One-pot Diels–Alder cycloaddition/gold(I)-catalyzed 6-endo-dig cyclization for the synthesis of the complex bicyclo[3.3.1]alkenone framework

• Boubacar Sow,
• Gabriel Bellavance,
• Francis Barabé and
• Louis Barriault

Beilstein J. Org. Chem. 2011, 7, 1007–1013, doi:10.3762/bjoc.7.114

• large substituents at the alkyne terminal position did not affect the efficacy of the reaction. Intermolecular cycloaddition/Au(I)-catalyzed cyclization of aryl acetylene dienes 33–35 provided the desired ketones 37–39 in yields ranging from 68 to 91% (Table 2, entries 1–3). Remarkably, enyne 36 was

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

• corresponding lysine conjugates shown in Figure 4. Results and Discussion Synthesis The regioisomeric diaryl alkynes were synthesized following the synthetic strategy previously outlined by us for compound 1 [25]. The Sonogashira coupling of the corresponding iodonitrobenzene with trimethylsilyl (TMS) acetylene

• 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

• act as a source of H-atoms, as a source of electrons in PET, or as a reactive π-system. Photocycloaddition of the three acetylene molecules with 1,4-CHD was investigated via irradiation in acetonitrile with a Luzchem LED photoreactor and UVB (310 nm) irradiation (Scheme 4). The m-substituted acetylene

Synthesis of 5-(2-methoxy-1-naphthyl)- and 5-[2-(methoxymethyl)-1-naphthyl]-11H-benzo[b]fluorene as 2,2'-disubstituted 1,1'-binaphthyls via benzannulated enyne–allenes

• Yu-Hsuan Wang,
• Joshua F. Bailey,
• Jeffrey L. Petersen and
• Kung K. Wang

Beilstein J. Org. Chem. 2011, 7, 496–502, doi:10.3762/bjoc.7.58

• )acetylene, boron tribromide, and (1S)-(−)-camphanoyl chloride were purchased from chemical suppliers and were used as received. 1-Iodo-2-[2-(trimethylsilyl)ethynyl]benzene was prepared by treatment of 1-bromo-2-[2-(trimethylsilyl)ethynyl]benzene in THF with n-butyllithium at −78 °C followed by treatment

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

• proved to be less successful for more complex pyrroles of which atorvastatin was an example (Scheme 1). In order to prepare the 5-isopropylpyrrole derivative 16 a more efficient [3 + 2] cycloaddition of an acetylene component with an amido acid 13 was developed. Unfortunately, reacting ethyl

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

• [(3-cyanopropyl)dimethylsilyl]acetylene (CPDMSA), and 2-methyl-3-butyn-2-ol (MEBYNOL). The trialkylsilyl groups can be easily removed by treatment with oxygen-based nucleophiles or fluoride at ambient temperature [10][11][12]. However, trialkylsilylacetylenes are rather expensive that their use is

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

• results shown in Table 1, quite a few of the diesters were good gelators for the solvents tested. In hexane, only the two short chain terminal acetylene compounds 9A and 10A formed gels. Several diesters were effective gelators for ethanol, including the benzoate 15A and the long chain diacetylene

• , several diester derivatives are effective gelators, and for both the diesters and the monoesters, terminal acetylene and aromatic functional groups seemed to facilitate gelation. Therefore, even though it was found to be less effective than the α-methoxy headgroup 1, the deoxy sugar headgroup 8 can be

Ene–yne cross-metathesis with ruthenium carbene catalysts

• Cédric Fischmeister and
• Christian Bruneau

Beilstein J. Org. Chem. 2011, 7, 156–166, doi:10.3762/bjoc.7.22

• the case of unsymmetrical alkynes, the products featuring less steric hindrance are formed. The stereoselectivity of the newly formed trisubstituted double bonds is still not controlled. It must be noted that no EYCM starting from acetylene has been described. On the contrary, polymerization of

• acetylene in the presence of ruthenium carbene complexes has been reported [11]. A challenge that has still to be faced is the EYCM starting from acyclic internal olefins. Selected ruthenium catalysts able to perform EYCM. Applications of EYCM with ethylene in natural product synthesis. Interaction of

