- Iodonium Cation-Pool Electrolysis for the Three-Component Synthesis of 1,3-Oxazoles
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The synthesis of 1,3-oxazoles from symmetrical and unsymmetrical alkynes was realized by an iodonium cation-pool electrolysis of I2 in acetonitrile with a well-defined water content. Mechanistic investigations suggest that the alkyne reacts with the acetonitrile-stabilized I+ ions, followed by a Ritter-type reaction of the solvent to a nitrilium ion, which is then attacked by water. The ring closure to the 1,3-oxazoles released molecular iodine, which was visible by the naked eye. Also, some unsymmetrical internal alkynes were tested and a regioselective formation of a single isomer was determined by two-dimensional NMR experiments.
- Sattler, Lars E.,Hilt, Gerhard
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p. 605 - 608
(2020/12/07)
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- Cobalt-Catalyzed Hydroalkynylation of Vinylaziridines
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Transition metal-catalyzed hydroalkynylation reactions are efficient transformations allowing the straightforward formation of functionalized alkynes. Therein, we disclose the cobalt-catalyzed hydroalkynylation of vinylaziridines giving rise to both linea
- Biletskyi, Bohdan,Kong, Lingyu,Tenaglia, Alphonse,Clavier, Hervé
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p. 2578 - 2585
(2021/03/18)
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- Synthesis and Photochemical Application of Hydrofluoroolefin (HFO) Based Fluoroalkyl Building Block
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A novel fluoroalkyl iodide was synthesized on multigram scale from refrigerant gas HFO-1234yf as cheap industrial starting material in a simple, solvent-free, and easily scalable process. We demonstrated its applicability in a metal-free photocatalytic ATRA reaction to synthesize valuable fluoroalkylated vinyl iodides and proved the straightforward transformability of the products in cross-coupling chemistry to obtain conjugated systems.
- Varga, Bálint,Tóth, Balázs L.,Béke, Ferenc,Csenki, János T.,Kotschy, András,Novák, Zoltán
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p. 4925 - 4929
(2021/07/01)
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- Frustrated Lewis pair-catalyzed double hydroarylation of alkynes with: N -substituted pyrroles
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Metal-free hydroarylation of alkynes with N-substituted pyrroles is shown to be most efficiently mediated by B(C6F5)3 to yield 12 variants of dipyrrole-alkanes, a mono-hydroarylation product and a tetrahydroarylation produ
- Guo, Jing,Cheong, Odelia,Bamford, Karlee L.,Zhou, Jiliang,Stephan, Douglas W.
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p. 1855 - 1858
(2020/02/22)
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- Copper-Catalyzed Ring Opening of [1.1.1]Propellane with Alkynes: Synthesis of Exocyclic Allenic Cyclobutanes
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Despite the long history and interesting properties of propellanes, these compounds still have tremendous potential to be exploited in synthetic organic chemistry. Herein we disclose an experimentally simple procedure to achieve cyclobutane-containing allenes and alkynes through a copper-catalyzed ring opening of [1.1.1]propellane and subsequent reaction with ethynes.
- Lasányi, Dániel,Tolnai, Gergely L.
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supporting information
p. 10057 - 10062
(2019/12/24)
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- SO2F2-Mediated Oxidative Dehydrogenation and Dehydration of Alcohols to Alkynes
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Direct synthesis of alkynes from inexpensive, abundant alcohols was achieved in high yields (greater than 40 examples, up to 95% yield) through a SO2F2-promoted dehydration and dehydrogenation process. This straightforward transformation of sp3-sp3 (C-C) bonds to sp-sp (C=C) bonds requires only inexpensive and readily available reagents (no transition metals) under mild conditions. The crude alkynes are sufficiently free of impurities to permit direct use in further transformations, as illustrated by regioselective Huisgen alkyne-azide cycloaddition reactions with PhN3 to give 1,4-substituted 1,2,3-traiazoles (16 examples, up to 92% yield) and Sonogashira couplings (10 examples, up to 77% yield).
