Visible-light photoredox catalyzed synthesis of pyrroloisoquinolines via organocatalytic oxidation/[3 + 2] cycloaddition/oxidative aromatization reaction cascade with Rose Bengal

• Carlos Vila,
• Jonathan Lau and
• Magnus Rueping

Beilstein J. Org. Chem. 2014, 10, 1233–1238, doi:10.3762/bjoc.10.122

• type of compounds [22][23][24][25][26]. Recently, several metal mediated syntheses using a [3 + 2] cycloaddition reaction have been described in the literature. Porco Jr. et al. [27] described a silver-catalyzed cycloisomerization/dipolar cycloaddition for the synthesis of the pyrrolo[2,1-a

Olefin cross metathesis based de novo synthesis of a partially protected L-amicetose and a fully protected L-cinerulose derivative

• Bernd Schmidt and
• Sylvia Hauke

Beilstein J. Org. Chem. 2014, 10, 1023–1031, doi:10.3762/bjoc.10.102

• sugar biosynthesis genes [5]. Comparatively few transition metal mediated or -catalyzed reactions have hitherto been used for the synthesis of 2,3,6-tridesoxy sugars such as amicetose. An example is the W-promoted cycloisomerization of lactaldehyde derived alkynols, which yields the glycal of amicetose

Allenylphosphine oxides as simple scaffolds for phosphinoylindoles and phosphinoylisocoumarins

• G. Gangadhararao,
• Ramesh Kotikalapudi,
• M. Nagarjuna Reddy and
• K. C. Kumara Swamy

Beilstein J. Org. Chem. 2014, 10, 996–1005, doi:10.3762/bjoc.10.99

• , over the last decade, allenes have attained a prominent position in organic transformations like cycloaddition, cycloisomerization, base or metal-catalyzed reactions [5][6][7]. In particular, cyclization reaction of allenes has emerged as a valuable tool in developing different methods leading to

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

• mechanism. This part of the review is divided in sections related to the nature of the activated functionalities. Reaction involving activation of carbon–carbon multiple bonds. This section primarily discusses cycloisomerization reactions involving the addition of imines to silver-activated carbon–carbon

• -catalyzed MCRs involving imines in cycloisomerization reactions follow the main reaction pathway shown in Scheme 18. Starting from a γ-ketoalkyne [51] encompassed in a (hetero)aromatic framework, a condensation step with a suitable G–NH2 group (amine or hydrazine) provides the imine intermediate, which

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

• Paris, UMR 8247, Ecole Nationale Supérieure de Chimie de Paris, Chimie ParisTech, 11 rue P. et M. Curie, F-75231 Paris Cedex 05, France 10.3762/bjoc.10.42 Abstract The scope and limitations of gold-catalyzed tandem cycloisomerization/fluorination reactions of unprotected 2-alkynylanilines to have

• wish to report herein a comprehensive study on gold-catalyzed tandem cycloisomerization/fluorination reactions to access 3,3-difluoro-2-aryl-3H-indoles and 3-fluoro-2-arylindoles, putting the stress on the scope and limitations of such systems. Results and Discussion Optimization of the catalytic

• ][46][47][48][49][50][51] and synthesized them together with new functionalized 2-alkynylanilines to evaluate the efficiency of the gold catalytic system. Scope and limitations of the catalytic system The prepared 2-substituted anilines were then engaged in the cycloisomerization/fluorination process

Boron-substituted 1,3-dienes and heterodienes as key elements in multicomponent processes

• Ludovic Eberlin,
• Fabien Tripoteau,
• François Carreaux,
• Andrew Whiting and
• Bertrand Carboni

Beilstein J. Org. Chem. 2014, 10, 237–250, doi:10.3762/bjoc.10.19

• -component adducts were isolated in good yields up to 92%. A single diastereomer was detected with maleimides; the diastereoselectivity being lower with methyl acrylate and vinyl oxazolidinone (Scheme 7). A one-pot, palladium-mediated cycloisomerization of ene-ynes 5 was applied to the synthesis of the

• -phenylmaleimide and 4-phenyltriazoline-3,5-dione. Asymmetric synthesis of a α-hydroxyalkylcyclohexane. Tandem [4 + 2]-cycloaddition/allylboration of 3-silyloxy- and 4-alkoxy-dienyl boronates. Metal-mediated cycloisomerization/Diels–Alder reaction/allylboration sequence. Cobalt-catalyzed Diels–Alder/allylboration

