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

• demonstrated to be amongst the best catalysts in many gold(I)-catalyzed cyclizations [6][58]. No reaction was observed with complex 5 after heating for 5 min at 70 °C in CH2Cl2 under microwave irradiation (Table 1, entry 1), whereas the more electrophilic 6, bearing a less donating phosphite ligand, led almost

• pathway. The cyclization of 9-(3-phenylprop-2-ynyl)-9H-fluorene (7a) to form 3-phenylfluoranthene (8a) [59] was also examined by using catalysts 5, 6, and GaCl3 (Table 2). Since the initial gold(I)-catalyzed reaction provided a mixture of 3-phenyl-1,10b-dihydrofluoranthene, 3-phenyl-1,2,3,10b

• 6. Proposed metal catalyzed annulation for the synthesis of triaryldiacenaphtho[1,2-j:1',2'-l]fluoranthenes 2. Pd(OAc)2-catalyzed isomerization of 7a to form (E)-9-(3-phenylallylidene)-9H-fluorene (9). Gold(I)-catalyzed hydroarylation of 7k to give 1,10b-dihydrofluoranthene 9. Gold(I)-catalyzed

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

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

• AgClO4 catalyzed intermolecular N-Michael addition and the subsequent gold(I)-catalyzed hydroalkylation is proposed. Keywords: cascade; cocatalyzed; gold(I)-catalyzed; intramolecular hydroalkylation; intermolecular N-Michael addition; pyrrolidine; silver(I)-catalyzed; Introduction Gold complexes are

• ) complexes can efficiently catalyze direct intramolecular hydroalkylation of unactivated alkenes with α-ketones, via the exo-trig cyclization, to build a variety of new five- and six-membered rings [24]. However, all of the substrates examined in this gold(I)-catalyzed reaction were prepared and isolated

• 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

• authors proposed that these intermediates formally behave as an all-carbon 1,4-dipole that intermolecularly reacts with the indole providing the final polycyclic furan adducts 9 in a regioselective fashion (Scheme 4) [46]. In 2009, J. Zhang reported a gold(I)-catalyzed tandem cyclization/(3 + 3

• -acyloxy migration of propargyl acetates can also participate in myriad gold-catalyzed cycloaddition reactions [82]. In 2006, Gagosz and co-workers reported a gold(I)-catalyzed isomerization of enynyl acetates such as 38 to afford bicyclo[3.1.0]hexenes 40 with excellent yields and stereoselectivities [83

• ]. Gold-catalyzed intramolecular (4 + 2) cycloadditions of unactivated alkynes and dienes [55]. Gold-catalyzed preparation of bicyclo[4.3.0]nonane derivatives from dienol silyl ethers [59]. Gold(I)-catalyzed intramolecular (4 + 2) cycloadditions of arylalkynes or 1,3-enynes with alkenes [60]. Gold(I

One-pot Diels–Alder cycloaddition/gold(I)-catalyzed 6-endo-dig cyclization for the synthesis of the complex bicyclo[3.3.1]alkenone framework

• Boubacar Sow,
• Gabriel Bellavance,
• Francis Barabé and
• Louis Barriault

Beilstein J. Org. Chem. 2011, 7, 1007–1013, doi:10.3762/bjoc.7.114

• generate carbon-bridged frameworks of various sizes through a gold(I)-catalyzed carbocyclization [13]. Although the cyclization of enol ether 5 can produce 5-exo and 6-endo products, we found that gold complexes 6, having bulky phosphine ligands such as 2-bis(tert-butylphosphino)biphenyl, gave exclusively

• ) are underway and will be reported in due course. Structures of naturally occurring PPAPs. Gold(I)-catalyzed 6-endo-dig cyclization. Synthesis of papuaforin A core 4. Proposed domino Diels–Alder reaction/gold(I)-catalyzed cyclization. One-pot Diels–Alder cycloaddition/gold(I) catalyzed carbocyclization

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

• demonstrated by our group, establishing a wider scope and sensibly higher enantioselectivities for the reactions performed in the presence of chiral phosphoramidite/silver(I) complexes [24]. Concerning enantioselective gold(I)-catalyzed 1,3-DC, the classical cycloaddition starting from iminoesters 6 has not

