Gold-catalyzed alcohol substitution Scope and limitations In the past few years, homogeneous gold catalysis has emerged as an efficient tool to activate triple bonds for the addition of various nucleophiles to alkynes. We initially anticipated that, through coordination to π-bond

• even after prolonged reaction at reflux (Scheme 14). Very recently, Darcel described the iron(III) hydration of terminal alkynes [65]. These conditions were attempted to cyclize 22a but in our hands only extensive decomposition was observed. We thus turned our attention to gold-catalyzed cyclization of

Gold-catalyzed oxidation of arylallenes: Synthesis of quinoxalines and benzimidazoles

• Dong-Mei Cui,
• Dan-Wen Zhuang,
• Ying Chen and
• Chen Zhang

Beilstein J. Org. Chem. 2011, 7, 860–865, doi:10.3762/bjoc.7.98

• Dong-Mei Cui Dan-Wen Zhuang Ying Chen Chen Zhang College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou 310014, PR China College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, PR China 10.3762/bjoc.7.98 Abstract A gold-catalyzed oxidation of arylallenes

• ; oxidation; quinoxaline; Introduction Recently, several research groups have developed gold-catalyzed homogeneous catalytic reactions [1]. A variety of organic transformations have been shown to be mediated by gold(I) or gold(III) complexes in solution. In addition to its ability to activate unsaturated C–C

• particular, water as a nucleophilic reagent has been used in the addition of alkynes and allenes [16][17][18]. In contrast, gold-catalyzed oxidation chemistry has been less well developed [25][26][27][28][29][30][31][32][33][34][35][36], although oxidative cleavage of carbon–carbon double bonds and carbon

When gold can do what iodine cannot do: A critical comparison

• Sara Hummel and
• Stefan F. Kirsch

Beilstein J. Org. Chem. 2011, 7, 847–859, doi:10.3762/bjoc.7.97

• domino processes, for which gold pre-catalysts were found to be outstandingly effective, were paralleled by employing iodine electrophiles in place of gold compounds. This review highlights how, in certain cases, iodonium activation can match gold-catalyzed reactions to construct identical product

• tolerance, there has also been a considerable increase in the applications of such complexes in target-oriented synthesis [21][22][23][24][25][26]. A simplified mechanistic scenario for domino processes initiated by gold-catalyzed alkyne activation is depicted in Scheme 1a. After nucleophilic attack at the

• with tethered alkynes can be accomplished by using simple iodine electrophiles [43][44][45][46][47][48][49][50][51][52][53][54], it would be of great interest to know to what extent transition metal-free processes can be substituted for gold-catalyzed processes. This review is intended to demonstrate

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

• existence of Au(I)/Au(III) catalytic cycles [26][27][28][29][30][31][32]. For instance, Zhang and co-workers have developed a gold-catalyzed oxidative cross-coupling reaction of arylboronic acids with propargyl esters [27], and Selectfluor® – a source of electrophilic fluorine – was used to oxidize the

• was observed under the above conditions. Taking into account the counter ion effects in gold-catalyzed reactions [33][34][35], Ph3PAuOTf, produced from a combination of Ph3PAuCl and AgOTf in a 1:1 ratio, was investigated. To our delight, the expected product 2a could be isolated in 56% yield (Table 1

• , commonly employed well recognized and commercially available phosphine ligands [17][18], such as dppm, dppe, dppp, dppf, and XPhos, were screened to test the feasibility of this gold-catalyzed cross-coupling (Table 1, entries 10–12, see also Supporting Information File 1). In addition, a series of

A comparative study of the Au-catalyzed cyclization of hydroxy-substituted allylic alcohols and ethers

• Berenger Biannic,
• Thomas Ghebreghiorgis and
• Aaron Aponick

Beilstein J. Org. Chem. 2011, 7, 802–807, doi:10.3762/bjoc.7.91

• sensitive functional groups. While cyclization reactions of highly elaborated substrates are desirable, mild chemoselective methods are necessary for this endeavor. Homogeneous gold-catalyzed reactions have emerged as a powerful new methodology for the construction of a diverse array of molecular

High chemoselectivity in the phenol synthesis

• Matthias Rudolph,
• Melissa Q. McCreery,
• Wolfgang Frey and
• A. Stephen K. Hashmi