Synthesis of Ru alkylidene complexes

• Renat Kadyrov and
• Anna Rosiak

Beilstein J. Org. Chem. 2011, 7, 104–110, doi:10.3762/bjoc.7.14

• /ClCH2CH2Cl in THF in the presence of excess PCy3 and hydrogen followed by subsequent reaction with acetylene [10]. We report herein on an improved protocol for the synthesis of the ethylidene complex (PCy3)2Cl2Ru=CHMe (1a) under mild conditions which is an efficient precursor for the preparation of wide

• acetylene along with formation of the benzylmethylidene complex (PCy3)2Cl2Ru=CHCH2Ph as described previously by Werner [7]. We have found that the use of trimethylsilylacetylene afforded the ethylidene complex 1a as the sole product in very good isolated yield (see Scheme 1). In sharp contrast, the use of 1

The cross-metathesis of methyl oleate with cis-2-butene-1,4-diyl diacetate and the influence of protecting groups

• Arno Behr and
• Jessica Pérez Gomes

Beilstein J. Org. Chem. 2011, 7, 1–8, doi:10.3762/bjoc.7.1

• synthesised by the catalytic reaction of 1,3-butadiene with acetic acid on a large scale. The classical preparative method for 1,4-butanediol is the copper catalysed reaction of acetylene with formaldehyde and subsequent hydrogenation of the intermediate [23]. Currently, the symmetric acylated substrate 2 is

Synthesis and crystal structures of multifunctional tosylates as basis for star-shaped poly(2-ethyl-2-oxazoline)s

• Richard Hoogenboom,
• Martin W. M. Fijten,
• Guido Kickelbick and
• Ulrich S. Schubert

Beilstein J. Org. Chem. 2010, 6, 773–783, doi:10.3762/bjoc.6.96

• recently reported a post-modification route for the synthesis of star-shaped poly(2-ethyl-2-oxazoline) by coupling of an acetylene-functionalized poly(2-ethyl-2-oxazoline) to a heptakis-azido functionalized β-cyclodextrin [18]. However, this method required chromatographic separation of the star-shaped

• polymer from the acetylene-precursor polymer. To overcome the limitations of multi-halide, multi-triflate initiators and post-modification methods, we investigated the use of multi-tosylate initiators for the CROP of 2-oxazolines as depicted in Figure 1. The advantages of multi-tosylate initiators are

Recent advances in carbocupration of α-heterosubstituted alkynes

• Ahmad Basheer and
• Ilan Marek

Beilstein J. Org. Chem. 2010, 6, No. 77, doi:10.3762/bjoc.6.77

• heteroatom. Alkoxy-substituted alkynes For alkoxy-substituted acetylene 4a, R2Cu•MgBr2, R2Cu•LiI or R22CuLi react equally well to give the branched products 6 in good to excellent yields [8][9][10]. The selectivity can be explained by the electrostatic charge distribution in the alkynes [11][12][13

• the organocopper by the oxygen of the THP completely reversed the regiochemistry of the carbocupration reaction [8]. Ethynyl carbamate is also an oxy-substituted acetylene (and therefore should lead to the branched product). However, the electron-withdrawing group properties of the carbamoyl group

New amphiphilic glycopolymers by click functionalization of random copolymers – application to the colloidal stabilisation of polymer nanoparticles and their interaction with concanavalin A lectin

• Otman Otman,
• Paul Boullanger,
• Eric Drockenmuller and
• Thierry Hamaide

Beilstein J. Org. Chem. 2010, 6, No. 58, doi:10.3762/bjoc.6.58

• to the acetylene groups has been reported on reaching high yields [18], no gel formation was observed in our case during polymerization, so that protection of the propargyl monomer was not required. Molecular weights were around 10000 g/mol with Mw/Mn ≈ 1.6–2.0. The molar fraction of PA units in the

Preparation of pyridine-3,4-diols, their crystal packing and their use as precursors for palladium-catalyzed cross-coupling reactions

• Tilman Lechel,
• Irene Brüdgam and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, No. 42, doi:10.3762/bjoc.6.42

• possible palladium-catalyzed cross-couplings we performed several Sonogashira-reactions [28][29][30]. As described in Scheme 3, the pyridinyl-bistriflates or -nonaflates 3 were coupled with alkynes like phenylacetylene or (triisopropylsilyl)acetylene using Pd(PPh3)4 or alternatively, Pd(OAc)2/PPh3 as

