Dimerisation, rhodium complex formation and rearrangements of N-heterocyclic carbenes of indazoles

• Zong Guan,
• Jan C. Namyslo,
• Martin H. H. Drafz,
• Martin Nieger and
• Andreas Schmidt

Beilstein J. Org. Chem. 2014, 10, 832–840, doi:10.3762/bjoc.10.79

• -ylidene with acetylenes. Indazol-3-ylidenes which possess an aryl ring at N1 rearrange to give substituted acridines by a ring-cleavage/pericyclic ring-closure reaction sequence (2→A→B→11) (Scheme 3). It proved to be advantageous to start these rearrangements from indazolium salts which are readily

Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

• Gijs Koopmanschap,
• Eelco Ruijter and
• Romano V.A. Orru

Beilstein J. Org. Chem. 2014, 10, 544–598, doi:10.3762/bjoc.10.50

• ]. Multicomponent reactions towards amide isosteres often involve an Ugi reaction followed by a Click reaction, in which two of the Ugi-inputs either contain an alkyne or an azide moiety. A well-known example of the latter reaction is the Copper(I) catalyzed azide–alkyne cycloaddition (CuAAC) between acetylenes and

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

• related cascade multicomponent processes of interest, which involve gold acetylides and imines. Among them, a new Au(I)-catalyzed entry to cyclic carbamimidates 17 starting from acetylenes, imines and p-toluenesulfonylisocyanate (18) was reported by Toste and Campbell [43]. The reaction gave mainly the 5

Practical synthesis of aryl-2-methyl-3-butyn-2-ols from aryl bromides via conventional and decarboxylative copper-free Sonogashira coupling reactions

• Andrea Caporale,
• Stefano Tartaggia,
• Andrea Castellin and
• Ottorino De Lucchi

Beilstein J. Org. Chem. 2014, 10, 384–393, doi:10.3762/bjoc.10.36

• -pentynoic acid with aryl bromides, using a catalyst containing Pd(OAc)2 in combination with SPhos or XPhos in the presence of tetra-n-butylammonium fluoride (TBAF) as the base and THF as the solvent. Therefore, new efficient approaches to the synthesis of terminal acetylenes from widely available aryl

• terminal acetylenes is the most straightforward method for the preparation of substituted alkynes [1][2][3][4][5][6], which are extensively used as building blocks in a great number of applications including the synthesis of pharmaceuticals [7][8][9], natural products and organic functional materials [10

• presence of a Cu/Pd bimetallic catalyst, followed by the basic cleavage of the protecting group [42][43][44][45][46]. Terminal alkynes are often used as starting materials for the synthesis of disubstituted acetylenes through a second coupling process with another aryl halide. Decarboxylative couplings

Advancements in the mechanistic understanding of the copper-catalyzed azide–alkyne cycloaddition

• Regina Berg and
• Bernd F. Straub

Beilstein J. Org. Chem. 2013, 9, 2715–2750, doi:10.3762/bjoc.9.308

• molecules in the rate-determining step, respectively. Alternatively, there could be only one pathway including two acetylenes in the rate-determining step, which is inhibited by higher concentrations of the alkyne. The latter proposition is supported by the fact that commercially available copper acetylides

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

• allowing the direct and regioselective C–H functionalization of benzofurans [12]. In this context, the introduction of an alkyne would be particularly useful, as acetylenes are important building blocks in synthetic chemistry, chemical biology and materials science [13]. Nevertheless, to the best of our

Efficient continuous-flow synthesis of novel 1,2,3-triazole-substituted β-aminocyclohexanecarboxylic acid derivatives with gram-scale production

• Sándor B. Ötvös,
• Ádám Georgiádes,
• István M. Mándity,
• Lóránd Kiss and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2013, 9, 1508–1516, doi:10.3762/bjoc.9.172

• acetylenes [16]. The classical Huisgen reaction, thermally induced, gives an approximate 1:1 mixture of 1,4- and 1,5-disubstituted 1,2,3-triazole isomers (Scheme 1) [17]. However, when Cu(I) catalysis is applied, the reaction becomes regioselective, exclusively yielding the 1,4-regioisomer within a