• of acrylates as dipolarophiles has only been explored with the 2-thienyliminoesters 6a. Therefore, based on our experience of silver(I)- and gold(I)-catalyzed 1,3-DC involving azomethine ylides derived from α-iminoester 6b and tert-butyl acrylate, we selected a series of known chiral phosphoramidite

• enantioselectivity (78% ee). However, DIPEA-mediated cycloaddition did not improve the enantioselectivity of the resulting endo-cycloadduct 5b. Unlike the results obtained with silver(I) catalytic complexes at lower temperatures (0 or −20 °C), the gold(I)-catalyzed cycloaddition could be successfully carried out at

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

• the zinc-catalyzed 7-exo-dig cyclization was reported specifically for a propargyl ether substrate [54]. Previously, we reported that semihollow-shaped triethylnylphosphine L1 (Figure 2) exerted marked acceleration effects in the gold(I)-catalyzed Conia-ene reactions of acetylenic keto esters and

• enhancement. Recently, we further developed the gold(I)-catalyzed 7-exo-dig cyclization of acetylenic silyl enol ethers with L1 [57]. In this context, we expected that the use of L1 as a ligand in the gold-catalyzed intramolecular hydroamination of alkynes would enable the construction of nitrogen-containing

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

• available heteroatom-substituted propargyl alcohols 10 has been developed by Aponick and co-workers [22]. For the formation of tetrahydropyran analogs 13 and 15, the gold(I)-catalyzed cyclization of monoallylic diols 12 and 14 is an efficient method (Scheme 2) [23][24]. In addition to common organic

• atoms to form the intermediates 26 or 27, which then rearrange to yield the oxonium intermediates 28 or 29, respectively. Gold(I)-catalyzed intramolecular cyclization of monopropargylic triols 32 has been reported to be a novel and mild approach [29] for producing olefin-containing spiroketals 33 (and

• series of alcohols generated the corresponding tert-allylic ethers 37 with high regioselectivity. Gold(I) catalysts were found to be unique and superior in terms of reactivity and regioselectivity. A notable observation in some of these studies is that gold(I) catalyzed rearrangement to furanones 39 and

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

• furnish the intermediate 9. The loss of a proton to allow aromatization of the system, followed by a protodemetalation step would finally give furan 7. In summary, we have developed a new gold(I)-catalyzed formation of polysubstituted furans, which is characterized by its efficiency, the mild conditions

• employed and the easy formation of quaternary centers. The selectivity observed in the structure of the final product is in agreement with the postulated Claisen-type rearrangement. Further studies related to the development of an asymmetric version of this new gold(I)-catalyzed process and its application

• to the synthesis of natural products are underway. Natural products possessing a 2-butenylfuran motif. Alkynyl and allenyl substrates in gold-catalyzed formation of furans. Synthetic approach to functionalized furans. Mechanistic proposal. Scope of the gold(I)-catalyzed formation of furans.a

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

• an one-pot, sequential, reaction with first a gold(III)-catalyzed propargylic substitution followed by a gold(I)-catalyzed cycloisomerization, the bicyclic compound 37 was obtained in 71% yield [24][80][81][82]. Very recently, a remarkable one-pot reaction using an original gold(III) catalyst has

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

• interested in the use of gold for simple and highly efficient transformations. Additionally, quinoxaline and benzimidazole skeletons are common building blocks for the preparation of substances with pronounced biological activities [39][40][41][42][43][44]. Herein, we report the gold(I)-catalyzed oxidation

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

• migration of R3 are strictly limited to compounds that bear a quaternary center (R3 = alkyl, R2 ≠ H). As shown for the gold(I)-catalyzed reaction of 1,5-enyne 53, the formation of the bicyclo[3.1.0]hexene 54 is driven by the release of ring strain. Enynes with R3 = H undergo exclusively a hydride shift to