- Zha, Gao-Feng,Fang, Wan-Yin,Li, You-Gui,Leng, Jing,Chen, Xing,Qin, Hua-Li
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supporting information
p. 17666 - 17673
(2019/01/04)
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- Au-Catalyzed Intermolecular [2+2] Cycloadditions between Chloroalkynes and Unactivated Alkenes
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The [2+2] cycloaddition is a versatile strategy for the synthesis of strained cyclobutenes of high synthetic value. In this study, two efficient intermolecular [2+2] cycloadditions between two different types of chloroalkynes and unactivated alkene are realized with gold catalysis. Of significance is that the reaction works with challenging monosubstituted unactivated alkenes, which is unprecedented in gold catalysis and scarcely documented in other metal-catalyzed/promoted reactions; moreover, the reaction exhibits excellent regioselectivities, which are much better than those reported in literature. With 1,2-disubstituted unactivated alkenes, the reaction is largely stereospecific. The cyclobutene products can be prepared in nearly gram scale and readily undergo further reactions including various cross-coupling reactions using the C(sp2)-Cl and/or C(sp2)-SPh bond, which in turn substantially broaden the scope of accessible cyclobutenes and enhance the synthetic utility of this bimolecular reaction.
- Bai, Yu-Bin,Luo, Zaigang,Wang, Yuguang,Gao, Jin-Ming,Zhang, Liming
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p. 5860 - 5865
(2018/05/14)
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- Blue-shifted aggregation-induced emission of siloles by simple structural modification and their application as nitro explosive chemosensors
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To induce blue-shifted emission of siloles, two tolyl-substituted derivatives-1,1-diphenyl-2,3,4,5-tetra(m-tolyl)-1H-silole (m-TS) and 1,1-diphenyl-2,3,4,5-tetra(o-tolyl)-1H-silole (o-TS)-were prepared, and their photophysical properties were compared with those of a reference compound, hexaphenylsilole (HPS). By substituting methyl groups at ortho positions of peripheral tetraphenyl rings on the silacyclopentadiene ring, intramolecular rotations could be successfully controlled and the photophysical properties were varied, while substituting methyl groups at meta positions showed similar photophysical properties compared with the case of HPS. That is, simple structural modification at the ortho position significantly affects the geometry and the photophysical properties of silole, which leads to blue-shifted emission. Finally, two tolyl-substituted siloles and HPS were employed as chemosensors for the detection of nitro explosives, and o-TS showed the highest sensing ability.
- Lee, Jiwon,Park, Yoona,Jung, Joori,Han, Won-Sik
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p. 1495 - 1501
(2017/10/19)
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- Palladium-catalyzed tandem C-H functionalization/cyclization strategy for the synthesis of 5-hydroxybenzofuran derivatives
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A palladium-catalyzed benzoquinone C-H functionalization/ cyclization strategy with terminal alkynes was employed for the synthesis of some biologically relevant 2, 3-disubstituted 5-hydroxybenzofuran derivatives. The benzoquinone acts as a reactant as well as an oxidant. During the process, an additional alkyne functionality can be introduced at the C3 position of the benzofuran. Base, ligand, and external oxidant are not required in this protocol.
- Ichake, Sachin S.,Konala, Ashok,Kavala, Veerababurao,Kuo, Chun-Wei,Yao, Ching-Fa
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supporting information
p. 54 - 57
(2017/11/28)
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- Reaction discovery using acetylene gas as the chemical feedstock accelerated by the stop-flow micro-tubing reactor system
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Acetylene gas has been applied as a feedstock under transition-metal catalysis and photo-redox conditions to produce important chemicals including terminal alkynes, fulvenes, and fluorinated styrene compounds. The reaction discovery process was accelerated through the use of stop-flow micro-tubing reactors. This reactor prototype was developed by joining elements from both continuous micro-flow and conventional batch reactors, which was convenient and effective for gas/liquid reaction screening. Notably, the developed transformations were either inefficient or unsuccessful in conventional batch reactors. Its success relies on the unique advantages provided by this stop-flow micro-tubing reactor system.
