- Iodonium Cation-Pool Electrolysis for the Three-Component Synthesis of 1,3-Oxazoles
-
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
-
supporting information
p. 605 - 608
(2020/12/07)
-
- Synthesis of Phenanthrenes via Palladium-Catalyzed Three-Component Domino Reaction of Aryl Iodides, Internal Alkynes, and o-Bromobenzoic Acids
-
A new palladium-catalyzed domino alkyne insertion/C-H activation/decarboxylation sequence has been developed, which provides an efficient approach for synthesizing a variety of functionalized phenanthrenes in moderate to good yields. The method shows broad substrate scope and good functional group tolerance by employing readily available materials, including aryl iodides, internal alkynes, and o-bromobenzoic acids, as three-component coupling partners.
- Deng, Guobo,Liang, Yun,Luo, Xiai,Yang, Xiumei,Yang, Yuan,Yang, Yuzhong,Zhou, Liwei
-
p. 1223 - 1230
(2020/04/15)
-
- Aggregation induced emission-emissive stannoles in the solid state
-
The optoelectronic and structural properties of six stannoles are reported. All revealed extremely weak emission in solution at 295 K, but intensive fluorescence in the solid state with quantum yields (ΦF) of up to 11.1% in the crystal, and of up to 24.4% (ΦF) in the thin film.
- Lork, Enno,Ramirez Y Medina, Isabel-Maria,Rohdenburg, Markus,Staubitz, Anne
-
supporting information
p. 9775 - 9778
(2020/09/07)
-
- Post synthetic exchange enables orthogonal click chemistry in a metal organic framework
-
Biphenyl-4,4′-dicarboxylic acid derivatives containing either azide or acetylene functional groups were inserted into UiO-67 metal organic frameworks (MOFs) via post synthetic linker exchange. Sequential and orthogonal click reactions could be performed o
- Fluch, Ulrike,McCarthy, Brian D.,Ott, Sascha
-
-
- Intermolecular Desymmetrizing Gold-Catalyzed Yne–Yne Reaction of Push–Pull Diarylalkynes
-
Push–pull diaryl alkynes are dimerized in the presence of a cationic gold catalyst. The polarized structure of the applied starting materials enables the generation of a highly reactive vinyl cation intermediate in an intermolecular reaction. Trapping of the vinyl cation by a nucleophilic attack of the electron-poor aryl unit then leads to the selective formation of highly substituted naphthalenes in a single step and in complete atom economy.
- Weingand, Vanessa,Wurm, Thomas,Vethacke, Vanessa,Dietl, Martin C.,Ehjeij, Daniel,Rudolph, Matthias,Rominger, Frank,Xie, Jin,Hashmi, A. Stephen K.
-
supporting information
p. 3725 - 3728
(2018/02/23)
-
- Trimethylsilyl-Protected Alkynes as Selective Cross-Coupling Partners in Titanium-Catalyzed [2+2+1] Pyrrole Synthesis
-
Trimethylsilyl (TMS)-protected alkynes served as selective alkyne cross-coupling partners in titanium-catalyzed [2+2+1] pyrrole synthesis. Reactions of TMS-protected alkynes with internal alkynes and azobenzene under the catalysis of titanium imido comple
- Chiu, Hsin-Chun,Tonks, Ian A.
-
supporting information
p. 6090 - 6094
(2018/05/30)
-
- Copper-Catalyzed Hydrogen/Iodine Exchange in Terminal and 1-Iodoalkynes
-
Detailed kinetic profiles of the copper-catalyzed exchange between the acetylenic proton and iodide of terminal and 1-iodophenylacetylenes are reported. The electronic nature of the alkynes does not influence the equilibrium of the exchange (Keq/sub
- Chung, Ryan,Vo, Anh,Hein, Jason E.
-
p. 2505 - 2510
(2017/06/01)
-
- Copper-Promoted Conversion of Aromatic Amines into Trifluoromethylated Arenes: One-Pot Sandmeyer Trifluoromethylation
-
A simple copper-promoted one-pot Sandmeyer trifluoromethylation of aromatic amines with Langlois’ reagent has been demonstrated. The reaction is performed in mild reaction conditions under an air atmosphere with good substrate scope and functional group compatibility. It provides an alternative and straightforward synthetic approach to access a variety of trifluoromethylated arenes.