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

• , temperature), in the gold(I)-catalyzed tandem reactions of 3-propargylindoles initiated by 1,2-indole migrations. We have been able to switch the preference of 3-propargylindoles, bearing (hetero)aromatic substituents at both propargylic and terminal positions of the alkyne moiety, from undergoing an aura-iso

Highly efficient gold(I)-catalyzed Overman rearrangement in water

• Dong Xing and
• Dan Yang

Beilstein J. Org. Chem. 2011, 7, 781–785, doi:10.3762/bjoc.7.88

• Dong Xing Dan Yang Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China 10.3762/bjoc.7.88 Abstract A highly efficient gold(I)-catalyzed Overman rearrangement of allylic trichloroacetimidates to allylic trichloroacetamides in water is reported. With this

• moderate yields were achieved [25][26][27][28]. Very recently, our group developed an efficient gold(I)-catalyzed decarboxylative aza-Claisen rearrangement of allylic N-tosylcarbamates for the synthesis of N-tosyl allylic amines [29]. This reaction was performed in water and therefore represented an

• 100 °C for 3 h (Table 1, entry 6), indicating that the gold(I) catalyst is indispensible for this transformation. This gold(I)-catalyzed reaction could be performed at room temperature, albeit with a prolonged reaction time (Table 1, entry 7). When the temperature was raised to 55 °C the reaction was

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

• the various approaches to access these ubiquitous scaffolds, the gold(I)-catalyzed ring expansion of cyclopropanols and cyclobutanols is considered one of the most powerful and versatile methods. In 2005, Toste and co-workers reported the treatment of 1-(phenylethynyl)cyclopropanol (11) with tris(4

• -trifluoromethylphenyl)phosphine gold(I) to give alkylidenecyclobutanone 12 quantitatively (Scheme 3, reaction 1) [19]. In an analogous manner, alkynylcyclobutanols were suitable substrates for gold(I)-catalyzed ring expansions only when a terminal alkyne group was present (Scheme 3, reaction 2). Thus, cyclobutanol 13

• , intermediates characterize these competitive processes, i.e., 1,2-migration via metal "carbenoid" 81 formation and [3,3]-sigmatropic rearrangement via allenyl acetate 82 as an intermediate (Scheme 24) [5][56][57]. In 2008, Toste and co-workers reported a gold(I)-catalyzed cycloisomerization of cis-pivaloyloxy

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

• followed by several other racemic and enantioselective syntheses [2][3][4][5][6][7][8][9][10][11][12][13][14]. Herein, we report a short formal total synthesis of racemic clavukerin A employing the gold(I)-catalyzed cycloisomerization of a 3-methoxy-1,6-enyne as the key strategy, which was recently

• cyclization (path B). The cycloheptenone 4 could then be synthesized from the enyne substrate 5 by gold(I)-catalyzed cycloisomerization. The synthesis of enyne substrate 5 commenced with the alkylation of methyl acetoacetate with the known bromide 6 [24] to provide compound 7 in 55% yield (Scheme 2

• proceeds via the initial heterocyclization intermediate 10 and the subsequently rearranged intermediate 11 (Scheme 3). Notably, when the gold(I)-catalyzed reaction was carried out on a multi-mmol scale, there was no decrease in the yield at the same catalyst loading. With ketone 4 in hand, the final stage

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

• –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

• (R’ = H) was employed as the substrate, none of the cyclization product was detected and the water insertion product 4g was obtained in 81% yield. A tentative mechanism for this gold(I)-catalyzed cascade insertion/cyclization is proposed in Scheme 2. Decomposition of diazo compound 1 by (IPr)AuCl

• mechanism is supported by the fact that when 4a was subjected to the gold(I)-catalyzed reaction under identical conditions 2a and 3a were obtained in similar yields. Conclusion In summary, we have developed a cascade insertion/cyclization of water with o-acetylenyl-substituted phenyldiazoacetates catalyzed

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

• . A gold(I)-catalyzed hydroarylation of indoles with styrenes as well as with aliphatic and cyclic alkenes was developed by Che et al. [64]. [AuCl(PPh3)]/AgOTf was the catalyst system of choice and the reaction was, depending on the substrate, performed under thermal or microwave-assisted conditions