- Xue, Fei,Deng, Hongping,Xue, Chengwen,Mohamed, Dara Khairunnisa Binte,Tang, Karen Yuanting,Wu, Jie
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p. 3623 - 3627
(2017/07/11)
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- A practical non-metal catalytic silicon of the amino protection of the new method (by machine translation)
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The invention relates to a high efficiency, mild organic silicon reagent carbon silicon key fracture of the new method. The method of this reaction to the alkali is cheap and easy to obtain metal catalyst, in order to common commercial solvent as a reaction solvent and a hydrogen source, in the air and in the under mild conditions can be successfully catalytic trimethyl aryl silicon reagent or aryl alkyne base silicon reagent selectively generating carbon silicon key cracking hydrogenation reaction, the substrate universality is wide, functional group compatibility outstanding. The first innovative to realize the non-transition metal catalyzed carbon silicon key breaking reaction, also overcome the traditional method requires the use of greatly excessive inorganic alkali or an expensive metal catalyst to the limitation of the silicon of the amino protection, for the laboratory preparation and industry in the production of the organosilicon group deprotection provides a completely new strategy. (by machine translation)
- -
-
Paragraph 0056; 0057
(2018/04/01)
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- Manganese-Catalyzed ortho-C?H Alkenylation of Aromatic N?H Imidates with Alkynes: Versatile Access to Mono-Alkenylated Aromatic Nitriles
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So far, the direct C?H alkenylation of aromatic nitriles with alkynes has not been achieved. Herein, we discribe the first manganese-catalyzed C?H alkenylation of aromatic N?H imidates to access mono-alkenylated aromatic nitriles. The reaction is accelerated by the presence of a catalytic amount of sodium pivalate. This protocol is also highlighted by the simple catalytic system, good compatibility of functional groups, and excellent mono-/dialkenylation selectivity as well as E/Z stereoselectivity. (Figure presented.).
- Yang, Xiaoxu,Jin, Xiqing,Wang, Congyang
-
supporting information
p. 2436 - 2442
(2016/08/16)
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- Pseudo five-component synthesis of 3-(hetero)arylmethyl-2,5-di(hetero)-aryl-substituted thiophenes via sonogashira-glaser cyclization sequence
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The Sonogashira-Glaser sequence combined with a microwave-assisted cyclization is a powerful tool to synthesize unsymmetrically substituted conjugated thiophenes. A variety of 3-(hetero)arylmethyl-2,5-di(hetero)aryl-substituted thiophenes could be synthesized in moderate to excellent yields using a single Pd/Cu catalyst system. The presented method is strikingly simple to perform using commercially available starting materials. The obtained trisubstituted oligothiophene derivatives are interesting molecules for materials science.
- Klukas, Fabian,Perkampus, J?rg,Urselmann, Dominik,Müller, Thomas J. J.
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p. 3415 - 3422
(2015/02/02)
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- Ti(OiPr)4/nBuLi: An attractive reagent system for [2+2+2] cyclotrimerisation reactions
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A convenient method for the [2+2+2] cyclotrimerisation of alkynes using Ti(OiPr)4/nBuLi is presented. Homotrimerisation of arylacetylenes proceeds within minutes with excellent regioselectivity. Moreover, the intermolecular construction of ABB heterotrimers can be achieved selectively from two different alkynes with similar electronic properties. The method is also suitable for the synthesis of pyridines.
- Rassadin,Nicolas,Six
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supporting information
p. 7666 - 7669
(2014/07/08)
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- Palladium nanoparticles catalyzed Sonogashira reactions for the one-pot synthesis of symmetrical and unsymmetrical diarylacetylenes
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A variety of symmetrical and unsymmetrical diarylacetylenes are synthesized by ligand-free palladium nanoparticles catalyzed copper-free and amine-free Sonogashira cross-coupling reactions between aryl iodides and trimethylsilylacetylene (TMSA) under mild reaction conditions.
- Mandali, Pavan Kumar,Chand, Dillip Kumar
-
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- Reactivity switch enabled by counterion: Highly chemoselective dimerization and hydration of terminal alkynes
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A counterion-controlled reactivity tuning in Pd-catalyzed highly chemoselective and regioselective dimerization and hydration of terminal alkynes is reported. The use of acetate as counterion favors the formation of an alkenyl alkynyl palladium intermediate which forms hitherto less reported 1,3-diaryl-substituted conjugated enynes after reductive elimination. Using chloride, which is a better leaving group, leads to anion exchange on the alkenylpalladium intermediate with hydroxide which after reductive elimination and tautomerization delivered the hydration products.