- Hong, Jianquan,Wang, Guifu,Huo, Lianguang,Zheng, Changge
-
supporting information
p. 1761 - 1767
(2017/09/06)
-
- Reaction discovery using acetylene gas as the chemical feedstock accelerated by the stop-flow micro-tubing reactor system
-
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
-
p. 3623 - 3627
(2017/07/11)
-
- Palladium-catalyzed tandem C-H functionalization/cyclization strategy for the synthesis of 5-hydroxybenzofuran derivatives
-
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
-
-
- A practical non-metal catalytic silicon of the amino protection of the new method (by machine translation)
-
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 0068; 0069
(2018/04/01)
-
- Electron-density distribution tuning for enhanced thermal stability of luminescent gold complexes
-
Structure-property relationships of newly synthesized luminescent gold complexes were examined from the viewpoint of material applications. In particular, we investigated the effect of controlling the molecular electron-density distribution by introducing trifluoromethyl substituents into the complexes. The structures of the molecular aggregates were not affected by the trifluoromethyl substituents, as all the complexes formed antiparallel dimers in the crystal state. Moreover, we found that the trifluoromethyl substituents enhanced the thermal stability of the complexes without significantly changing the luminescence behaviour. Thus, while the thermal stability of these materials depends on the molecular structure, i.e. the molecular electron-density distribution, the luminescence behaviour mainly depends on the molecular aggregate structure. These results suggest that various material properties, e.g. luminescence colour and thermal stability, can be controlled independently by tuning the structures of molecules and molecular aggregates using trifluoromethyl substituents.
- Yamada, Shigeyuki,Yamaguchi, Shun,Tsutsumi, Osamu
-
p. 7977 - 7984
(2017/08/17)
-
- Rapid access to unsymmetrical tolanes and alkynones by sequentially palladium-catalyzed one-pot processes
-
Alkynones as well as unsymmetrically substituted tolanes (diarylalkynes) can be rapidly generated in a one-pot fashion via sequential palladium catalysis. Terminal alkynes, formed in situ by protecting-group free palladium-catalyzed coupling of aryl iodides with ethynyl magnesium bromide, are subsequently transformed by Sonogashira coupling with aryl halides or aroyl chlorides to furnish unsymmetrically substituted alkynes in good to excellent yields.
- G?tzinger, Alissa C.,Müller, Thomas. J. J.
-
supporting information
p. 3498 - 3500
(2016/04/19)
-
- 2-Aryl-8-aza-3-deazaadenosine analogues of 5′-O-[N-(salicyl)sulfamoyl]adenosine: Nucleoside antibiotics that block siderophore biosynthesis in Mycobacterium tuberculosis
-
A series of 5′-O-[N-(salicyl)sulfamoyl]-2-aryl-8-aza-3-deazaadenosines were designed to block mycobactin biosynthesis in Mycobacterium tuberculosis (Mtb) through inhibition of the essential adenylating enzyme MbtA. The synthesis of the 2-aryl-8-aza-3-deaz
- Krajczyk, Anna,Zeidler, Joanna,Januszczyk, Piotr,Dawadi, Surendra,Boshoff, Helena I.,Barry, Clifton E.,Ostrowski, Tomasz,Aldrich, Courtney C.
-
supporting information
p. 3133 - 3143
(2016/07/06)
-
- Anionic sigmatropic-electrocyclic-chugaev cascades: Accessing 12-aryl-5-(methylthiocarbonylthio)tetracenes and a related anthra[2,3-b]thiophene
-
1,4-Diols resulting from the double addition of ArCCLi (Ar = Ph, substituted phenyl, 2-thienyl) to ortho-C6H4(CHO)2 undergo cascades to tetracenes on simple admixture of LiHDMS, CS2 and MeI. Acene formation proceeds by [3,3]-sigmatropic rearrangement of xanthate anions followed by 6π electrocyclisations. The reactions are terminated by E2 or anionic Chugaev-type eliminations. Structural packing motifs and electronic properties are reported for the tetracenes.