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

• cycloheptadiene 265 via 264 in good yields. Further contributions to the topic have been put forward by the group of Echavarren [207] and Gung [208]. Cycloisomerization involving DVCPR Iwasawa and coworkers [209] discovered a cyclopropanation/DVCPR sequence of alkyne-substituted silyl enol ethers (for example 274

• 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

• towards the total synthesis of salvileucalin B (292, see Scheme 35) isolated from the plant Salvia leucantha [213]. Starting from enantiopure trialkyne 282, desilylation was affected using TBAF, followed by ruthenium-catalyzed cycloisomerization [214] and cleavage of the chiral auxiliary to obtain

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

• ; Introduction The cycloisomerization reactions of enynes catalyzed by gold complexes are a powerful tool for accessing complex products from rather simple starting materials under soft and straightforward conditions [1][2][3][4]. In this context, 1,6-enynes have been extensively studied, mainly by Echavarren

• for the initial experiments (Scheme 4). Its reaction with (Ph3P)AuNTf2, reported by Gagosz and co-workers as a very active catalyst for the cycloisomerization of closely related 7-aryl-1,6-enynes [35], gave rise to a ca. 3:1 mixture of dihydronaphthalene derivative 2a and tetracyclic compound 3a along

• -catalyzed cycloisomerization of these substrates. The new oxygen-functionalized dihydronaphthalene derivatives have been synthesized in high yields. Gold(I)-catalyzed reactions of 1,6-enynes. Cyclization of o-(alkynyl)-(3-methylbut-2-enyl)benzenes 1. Previous work and proposed pathways. Synthesis of o

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

• a variety of functional groups and, interestingly, it is compatible with the presence of strong electron-withdrawing groups attached to the arene. The overall transformation can be termed as a new example of a migratory cycloisomerization and, formally, it involves well-blended 1,2-iodine shift and

• 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

• accomplish a reaction manifold earlier recognized in the synthesis of regioisomeric halogenated phenanthrenes, but they are using two different metals [45]. Catalytic cycloisomerization reactions of heteroatom-substituted alkynes that take place without heteroatom migration are known [46][47][48]. On this

An approach towards azafuranomycin analogs by gold-catalyzed cycloisomerization of allenes: synthesis of (αS,2R)-(2,5-dihydro-1H-pyrrol-2-yl)glycine

• Jörg Erdsack and
• Norbert Krause

Beilstein J. Org. Chem. 2013, 9, 1936–1942, doi:10.3762/bjoc.9.229

• Jorg Erdsack Norbert Krause Organic Chemistry, Dortmund University of Technology, Otto-Hahn-Strasse 6, D-44227 Dortmund, Germany 10.3762/bjoc.9.229 Abstract The synthesis of (αS,2R)-(2,5-dihydro-1H-pyrrol-2-yl)glycine (22, normethylazafuranomycin) by the gold-catalyzed cycloisomerization of α

• , removal of the double bond, or change of the relative configuration [14][16]. Likewise, carbafuranomycin (1b) showed insufficient biological activity [17]. In 2007, we reported a synthesis of furanomycin derivatives by gold-catalyzed endo-selective cycloisomerization of α-hydroxyallenes [19]. This method

• -catalyzed cycloisomerization of various protected or unprotected α-aminoallenes affords 2,5-dihydropyrroles [29][30][31][32][38][39]. Due to the difference in biological activity of furanomycin (1a) and carbafuranomycin (1b), we became interested in the synthesis of derivatives of the (so far unknown

Gold(I)-catalyzed formation of furans from γ-acyloxyalkynyl ketones

• Marie Hoffmann,
• Solène Miaskiewicz,
• Jean-Marc Weibel,
• Patrick Pale and
• Aurélien Blanc

Beilstein J. Org. Chem. 2013, 9, 1774–1780, doi:10.3762/bjoc.9.206

• -acyloxyalkynyl ketones were efficiently converted into highly substituted furans with 2.5 mol % of triflimide (triphenylphosphine)gold(I) as a catalyst in dichloroethane at 70 °C. Keywords: alkynyl ketones; cycloisomerization; furans; gold-catalysis; 1,2-migration; Introduction Furans are an important class of

• latter have already been described to rearrange into furans by using copper catalysts. Indeed, Gevorgyan et al. showed that the combination of copper(I) chloride and triethylamine catalyzed the 1,2-migration/cycloisomerization of γ-acyloxyalkynyl ketones in dimethylacetamide (DMA) at 130 °C (Scheme 2

• the crude residue was purified by silica gel flash chromatography (pentane/Et2O). Gold(I) or gold(III)-catalyzed furan syntheses with or without nucleophiles. Copper(I)-catalyzed 1,2-migration/cycloisomerization of γ-acyloxyalkynyl ketones. Mechanistic hypothesis for gold(I)-catalyzed conversion of γ