- Xu, Caixia,Du, Weiyuan,Zeng, Yi,Dai, Bin,Guo, Hao
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supporting information
p. 948 - 951
(2014/03/21)
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- Aerobic oxidation in nanomicelles of aryl alkynes, in water at room temperature
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On the basis of the far higher solubility of oxygen gas inside the hydrocarbon core of nanomicelles, metal and peroxide free aerobic oxidation of aryl alkynes to β-ketosulfones has been achieved in water at room temperature. Many examples are offered that illustrate broad functional group tolerance. The overall process is environmentally friendly, documented by the associated low E Factors. It's all happenin' in the micelle! The highly preferential dissolution of oxygen gas within the lipophilic cores inside nanomicelles leads to efficient trapping of in situ generated vinyl radicals. These intermediate radicals, derived from arylalkynes and sulfinic acids, lead to β-ketosulfone products, formed under especially mild and green conditions: no metals, no heating or cooling, recyclable aqueous media, and low E Factors.
- Handa, Sachin,Fennewald, James C.,Lipshutz, Bruce H.
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supporting information
p. 3432 - 3435
(2014/04/03)
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- Mn-catalyzed aromatic C-H alkenylation with terminal alkynes
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The first manganese-catalyzed aromatic C-H alkenylation with terminal alkynes is described. The procedure features an operationally simple catalyst system containing commercially available MnBr(CO)5 and dicyclohexylamine (Cy2NH). The reaction occurs readily in a highly chemo-, regio-, and stereoselective manner delivering anti-Markovnikov E-configured olefins in high yields. Experimental study and DFT calculations reveal that (1) the reaction is initiated by a C-H activation step via the cooperation of manganese and base; (2) manganacycle and alkynylmanganese species are the key reaction intermediates; and (3) the ligand-to-ligand H-transfer and alkynyl-assisted C-H activation are the key steps rendering the reaction catalytic in manganese.
- Zhou, Bingwei,Chen, Hui,Wang, Congyang
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p. 1264 - 1267
(2013/03/14)
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- Regioselective, stereoselective, and conformationally controlled synthesis of(η4-tetraarylcyclobutadiene)(η5- carbomethoxycyclopentadienyl)cobalt metallocenes
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The Friedel - Crafts reaction of (η4- tetraphenylcyclobutadiene)(η5-carbomethoxycyclopentadienyl) cobalt with acid chlorides/aluminum chloride resulted exclusively in para-phenyl acylation. Both monoacylated (1.1 equiv of RCOCl/AlCl
- Cassar, Doyle J.,Nagaradja, Elisabeth,Butler, David C. D.,Villemin, Didier,Richards, Christopher J.
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p. 894 - 897
(2012/03/26)
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- Synthesis of aryl alkynyl carboxylic acids and aryl alkynes from propiolic acid and aryl halides by site selective coupling and decarboxylation
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The coupling of propiolic acid with aryl iodides afforded the aryl alkynyl carboxylic acids and aryl alkynes in generally good yields. Aryl alkynyl carboxylic acids were obtained when the reaction was performed in the presence of Pd(PPh3)2Cl2 (2.5 mol %), dppb (5.0 mol %) and DBU (5 equiv) at 50°C. For the synthesis of the terminal aryl alkynes, the reaction was conducted in the presence of Pd(PPh3) 2Cl2 (2.5 mol %), dppb (5.0 mol %), DBU (5.0 equiv), and Cu(acac)2 (10 mol %) at 25°C for 5 h, and further reacted at 60°C for 6 h.
- Park, Kyungho,Palani, Thiruvengadam,Pyo, Ayoung,Lee, Sunwoo
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experimental part
p. 733 - 737
(2012/03/08)
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- Efficient approach to 1,2-diazepines via formal diazomethylene insertion into the C-C bond of cyclobutenones
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Efficient monocyclic 1,2-diazepine formation via a tandem electrocyclization reaction of cyclobutenones with lithiodiazoacetate is demonstrated. The reaction proceeds through an oxy anion-accelerated 4π-ring opening of cyclobutene followed by an 8π-ring closure of the resultant oxy anion-substituted diazo-diene under mild conditions to furnish a 1,2-diazepine via formal diazomethylene insertion into the C-C bond of cyclobutenone.
