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

• 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

New highlights of the syntheses of pyrrolo[1,2-a]quinoxalin-4-ones

• Emilian Georgescu,
• Alina Nicolescu,
• Florentina Georgescu,
• Florina Teodorescu,
• Daniela Marinescu,
• Ana-Maria Macsim and
• Calin Deleanu

Beilstein J. Org. Chem. 2014, 10, 2377–2387, doi:10.3762/bjoc.10.248

• constituent of several bioactive heterocyclic compounds that demonstrate interesting activity against Mycobacterium tuberculosis [1], anti-HIV [2], anticancer [3], and it modulates the estrogen receptor activity [4]. Synthetic methods towards pyrrolo[1,2-a]quinoxaline derivatives based on pyrroles [5], or

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

• series include phosphonobenzofurans/indenones [21][22], -pyrazoles [23], -chromenes/thiochromenes [24][25], -pyrroles [26], multiply substituted furans [27], indolopyran-1-ones [28], N-hydroxyindolinones [29], and oxindoles [30]. In the reaction shown in Scheme 1a, for the formation of the

One-pot three-component synthesis and photophysical characteristics of novel triene merocyanines

• Christian Muschelknautz,
• Robin Visse,
• Jan Nordmann and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 599–612, doi:10.3762/bjoc.10.51

• convergent strategies paved the way to luminescent push–pull dienes 1–4 with conformationally flexible and fixed acceptor units (Figure 1) [30][31][32], pyrazoles [33][34], benzodiazepines [35], furans and pyrroles [36][37] by consecutive multicomponent reactions and to highly emissive spirocycles [38][39

Simple two-step synthesis of 2,4-disubstituted pyrroles and 3,5-disubstituted pyrrole-2-carbonitriles from enones

• Murat Kucukdisli,
• Dorota Ferenc,
• Marcel Heinz,
• Christine Wiebe and
• Till Opatz

Beilstein J. Org. Chem. 2014, 10, 466–470, doi:10.3762/bjoc.10.44

• .10.44 Abstract The cyclocondensation of enones with aminoacetonitrile furnishes 3,4-dihydro-2H-pyrrole-2-carbonitriles which can be readily converted to 2,4-disubstituted pyrroles by microwave-induced dehydrocyanation. Alternatively, oxidation of the intermediates produces 3,5-disubstituted pyrrole-2

• -carbonitriles. Keywords: α-aminonitriles; cyclization; heterocycles; microwave-assisted synthesis; pyrroles; Introduction Heterocycles are the largest class of organic compounds [1]. Among them, pyrroles have a distinguished position in the chemistry of living organisms due to their close biogenetic

• )nitriles can be used as versatile and readily accessible pronucleophiles, e.g. for the construction of γ-amino acids [32], pyrrolidines [33], as well as pyrroles [34][35]. If an additional conjugated double bond is present, the anions of α-(alkylideneamino)nitriles 3 can undergo an electrocyclic ring

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

• Alexander O. Terent'ev,
• Dmitry A. Borisov,
• Vera A. Vil’ and
• Valery M. Dembitsky

Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6

• -phenoxyphenyl)hexahydro[1,2]dioxolo[3,4-b]pyrroles 24a and 24b were synthesized from (Z)-N-(hex-3-enyl)-N-(4-phenoxyphenyl)acetamide (22). It was suggested that aminocyclopropane 23 is formed in situ, which is subsequently oxidized in air on silica gel (Scheme 8) [238]. The total yield of both isomers 24 was 31

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• -subsituted alkenes were sometimes obtained along with the desired addition products (Scheme 9). Afterwards, N. Kamigata et al. applied this system to arenes [99] and heteroarenes (furans, pyrroles and thiophenes) [102][103][104] and gave a full account of this work (Scheme 9) [101]. Monosubstituted benzenes

• is applicable to pyrroles bearing a small group on nitrogen, which gave the 2-perfluoroalkylated compound as the major product. For instance, N-TMS-pyrrole afforded a global yield of 78% of the 2-functionalized product as a mixture of the silylated and hydrolized compounds. On the other hand, the

• of N. Kamigata et al. is that the reaction takes place under photoredox catalysis, allowing much milder reaction conditions (23 °C for D. W. C. MacMillan et al. vs 120 °C for N. Kamigata et al.). Higher yields were obtained, especially in the case of pyrroles (2-Rf-pyrrole: 88% yield for D. W. C

Microwave-assisted synthesis of 5,6-dihydroindolo[1,2-a]quinoxaline derivatives through copper-catalyzed intramolecular N-arylation

• Fei Zhao,
• Lei Zhang,
• Hailong Liu,
• Shengbin Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2013, 9, 2463–2469, doi:10.3762/bjoc.9.285