Practical synthesis of indoles and benzofurans in water using a heterogeneous bimetallic catalyst

• Cybille Rossy,
• Eric Fouquet and
• François-Xavier Felpin

Beilstein J. Org. Chem. 2013, 9, 1426–1431, doi:10.3762/bjoc.9.160

• with aryl acetylenes suggesting a strong halide effect and a sensitivity of the Pd–X bond under our reaction conditions. Indeed, the coupling of aryl acetylenes with bromo-anilines and bromo-phenols showed lower conversion compared to the iodo-congeners. We further evaluated the potential of our Pd–Cu

• /C catalyst for the alkynylation–cyclization of 2-iodophenols in view of preparing benzofurans. As already observed with the synthesis of indoles, aliphatic alkynes gave slightly lower yields than aryl acetylenes. A remarkable tolerance toward reactive functions such as ketones and alcohols

Design and synthesis of tag-free photoprobes for the identification of the molecular target for CCG-1423, a novel inhibitor of the Rho/MKL1/SRF signaling pathway

• Jessica L. Bell,
• Andrew J. Haak,
• Susan M. Wade,
• Yihan Sun,
• Richard R. Neubig and
• Scott D. Larsen

Beilstein J. Org. Chem. 2013, 9, 966–973, doi:10.3762/bjoc.9.111

• of the model probes retained good activity relative to the lead compound 2 with little to no cytotoxicity. Based on these results we decided to install acetylenes in our final probes through ether linkages at the positions of the methoxy groups of the most active models 8a, 8c and 14. Preparation of

Regio- and stereoselective carbometallation reactions of N-alkynylamides and sulfonamides

• Yury Minko,
• Morgane Pasco,
• Helena Chechik and
• Ilan Marek

Beilstein J. Org. Chem. 2013, 9, 526–532, doi:10.3762/bjoc.9.57

• carbamate moiety. Molecular structure of 9f (hydrogen atoms except of H9 and H10 are omitted for clarity). Possible regioisomers obtained in the carbocupration reaction of α-heterosubstituted acetylenes 1. Regioselective carbometallation of N-alkynylsulfonamide 2. Regioselective carbometallation of ynamide

Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation

• Kei Murakami and
• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 278–302, doi:10.3762/bjoc.9.34

• the reactions of simple dialkylacetylenes, benzylzinc bromide was effective (Scheme 36, top). On the other hand, dibenzylzinc reagent was effective for the reactions of aryl(alkyl)acetylenes (Scheme 36, bottom). They applied the reaction toward the synthesis of an estrogen-receptor antagonist (Scheme

• -catalyzed carbozincation of arylacetylenes and its application to the synthesis of tamoxifen. Bristol-Myers Squibb’s nickel-catalyzed phenylzincation. Iron/NHC-catalyzed arylmagnesiation of aryl(alkyl)acetylene. Iron/copper-cocatalyzed alkylmagnesiation of aryl(alkyl)acetylenes. Iron-catalyzed

• and aryl(alkyl)acetylenes. Synthesis of estrogen receptor antagonist. Cobalt-catalyzed allylzincation of aryl-substituted alkynes. Silver-catalyzed alkylmagnesiation of terminal alkyne. Proposed mechanism of silver-catalyzed alkylmagnesiation. Zirconium-catalyzed ethylzincation of terminal alkenes

Stereoselective synthesis of tetrasubstituted alkenes via a sequential carbocupration and a new sulfur–lithium exchange

• Andreas Unsinn,
• Cora Dunst and
• Paul Knochel

Beilstein J. Org. Chem. 2012, 8, 2202–2206, doi:10.3762/bjoc.8.248

• ][9]. The Normant carbocupration of terminal acetylenes allows the stereoselective preparation of trisubstituted alkenes with excellent E/Z ratio [10][11][12]. However, in order to obtain tetrasubstituted alkenes, a carbometalation of an internal alkene is required. This reaction is usually difficult

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

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

• substituents has been prepared recently by a Zr-promoted linear coupling of different aryl and hetaryl acetylenes in high yield (Scheme 17) [66]. Treating, e.g., phenylacetylene (78) first with n-butyllithium and subsequently with bis(cyclopentadienyl)zirconium dichloride generates the trimeric metal complex