• ), (triisopropylsilyl)acetylene (215 mg, 1.18 mmol) in DMF (2.3 mL) and diisopropylamine (1.2 mL) was heated to 60 °C for 4 h under an argon atmosphere. The mixture was allowed to cool to room temperature, diluted with brine (5 mL) and extracted three times with diethyl ether (5 mL). The combined organic phases were

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

Synthetic incorporation of Nile Blue into DNA using 2′-deoxyriboside substitutes: Representative comparison of (R)- and (S)-aminopropanediol as an acyclic linker

• Daniel Lachmann,
• Sina Berndl,
• Otto S. Wolfbeis and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2010, 6, No. 13, doi:10.3762/bjoc.6.13

• modified with the acyclic linked acetylene was performed using a modified protocol. Activator solution (0.45 M tetrazole in acetonitrile) was pumped together with the building block (0.15 M in acetonitrile) through the CPG vial. The coupling time was extended to 61 min with an intervening step after 30.8

Gold film- catalysed benzannulation by Microwave- Assisted, Continuous Flow Organic Synthesis (MACOS)

• Gjergji Shore,
• Michael Tsimerman and
• Michael G. Organ

Beilstein J. Org. Chem. 2009, 5, No. 35, doi:10.3762/bjoc.5.35

• -(3-trimethylsilanyl-naphthalen-1-yl)-methanone (4b). Following the general MACOS benzannulation protocol, 2-(2-phenylethynyl)-benzaldehyde (1a) and TMS-acetylene were reacted and 740 μL of the crude reaction mixture were collected. Purification by flash chromatography (15% ethyl acetate in hexane

• )-nicotinaldehyde (1f) and phenyl acetylene were reacted and 780 μL of the crude reaction mixture were collected. Purification by flash chromatography (20% ethyl acetate in pentane) afforded 77.8 mg of 3f and 4f isomers as pale-yellow oils (64% combined yield). (3f) 1H NMR (400 MHz, CDCl3): δ 8.88 (dd, J = 4.1, 1.5

• acetylene were reacted and 800 μL of the crude reaction mixture were collected. Purification by flash chromatography (20% ethyl acetate in pentane) afforded 70.0 mg of 4h as a pale-brown oil (58% yield). 1H NMR (400 MHz, CDCl3): δ 8.82 (dd, J = 4.1, 1.5 Hz, 1H), 8.21 (dd, J = 8.1, 1.5 Hz, 1H), 8.11 (d, J

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

Synthesis of novel photochromic pyrans via palladium- mediated reactions

• Christoph Böttcher,
• Gehad Zeyat,
• Saleh A. Ahmed,
• Elisabeth Irran,
• Thorben Cordes,
• Cord Elsner,
• Wolfgang Zinth and
• Karola Rueck-Braun

Beilstein J. Org. Chem. 2009, 5, No. 25, doi:10.3762/bjoc.5.25

• THF, (trimethylsilyl)acetylene was reacted with 1 for 45 h to yield 4 in 53% after work-up and purification by flash chromatography (Scheme 5). The Zn(CN)2-based cyanation protocol was also successfully utilized in the transformation of the sterically demanding vinyl bromides 2a/b, affording 5a and 5b

A biphasic oxidation of alcohols to aldehydes and ketones using a simplified packed- bed microreactor

• Andrew Bogdan and
• D. Tyler McQuade

Beilstein J. Org. Chem. 2009, 5, No. 17, doi:10.3762/bjoc.5.17

• catalysts functionalized with an acetylene moiety can be tethered to AO using a Huisgen cycloaddition [39]. Azide-functionalized AO resin (AO-N3, 2) was prepared by treating AO with sodium azide (Scheme 1) [41]. The coupling of 4-hydroxy-TEMPO 3 with propargyl bromide (4) using sodium hydride yielded the

• acetylene-modified TEMPO species 5 [33][34][37]. TEMPO derivative 5 was then covalently bound to AO-N3 using copper(I) iodide [42][43][44][45], yielding the TEMPO-functionalized resin (AO-TEMPO, 6, Scheme 2, 0.46 mmol TEMPO/g resin). Using a simplified procedure developed by ourselves and others [39][46][47