- Sugimoto, Kenji,Hayashi, Rie,Nemoto, Hideo,Toyooka, Naoki,Matsuya, Yuji
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supporting information; experimental part
p. 3510 - 3513
(2012/07/31)
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- One-pot procedure for the synthesis of unsymmetrical diarylalkynes
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Unsymmetrical diarylalkynes are accessible by a one-pot procedure from two different aryl halides and (trimethylsilyl)acetylene. The three-component coupling is initialized by a Pd/Cu-catalyzed Sonogashira coupling of an aryl halide with (trimethylsilyl)a
- Severin, Rene,Reimer, Jessica,Doye, Sven
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supporting information; experimental part
p. 3518 - 3521
(2010/07/17)
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- One-pot desilylation/dimerization of terminal alkynes by ruthenium and acid-promoted (RAP) catalysis
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The dimerization of terminal arylalkynes promoted by the (p-cymene)ruthenium dichloride dimer/acetic acid system {[RuCl 2(p-cymene)]2/AcOH} can be performed starting from the trimethylsilylethynyl derivatives (12 substrates), deprotected in situ, to afford 1,4-disubstituted 1-en-3-ynes with high regio- and (E)-stereoselectivity, at room temperature. The extension of this unprecedented two-reaction sequence to a diyne substrate affords a fluorene-based conjugated oligomer. The reaction mixture resulting from the desylilation-dimerization process dimerizes additional aliquots of phenylacetylene. The one-pot protocol results in shorter reaction times due to the presence of acetate salts which increase the concentration of active catalytic species, in which the acetate ligand acts as base toward the bound alkyne. The ruthenium source is transformed into a new trihapto-hexa-1,3-dien-5-yn-3-yl complex, formed by metal-assisted coupling of the enyne product and the terminal alkyne, and still maintaining catalytic activity. Selectivity, endurance, medium and functional group compatibility are the key features of the catalytic system obtained from the p-cymene ruthenium dimer under the one-pot conditions.
- Pasquini, Chiara,Bassetti, Mauro
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supporting information; experimental part
p. 2405 - 2410
(2010/12/29)
-
- Photochemical behavior of (diphosphine)(η2-tolane)Pt 0 complexes. Part A: Experimental considerations in solution and in the solid state
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A series of various (diphosphine)(η2-tolane)Pt0 complexes exhibiting manifold substitution pattern of the tolane ligand (5a-g) and different rigid diphosphines defining various bite angles at the Pt center (9a-b) have been synthesized. All compounds were isolated and characterized by means of spectroscopic methods and additionally by X-ray structure determination (5a-e, 9a-b). In view of potential Caryl-Cethynyl bond activation, we investigated their photochemical behavior in the solid state as well as in solution by irradiating with sunlight. The reactivity towards C aryl-Cethynyl bond activation in the crystalline state and in solution is discussed in relation to substituents attached to the tolane ligand and on the extent of the torsion of its phenyl rings. Complexes 5a-c and 9a either bearing electron withdrawing bromides or possessing a large dihedral angle of the phenyl rings, showed selective oxidative addition of the C aryl-Cethynyl bond to the Pt center in the solid state, yielding complexes 6a-c and 10a, respectively. In contrast, 5d-f and 9b proved to be unreactive under similar conditions because of their electron donating methoxy groups as well as the reduced twisting of their phenyl or pyridyl moieties of the tolane ligands. Irradiation of complexes 5a and 5b with sunlight in solution revealed the formation of the appropriate C-Br activated compounds 7a and 7b along with 6a and 6b in a 1:1 mixture. The observed photochemical Caryl-Cethynyl bond activation is reversible under thermal conditions, regaining the appropriate Pt0 complexes by reductive elimination.
- Weisheit, Thomas,Escudero, Danie,Petzold, Holm,Goerls, Helmar,Gonzalez, Leticia,Weigand, Wolfgang
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experimental part
p. 9493 - 9504
(2011/01/11)
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- Thieme Chemistry Journal Awardees - Where are they now? A general one-step synthesis of alkynes from enolisable carbonyl compounds
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Terminal and internal acetylenes were obtained in good to excellent isolated yields from carbonyl compounds by converting the carbonyl functionality into the enol nonaflate intermediate followed by elimination to give the C-C triple bond. The one-pot transformations were uniformly induced by phosphazene bases combined with mildly electrophilic nonafluorobutane-1-sulfonyl fluoride. The method is the most general among those reported to date as it applies to both acyclic ketones and aldehydes. Only moderate kinetic regioselectivity in favour of alk-1-yne achieved from methyl n-alkyl ketone represents a limitation of the method. In all the other instances, individual acetylenic products were obtained. Georg Thieme Verlag Stuttgart.