• , the copper-catalyzed N-arylation has been extensively utilized for C–N coupling, especially for the arylation of N-containing heterocycles such as indoles, imidazoles, indazoles, pyrroles, pyrazoles and triazoles [25][26][27][28] to construct more fused heterocycles. In recent years, several

Zinc–gold cooperative catalysis for the direct alkynylation of benzofurans

• Yifan Li and
• Jérôme Waser

Beilstein J. Org. Chem. 2013, 9, 1763–1767, doi:10.3762/bjoc.9.204

• knowledge, the direct alkynylation of benzofurans is still an unknown process. Since 2009, our group has developed a mild gold-catalyzed [14][15][16][17] method for the alkynylation of electron-rich aryls such as indoles and pyrroles [18], thiophenes [19], anilines [20] and furans [21]. Key for success was

An organocatalytic route to 2-heteroarylmethylene decorated N-arylpyrroles

• Alexandre Jean,
• Jérôme Blanchet,
• Jacques Rouden,
• Jacques Maddaluno and
• Michaël De Paolis

Beilstein J. Org. Chem. 2013, 9, 1480–1486, doi:10.3762/bjoc.9.168

• preparation of N-arylpyrroles is an active field of investigation [5]. Depending on their substituents, N-arylpyrroles could also be electron donor/acceptor molecules with a dual fluorescence ability suggesting attractive optoelectronic applications [6][7]. If the N-arylation of pyrroles is possible by

• Ullmann-type condensation [8][9][10], the regioselective functionalization of pyrroles is less trivial when asymmetric substrates are targeted. An indirect solution, based on the construction of substituted pyrrolidines that oxidize into elaborated pyrroles, can be employed fruitfully [11][12]. We

• –h were transformed into the corresponding pyrroles 5b–i with homogeneous efficiency. Hence, the chemistry proved to be compatible with substrates containing meta-, para-pyridyl and quinolinyl substituents, allowing the preparation of 5b (81%), 5c (78%) and 5d (98%). Pyrrolidine 4e containing an

Expeditious, mechanochemical synthesis of BODIPY dyes

• Laramie P. Jameson and
• Sergei V. Dzyuba

Beilstein J. Org. Chem. 2013, 9, 786–790, doi:10.3762/bjoc.9.89

• . Accordingly, the condensation of pyrroles with aldehydes (Scheme 1a) is the more commonly utilized synthetic approach [1][2]. Notably, both approaches are carried out under an inert atmosphere. Overall, based on literature accounts, BODIPY synthesis requires long reaction times (several hours to several days

• ) and isolation of the dyes is performed by chromatography, with poor to moderate (10–50%) yields. In this light, a more expedient synthesis of the BODIPY dyes is desired. Toward this end, we reasoned that the condensation step between the 2-substituted pyrroles and aldehydes (or acid chlorides) should

• condensation between pyrroles and acid chlorides produced dyes 8 and 9 in relatively low yields of 21% and 10%, respectively. It should be pointed out that in the case of dye 9 (and unlike the synthesis of 8), the condensation step between 2,4-dimethylpyrrole and benzoyl chloride appeared to be sluggish

3-Pyridylnitrene, 2- and 4-pyrimidinylcarbenes, 3-quinolylnitrenes, and 4-quinazolinylcarbenes. Interconversion, ring expansion to diazacycloheptatetraenes, ring opening to nitrile ylides, and ring contraction to cyanopyrroles and cyanoindoles

• Curt Wentrup,
• Nguyen Mong Lan,
• Adelheid Lukosch,
• Pawel Bednarek and
• David Kvaskoff

Beilstein J. Org. Chem. 2013, 9, 743–753, doi:10.3762/bjoc.9.84

• undergo ring opening to the nitrile ylide 37. Sigmatropic shifts of H, CN, or CH3 in the 3H-pyrroles 32 and 38 lead to the final products. We have previously reported strong evidence for the ring expansion of a 2-pyrimidinylcarbene 39 to a diazacycloheptatetraene 40 and subsequent ring contraction to a 3

• separated by GC on the Carbowax column. The yields of 2,6-dimethyl-3-cyanopyrrole (25), 2,4-dimethyl-3-cyanopyrrole (26) and 3,5-dimethyl-2-cyanopyrrole (27) at various temperatures are collected in Table 1. Yields were determined by GC, and the pyrroles were characterized as follows: 2,6-Dimethyl-3

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

• )anilines with alkynes to form 4,5-dihydropyrrolo[1,2-a]quinoxalines [23][24]. Kobayashi and co-workers have described the Lewis acid catalyzed cyclization of 1-(2-isocyanophenyl)pyrroles to give pyrrolo[1,2-a]quinoxalines in good yields; however, the isocyanide substrates required multistep synthesis [25