Thiophene-based donor–acceptor co-oligomers by copper-catalyzed 1,3-dipolar cycloaddition

• Stefanie Potratz,
• Amaresh Mishra and
• Peter Bäuerle

Beilstein J. Org. Chem. 2012, 8, 683–692, doi:10.3762/bjoc.8.76

• high yield and purity. Click reactions generally involve a Cu(I)-catalyzed version of the Huisgen 1,3-dipolar cycloaddition of terminal acetylenes and azides (CuAAC), to regioselectively yield 1,4-disubstituted 1H-1,2,3-triazoles [11][12]. In the meanwhile, this type of click reaction has become very

• form co-oligomer 5. Synthesis of 1,4-disubstituted 1,2,3-triazoles from corresponding halides (1 equiv), terminal acetylenes (1 equiv) and sodium azide (2 equiv) in the presence of copper(I) iodide (10 mol %), sodium ascorbate (10 mol %) and N,N’-dimethylethylenediamine (DMEDA, 20 mol %) in ethanol

Branching out at C-2 of septanosides. Synthesis of 2-deoxy-2-C-alkyl/aryl septanosides from a bromo-oxepine

• Supriya Dey and
• Narayanaswamy Jayaraman

Beilstein J. Org. Chem. 2012, 8, 522–527, doi:10.3762/bjoc.8.59

• reaction, namely, Sonogashira coupling [28][29]. Reactions of 2 with acetylenes were performed in the presence of Pd(PPh3)2Cl2 (20 mol %) and CuI (10 mol %) in a DMF/THF/Et3N 5:3:2 solvent mixture as the optimized protocol. The use of Pd(OAc)2 as a catalyst or Et3N as the base did not promote the reaction

A concise synthesis of 3-(1-alkenyl)isoindolin-1-ones and 5-(1-alkenyl)pyrrol-2-ones by the intermolecular coupling reactions of N-acyliminium ions with unactivated olefins

• Nianhong Lu,
• Lihong Wang,
• Zhanshan Li and
• Wei Zhang

Beilstein J. Org. Chem. 2012, 8, 192–200, doi:10.3762/bjoc.8.21

• terminal alkynes to give the doubly alkyl-substituted acetylenes [1][2][3]; the Brønsted acid and Lewis acid catalyzed coupling of alcohols with indoles to give the 3-alkyl-substituted indoles [4][5][6]; and the Brønsted acid and Lewis acid-catalyzed coupling of alcohols with 1,3-dicarbonyls to give the 2

Valence isomerization of cyclohepta-1,3,5-triene and its heteroelement analogues

• Helen Jansen,
• J. Chris Slootweg and
• Koop Lammertsma

Beilstein J. Org. Chem. 2011, 7, 1713–1721, doi:10.3762/bjoc.7.201

• + 2] cycloadditions of the in situ generated singlet phosphinidene 35 with olefins or acetylenes (Scheme 7) [5][6][7][8][9]. This approach has even lead to the detection of the transient phosphinidene species by employing electrospray ionization tandem mass spectrometry (ESIMS/MS); its gas-phase

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

• -substituted acetylenes (Table 2, entries 9 and 10) as well as simple aliphatic acetylenes (Table 2, entries 2, 11, and 12) were successfully employed. Finally, propargylaldehyde diethylacetal (Table 2, entry 13) and TIPS-protected acetylene (Table 2, entry 14) also participated in the sequence, although

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

• gold pre-catalyst 125 featuring a P,N-ligand that has significantly extended the substrate scope and synthetic utility of alkyne hydroamination [60]. The hydroamination of unsymmetrical internal aryl acetylenes 126 with dialkylamines 127 has been achieved with synthetically useful regioselectivities

Fine-tuning alkyne cycloadditions: Insights into photochemistry responsible for the double-strand DNA cleavage via structural perturbations in diaryl alkyne conjugates

• Wang-Yong Yang,
• Samantha A. Marrone,
• Nalisha Minors,
• Diego A. R. Zorio and
• Igor V. Alabugin