- Lyapkalo, Ilya M.,Vogel, Michael A. K.,Boltukhina, Ekaterina V.,Vav?ík, Ji?í
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scheme or table
p. 558 - 561
(2009/07/09)
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- 7H-PYRIDO[3,4-D]PYRIMIDIN-8-ONES, THEIR MANUFACTURE AND USE AS PROTEIN KINASE INHIBITORS
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Objects of the present invention are the compounds of formula (I) their pharmaceutically acceptable salts, enantiomeric forms, diastereoisomers and racemates, the preparation of the above compounds, medicaments containing them and their manufacture, as we
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-
Page/Page column 32
(2008/06/13)
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- (Z)-Selective cross-dimerization of arylacetylenes with silylacetylenes catalyzed by vinylideneruthenium complexes
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The vinylideneruthenium(II) complexes bearing bulky and basic tertiary phosphine ligands, RuCl2(=C=CHPh)L2 (L = PPr i3, PCy3), serves as a good catalyst precursor for (Z)-selective cross-dimerization between arylacetylenes and silylacetylenes in the presence of N-methylpyrrolidine. The Royal Society of Chemistry 2005.
- Katayama, Hiroyuki,Yari, Hiroshi,Tanaka, Masaki,Ozawa, Fumiyuki
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p. 4336 - 4338
(2008/02/08)
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- Formation of new alkynyl(phenyl)iodonium salts and their use in the synthesis of phenylsulfonyl indenes and acetylenes http://www.mdpi.org
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The preparation of phenylsulfonyl indene derivatives and phenylsulfonyl-acetylenes from readily available alkynyl(phenyl)iodonium tetrafluoroborates and triflates was investigated using phenylsulfinate as nucleophile.
- Koumbis, Alexandros E.,Kyzas, Christos M.,Savva, Antri,Varvoglis, Anastasios
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p. 1340 - 1350
(2007/10/03)
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- ANTIBACTERIAL BENZOIC ACID DERIVATIVES
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The invention provides antimicrobial agents and methods of using the agents for sterilization, sanitation, antisepsis, disinfection, and treatment of infections in mammals.
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-
- A comparison of linear optical properties and redox properties in chalcogenopyrylium dyes bearing ortho-substituted aryl substituents and tert-butyl substituents
-
A series of thiapyrylium pentamethine dyes (4 and 12-15) bearing 2,2′-di-tert-butyl-6,6′-diphenyl, 2,2′-di-tert-butyl-6,6′-bis(2,6-dimethylphenyl), 2,2′-di-tert-butyl-6,6′-bis(2-methylphenyl), 2,2′,6,6′-tetrakis(2,6-dimethylphenyl), and 2,2′,6,6′-tetrakis(2-methylphenyl) substituents, respectively, were prepared and their linear optical properties and electrochemical redox properties were measured and compared to thiapyrylium pentamethine dyes 3 and 5. The tert-butyl and 2,6-dimethylphenyl substituents give nearly identical chromophores with respect to values of λmax, molar extinction coefficients (ε), bandwidths at half-height (ν1/2), and lack of absorption in the visible spectrum. The 2-methylphenyl substituent imparts linear optical properties that are intermediate between those of the tert-butyl and phenyl substituents. The 2,6-dimethylphenyl and 2-methylphenyl substituents impart greater oxidative stability based on anodic shifts in oxidation potential.
- Panda, Jagannath,Virkler, Peter R.,Detty, Michael R.
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p. 1804 - 1809
(2007/10/03)
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- Substituted indoles and their use as integrin antagonists
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The present invention relates to novel substituted indole compounds that are antagonists of alpha V (αv) integrins, for example αvβ3 and αvβ5 integrins, their pharmaceutically acceptable salts, and pharmaceutical compositions thereof. The compounds may be used in the treatment of pathological conditions mediated by αvβ3 and αvβ5 integrins, including such conditions as tumor growth, metastasis, restenosis, osteoporosis, inflammation, macular degeneration, diabetic retinopathy, and rheumatoid arthritis. The compounds have the general formula: where R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, D, X, W, a, m, n, i, j, k and v are defined herein.
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-
-
- Formation of benzo[b]fluorenes and the benzo[a]fluorene core of the fluostatins by cyclization of diaryldiynones.