Beilstein J. Org. Chem. 2011, 7, 794–801, doi:10.3762/bjoc.7.90

• 10.3762/bjoc.7.90 Abstract Efforts to trap early intermediates of the gold-catalyzed phenol synthesis failed. Neither inter- nor intramolecularly offered vinyl groups, ketones or alcohols were able to intercept the gold carbenoid species. This indicates that the competing steps of the gold-catalyzed

• organic chemistry [13][14]. One of these early examples is the gold-catalyzed phenol synthesis [12] in which the furan-ynes 1 used as substrates represent the first ene–yne-type compounds ever used in gold catalysis. While many investigations in the field focused on methodology, mechanistic research was

• much less widespread [2][3][15]. The gold-catalyzed ene–yne cycloisomerization reactions are, mechanistically, very complex reactions [16][17][18], and the furan–yne cycloisomerization is no exception. For the latter reaction arene oxides D [19] and oxepines C [20] could be detected as intermediates

Solvent- and ligand-induced switch of selectivity in gold(I)-catalyzed tandem reactions of 3-propargylindoles

• Estela Álvarez,
• Delia Miguel,
• Patricia García-García,
• Manuel A. Fernández-Rodríguez,
• Félix Rodríguez and
• Roberto Sanz

Beilstein J. Org. Chem. 2011, 7, 786–793, doi:10.3762/bjoc.7.89

• Organometálica “Enrique Moles”, Universidad de Oviedo, C/Julián Clavería 8, 33006 Oviedo, Spain 10.3762/bjoc.7.89 Abstract The selectivity of our previously described gold-catalyzed tandem reaction, 1,2-indole migration followed by aura-iso-Nazarov cyclization, of 3-propargylindoles bearing (hetero)aromatic

• related 1,2-sulfur migrations [12]. Within this area we have reported the first examples of gold-catalyzed migration reactions in propargylic systems that involve a carbon-centered moiety, implying that carbon–carbon bonds are broken and formed instead of carbon–heteroatom bonds [13][14]. Based on the

• nucleophilic nature of indoles [15], which are known to react with gold-activated alkynes or allenes [16][17], and by taking advantage of our reported methodology for the synthesis of 3-propargylindoles [18][19], we have shown that the indole nucleus is able to participate in gold-catalyzed 1,2-migration

Synthetic applications of gold-catalyzed ring expansions

• David Garayalde and
• Cristina Nevado

Beilstein J. Org. Chem. 2011, 7, 767–780, doi:10.3762/bjoc.7.87

• venues for the synthesis of structurally complex molecules with interesting biological activities. Herein we summarize, from both a synthetic as well as a mechanistic point of view, the most recent developments in gold-catalyzed ring expansions. Keywords: cycloisomerizations; gold; homogeneous catalysis

• powerful in triggering ring-expansion processes to introduce structural complexity into organic molecules. The gold-catalyzed ring expansion of strained rings is viewed nowadays as a flexible synthetic tool in organic synthesis [7][8][9]. In this review, we aim to summarize the most recent developments in

• gold-catalyzed ring expansions, from both a synthetic and a mechanistic point of view. A deeper understanding of the processes governing gold-chemistry allows organic chemists to become more creative in designing novel processes, which might provide access to architectures that were so far inaccessible

A racemic formal total synthesis of clavukerin A using gold(I)-catalyzed cycloisomerization of 3-methoxy-1,6-enynes as the key strategy

• Jae Youp Cheong and
• Young Ho Rhee

Beilstein J. Org. Chem. 2011, 7, 740–743, doi:10.3762/bjoc.7.84

• developed by us [15]. This reaction provides cycloheptane frameworks in a unique manner and illustrates the utility of the gold-catalyzed reactions [16][17][18][19][20][21][22][23]. From a retrosynthetic point of view, we envisioned two different approaches to the key enone intermediate 1 [3] to clavukerin

• spectrum of the crude reaction product. Subsequent methylation gave the 1,6-enyne 5 in 88% yield. We then investigated the gold-catalyzed cycloisomerization of enyne 5 using the optimized conditions from our previous study [15]. The use of the pre-generated complex Au[P(C6F5)3]+SbF6− (2 mol %) provided the