Inter- and intramolecular enantioselective carbolithiation reactions

• Asier Gómez-SanJuan,
• Nuria Sotomayor and
• Esther Lete

Beilstein J. Org. Chem. 2013, 9, 313–322, doi:10.3762/bjoc.9.36

•  10) [40]. The stereochemical outcome is explained assuming that the (−)-sparteine-mediated enantioselective deprotonation leads to an (S)-configurated (α-carbamoyloxy)alkyllithium intermediate 26. Then, the cycloisomerization occurs through a syn addition to the π-bond to give a stabilized

• enantioselectivity. The addition of TMEDA increases the rate of racemization, resulting in an inversion of diastereoselectivity to obtain 36, albeit in racemic form [44]. The enantioselective cycloisomerization of achiral organolithiums in the presence of a chiral ligand has been reported with aryllithium reagents

Tandem aldehyde–alkyne–amine coupling/cycloisomerization: A new synthesis of coumarins

• Maddi Sridhar Reddy,
• Nuligonda Thirupathi and
• Madala Haribabu

Beilstein J. Org. Chem. 2013, 9, 180–184, doi:10.3762/bjoc.9.21

• , pyrrolidine and salicylaldehydes led to a concomitant cycloisomerization followed by hydrolysis of the resultant vinyl ether to afford coumarins in a cascade process. The reaction proceeded through exclusive 6-endo-dig cyclization and is compatible with halo and keto groups giving coumarins in good to

• moderate yields. Keywords: A3 coupling; cooperative catalysis; coumarin synthesis; cycloisomerization; transition-metal catalysts; Introduction An alkyne, an aldehyde and an amine coupling, referred to as A3 coupling [1], has been found as an efficient method for C–N and C–C bond formation that results

• , cobalt, iridium and iron. Similarly, cycloisomerization of alkynols and alkynamines has also been an attractive approach for the synthesis of various known and new heterocyclic frameworks [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Various alkynophilic catalysts such as

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

• steps (high step economy). Keywords: alicyclic; bisallenes; cyclic; cycloadditions; cycloisomerization; isomerization; molecular complexity; step economy; Table of Contents Introduction Review Acyclic conjugated bisallenes 1.1 Synthesis of hydrocarbons 1.2 Synthesis of functionalized systems 1.3

• the direct cycloisomerization product of the bisallene, hydrocarbon 220, and the symmetrical dimer 221 are isolated. In the presence of the mixed ligand complex Ni(COD)(PPh3) a mixture of 220 and 221 is produced. The metalations of bisacetylenic and bisallenic hydrocarbons already referred to (Section

Iridium-catalyzed intramolecular [4 + 2] cycloadditions of alkynyl halides

• Andrew Tigchelaar and
• William Tam

Beilstein J. Org. Chem. 2012, 8, 1765–1770, doi:10.3762/bjoc.8.201

• , including homogeneous hydrogenation [1][2], C–H activation [3][4][5], asymmetric ring-opening reactions [6], and a variety of cycloisomerizations [7][8][9][10], and cycloadditions [11][12][13][14][15][16][17][18][19][20]. Traditionally these types of cycloisomerization and cycloaddition reactions are

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

• cycloisomerizations of diynyl o-benzaldehyde substrates to access novel polycyclic cyclopropanes are reported. The reaction sequence involves initial Cu(I)-mediated cycloisomerization/nucleophilic addition to an isochromene followed by diastereoselective Pt(II)-catalyzed enyne cycloisomerization. Keywords: chemical

• diversity; cycloisomerization; cyclopropane; diyne; isochromene; π-acid; Introduction Our laboratory has an ongoing interest in discovering transformations that afford novel chemotypes [1][2][3][4]. To this end, we have developed a reaction screening paradigm that enables the discovery of new reaction

• ). The chemotypes discovered in initial pilot studies have been further developed into library scaffolds and identified as biologically interesting structures [6]. Herein, we report the expanded utility of alkynyl o-benzaldehydes through a sequential metal-catalyzed cycloisomerization process to afford a

On the proposed structures and stereocontrolled synthesis of the cephalosporolides

• Sami F. Tlais and
• Gregory B. Dudley

Beilstein J. Org. Chem. 2012, 8, 1287–1292, doi:10.3762/bjoc.8.146

• internal alkyne 6, which was submitted to gold-catalyzed cycloisomerization [33] to afford spiroketals 7a and 7b (the silyl ether is concomitantly hydrolyzed) as a 1:1 mixture of isomers. Exposure of this mixture to zinc chloride promoted isomerization to provide 7a in >20:1 dr. TEMPO oxidation then