- Burroughs, Laurence,Ritchie, John,Ngwenya, Mkhethwa,Khan, Dilfaraz,Lewis, William,Woodward, Simon
-
p. 273 - 279
(2015/06/23)
-
- Structure-based design, synthesis and evaluation in vitro of arylnaphthyridinones, arylpyridopyrimidinones and their tetrahydro derivatives as inhibitors of the tankyrases
-
Abstract The tankyrases are members of the PARP superfamily; they poly(ADP-ribosyl)ate their target proteins using NAD+ as a source of electrophilic ADP-ribosyl units. The three principal protein substrates of the tankyrases (TRF1, NuMA and axin) are involved in replication of cancer cells; thus inhibitors of the tankyrases may have anticancer activity. Using structure-based drug design and by analogy with known 3-arylisoquinolin-1-one and 2-arylquinazolin-4-one inhibitors, series of arylnaphthyridinones, arylpyridinopyrimidinones and their tetrahydro-derivatives were synthesised and evaluated in vitro. 7-Aryl-1,6-naphthyridin-5-ones, 3-aryl-2,6-naphthyridin-1-ones and 3-aryl-2,7-naphthyridin-1-ones were prepared by acid-catalysed cyclisation of the corresponding arylethynylpyridinenitriles or reaction of bromopyridinecarboxylic acids with β-diketones, followed by treatment with NH3. The 7-aryl-1,6-naphthyridin-5-ones were methylated at 1-N and reduced to 7-aryl-1-methyl-1,2,3,4-tetrahydro-1,6-naphthyridin-5-ones. Cu-catalysed reaction of benzamidines with bromopyridinecarboxylic acids furnished 2-arylpyrido[2,3-d]pyrimidin-4-ones. Condensation of benzamidines with methyl 1-benzyl-4-oxopiperidine-3-carboxylate and deprotection gave 2-aryl-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidin-4-ones, aza analogues of the known inhibitor XAV939. Introduction of the ring-N in the arylnaphthyridinones and the arylpyridopyrimidinones caused >1000-fold loss in activity, compared with their carbocyclic isoquinolinone and quinazolinone analogues. However, the 7-aryl-1-methyl-1,2,3,4-tetrahydro-1,6-naphthyridin-5-ones showed excellent inhibition of the tankyrases, with some examples having IC50 = 2 nM. One compound (7-(4-bromophenyl)-1-methyl-1,2,3,4-tetrahydro-1,6-naphthyridin-5-one) showed 70-fold selectivity for inhibition of tankyrase-2 versus tankyrase-1. The mode of binding was explored through crystal structures of inhibitors in complex with tankyrase-2.
- Kumpan, Katerina,Nathubhai, Amit,Zhang, Chenlu,Wood, Pauline J.,Lloyd, Matthew D.,Thompson, Andrew S.,Haikarainen, Teemu,Lehti?, Lari,Threadgill, Michael D.
-
p. 3013 - 3032
(2015/08/03)
-
- Rh(III)-catalyzed cyclization reaction of azoles with alkynes: Efficient synthesis of azole-fused-pyridines
-
A Rh(III)-catalyzed cyclization of azoles with alkynes has been developed. A variety of azole-fused-pyridines were obtained in good to excellent yields and regioselectivity. Both the C5 and the C4 position of azoles were suitable for the reaction.
- Chen, Xuebing,Wu, Youzhi,Xu, Jinyi,Yao, Hequan,Lin, Aijun,Huang, Yue
-
p. 9186 - 9189
(2015/09/07)
-
- Versatile bisethynyl[60]fulleropyrrolidine scaffolds for mimicking artificial light-harvesting photoreaction centers
-
Fullerene-based tetrads, triads, and dyads are presented in which [60]fulleropyrrolidine synthons are linked to an oligo(p-phenyleneethynylene) antenna at the nitrogen atom and to electron-donor phenothiazine (PTZ) and/or ferrocene (Fc) moieties at the ?±
- Kremer, Adrian,Bietlot, Emerance,Zanelli, Alberto,Malicka, Joanna M.,Armaroli, Nicola,Bonifazi, Davide
-
supporting information
p. 1108 - 1117
(2015/03/05)
-
- Tunable electron acceptors based on cyclopenta[hi]aceanthrylenes
-
A series of substituted cyclopenta[hi]aceanthrylene derivatives with electron donating (NH2, OCH3), neutral (H), and electron withdrawing (COOH, CF3, CN, NO2) substituents were prepared. A room-temperature Sonogashira cross-coupling reaction between 2,7-dibromocyclopenta[hi]aceanthrylene and an appropriately functionalized phenylene ethynylene precursor was utilized to access the materials that were characterized by Nuclear Magnetic Resonance Spectroscopy (NMR), cyclic voltammetry (CV), and UV-Vis spectroscopy. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were systematically varied when proceeding from electron donating to electron withdrawing substituents. The optical band gap was significantly altered for the most electron donating species, while little change was observed between different electron withdrawing substituents. This study demonstrates the ability to control the frontier orbital energies of this class of cyclopenta-fused polycyclic aromatic hydrocarbon materials through selective substitution.
- Zhu, Xinju,Yuan, Bingxin,Plunkett, Kyle N.