(−)-Complanine, an inflammatory substance of marine fireworm: a synthetic study

• Kazuhiko Nakamura,
• Yu Tachikawa and
• Daisuke Uemura

Beilstein J. Org. Chem. 2009, 5, No. 12, doi:10.3762/bjoc.5.12

• acetylene 4 in 51% yield [7]. The bromomagnesium salt of 4 generated with EtMgBr was successively treated with 1-iodopent-2-yne in the presence of CuI to give the corresponding diyne compound 5 in 43% yield [8]. The partial reduction was achieved by using Lindlar catalyst to give the desired Z olefin, which

• ) of both enantiomers are under consideration at the present time. In conclusion, (−)-complanine was successfully synthesized from (R)-malic acid by acetylene coupling and catalytic hydrogenation as key steps. The absolute configuration of the natural product was determined to be R. Experimental

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

• π-conjugated linkers are described. Either unsubstituted or 4-donor substituted π-linkers bearing a styryl, biphenyl, phenylethenylphenyl, and phenylethynylphenyl π-conjugated backbone are functionalized with boronic pinacol esters as well as with terminal acetylene moieties allowing their further

• moieties is usually accomplished by cross-coupling reactions, in particular by the Suzuki–Miyaura [26][27] or the Sonogashira [28] reactions. Consequently, the availability of the suitably substituted π-conjugated linkers of various lengths bearing boronic ester functionality or terminal acetylene is

• the commercially available terminal acetylene 2c with catecholborane was examined. Despite all attempts to optimize the reaction conditions, 3c could not be prepared this way and was not even detected in the crude reaction mixture. Thus the above hydroboration reported by Perner and co-workers [33

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

• enantioselectively controlled manner (Scheme 30) [85]. The appropriate bis-THF ring system 227 was constructed using a Williamson type etherification reaction on a functionalized bis-mesylate intermediate. A Sonogashira cross-coupling reaction of the terminal acetylene 228 with vinyl iodide 229 followed by

Facile synthesis of two diastereomeric indolizidines corresponding to the postulated structure of alkaloid 5,9E- 259B from a Bufonid toad (Melanophryniscus)

• Angela Nelson,
• H. Martin Garraffo,
• Thomas F. Spande,
• John W. Daly and
• Paul J. Stevenson

Beilstein J. Org. Chem. 2008, 4, No. 6, doi:10.1186/1860-5397-4-6

• periodinane, 77%. (b) Ph3P+CH2I I-, NaN(SiMe3)2 51%. (c) TMS acetylene, CuI, Pd(Ph3P)3, Et3N then K2CO3 MeOH, 69%. Supporting Information Supporting Information File 28: Experimental. Details of experimental procedures and data for characterisation of new compounds. Acknowledgements We would like to thank

Shape- persistent macrocycle with intraannular alkyl groups: some structural limits of discotic liquid crystals with an inverted structure

• Sigurd Höger,
• Jill Weber,
• Andreas Leppert and
• Volker Enkelmann

Beilstein J. Org. Chem. 2008, 4, No. 1, doi:10.1186/1860-5397-4-1

• interior in the nanometer regime has considerably increased. From the structural point of view, most compounds are based on the phenylene, phenylene acetylene or phenylene butadiynylene backbone, or they contain a mixture of these structural elements. However, apart from meeting the synthetic challenge

• compared to macrocycle 1. 3,5-Diiodo-4-methylbenzene (2) was treated with trimethylsilyl(TMS)acetylene under standard Hagihara-Sonogashira coupling conditions and subsequently deprotected with K2CO3 in MeOH/THF. As expected, the Pd-catalyzed coupling reaction runs under milder conditions and with higher

• yields compared to the preparation of 3 from the corresponding dibromo compound [27]. Reaction of 4 with an excess of 5 [28], coupling of 6 with TMS-acetylene and deprotection, again with K2CO3 in MeOH/THF, gave the bisacetylenic half-ring 7. The oxidative dimerization of 7 was performed by slow addition

An asymmetric synthesis of all stereoisomers of piclavines A1-4 using an iterative asymmetric dihydroxylation

• Yukako Saito,
• Naoki Okamoto and
• Hiroki Takahata

Beilstein J. Org. Chem. 2007, 3, No. 37, doi:10.1186/1860-5397-3-37

• ])-16 in 94%. It is impossible to utilize hydrogenolysis due to reactivity of the acetylene unit. Indeed, the N-protecting group exchange of benzyloxycarbonyl (Cbz) for 2,2,2-trichloroethoxycarbonyl (Troc) in 17 was examined. The use of basic reagents such as Ba(OH)2[11] and KOH[12] failed to afford