N-Heterocyclic carbene–palladium catalysts for the direct arylation of pyrrole derivatives with aryl chlorides

• Ismail Özdemir,
• Nevin Gürbüz,
• Nazan Kaloğlu,
• Öznur Doğan,
• Murat Kaloğlu,
• Christian Bruneau and
• Henri Doucet

Beilstein J. Org. Chem. 2013, 9, 303–312, doi:10.3762/bjoc.9.35

• with heteroarenes. Keywords: aryl chlorides; atom-economy; C–H bond activation; C–H functionalization; carbenes; palladium; pyrroles; Introduction N-Heterocyclic carbenes (NHC) have emerged as an important class of ligands in the development of homogeneous catalysis [1][2][3][4][5][6][7][8][9]. Such

• ]. This is especially true for palladium-catalyzed coupling reactions. Pd–NHC catalysts [15] have proven to be excellent alternatives to catalytic systems involving palladium associated to tertiary phosphine ligands [16][17][18][19]. The introduction of aryl groups at C2 or C5 positions of pyrroles is an

• palladium-catalyzed direct arylation of various heteroaromatics including pyrroles by a C–H bond activation using aryl halides has met great success in recent years, allowing the synthesis of a wide variety of arylated heteroaromatics in only one step [20][21][22][23][24][25]. However, there are still

Palladium-catalyzed dual C–H or N–H functionalization of unfunctionalized indole derivatives with alkenes and arenes

• Gianluigi Broggini,
• Egle M. Beccalli,
• Andrea Fasana and
• Silvia Gazzola

Beilstein J. Org. Chem. 2012, 8, 1730–1746, doi:10.3762/bjoc.8.198

• intramolecular alkenylation on a range of other electron-rich heterocycles, including pyrroles, furans and thiophenes [63][64]. The intramolecular Pd(II)-catalyzed reaction of the 3-alkenylindoles 14 gave rise to the carbocyclic 5-membered ring-fused products 15 (Scheme 12) [65][66]. This procedure involves O2

A quantitative approach to nucleophilic organocatalysis

• Herbert Mayr,
• Sami Lakhdar,
• Biplab Maji and
• Armin R. Ofial

Beilstein J. Org. Chem. 2012, 8, 1458–1478, doi:10.3762/bjoc.8.166

• k2 for the attack of the iminium ion 3a at the pyrroles 12a–12f, and Figure 9 shows that the observed rate constants agree, within a factor of five, with those calculated by using Equation 1. We consider this agreement remarkable, as the E parameter for 3a has been derived from rate constants with a

• large variety of nucleophiles [37] and the N and sN parameters of the pyrroles 12a–12f have been derived from their reactivities toward benzhydrylium ions [57]. As Equation 1 is employed for calculating absolute rate constants k2 in a reactivity range of 40 orders of magnitude with only three parameters

Organocatalytic C–H activation reactions

• Subhas Chandra Pan

Beilstein J. Org. Chem. 2012, 8, 1374–1384, doi:10.3762/bjoc.8.159

• generate iminium ion 6. Finally, ring closure and proton loss provides the formation of the product 3. Redox alkylation In 2009, Tunge and co-workers demonstrated the synthesis of N-alkyl-pyrroles by redox isomerisation from the reaction of 3-pyrroline and aldehydes or ketones (Scheme 6) [17]. A series of

Carbohydrate-auxiliary assisted preparation of enantiopure 1,2-oxazine derivatives and aminopolyols

• Marcin Jasiński,
• Dieter Lentz and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2012, 8, 662–674, doi:10.3762/bjoc.8.74

• samarium diiodide leading to enantiopure acyclic aminopolyols. We also report on our attempts to convert these compounds into enantiopure hydroxylated pyrrolidine derivatives. Keywords: aminopolyols; carbohydrates; chiral auxiliaries; lithiated alkoxyallenes; 1,2-oxazines; pyrroles; pyrrolidines; samarium

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

• -substituted alkynes have been demonstrated as efficient substrates for the construction of heteropolycyclic compounds. In particular, alkynyl indoles and pyrroles were successfully used to afford β-carbolines [16][17], pyrrolo-azepines [18], azepino-indoles and azocino-indoles [19] under mild conditions

• terminal alkynes with pyrroles is shown in Scheme 2. It is highly probable that the products arise from the vinyl gold species B and F, in turn generated from alkynes 4 after coordination to AuCl3. The formation of F can result by a migration of the acyl group from the spiro center of the transient

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• substituted pyrroles involving a dihalogeno substrate and a sequential Sonogashira coupling followed by an hydroamination was developed by Duchêne and Parrain [32]. In this one-pot sequence, the first reaction is an allylic amination between the 3,4-diiodobut-2-enoic acid (54) and a primary amine, which can

