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

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

• acetylene moiety would take place through an initial 5-exo cyclization that in the case of aryl-substituted enynes (R = Ar) would give rise to a formal [4 + 2] cycloaddition product XIV [18][19], or alternatively, through a relatively less common 6-endo-dig pathway via gold species XV, which could be

Synthesis, characterization and luminescence studies of gold(I)–NHC amide complexes

• Adrián Gómez-Suárez,
• David J. Nelson,
• David G. Thompson,
• David B. Cordes,
• Duncan Graham,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2013, 9, 2216–2223, doi:10.3762/bjoc.9.260

• acetylene, phenyl and phenol derivatives. These reactions can be carried out using reagent-grade materials, without the requirement to exclude light, air or moisture; providing an easy, straightforward 3-step route for the synthesis of organogold–NHC complexes from readily available gold sources, such as

Flexible synthesis of anthracycline aglycone mimics via domino carbopalladation reactions

• Markus Leibeling and
• Daniel B. Werz

Beilstein J. Org. Chem. 2013, 9, 2194–2201, doi:10.3762/bjoc.9.258

• only one silyl group at a dialkyne with two terminal acetylene moieties presented difficulties. Thus, we sought for a consecutive introduction of the corresponding silylacetylene functionalities. An appropriate starting material was selected to achieve a highly convergent and convenient synthetic

• installation of a suitable leaving group sets the stage for the introduction of the first silylacetylene. Four different terminal alkynes 21 (a: Si = TMS; b: Si = SiMe2Ph; c: Si = SiMe2Bn; d: Si = Si(iPr)2H) were employed. Best results with yields of over 80% were obtained by the use of acetylene 21a

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

• method could also be successful in the case of more complex benzofuran-containing natural products and drugs. We were pleased to see that the alkynylation of 8-methoxypsoralen (2) was indeed possible. The major product 10 bearing the acetylene group at the C5’ position was obtained in 37% yield (Scheme 4

Gold-catalyzed intermolecular coupling of sulfonylacetylene with allyl ethers: [3,3]- and [1,3]-rearrangements

• Jungho Jun,
• Hyu-Suk Yeom,
• Jun-Hyun An and
• Seunghoon Shin

Beilstein J. Org. Chem. 2013, 9, 1724–1729, doi:10.3762/bjoc.9.198

• investigate the reaction mechanism. Optimization of the reaction conditions.a Scope of the carboalkoxylation of sulfonyl acetylene (1).a Supporting Information Supporting Information File 266: Characterization of starting materials, general procedure for the carboalkoxylation, characterization of products

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

• 1 equivalent of the azide and 1.5 equivalents of the acetylene were pumped through the reactor in each run with a a flow rate of 0.5 mL min–1. At this flow rate the residence time on the catalyst bed was as low as 1.5 min and it took only 5 min of process time to pump the 2.5 mL aliquots through the

• experiment at 100 bar and rt in the presence of the additives (conditions B) so as to ensure maximum safety throughout the procedure. A CH2Cl2 solution of the reaction mixture containing 1 equivalent of the azide (cazide = 0.085 M), 1.5 equivalents of the acetylene and 0.04 equivalents of each additive was

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

• efficiency of our catalytic system highlighting the role of water in solvating the substrates. We then evaluated the influence of the nitrogen protecting group for the cascade Sonogashira coupling–cyclization sequence on two model reactions (Scheme 2). We observed that the coupling of phenyl acetylene (2

• , 1.0 equiv), PPh3 (5 mol %) and catalyst Pd–Cu/C (2 mol %) were suspended in H2O (3 mL) previously degassed. Then, acetylene derivative (1.0 mmol, 2.0 equiv) and ethanolamine (1.5 mmol, 3.0 equiv) were added. The resulting mixture was stirred 20 h at 80 °C under argon atmosphere. After cooling to room

Anionic cascade reactions. One-pot assembly of (Z)-chloro-exo-methylenetetrahydrofurans from β-hydroxyketones

• István E. Markó and
• Florian T. Schevenels

Beilstein J. Org. Chem. 2013, 9, 1319–1325, doi:10.3762/bjoc.9.148

• , possessing unique structural features. Keywords: acetylene addition; dichloroethylene; dimerisation; dioxanes; tetrahydrofurans; Introduction Recently, we have shown that simple ketones reacted with 1,1-dichloroethylene, in the presence of potassium tert-butoxide, to afford rare (Z)-chloro-exo