-
[figure: see text] Thermal cyclization of 1-[2-(trimethylsilylethynyl)phenyl]-3-arylpropinones was expected to give benzo[b]fluorenones. However, benzo[a]-fluorenones were also formed as a result of a new rearrangement. These tetracycles possess the core structure of the fluostatins and isoprekinamycin.
- Atienza,Mateo,de Frutos,Echavarren
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p. 153 - 155
(2007/10/03)
-
- Ultraviolet photochemistry of diacetylene: Reactions with benzene and toluene
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The reactions of metastable diacetylene with benzene and toluene are explored using a molecular beam pump-probe time-of-flight mass spectrometer. Diacetylene is laser-excited to the 210610 band of the 1Δu←X1Σ+g transition, whereupon rapid intersystem crossing occurs to the lowest triplet states. The triplet state diacetylene then reacts with either benzene or toluene as the gas mixture traverses a short reaction tube (approximately 20 μs). The reactions are quenched as the gas mixture expands into the ion source region of a time-of-flight mass spectrometer where the primary photoproducts are detected using vacuum ultraviolet (VUV) photoionization or resonant two-photon ionization (R2PI). The major products from the reaction of diacetylene and benzene have molecular formulas C8H6 and C10H6, and are identified as phenylacetylene and phenyldiacetylene using R2PI spectroscopy. The major products from metastable diacetylene's reaction with toluene are C9H8 and C11H8. The C9H8 product is confirmed as a mixture of o-, m-, and p-ethynyltoluene, with the ortho product dominating. Mechanisms for the formation of the above products are proposed based on deuterium substitution studies of the reactions. The potential importance of these reactions is discussed as they relate to hydrocarbon growth in sooting flames.
- Robinson, Allison G.,Winter, Paul R.,Ramos, Christopher,Zwier, Timothy S.
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p. 10312 - 10320
(2007/10/03)
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- Forbidden reactions, II. - The disrotatory cyclobutene ringopening
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The energy profiles for the con- and disrotatory opening of benzocyclobutene, methylenecyclobutene, and cyclobutene derivatives were established by NO and oxygen trapping. The enthalpy for the transition states for the "forbidden" reactions proofed to be identical with the heat of formation of the orthogonal diradicals derived by geometrical isomerization of the dienes formed in these reactions. These diradicals describe very well the activation barriers observed for the disrotatory opening of bicyclic cyclobutenes ([3.2.0] and [2.2.0] systems), but not for bicyclo[2.1.0]pent-2-ene, indicating here a truly forbidden reaction. VCH Verlagsgesellschaft mbH, 1996.
- Roth, Wolfgang R.,Rekowski, Volker,Boerner, Sabine,Quast, Michael
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p. 409 - 430
(2007/10/03)
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- Flash Vacuum Pyrolysis of Stabilised Phosphorus Ylides. Part 2. Two-step Conversion of Acid Chlorides into Acetylenic Esters and Terminal Alkynes
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The known thermal extrusion of Ph3PO from α-acyl-α-ethoxycarbonyl ylides 1 to give acetylenic esters 2 can be accomplished in excellent yield by using flash vacuum (FVP) at 500 deg C.Upon rasing the furnace temperature to 750 deg C, this reaction is accompanied by unexpected loss of the ethoxycarbonyl group to give the terminal alkynes 7 in moderate yield.A mechanism is proposed for this reaction based on isotopic labelling studies.Ten new examples of ylides 1 have been prepared for the first time.
- Aitken, R. Alan,Horsburg, Caroline E. R.,McCreadie, J. Graeme,Seth, Shirley
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p. 1727 - 1732
(2007/10/02)
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- Gas-Phase Reactions of Charged Electrophiles with Styrene and Phenylacetylene
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The reactions of styrene and phenylacetylene toward charged electrophiles have been studied in the gas phase by a radiolytic technique, supported by chemical ionization mass spectrometry.The two substrates undergo a methylation reaction by Me2F(1+) both at the ring and at the side chain, at variance with the side-chain electrophilic attack prevailing in condensed phase.The nitrating (MeONO2)H(1+) ion selectively nitrates the orto position of styrene, an unprecedented ring nitration on this substrate.The formation of neutral isomeric products is determined by the efficiency of deprotonation of their ionic precursors and is sensitive interalia to the presence of oxygen nucleophiles.The overall reactivity pattern is rationalized in terms of preferential electrostatic interactions between the reactants in a preliminary collision complex, whereby an incoming ROH molecule can simulate a "solvating" environment, shifting the reactivity in the direction observed in solution.
