- An on-surface Diels–Alder reaction
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The Diels–Alder reaction is one of the most popular reactions in organic chemistry. However, its use in the field of on-surface synthesis is hampered by the spatial restrictions of this cycloaddition reaction. Herein we selected a cyclic strained triyne t
- Albrecht, Florian,Castro-Esteban, Jesús,Fatayer, Shadi,Gross, Leo,Pérez, Dolores,Pe?a, Diego
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supporting information
p. 26346 - 26350
(2021/11/13)
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- Alumina-Mediated π-Activation of Alkynes
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The ability to induce powerful atom-economic transformation of alkynes is the key feature of carbophilic π-Lewis acids such as gold- and platinum-based catalysts. The unique catalytic activity of these compounds in electrophilic activations of alkynes is explained through relativistic effects, enabling efficient orbital overlapping with π-systems. For this reason, it is believed that noble metals are indispensable components in the catalysis of such reactions. In this study, we report that thermally activated γ-Al2O3activates enynes, diynes, and arene-ynes in a manner enabling reactions that were typically assigned to the softest π-Lewis acids, while some were known to be triggered exclusively by gold catalysts. We demonstrate the scope of these transformations and suggest a qualitative explanation of this phenomenon based on the Dewar-Chatt-Duncanson model confirmed by density functional theory calculations.
- Akhmetov, Vladimir,Amsharov, Konstantin,Feofanov, Mikhail,Sharapa, Dmitry I.
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supporting information
p. 15420 - 15426
(2021/09/30)
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- Selective Synthesis of Phenanthrenes and Dihydrophenanthrenes via Gold-Catalyzed Cycloisomerization of Biphenyl Embedded Trienynes
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Readily available o′-alkenyl-o-alkynylbiaryls, a particular type of 1,7-enynes, undergo a selective cycloisomerization reaction in the presence of a gold(I) catalyst to give interesting phenanthrene and dihydrophenanthrene derivatives in high yields. The solvent used provokes a switch in the evolution of the gold intermediate and plays a key role in the reaction outcome.
- Milián, Ana,Garciá-Garciá, Patricia,Pérez-Redondo, Adrián,Sanz, Roberto,Vaquero, Juan J.,Fernández-Rodríguez, Manuel A.
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supporting information
p. 8464 - 8469
(2020/11/02)
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- Sterically Controlled Late-Stage C-H Alkynylation of Arenes
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Phenylacetylenes are key structural motifs in organic chemistry, which find widespread applications in bioactive molecules, synthetic intermediates, functional materials, and reagents. These molecules are typically prepared from prefunctionalized starting materials, e.g. using the Sonogashira coupling, or using directing group-based C-H activation strategies. While highly efficient, these approaches remain limited by their inherent selectivities for specific regioisomers. Herein we present a complementary approach based on an arene-limited nondirected C-H activation. The reaction is predominantly controlled by steric rather than electronic factors and thereby gives access to a complementary product spectrum with respect to traditional methods. A broad scope as well as the suitability of this protocol for late-stage functionalization are demonstrated.
- Mondal, Arup,Chen, Hao,Fl?mig, Lea,Wedi, Philipp,Van Gemmeren, Manuel
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supporting information
p. 18662 - 18667
(2019/11/28)
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- Syntheses of substituted benzosiloles and siloles by diisobutylaluminium hydride-promoted cyclization of 1-silyl-2-(2-silylethynyl)benzenes and 1,4-disilylalk-3-en-1-ynes
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An efficient method for preparing substituted benzosiloles and unsymmetrically substituted siloles by intramolecular C-Si bond formation has been developed. The reaction of 1-methoxysilyl-2-[2-(trimethylsilyl)ethynyl]benzenes with 1.5 equiv of diisobutylaluminium hydride (DIBAL-H) gave benzosiloles in good to high yields. Similarly 4-methoxysilyl-1-silylalk-3-en-1-ynes were cyclized to multisubstituted siloles. Mechanistic study of this transformation uncovered that the methoxysilyl group was initially converted into the corresponding hydrosilyl group by the action of DIBAL-H, and that the resultant hydrosilanes underwent the DIBAL-H-promoted cyclization to benzosiloles. When 1-hydrosilyl-2-[2-(trimethylsilyl)ethynyl]benzenes were used as substrates, a substoichiometric amount of DIBAL-H was enough for the cyclization. The DIBAL-H-promoted transformation could be applied to regio-defined synthesis of unsymmetrically substituted siloles from 4-hydrosilyl-1-silylalk-3-en-1-ynes. This pre-installation approach provides a straightforward access to multisubstituted siloles with complete regioselection.
- Kinoshita, Hidenori,Fukumoto, Hiroki,Ueda, Akihiro,Miura, Katsukiyo
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p. 1632 - 1645
(2018/02/19)
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- Adding Four Extra K-Regions to Hexa-peri-hexabenzocoronene
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A multistep synthesis of hexa-peri-hexabenzocoronene (HBC) with four additional K-regions was developed through a precursor based on two benzotetraphene units bridged with p-phenylene, featuring preinstalled zigzag moieties. Characterization by laser deso
- Dumslaff, Tim,Yang, Bo,Maghsoumi, Ali,Velpula, Gangamallaiah,Mali, Kunal S.,Castiglioni, Chiara,De Feyter, Steven,Tommasini, Matteo,Narita, Akimitsu,Feng, Xinliang,Müllen, Klaus
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supporting information
p. 4726 - 4729
(2016/05/09)
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- Synthesis and photophysical properties of biphenyl and terphenyl arylene-ethynylene macrocycles
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A series of single-walled carbon nanotube precursors, C3h- symmetric cyclotri(ethynylene)(biphenyl-2,4′-diyl) and cyclotri(ethynylene)(p-terphenyl-2,4″-diyl), have been prepared by a linear stepwise oligomerization-cyclization route and by stat
- Korich, Andrew L.,McBee, Ian A.,Bennion, Jonathan C.,Gifford, Jenna I.,Hughes, Thomas S.