• -dichloroethylene is converted into the corresponding chloro-acetylene anion 9 [4][5]. This nucleophilic species adds rapidly, though reversibly, to acetone, leading ultimately to the formation of 5. However, in this case, competitive aldol reaction appears to take place, delivering the adduct 8. The subsequent

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

• group in performing activity-based protein profiling (ABPP) [19][20]. This entails the incorporation of a ligand for recognition by the target, a reactive functionality for covalently bonding to the target, and either an azide or acetylene moiety as a latent linker for subsequent ligation of a tag for

• benzophenone is tolerated on the benzamide ring with retention of the biological activity (3, Table 1) [23]. In addition to a PG, we needed a suitable linking functionality for attachment of a clickable acetylene group. Preliminary work (data not shown) established that an ether (versus amide) linker was

• azide and acetylene, was prepared from aniline 26. Introduction of the azide was accomplished via diazotization/azidation, followed by standard amide coupling of 27 and 18 to afford final aryl azide photoprobe 28. Table 2 summaries the biological data for the four final candidate photoprobes

Synthesis, photophysical and electrochemical characterization of terpyridine-functionalized dendritic oligothiophenes and their Ru(II) complexes

• Amaresh Mishra,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2013, 9, 866–876, doi:10.3762/bjoc.9.100

• (Figure 2). For both complexes the tpy-acetylene-thiophene units are coplanar thereby providing an extended conjugation pathway from the tpy ligand to the oligothiophene dendron. Due to the high molecular symmetry, the highest occupied molecular orbitals (HOMO and HOMO-1) for 1 were found to be degenerate

Photoionisation of the tropyl radical

• Kathrin H. Fischer,
• Patrick Hemberger,
• Andras Bodi and
• Ingo Fischer

Beilstein J. Org. Chem. 2013, 9, 681–688, doi:10.3762/bjoc.9.77

• the “pyrolysis on” spectra corresponding to the dissociative photoionisation of the tropyl radical, yielding the cyclopentadienyl cation and acetylene. Figure 3 shows the region of the ionisation onset of the tropyl radical in high resolution while Figure 4 (see below) exhibits the complete spectrum

• metastable parent ion [40]. Formation of the cyclopentadienyl ion and acetylene upon dissociative photoionisation of tropyl can explain the rise in the mass channel above 10.55 eV and the asymmetric peak shape. Thermochemical calculations reveal that the channel is accessible at 10.52 eV, utilizing the heat

• of formation at 0 K of C7H7+ (896 kJ mol−1) [41], the ∆fHo of cyclopentadienyl radical (276 kJ mol−1) [42], its adiabatic IE (8.428 eV = 813.18 kJ mol−1) [39], and the ∆fHo of acetylene (226.88 kJ mol−1) [43]. This corresponds to around 4.3 eV internal energy in the ion before it dissociates, being

Spin state switching in iron coordination compounds

• Philipp Gütlich,
• Ana B. Gaspar and
• Yann Garcia

Beilstein J. Org. Chem. 2013, 9, 342–391, doi:10.3762/bjoc.9.39

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

• -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

Efficient synthesis of phenylene-ethynylene rods and their use as rigid spacers in divalent inhibitors

• Francesca Pertici,
• Norbert Varga,
• Arnoud van Duijn,
• Matias Rey-Carrizo,
• Anna Bernardi and
• Roland J. Pieters

Beilstein J. Org. Chem. 2013, 9, 215–222, doi:10.3762/bjoc.9.25

• was used as a side chain, which terminated as a free hydroxy group for 1 and a methoxy group for 2. Silyl groups were used as selective protective groups for the alkyne moiety. Monoalkyne 3 and bisalkyne 4 were made from 1 [29] by a Sonogashira reaction with TIPS-acetylene in 31% and 50%, respectively

• Figure 3 was applied to the synthesis of the two-unit spacer. In order to obtain our orthogonally protected intermediate 7, mono-iodo compound 5 was coupled with tert-butyl(ethynyl)dimethylsilane (TBDMS-acetylene, Scheme 2). From 7 the more labile TMS group was removed by using K2CO3 to give 8. This

Polar reactions of acyclic conjugated bisallenes

• Reiner Stamm and
• Henning Hopf

Beilstein J. Org. Chem. 2013, 9, 36–48, doi:10.3762/bjoc.9.5

• propargyl structure. The “half-rearranged” diol 24 is a slightly yellow oil at room temperature. Structure-defining are the missing allene proton and three signals for carbon atoms not connected to a hydrogen atom: the central allene carbon atom at 210.0 ppm and the two acetylene carbon atoms at δ 72.0 and