• Jae Youp Cheong Young Ho Rhee Department of Chemistry, POSTECH (Pohang University of Science and Technology), Hyoja-dong san 31, Nam-gu, Pohang, Kyungbook, Republic of Korea 790-784 10.3762/bjoc.7.84 Abstract An efficient formal total synthesis of (±)-clavukerin A was accomplished via a gold

When cyclopropenes meet gold catalysts

• Frédéric Miege,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2011, 7, 717–734, doi:10.3762/bjoc.7.82

• in a variety of gold-catalyzed reactions. The different contributions in this growing research area are summarized in this review. Keywords: cyclopropenes; gold carbenes; gold catalysis; gold-stabilized allylic cations; ring-opening; Review Introduction Homogeneous gold catalysis has become a

• bonds [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Whereas alkynes, alkenes and allenes have been widely used as substrates or partners in gold-catalyzed reactions, it was only rather recently, in 2008, that cyclopropenes entered the field of gold catalysis despite their well-known high and

• versatile reactivity in transition metal-catalyzed reactions [15]. As has been observed with other transition metals, the reactivity of cyclopropenes A in gold-catalyzed reactions is essentially (but not exclusively) related to their ability to act as ligands for π-acidic gold complexes, and hence, to

Gold-catalyzed naphthalene functionalization

• Pedro J. Pérez,
• M. Mar Díaz-Requejo and
• Iván Rivilla

Beilstein J. Org. Chem. 2011, 7, 653–657, doi:10.3762/bjoc.7.77

• . The Buchner reaction applied to naphthalene. (a) Teyssié's system. (b) Müller's system. The gold-catalyzed reaction of benzene and EDA. The functionalization of naphthalene with ethyl diazoacetate catalyzed by the complexes (a) 1a and (b) 1b. The functionalization of naphthalene with ethyl 2

Gold-catalyzed alkylation of silyl enol ethers with ortho-alkynylbenzoic acid esters

• Haruo Aikawa,
• Tetsuro Kaneko,
• Naoki Asao and
• Yoshinori Yamamoto

Beilstein J. Org. Chem. 2011, 7, 648–652, doi:10.3762/bjoc.7.76

• , the Lewis acid-catalyzed reaction of silyl enol ethers with alkyl halides is well known as one of the most efficient preparative methods for regio-defined α-alkylated ketones (path a in Scheme 1) [5][6][7][8][9][10][11][12][13][14][15][16][17]. In contrast, in this paper, we report a gold-catalyzed

• 1a with allyl ester 2d proceeded smoothly and the corresponding allylated product 3f was obtained in 70% yield (entry 5) [42]. A plausible mechanism for the gold-catalyzed alkylation of silyl enol ethers is shown in Scheme 2. The gold catalyst enhances the electrophilicity of the alkynyl moiety of 2

• -position, such as 1f. Further studies to elucidate the mechanism of this reaction and to extend the scope of synthetic utility are underway. Alkylation of silyl enol ethers. Plausible mechanism for the alkylation of silyl enol ether. Gold-catalyzed isomerism of silyl enol ether. Gold-catalyzed alkylation

Sequential Au(I)-catalyzed reaction of water with o-acetylenyl-substituted phenyldiazoacetates

• Lei Zhou,
• Yizhou Liu,
• Yan Zhang and
• Jianbo Wang

Beilstein J. Org. Chem. 2011, 7, 631–637, doi:10.3762/bjoc.7.74

• transfer a carbene unit to saturated or unsaturated organic substrates [3]. However, compared to the other group 11 metals, i.e., copper and silver, there are only a few reports on gold-catalyzed carbene transfer reactions of diazo compounds [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. In 2005

• –alkyne cyclization. Since gold complexes are well-known for their efficacy in activating alkynes, we reasoned that a concurrent catalysis based on gold-catalyzed reaction of diazo compounds and alkynes might be possible [30]. Herein we report such a catalytic system, namely a gold(I)-catalyzed insertion

• ][40][41][42][43][44][45][46][47][48][49][50][51]. Moreover, this study further demonstrates the possibility to incorporate gold-catalyzed reaction of diazo compounds with various other gold-catalyzed transformations. Further studies to broaden the scope of these reactions are currently underway

