Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

• intramolecular hydroarylation or via iodo-catalysed regioselective 6-endo-dig electrophilic cyclization. Kitson et al. synthesized a class of 2,3-dihydro-12H-pyrrolo[1,2-f]phenanthridine (DPP) derivatives starting from malononitrile and 1,3-indandione as the initial nucleophiles, which reacted with N

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

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

• realizing an efficient synthesis of dihydrobenzofuran derivatives 3 (Scheme 2a) [28]. The protocol was assumed to proceed via a two-step mechanism: involving an initial hydroarylation of the double bond followed by an intramolecular phenol addition (Scheme 2b). Shortly after, Zhang and Corma considerably

• , affording 5-, 6-membered lactams and spiro-lactams 61 in excellent yields and high trans diastereoselectivity (Scheme 16). 4.2 The hydroarylation reaction In addition to methylene active compounds, electron-rich benzenes and heteroaromatics can be added to gold activated alkenes under suitable conditions

• . In this context, in situ made [Ph3PAuOTf] was found to be an efficient catalyst for the addition of indoles 62 to styrenes and aryldienes in toluene at 85 °C (Scheme 17a,b). Less reactive aliphatic alkenes required harsher reaction conditions, however the corresponding hydroarylation products 66 were

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

• hydroarylation steps. Keywords: alkyne; chromene; gold; gold catalysis; hydroarylation; iodine; Introduction The structure of 2H-chromene embodies a relevant heterocyclic motif, which is present in naturally occurring compounds [1][2][3][4][5][6] and encodes interesting properties that renders it attractive

• of an increase in the molecular diversity, offering a suitable strategy intended for library discovery. It is well known that metal-catalyzed hydroarylation is a powerful reaction to prepare benzofused heterocyclic compounds [29][30][31]. Pt(IV) [32], Pt(II) and Au(I) [33] complexes were early

• outlined in Table 1 entry 7 were chosen to broach the potential of this 1,2-iodine migration–hydroarylation process using different iodinated propargyl aryl ethers. The results are summarized in Table 2. Interestingly, as no further additives are required, heating the corresponding aryl propargyl ether in

Post-Ugi gold-catalyzed diastereoselective domino cyclization for the synthesis of diversely substituted spiroindolines

• Amit Kumar,
• Dipak D. Vachhani,
• Sachin G. Modha,
• Sunil K. Sharma,
• Virinder S. Parmar and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2013, 9, 2097–2102, doi:10.3762/bjoc.9.246

• adducts which are subjected to a cationic gold-catalyzed diastereoselective domino cyclization to furnish diversely substituted spiroindolines. All the reactions run via an exo-dig attack in the hydroarylation step followed by an intramolecular diastereoselective trapping of the imminium ion. The whole

• step is a cationic gold-catalyzed intramolecular hydroarylation tandem cyclization to produce spiroindolines with complete diastereoselectivity. This synthetic sequence is atom economic and mild conditions are applied to generate a very complex molecular structure from readily available starting

• hydroarylation [44]. Reaction of 5a with 5 mol % of Au(PPh3)SbF6 in chloroform at room temperature produced the desired spiroindoline 6a in a moderate yield of 55% along with some unidentified byproducts (Table 1, entry 1). The use of a protic acid with a gold catalyst is known in the literature [61][62][63][64

A one-pot catalyst-free synthesis of functionalized pyrrolo[1,2-a]quinoxaline derivatives from benzene-1,2-diamine, acetylenedicarboxylates and ethyl bromopyruvate

• Mohammad Piltan,
• Loghman Moradi,
• Golaleh Abasi and
• Seyed Amir Zarei

Beilstein J. Org. Chem. 2013, 9, 510–515, doi:10.3762/bjoc.9.55

• reaction times and displayed limited reaction tolerance and low reaction selectivity [20][21]. Cheeseman and Tuck reported the first pyrrolo[1,2-a]quinoxaline in 1965 [22]. Recently, Patil et al. developed the PtBr2 and Au(I)-catalyzed hydroamination–hydroarylation cascade reactions of 2-(1H-pyrrol-1-yl

Alkyne hydroarylation with Au N-heterocyclic carbene catalysts

• Cristina Tubaro,
• Marco Baron,
• Andrea Biffis and
• Marino Basato

Beilstein J. Org. Chem. 2013, 9, 246–253, doi:10.3762/bjoc.9.29

• the intermolecular hydroarylation of alkynes with simple unfunctionalised arenes. Both mono- and dinuclear gold(III) complexes were able to catalyze the reaction; however, the best results were obtained with the mononuclear gold(I) complex IPrAuCl. This complex, activated with one equivalent of silver

• ; gold; hydroarylation; N-heterocyclic carbenes; Introduction The hydroarylation of alkynes (Scheme 1) is arguably one of the most intensively studied reactions leading to aromatic C–H bond functionalization [1][2][3][4][5][6][7]. In this reaction, the C–H bond of an arene adds formally trans to the

• triple bond of an alkyne, generally forming the thermodynamically less favoured cis-arylalkene as the major product. The study of this reaction was pioneered by the group of Fujiwara (hence the alternative name “Fujiwara reaction” for the intermolecular hydroarylation of alkynes) using mainly palladium

Iron-containing mesoporous aluminosilicate catalyzed direct alkenylation of phenols: Facile synthesis of 1,1-diarylalkenes