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

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

• example we could find in the chemical literature for building up a bisallene derivative by a trimerization protocol from the same C2-precursor (acetylene). Many other silylated derivatives of 2 have been described. For example, derivative 83 can be obtained in good yield by a C3-coupling route, as

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

• under mild conditions [37]. They can be seen as a dual functionalized molecule in TMC reactions, with the two main modes of reactivity proceeding by insertion of a metal into the carbon–halide bond (Scheme 2, type 1), or coordination of the π-system of the acetylene to the metal in a η2 fashion (Scheme

Diarylethene-modified nucleotides for switching optical properties in DNA

• Sebastian Barrois and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2012, 8, 905–914, doi:10.3762/bjoc.8.103

• , forms the central cyclopentane ring of diarylethene 10. Subsequently, the ethynyl linker is attached to 10 by treatment with TMS-protected acetylene in a Pd-catalyzed cross-coupling reaction. Careful evaluation of this synthetic step revealed that the best yield (43%) of the mono-ethinylated product 11

• is obtained with 2 equiv of TMS-acetylene in the reaction mixture. The competitively formed doubly ethinylated diarylethene 12 is, of course, easier to obtain. In the latter case, a strong excess of TMS-acetylene (10 equiv) helps to increase the yield of product 12 to 85%. The synthesis of the first

• diarylethene 6 shows absorption at 254 and 350 nm (Figure 1E). Irradiation at 250 nm indeed shows the formation of the colored form at 450 nm, but to a much smaller extent when compared with 4 or 5. Obviously, the conjugation of the terminal acetylene group of nucleoside 5 to a second 2’-deoxyuridine in 6

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

• -triazole co-oligomers were investigated by UV–vis spectroscopy and cyclic voltammetry. Several co-oligomers were electropolymerized to the corresponding conjugated polymers. Keywords: acetylene; azide; click chemistry; thiophene; triazole; Introduction Oligo- and polythiophenes are among the most

• -triazoles Halide (1 equiv) and terminal acetylene (1 equiv) were dissolved in an ethanol/water mixture (4 mL, 7:3). After the addition of sodium azide (2 equiv), sodium ascorbate (10 mol %), N,N’-dimethylethylenediamine (DMEDA, 20 mol %) and copper(I) iodide (10 mol %), the mixture was stirred in a closed

Discovery of practical production processes for arylsulfur pentafluorides and their higher homologues, bis- and tris(sulfur pentafluorides): Beginning of a new era of “super-trifluoromethyl” arene chemistry and its industry

• Teruo Umemoto,
• Lloyd M. Garrick and
• Norimichi Saito

Beilstein J. Org. Chem. 2012, 8, 461–471, doi:10.3762/bjoc.8.53

• gaseous SF5Cl with acetylene, followed by bromination, dehydrobromination, and reduction with zinc, giving pentafluorosulfanylacetylene (HC≡CSF5), which was then reacted with butadiene, followed by an aromatization reaction at very high temperature, gave phenylsulfur pentafluoride [35]. Recently

• AgF2 in 12% yield [3]. Two isomers of phenyl tris(sulfur pentafluorides) were synthesized by many steps starting from the reaction of SF5Cl with acetylene via HC≡CSF5 [42]. Complex Co(CO)4(HC≡CSF5) derived from HC≡CSF5 and Co2(CO)8 was decomposed in the presence of Br2 to give phenyl-1,2,4-tris(sulfur

Syntheses and applications of furanyl-functionalised 2,2’:6’,2’’-terpyridines

• Jérôme Husson and
• Michael Knorr

Beilstein J. Org. Chem. 2012, 8, 379–389, doi:10.3762/bjoc.8.41

• used as a starting material and reacted with trimethylsilyl acetylene in a Sonogashira reaction. After deprotection of the trimethylsilyl moiety with tetrabutylammonium fluoride, terpyridine 63 was obtained. Reaction of the latter with 3-azidopropanol afforded the triazinyl-containing compound 64

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

• precursor 49 in situ through a Pd/Cu mediated coupling reaction between (trimethylsilyl)acetylene (TMSA) with an aryl iodide, followed by a desilylation reaction. The subsequent addition of the third partner, an o-iodoanilide derivative, allowed a Pd/Cu tandem C–C/C–N-bond-forming reaction. The main

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