• completed the synthesis of 1, the reported structure of cephalosporolide H. The opposite spiroketal isomer 1a was prepared from 6 by palladium-catalyzed cycloisomerization (steric control), desilylation and TEMPO oxidation. In neither case did the characterization data match that of the natural material

• alkyne 5 with (S)-1,2 epoxynonane. Gold-catalyzed cycloisomerization (with desilylation) provided spiroketal diols 10a and 10b in a 32:68 ratio and in 89% total yield. Major spiroketal 10b could be converted to 10a in 15:1 dr by zinc-catalyzed isomerization. Both isomers (10a and 10b) were independently

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

• the elucidation of the mechanism and Selectfluor was suggested to play the double role of promoting the oxidation of gold(I) to a gold(III) active species and also the electrophilic fluorination of the enamine intermediates. Keywords: cycloisomerization reactions; fluorinated pyrrolidines; gold

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

• , was reported in moderate to good yields and in enantiomeric excesses up to 99%. Keywords: asymmetric catalysis; bicycloheptene; cycloisomerization reactions; enynes; gold; Introduction Metal-catalyzed cycloisomerization reactions of 1,n-enynes have emerged as efficient processes that contribute to

• cycloisomerization reaction of allyl propynyl ethers leading to oxabicyclo[4.1.0]heptenes [14] (Scheme 1, reaction 1). The group of Murai observed a similar reactivity in the presence of PtCl2, although in a lower yield [15]. These seminal contributions were then followed by several comprehensive studies involving

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

• the gold-catalyzed cycloisomerization of α-hydroxyallenes 16 to 2,5-dihydrofurans 17 (Scheme 3) [25]. The best system was found to be AuBr3 in [BMIM][PF6]. The cycloisomerization of various alkyl- or arylsubstituted α-hydroxyallenes gave corresponding 2,5-dihydrofuran with complete axis-to-center

• tetrahydropyran 24 were produced by an efficient gold(I) chloride catalyzed cycloisomerization of 2-alkynyl-1,5-diol 22 [28]. A plausible mechanism for the gold-catalyzed transformation of dioxabicyclo[4.2.1]ketal 25 to tetrahydropyran 31 is outlined in Scheme 5. The gold catalyst activates one of the oxygen

• gold-catalyzed cyclization of alk-4-yn-1-ones 79 depending on the substitution pattern in the substrate and the reaction solvent. Thus, alkynones with one substituent at C-3 undergo a 5-exo-dig cycloisomerization to yield substituted furans 81, whilst substrates bearing two substituents at C-3 undergo

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

• , whatever substrate was used [67]. Substrates 6b and 6e, which were used as a mixture of Z/E isomers, each afforded a single product, i.e., the furans 7b and 7e, respectively (entries 2 and 5). The cycloisomerization of compounds 6f, 6g, 6o, 6q and 6s, which possess an exocyclic allyl moiety, furnished the

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

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

• the same core unit. In 2006, a substantial variation to the traditional synthesis of furanones was developed by Kirsch and co-workers from readily accessible 2-hydroxy-2-alkynylcarbonyl compounds by a gold-catalyzed cycloisomerization approach [69]. The gold-catalyzed cyclization of 1, containing a

• carbocyclizations have been mainly restricted to the intramolecular arylation of alkynes (i.e., arene nucleophiles) [85][86][87][88] whilst simple olefins have been rarely used in this way. Analogous cyclization modes Several processes involving the cycloisomerization of 1,5-enynes have been realized in an

• of an asymmetric halocyclization towards indenes remains an ongoing task [93][94][95][96]. Notably, 1,5-enynes that do not contain an aryl system react in quite a similar manner when disubstituted at C1. For example, Michelet and co-workers reported the diastereoselective cycloisomerization of 1,5

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

• 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

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

• intermolecular nucleophilic attack to give intermediate 47, which upon cycloisomerization affords the aromatic product (Scheme 14, path b). Toste and co-workers reported an intramolecular acetylenic Schmidt reaction using azides as internal nucleophiles to give substituted pyrroles (Scheme 15) [42]. Gold

• cyclopropenes Highly strained cyclopropenes can undergo a wide variety of transformations in the presence of Lewis acids. Shi and co-workers reported in 2008 a gold-catalyzed cycloisomerization of aryl vinyl cyclopropenes to produce, selectively, 2-vinyl-1H-indene derivatives in high yields (Scheme 18). Upon

• , 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