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

• Científicas (CSIC), Juan de la Cierva 3, 28006-Madrid, Spain 10.3762/bjoc.7.73 Abstract New gold-catalyzed methods using the β-lactam scaffold have been recently developed for the synthesis of different sized heterocycles. This overview focuses on heterocyclization reactions of allenic and alkynic β-lactams

• catalyzed by gold complexes because of their powerful soft Lewis acidic nature [10][11][12][13][14][15][16]. In particular, gold-catalyzed intramolecular addition of oxygen and nitrogen nucleophiles across an allene or a carbon–carbon triple bond is intriguing from the point of view of regioselectivity

• four-membered ring, using the chirality and functionalization of the β-lactam ring as a stereo-controlling element [29][30]. This overview focuses on gold-catalyzed heterocyclization reactions of allenic and alkynic β-lactams which rely on the activation of the allene and alkyne component. The

Construction of cyclic enones via gold-catalyzed oxygen transfer reactions

• Leping Liu,
• Bo Xu and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2011, 7, 606–614, doi:10.3762/bjoc.7.71

• Leping Liu Bo Xu Gerald B. Hammond Department of Chemistry, University of Louisville, 2320 South Brook Street, Louisville, KY 40292, USA 10.3762/bjoc.7.71 Abstract During the last decade, gold-catalyzed reactions have become a tour de force in organic synthesis. Recently, the gold-, Brønsted acid

• chemistry. This mini-review focuses on the most recent achievements on gold-catalyzed oxygen transfer reactions of tethered alkynones, diynes or alkynyl epoxides to cyclic enones. The corresponding mechanisms for the transformations are also discussed. Keywords: alkyne–carbonyl metathesis; cyclic enones

• ; gold-catalyzed; oxonium; oxygen transfer; Review α,β-Unsaturated carbonyl derivatives are not only important building blocks in synthetic organic chemistry, but are also a significant motif in natural products and biologically active compounds [1][2][3][4][5][6][7][8]. The construction of the

Gold-catalyzed regioselective oxidation of terminal allenes: formation of α-methanesulfonyloxy methyl ketones

• Yingdong Luo,
• Guozhu Zhang,
• Erik S. Hwang,
• Thomas A. Wilcoxon and
• Liming Zhang

Beilstein J. Org. Chem. 2011, 7, 596–600, doi:10.3762/bjoc.7.69

• from terminal allenes in fair to good yields. The chemistry relies on a gold-catalyzed intermolecular oxidation of the 1,2-diene unit using 3,5-dichloropyridine N-oxide as the oxidant. The reaction tolerates a range of functional groups and shows excellent regioselectivity. Keywords: allene; catalysis

• , whilst the latter suffers from low regioselectivities. This gold-catalyzed approach offers an attractive alternative that is highly regioselective, catalytic on gold and takes place under relatively mild reaction conditions. The mechanism of this highly regioselective gold-catalyzed oxidation of allenes

• first gold-catalyzed intermolecular oxidation of allenes. With 3,5-dichloropyridine N-oxide as the oxidant and in the presence of MsOH, α-methanesulfonyloxy methyl ketones are formed in one step in fair to good yield with excellent regioselectivities under relatively mild reaction conditions. The

One-pot gold-catalyzed synthesis of 3-silylethynyl indoles from unprotected o-alkynylanilines

• Jonathan P. Brand,
• Clara Chevalley and
• Jérôme Waser

Beilstein J. Org. Chem. 2011, 7, 565–569, doi:10.3762/bjoc.7.65

• capable of promoting nucleophilic attack on acetylenes, gold has recently attracted interest from the synthetic chemistry community [11][12][13][14]. Gold catalysts have also been used in domino sequences starting from o-alkynylanilines. Arcadi and Marinelli reported that gold-catalyzed cyclization of 2

• first results on the direct alkynylation reaction combined in a one-pot procedure with gold-catalyzed indole ring formation are promising, and analogous strategies combining palladium-catalyzed synthesis of indoles [3] and gold-catalyzed alkynylation could also be envisaged. The next step will be to

• reactions of 2-alkynylanilines. Gold-catalyzed direct alkynylation of indoles with TIPS-EBX (1). One-pot alkynylaniline cyclization/direct alkynylation. Synthesis of 2-alkynylanilines 2. Domino cyclization–alkynylation of aniline 2a. Scope of the reaction. Supporting Information Supporting Information File