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p. 1594 - 1610
(2014/03/21)
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- Dihydrobiphenylenes through ruthenium-catalyzed [2+2+2] cycloadditions of ortho-alkenylarylacetylenes with alkynes
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A new synthetic route to dihydrobiphenylenes has been developed. The process involves a mild RuII-catalyzed [2+2+2] dimerization of ortho-alkenylarylacetylenes or its more versatile variant, the Ru-catalyzed [2+2+2] cycloaddition of ortho-ethynylstyrenes with alkynes. Mechanistic aspects of this [2+2+2] cycloaddition are discussed. A new synthetic route to dihydrobiphenylenes involves a mild RuII-catalyzed [2+2+2] dimerization of ortho-alkenylarylacetylenes or its more versatile variant, the Ru-catalyzed [2+2+2] cycloaddition of ortho-ethynylstyrenes with alkynes. The mechanistic aspects of this [2+2+2] cycloaddition are also discussed. Copyright
- Garcia-Rubin, Silvia,Gonzalez-Rodriguez, Carlos,Garcia-Yebra, Cristina,Varela, Jesus A.,Esteruelas, Miguel A.,Saa, Carlos
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supporting information
p. 1841 - 1844
(2014/03/21)
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- Strained and unstrained macrocycles composed of carbazole and butadiyne units: Electronic state and optical properties
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Cu(OAc)2 catalyzes dehydrogenative condensation of 3,6-bis(2-ethynylphenyl)carbazole in the presence of O2 to afford the cyclization product 1 and cyclodimer 2. Compound 1 contains bent carbazole and butadiyne groups, while 2 has a l
- Ide, Tomohito,Sakamoto, Sho,Takeuchi, Daisuke,Osakada, Kohtaro,MacHida, Shigeru
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experimental part
p. 4837 - 4841
(2012/07/28)
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- Synthesis of dendritic metalloporphyrins with distal H-bond donors as model systems for hemoglobin
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We report the synthesis of the first- (G1) and second-generation (G2) dendritic FeII porphyrins 1-Fe-4-Fe (G1) and 6 · Fe (G2) bearing distal H-bond donors ideally positioned for stabilization of Fe II-O2 adducts by H-bonding (Fig. 1). A first approach towards the construction of these novel biomimetic systems failed unexpectedly: the Suzuki cross-coupling between appropriately functionalized ZnII porphyrins and orthoethynylated aryl derivatives, serving as anchors for the distal H-bond donor moieties, was unsuccessful (Schemes 1, 3, and 5), presumably due to steric hindrance resulting from unfavorable coordination of the ethynyl residue to the Pd species in the catalytic cycle (Scheme 6). The target molecules were finally prepared by a route in which the ortho-ethynylated meso-aryl ring is introduced during porphyrin construction in a mixed condensation involving the two dipyrrylmethanes 33 and 34, and aldehyde 36 (Schemes 7 and 8). Following attachment of the dendrons (Scheme 11), the distal H-bond donors were introduced by Sonogashira cross-coupling (Scheme 12), and subsequent metallation afforded the dendritic FeII porphyrins 1 · Fe-6 · Fe. 1H-NMR Spectroscopy proved the location of the H-bond donor moiety atop the porphyrin surface, and X-ray crystal-structure analysis of model system 45 (Fig. 2} revealed that this moiety would not sterically interfere with gas binding. With 1,2-dimethyl-1H-imidazole (DiMeIm) as ligand, the dendritic FeII porphyrins formed five-coordinate high-spin complexes (Figs. 3 and 4) and addition of CO led reversibly to the corresponding stable six-coordinate gas complexes (Fig. 6). Oxygenation, however, did not result in defined FeII-O2 complexes as rapid decomposition to FeIII species took place immediately, even in the case of the G2 dendrimer 6·Fe(DiMeIm) (Fig. 7). In contrast, stable gas adducts are formed between dendritic CoII porphyrins and O 2 in the presence of DiMeIm as axial ligand, as revealed by electron paramagnetic resonance (EPR). The possible stabilization of these complexes through H-bonding involving the distal ligand is currently under investigation in multidimensional and multifrequency pulse EPR experiments.
- Felber, Beatrice,Diederich, Francois
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p. 120 - 153
(2007/10/03)
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- The synthesis of a novel strained diyneparacyclophane and its dimer by metal-mediated coupling
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Relieve strain with a twist! Synthesis of the paracyclophane 1 and its dimer 2 employed a sequence of metal-mediated couplings. The X-ray analysis of 2 revealed a helical twist inherent in this structure, which created extended arms, that trapped a molecule of solvent. A carboxylic acid derivative of 1 was also prepared, and its structure indicated the diyne rod moiety of 1 is distorted more than in analogous compounds.
- Collins, Shawn K.,Yap, Glenn P.A.,Fallis, Alex G.
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p. 385 - 388
(2007/10/03)
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