-
supporting information
p. 7105 - 7107
(2015/12/01)
-
- "quick and click" assembly of functionalised indole rings via metal-promoted cyclative tandem reactions
-
An efficient and convenient synthesis of a variety of decorated indoles using a three-component tandem metal-catalysed process is described. We propose here a new "synthetic kit" that allows for the "quick and click" assembly of indole rings using readily available, and inexpensive starting materials under environmentally friendly reaction conditions. This journal is
- Capitta, Francesca,De Luca, Lidia,Porcheddu, Andrea
-
p. 59297 - 59301
(2015/02/19)
-
- Rhodium(I)-catalyzed carbonylative arylation of alkynes with arylboronic acids using formaldehyde as a carbonyl source
-
The rhodium(I)-catalyzed reaction of alkynes with arylboronic acids in the presence of formaldehyde resulted in a carbon monoxide gas-free carbonylative arylation to yield α,β-enones. The simultaneous loading of phosphine-ligated and phosphine-free rhodium(I) complexes is required for efficient catalysis, which catalyze the abstraction of a carbonyl moiety from formaldehyde (decarbonylation) and its subsequent introduction into the substrate (carbonylation), respectively. Georg Thieme Verlag Stuttgart New York.
- Wang, Chuang,Morimoto, Tsumoru,Kanashiro, Hiroyuki,Tanimoto, Hiroki,Nishiyama, Yasuhiro,Kakiuchi, Kiyomi,Artok, Levent
-
p. 1155 - 1159
(2014/05/20)
-
- Palladium nanoparticles catalyzed Sonogashira reactions for the one-pot synthesis of symmetrical and unsymmetrical diarylacetylenes
-
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
-
-
- Investigation of quantitative structure-reactivity relationships in the aliphatic Claisen rearrangement of bis-vinyl ethers reveals a dipolar, dissociative mechanism
-
Kinetic investigations of substituent effects in the thermal rearrangement of bis-vinyl ether substrates are reported. Findings indicate that the influence of the various substituent patterns on the rate of rearrangement in these compounds differs from that documented in the literature for the analogous [3,3]-sigmatropic rearrangement of allyl vinyl ethers. In addition, the thermochemical data collected suggests the existence of a dissociative transition state with significant dipolar character. These findings provide a unique contribution to the already extensive body of literature dedicated to mechanistic investigation of the Claisen rearrangement of aliphatic allyl vinyl ethers.
- O'Rourke, Natasha F.,Wulff, Jeremy E.
-
p. 1292 - 1308
(2014/03/21)
-
- Formal anti-markovnikov hydroamination of terminal aryl alkynes with pinacolborane and hydroxylamines via Zr/Cu sequential catalysis
-
We have explored a novel dry plasma process for the fabrication of electrodes on Nafion surfaces. Nanosized pillar structures were prepared through argon ion (Ar+) plasma treatment. The shear strengths of Au electrodes on plasma-treated Nafion surfaces were investigated. We found that the maximum shear strength (1.08 MPa) of Au-Nafion was observed under the optimal conditions (8 min, 100 W, 5 Pa, Ar+). Finally, we successfully prepared strongly bonded Au electrodes on Nafion through plasma surface treatment without using a wet plating process.
- Sakae, Ryosuke,Hirano, Koji,Satoh, Tetsuya,Miura, Masahiro
-
p. 1128 - 1130
(2013/10/22)
-
- Microwave-accelerated Ru-catalyzed hydrovinylation of alkynes and enynes: A straightforward approach toward 1,3-dienes and 1,3,5-trienes
-
Quick, but not dirty! Microwave heating was found to have a significant effect on the Ru-catalyzed hydrovinylations of alkynes. A broad range of different terminal alkynes were coupled to methyl acrylate within just 30min in good to excellent yields (see scheme). This new protocol was transferred to the hydrovinylation of enynes as novel coupling partners in C-H-activation chemistry giving different 1,3,5-trienes as the sole products. Copyright
- Schabel, Tobias,Plietker, Bernd
-
supporting information
p. 6938 - 6941
(2013/06/27)
-
- One-pot, two-step conversion of aldehydes to phosphonyl- and sulfonylpyrazoles using Bestmann-Ohira reagent
-
A one-pot, two-step, three-component method for the conversion of commercially available aldehydes to phosphonylpyrazoles has been developed, demonstrating, for the first time, the dual reactivity of the Bestmann-Ohira reagent (BOR) in a single-pot transformation. This method, extended to the synthesis of sulfonylpyrazoles by employing BOR in the first step and a diazomethyl sulfone in the second step, is complementary, with regard to regioselectivity, to the previous methods for the synthesis of such functionalized pyrazoles.