• Satyajit Haldar and
• Subratanath Koner

Beilstein J. Org. Chem. 2013, 9, 49–55, doi:10.3762/bjoc.9.6

• combination of Cu(OTf)2/TMSA (TMSA = trifluoromethanesulfonic acid) [30]. The same reaction was also successfully carried out by Li and co-workers using FeCl3 as catalyst in a homogeneous medium [31]. Further Yadav et al. demonstrated an elegant hydroarylation of different phenols in the presence of gallium

• made their employment an attractive choice. Recently, we have successfully employed a Fe-Al-MCM-41 catalyst in a Friedel–Crafts-type hydroarylation reaction of styrenes [33]. The catalyst demonstrated high yields of products with good selectivities within a short reaction time under “open flask

Metal–ligand multiple bonds as frustrated Lewis pairs for C–H functionalization

• Matthew T. Whited

Beilstein J. Org. Chem. 2012, 8, 1554–1563, doi:10.3762/bjoc.8.177

• , followed by insertion of an unsaturated substrate (olefin, alkyne) and either a 1,2-elimination (to afford a hydroalkylation or hydroarylation product) or reductive elimination as described above. However, to the best of our knowledge, this type of reactivity has not been observed at early metal imido or

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

• /n, 43007 Tarragona, Spain 10.3762/bjoc.7.178 Abstract Electrophilic gold(I) catalyst 6 competes with GaCl3 as the catalyst of choice in the synthesis of fluoranthenes by intramolecular hydroarylation of alkynes. The potential of this catalyst for the preparation of polyarenes is illustrated by a

• synthesis of two functionalized decacyclenes in a one-pot transformation in which three C–C bonds are formed with high efficiency. Keywords: alkynes; gold(I) catalysis; hydroarylation; polyarenes; Introduction Electrophilic activation of alkynes in functionalized substrates by gold catalysts allows for

• the synthesis of complex molecules under mild conditions [1][2][3][4][5][6][7][8]. Alkynes can react in gold-catalyzed Friedel–Crafts-type reactions with arenes to give products resulting from the intermolecular hydroarylation of the alkynes (or alkenylation of the arenes) [9][10][11][12][13][14][15

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

• Verona, Italy 10.3762/bjoc.7.170 Abstract In a simple procedure, the intramolecular hydroarylation of N-propargyl-pyrrole-2-carboxamides was accomplished with the aid of gold(III) catalysis. The reaction led to differently substituted pyrrolo[2,3-c]pyridine and pyrrolo[3,2-c]pyridine derivatives arising

• chemists. Gold catalysis has recently emerged as a suitable way to achieve such a goal, mainly thanks to the chemoselective alkynophilic properties of this attractive metal in different types of reactions [6][7][8][9][10][11][12][13][14][15]. Among the hydroarylation reactions, various kinds of heteroaryl

• hydroarylation of alkynyl-tethered pyrrole-2-carboxamides in order to have an alternative protocol to access pyrrolo-fused pyridine skeletons. The importance of pyrrolo[2,3-c]pyridine and pyrrolo[3,2-c]pyridine derivatives from the biological point of view [36][37][38][39][40][41][42][43][44][45][46][47][48][49

Cationic gold(I) axially chiral biaryl bisphosphine complex-catalyzed atropselective synthesis of heterobiaryls

• Tetsuro Shibuya,
• Kyosuke Nakamura and
• Ken Tanaka

Beilstein J. Org. Chem. 2011, 7, 944–950, doi:10.3762/bjoc.7.105

• complex catalyzes the atropselective intramolecular hydroarylation of alkynes leading to enantioenriched axially chiral 4-aryl-2-quinolinones and 4-arylcoumarins with up to 61% ee. Keywords: asymmetric catalysis; axial chirality; gold; heterobiaryls; hydroarylation; Introduction Atropselective biaryl

• hydroalkenylation and hydroarylation reactions [9][10][11][12][13][14][15]. In this context, our research group developed the cationic gold(I)/PPh3-complex catalyzed intramolecular hydroalkenylation of N-alkenyl-arylethynylamides leading to 4-aryl-2-pyridones (Scheme 1) [16][17]. The atropselective synthesis of 6

• the highest enantioselectivity (Scheme 2) [42]. In addition, the cationic palladium(II)/axially chiral biaryl bisphosphine complexes were able to catalyze the asymmetric intramolecular hydroarylation of N-aryl-arylethynylamides leading to axially chiral 4-aryl-2-quinolinones, and the cationic

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

• ]. Tarselli et al. reported a gold(I)-catalyzed intramolecular hydroarylation of allenes [138]. Gold(I) complexes react with 4-allenylarenes 256 in an exo fashion to furnish vinyl-substituted benzocycles 257. Interestingly, if 1-arylbuta-2,3-dienyl acetate 258 was used as the substrate, naphthalenes 259 are

• formed through a AuPPh3Cl catalyzed cyclization reaction [139]. Using gold complex [XPhosAu(NCCH3)SbF6] as the catalyst, Jurberg and Gagosz prepared the cinnoline derivatives 261 by the hydroarylation of N-propargyl-N-arylhydrazines 260 [140]. With the gold complex [Mes3PAu]NTf2, an alkynyl ether moiety

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

• –Crafts alkylation; green chemistry; hydroalkylation; hydroarylation; Lewis-acid catalysis; propargyl alcohols; Introduction In 1887 Charles Friedel and James Mason Crafts isolated amylbenzene after the treatment of amyl chloride with AlCl3 in benzene (Scheme 1) [1]. This was not only one of the first

• -diarylalkanes, efficient hydroarylation procedures employing styrenes and other activated double bonds are needed (Scheme 15). Due to their availability, styrenes are most suitable substrates for potential hydroarylation methods and a fast synthesis of compound libraries should be feasible. Although, the Murai

• . 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