Beilstein J. Org. Chem. 2011, 7, 813–823, doi:10.3762/bjoc.7.93

• Wang-Yong Yang Samantha A. Marrone Nalisha Minors Diego A. R. Zorio Igor V. Alabugin Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306-4390, USA 10.3762/bjoc.7.93 Abstract Hybrid molecules combining photoactivated aryl acetylenes and a dicationic lysine

• alkylation remains a likely origin of the photodamaging ability of such alkynes. Such reactivity is consistent with the above-mentioned ability of alkynes to act as electrophilic alkylating agents toward electron-rich π-systems observed in triplet photocycloaddition of TFP-substituted diaryl acetylenes [53

• produced acetylenes 8a–c. The TMS group of acetylene 8 was directly substituted with a tetrafluoropyridyl (TFP) group by a CsF-promoted reaction with pentafluoropyridine in DMF. Reduction of the nitrobenzenes 9a–c with SnCl2 produced anilines 10a–c, which were reacted with acetyl chloride to form amides 3

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

• carbonyl groups, but using platinum catalysts [25][26][27][28]. To date, there are no gold- or platinum-catalyzed methods for the introduction of acetylenes as electrophiles. However, Cacchi developed a palladium-catalyzed domino sequence including cyclization of o-alkynyltrifluoroacetanilides and

A rapid and efficient synthetic route to terminal arylacetylenes by tetrabutylammonium hydroxide- and methanol-catalyzed cleavage of 4-aryl-2-methyl-3-butyn-2-ols

• Jie Li and
• Pengcheng Huang

Beilstein J. Org. Chem. 2011, 7, 426–431, doi:10.3762/bjoc.7.55

• -protected acetylene and the subsequent removal of the protecting group is an important synthetic approach to access terminal arylacetylenes [10][11][12][13]. The commonly used mono-protected acetylenes are trialkylsilylacetylenes such as trimethylsilylacetylene (TMSA), triisopropylsilylacetylene (TIPSA) and

Synthesis and self-assembly of 1-deoxyglucose derivatives as low molecular weight organogelators

• Guijun Wang,
• Hao Yang,
• Sherwin Cheuk and
• Sherman Coleman

Beilstein J. Org. Chem. 2011, 7, 234–242, doi:10.3762/bjoc.7.31

• synthesized the terminal acetylenes 9–11, saturated hydrocarbons 12–14, aryl derivatives 15,16, and two long chain diacetylene containing glycolipids 17,18. After we obtained these compounds, we then screened them for gelation in several solvents. These results are shown in Table 1. From the gelation test

Light-induced olefin metathesis

• Yuval Vidavsky and
• N. Gabriel Lemcoff

Beilstein J. Org. Chem. 2010, 6, 1106–1119, doi:10.3762/bjoc.6.127

• phenylacetylene. These works were based on earlier observations by Katz et al. [56][57] and Geoffrey et al. [58] that acetylenes irradiated in the presence of tungsten complexes form metal carbenes that can produce polymeric species. Well-defined tungsten catalysed photometathesis The first example of well

Convenient methods for preparing π-conjugated linkers as building blocks for modular chemistry

• Jiří Kulhánek,
• Filip Bureš and
• Miroslav Ludwig

Beilstein J. Org. Chem. 2009, 5, No. 11, doi:10.3762/bjoc.5.11

• )-phenylethenylphenyl (series 5), and phenylethynylphenyl (series 6) linkers and H (series a), OMe (series b), and NMe2 (series c) groups as the substituent R, respectively (Figure 1, Table 1). The terminal acetylenes 7c–9c possess only the strongest NMe2 donor and have an identical backbone to the one described above

• pinacol ester of 4-iodophenylboronic acid [39] and terminal acetylenes 2a–c (Scheme 1, Method D) in 72–91% yield. Table 1 (entries 1–9) summarizes the used synthetic methods and yields for the particular dioxaborolanes 3–6. Synthesis of terminal acetylenes 7–9 Synthesis of N,N-dimethylamino substituted

• terminal acetylenes 7c–9c was accomplished by Sonogashira cross-coupling as shown on the Scheme 2 (Method E). The reaction utilizes the 4-bromo derivatives used as precursors for the construction of dioxaborolanes 4–6 and the product of the Sonogashira cross-coupling between 2c and 1,4-diiodobenzene (54