- Kumar, Rahul,Verma, Deepti,Mobin, Shaikh M.,Namboothiri, Irishi N. N.
-
supporting information; experimental part
p. 4070 - 4073
(2012/09/21)
-
- Convenient synthesis of terminal alkynes from anti-3-aryl-2,3- dibromopropanoic acids using a K2CO3/DMSO system
-
A convenient, efficient, and generally applicable method was developed for the synthesis of terminal alkynes from anti-3-aryl-2,3-dibromopropanoic acids in the presence of DMSO and K2CO3.
- Cheng, Xuezhi,Jia, Jun,Kuang, Chunxiang
-
experimental part
p. 2350 - 2354
(2012/02/03)
-
- Cs2CO3-mediated synthesis of terminal alkynes from 1,1-dibromo-1-alkenes
-
An unprecedented route to prepare terminal alkynes from 1,1-dibromo-1-alkenes mediated by Cs2CO3 was proven. 1,1-Dibromo-1-alkenes bearing various functional groups were efficiently converted to corresponding terminal alkynes in moderate to excellent yields.
- Zhao, Ming,Kuang, Chunxiang,Yang, Qing,Cheng, Xuezhi
-
scheme or table
p. 992 - 994
(2011/03/22)
-
- Synthesis of novel structurally simplified estrogen analogues
-
A library of 17 novel estrogen analogues 3 and 4 containing different substituents at rings A and D (steroid nomenclature) was prepared in a five- to seven-step synthesis. The key transformation is a Sonogashira-coupling of cyclic vinyl iodides of type 7
- Tietze, Lutz F.,Vock, Carsten A.,Krimmelbein, Ilsa K.,Wiegand, J. Matthias,Nacke, Linda,Ramachandar, Tokala,Islam, Kazi M. D.,Gatz, Christiane
-
experimental part
p. 3670 - 3679
(2009/04/11)
-
- Novel 3-phenylprop-2-ynylamines as inhibitors of mammalian squalene epoxidase.
-
The synthesis of a novel series of 3-phenylprop-2-ynylamines as selective mammalian squalene epoxidase inhibitors is described. Structure activity relationship studies led to the discovery of compound 19, 1-[3-(3,5-dichlorophenyl)-prop-2-ynyl]-3- methylpiperidine hydrochloride with an IC50 of 2.8 +/- 0.6 microM against rat liver squalene epoxidase. Against 23 strains of fungal squalene epoxidase compound 19 was found to be inactive.
- Musso, David L,Clarke, Morris J,Kelley, James L,Boswell, G Evan,Chen, Grace
-
p. 498 - 506
(2007/10/03)
-
- Asymmetric synthesis of 1-aryl-1,2-ethanediols from arylacetylenes by palladium-catalyzed asymmetric hydrosilylation as a key step
-
Double hydrosilylation of arylacetylenes with trichlorosilane catalyzed first by platinum and second by a chiral monophosphine-palladium complex generated the corresponding 1,2-bis(silyl)-1-arylethanes, the oxidation of which with hydrogen peroxide gave 1-aryl-1,2-diols of high enantiomeric purity (94-98% ee) in high yields. Copyright
- Shimada, Toyoshi,Mukaide, Kotaro,Shinohara, Akihiro,Han, Jin Wook,Hayashi, Tamio
-
p. 1584 - 1585
(2007/10/03)
-
- A strictly "pair"-selective synthesis of conjugated diynes via Pd-catalyzed cross coupling of 1,3-diynylzincs: A superior alternative to the Cadiot-Chodkiewicz reaction
-
(matrix presented) A strictly "pair"-selective synthesis of conjugated diynes via Pd-catalyzed cross coupling of 1,3-diynylzincs is described. This method, like the Cadiot-Chodkiewicz reaction, requires three steps for the synthesis of R1C≡CC≡CR2 from R1C≡CH, R2X, and HC≡CH. However, the high "pair"-selectivity permitting high-yield production of the desired conjugated diynes without separation of symmetrical diynes promises to make the present protocol superior to the Cadiot-Chodkiewicz reaction in many cases.