• be in competition with the intramolecular lactonization reaction. The best yields of the expected pyrroles were obtained when the three-component reaction was conducted, with five equivalents of the amine partner, at room temperature in DMF, with PdCl2(PPh3)2/CuI as the catalyst system. The initial C

• . Synthesis of pyrroles by cyclization of propargyl amines. Isoindolone and phthalazone synthesis by cyclization of acylhydrazides. Sultam synthesis by cyclization of sulfonamides. Synthesis of sulfonamides by aminosulfonylation of aryl iodides. Pyrrolidine synthesis by carbopalladation of allylamines

NMR studies of anion-induced conformational changes in diindolylureas and diindolylthioureas

• Damjan Makuc,
• Jennifer R. Hiscock,
• Mark E. Light,
• Philip A. Gale and
• Janez Plavec

Beilstein J. Org. Chem. 2011, 7, 1205–1214, doi:10.3762/bjoc.7.140

• extensively employed in synthetic anion receptors comprising groups such as amides, pyrroles, indoles, ureas and triazoles, as well as in ammonium, guanidinium and imidazolium moieties used as hydrogen bond donors [16][17][18][19][20][21][22][23]. Amongst neutral anion receptor systems, indole and related

One-pot four-component synthesis of pyrimidyl and pyrazolyl substituted azulenes by glyoxylation–decarbonylative alkynylation–cyclocondensation sequences

• Charlotte F. Gers,
• Julia Rosellen,
• Eugen Merkul and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2011, 7, 1173–1181, doi:10.3762/bjoc.7.136

• glyoxylation of electron rich N-heterocycles, such as indoles and pyrroles, leads to the formation of glyoxylyl chlorides, which can be reacted without isolation by decarbonylative Sonogashira coupling to form the desired ynones. So far, only one example of the synthesis of azulenylynones has been described

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

• % PPh3AuCl/5 mol % AgOTf in dichloroethane at 80 °C gave alkylidenecyclobutanamine 160 in 65% yield as a single olefin isomer (Scheme 28). The formation of tri- and tetrasubstituted pyrroles 163 [74] via cationic N-heterocyclic carbene–gold(I) complex catalyzed amino Claisen rearrangement of N-propargyl-β

• the pyrazolidinone generally provides the bicyclic product 166 with high cis selectivity, which is determined during ring closing rather than in the formation of allyl–gold intermediate [76]. Gold-catalyzed cycloisomerization reaction of alkynyl aziridines 167 can give 2,5-disubstituted pyrroles 168

• formation of 2,5-substituted pyrroles 170 proceeds with PPh3AuOTs as the catalyst whilst a novel reaction pathway is accessed on changing the catalyst system to PPh3AuOTf and leads to 2,4-substituted pyrroles 171. Recently, the same group reported an efficient and selective synthesis of 2,5-substituted

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

• (X = NTs) could be converted under mild experimental conditions into functionalized pyrroles 3 (X = NTs) in the presence of a gold(I) catalyst (Scheme 2) [52]. In contrast to Fürstners observations for the rearrangement of allyl pent-4-ynyl ethers [53][54], the results obtained during this study

• strongly suggested that no allyl cation was formed during the reaction. The substitution pattern of the pyrroles thus obtained point toward the involvement of a more concerted aza-Claisen-type rearrangement mechanism (2 → 3) and tend to exclude the possibility of a simple N to C allyl shift (2 → 4 → 5

• ). Thus, a wide range of ynenyl allyl ethers 6a–s was synthesized (see Supporting Information File 1) and reacted under the conditions that were found to be optimal for the analogous formation of pyrroles from ynenyl allyl tosylamides, that is, 2 mol % of the gold catalyst {[(p-CF3-C6H4)3P]-Au-NTf2} [66

Isotopic labelling studies for a gold-catalysed skeletal rearrangement of alkynyl aziridines

• Paul W. Davies,
• Nicolas Martin and
• Neil Spencer

Beilstein J. Org. Chem. 2011, 7, 839–846, doi:10.3762/bjoc.7.96

• aziridines into 2,4-disubstituted pyrroles. Two isotopomers of the expected skeletal rearrangement product were identified using 13C-labelling and led to a revised mechanism featuring two distinct skeletal rearrangements. The mechanistic proposal has been rationalised against the reaction of a range of 13C

• : 2,4-Disubstituted pyrroles were only observed in appreciable quantities when the reaction was performed with a non basic solvent and counter ion combination that allows for formation of a separated ion pair, such as dichloromethane and triflate (Scheme 1). This selectivity was switched and the 2,5

• indentified from the reaction mixture. Though H/D exchange in pyrroles has been noted in gold-catalysed reactions [13], control reactions had shown that no H/D exchange occurred in this specific system [18][19]. There was also no interconversion between 2,4- and 2,5-isomers under the same reaction conditions