- Crestoni, Maria Elisa,Fornarini, Simonetta
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p. 6008 - 6014
(2007/10/02)
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- Dimetallation of phenylacetylene. Synthesis of ortho-susbtituted derivatives of phenylacetylene, benzoselenophene and benzotellurophene
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Phenylacetylene can be dimetallated in two ways. o-K-C6H4-CC-Li is formed by treating phenylacetylene at -70 deg C with two equivalents of butyllithium and one equivalent of potassium tert-butoxide in a mixture of tetrahydrofuran and hexane.The dimetallation with BuLi*N,N,N',N'-tetramethylethanediamine (TMEDA) affords a mixture of about 15percent (m + p)-Li-C6H4-CCLi and 85percent o-LiC6H4-CC-Li.Ortho-K-C6H4-CC-Li can be transformed into the dilithio or di-Grignard derivatives by addition of anhydrous lithium bromide or magnesium bromide etherate.Reaction of the dilithio derivative with elemental selenium and tellurium, followed by successive addition of tert-butyl alcohol and hexamethylphosphoric triamide (HMPT), gives benzoselenophene and benzotellurophene in good yields.Regiospecific functionalization of the nucleus via dimetal derivatives succeeds in the case of alkylation, halogenation, sulfenylation and acylation (with dimethylformamide and dimethylacetamide).Trimethylchlorosilane, chloromethyl methyl ether, aldehydes and ketones do not however react regiospecifically.
- Brandsma, L.,Hommes, H.,Verkruijsse, H. D.,Jong, R. L. P. de
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p. 226 - 230
(2007/10/02)
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- Choix des methodes pour la synthese univoque de carbures acetyleniques. Troisieme partie : Arylacetylenes et aryl-1 alcynes-1
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The range of applicability of six syntheses of pure alkynes with one aryl group has been defined; a short review of other possible procedures is included.We have specified the best method to obtain selectively the alkynes Ar-CCH and Ar-CC-R, according to the nature of the substituents of the aryl group and according to the developed structure of the R group.It is thus possible to recommend with the largest probability of success the method to obtain, in homogenous series, alkynes corresponding to still more complicated structures.
- Mesnard, Danielle,Bernadou, Francoise,Miginiac, Leone
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p. 3216 - 3245
(2007/10/02)
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- Dimetallation of Phenylacetylene. Selective ortho-Substitution
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Reaction of lithium phenylacetylide with the complex BuLi-ButOK in a mixture of tetrahydrofuran and hexane leads to the ortho-metallated phenylacetylide; subsequent addition of methyl iodide, dimethyl disulphide, trimethylchlorosilane, and sele
- Hommes, Hendrik,Verkruijsse, Hermann D.,Brandsma, Lambert
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p. 366 - 367
(2007/10/02)
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- Vinyl Cation Intermediates in Solvolytic and Electrophilic Reactions. 1. Solvolysis of α-Arylvinyl Derivatives
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The solvolysis of 16 α-arylvinyl tosylates, bromides, and chlorides has been investigated in various alcohol-water mixtures and in acetic acid at several temperatures.All substrates were substituted with either 2-methyl or 2,6-dimethyl groups to accelerate the rates of reaction.The major or exclusive product isolated in most cases was the acetophenone arising from hydrolysis of the expected enol ethers or acetates during workup.The kinetics were simple first order in the vast majority of cases, with excess base added to prevent side reactions.Leaving group effects, Winstein-Grunwald m values, Schleyer Q values, and effects of solvent nucleophilicity all point to a limiting SN1 ionization generating a vinyl cation intermediate, in which there is little rear-side nucleophilic assistance by solvent.Substituent effects led to ρ values in the range -3.9 to -5.3 vs. ?+.Activation parameters are typical for an SN1 process, and ΔS% is insensitive to the presence of zero, one, or two o-methyl groups, as are the effects of solvent polarity on the rates.The results should therefore be directly comparable with other solvolytic or electrophilic reactions generating formally similar vinyl cation intermediates.
- Yates, Keith,Mandrapilias, George
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p. 3892 - 3902
(2007/10/02)
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