- Negishi, Ei-Ichi,Hata, Mitsuhiro,Xu, Caiding
-
p. 3687 - 3689
(2007/10/03)
-
- Cyclobutene photochemistry. Substituent effects on the photochemistry of 1-phenylcyclobutene
-
The photochemistry and photophysic of 1-phenylcyclobutene and five aryl-substituted derivatives have been studied in various solvents at room temperature.All six compounds fluoresce with quantum yields in the 0.2-0.3 range in cyclohexane and acetonitrile solution. 1-Phenylcyclobutene undergoes -cycloreversion (γ = 0.09) to yield phenylacetylene upon photolysis in either hydrocarbon or acetonitrile solution, and undergoes (Markovnikov) solvent addition upon irradiation in methanol solution (γ = 0.08) in addition to cycloreversion.Triplet sensitization and quenching experiments indicate that cycloreversion and methanol addition are both excited singlet state processes.None of the six compounds studied undergo ring opening to the corresponding 2-aryl-1,3-butadiene in detectable yield.Quantum yields for cycloreversion in cyclohexane, acetonitrile, and methanol solution and methanol addition have been determined for the six compounds, along with excited singlet state lifetimes.The quantum yields and rate constants for cycloreversion and methanol addition are both enhanced by substitution with electron-donating groups.The variation in the rate constant for cycloreversion with substituent indicates that there is substantial dipolar character developed in the cyclobutenyl ?-bond framework during the reaction, in almost exact correspondence with that developed in the ? system during photoprotonation.No deuterium scrambling is observed in 1-phenylcyclobutene-2,4,4-d3 after photolysis in pentane solution to ca. 80percent conversion, indicating that sleletal rearrangements leading to cyclopropyl carbenes do not occur in the direct photolysis of arylcyclobutene derivatives.A pericyclic mechanism for the photocycloreversion reaction is suggested.Triplet-triplet absorption spectra and triplet lifetimes of 1-phenyl-, 1-(para-methylphenyl)-, and 1-(para-trifluoromethylphenyl)cyclobutene in hydrocarbon solution are also reported. Key words: photochemistry, cyclobutene, fluorescence, -cycloreversion, substituent effects, nanosecond laser flash photolysis, lifetime, triplet state, styrene, photoaddition
- Leigh, William J.,Postigo, J. Alberto
-
p. 191 - 203
(2007/10/02)
-
- Ethynylbenzothiophene pesticides
-
Ethynylbenzothiophene compounds of the following formula are effective as pesticides. STR1 wherein R is selected from STR2 R1 is selected from hydrogen, halogen, lower alkyl, lower haloalkyl, and phenylethynyl; R2 is selected from hy
- -
-
-
- Preparation of Fluorine-Containing Phenylacetylenes by the Method of Introduction of the Ethynyl Group Using 1,1-Dichloro-2,2-difluroethene
-
Phenylacetylenes (ArCCH) having fluoro- or trifluoromethyl substituents (o-, m-, p-F; o-, m-, p-CF3; 2,4-, 2,5-, 2,6-, 3,5-(CF3)2) have been prepared from bromobenzenes (ArBr) and benzenes (ArH) using 1,1,-dichloro-2,2-difluoroethene (1) by a two-step route: ArLi or ArMgBr->ArCF=CCl2->ArCCLi.Upon careful treatment at -70 deg C with 1, o-fluorophenyllithium gave o-FC6H4CF=CCl2 in good yield, together with benzyne-derived products, such as o-(o-FC6H4)C6H4CF=CCl2.Lithiation of m-bis(trifluoromethyl)benzene at 0 deg C for 9 h (24 h) followed by treatment with bromine gave 1-bromo-2,4-, 2,6-, and 3,5-bis(trifluoromethyl)benzene in 35 (38), 31 (36), and 8percent (6percent) yield, respectively.
- Kodaira, Kazuo,Okuhara, Kunio
-
p. 1625 - 1632
(2007/10/02)
-
- Stereomutation in the Seyferth Reaction
-
The cyclopropanation reaction between dibromomethylene (:CBr2) from the Seyferth reagent (PhHgCBr3) and electron-deficient alkenes is nonstereospecific.Thus fumaronitrile, styrene-cis-β-d, and trans-1,2-dichloroethene give mixtures of the respective cis a
- Lambert, Joseph B.,Larson, Eric G.,Bosch, Richard J.,Vrucht, Mollie L. E. Te
-
p. 5443 - 5447
(2007/10/02)
-
- Choix des methodes pour la synthese univoque de carbures acetyleniques. Troisieme partie : Arylacetylenes et aryl-1 alcynes-1
-
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
-
p. 3216 - 3245
(2007/10/02)
-