- Reactivity of Lutetacyclopropene toward Benzyl, Benzoyl, and Trimethylsilyl Nitriles Affording Diversified Lutetium Complexes
-
Although the reaction of metallacyclopropenes toward alkyl and aryl nitriles has been extensively studied, their reactivity toward other types of nitriles, e.g., benzyl and benzoyl nitriles, that often behave multifunctionally was rarely explored. Herein,
- Lv, Ze-Jie,Zhu, Miaomiao,Liu, Wei,Chai, Zhengqi,Wei, Junnian,Zhang, Wen-Xiong
-
supporting information
p. 3992 - 3998
(2021/12/02)
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- Cyanine-based near infra-red organic photoredox catalysis
-
Direct metal-free near infra-red photoredox catalysis is applied to organic oxidation, photosensitization and reduction, involving cyanines as photocatalysts. This photocatalyst is competitive with conventional reactions catalyzed under visible light. Kin
- Baralle, Alexandre,Cormier, Morgan,Goddard, Jean-Philippe,Obah Kosso, Anne Roly,Sellet, Nicolas
-
p. 6964 - 6968
(2021/06/02)
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- Gold-Catalyzed Oxidative [2+2+1] Annulations of Aryldiazo Nitriles with Imines To Yield Polyarylated Imidazolium Salts
-
Gold-catalyzed oxidative [2+2+1] annulations between two imines and one α-cyano arylgold carbene afforded polyarylated imidazolium salts and molecular hydrogen efficiently. Control experiments suggest that the gold catalyst alone facilitates the main annulation, whereas Ag+ avoids the formation of inactive LAuCN. DFT calculations suggest that the success of this annulation relies on a 6 π-electrocyclization of cyano-free intermediates with cis-configured imines as initial reagents.
- Pawar, Samir Kundlik,Yang, Ming-Chung,Su, Ming-Der,Liu, Rai-Shung
-
supporting information
p. 5035 - 5039
(2017/04/24)
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- Visible-light-mediated oxidative dimerization of arylalkynes in the open air: Stereoselective synthesis of (Z)-1,4-enediones
-
An organic photoredox catalytic one-pot protocol is developed for the highly stereoselective synthesis of (Z)-1,4-enediones. The reaction starts directly from alkyne precursors, using 4-(4-cyanophenyl)-2,6-diphenylpyrylium tetrafluoroborate (CN-TPT) as an efficient photosensitizer and dioxygen in the air as a green oxidant. A Csp-Csp oxidative coupling/[4 + 2] cyclization (with dioxygen)/fragmentive isomerization cascade mechanism was proposed. The predominant formation of (Z)-1,4-enediones is attributed to the efficient visible-light illumination from blue LEDs, along with possible energy transfer from the photosensitizer CN-TPT to the E-isomers.
- Wei, Donglei,Liang, Fushun
-
supporting information
p. 5860 - 5863
(2016/11/29)
-
- Microphotochemistry using 5-mm light-emitting diodes: Energy-efficient photooxidations
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Commercial, inexpensive 5-mm milliwatt light-emitting diodes are effective sources for batch microphotochemical oxidations. Using limited quantities of singlet oxygen, these oxidations are atom economical and therefore useful for labeling experiments with rare isotopes. Georg Thieme Verlag Stuttgart · New York.
- Carney, John M.,Hammer, Reagan J.,Hulce, Martin,Lomas, Chad M.,Miyashiro, Dayna
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experimental part
p. 2560 - 2566
(2012/09/07)
-
- High-efficiency microphotooxidation using milliwatt LED sources
-
Inexpensive milliwatt light emitting diode (LED) sources allow energy- and atom-efficient microphotochemical reactions. Thus, sources constructed from three 120 mW 5 mm diameter 627 nm LED's enable μmol-mmol scale methylene blue-sensitized singlet oxygen photooxidations of various arenes and cyclopentadienones using a 3-5 M excess of oxygen in 82-98% yields.
- Carney, John M.,Hammer, Reagan J.,Hulce, Martin,Lomas, Chad M.,Miyashiro, Dayna
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supporting information; experimental part
p. 352 - 355
(2011/02/28)
-
- Oxidation of aromatic compounds: XVII. Oxidative cross-dimerization of diarylacetylenes in the system CF3CO2H-CH 2Cl2-PbO2. Characteristic of cation-radicals of diarylacetylenes by cyclic voltammetry and ESR spectroscopy
-
The oxidation of mixtures of diarylacetylene ArC≡CAr and Ar′C≡CAr′ in a system CF3CO2H-CH 2Cl2-PbO2 (0°C, 1.5 h) results in products of cross-dimerization, (Z)-1,2,3,4-tetraarylbut-2-ene-1,4-diones Ar(ArCO) C=C(COAr′)Ar′. The routes of transformation of intermediate cation-radicals of diarylacetylenes [ArC≡CAr]+? into the final products of oxidative dimerization are elucidated. By cyclic voltammetry and ESR spectroscopy the high reactivity of the diarylacetylene cation-radicals is demonstrated, the character of their singly occupied molecular orbitals (a2 or b1) has been revealed by ESR method.
- Vasil'ev,Rudenko
-
experimental part
p. 1282 - 1289
(2010/12/19)
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- Synthesis of tetrasubstituted furans via sequential Pd(OAc) 2/Zn(OTf)2-catalyzed oxidation and cydization of aromatic alkynes with molecular oxygen
-
The development of a new method for the synthesis of tetrasubstituted furans using aromatic alkynes is reported. The strategy involves a tandem process of palladium-catalyzed oxidation and Zn(OTf)2-catalyzed cyclization in the presence of molecular oxygen.
- Wang, Azhong,Jiang, Huanfeng,Xu, Qiuxiang
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scheme or table
p. 929 - 932
(2009/09/29)
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- Thermal oxidation of tetracyclones (2,3,4,5-tetraarylcyclopentadienones)
-
Tetracyclones are transformed to a mixture of diacylstilbenes and a-pyrones, when they are heated in diphenylether saturated with oxygen.
- Thiemann, Thies,Iniesta, Jesus,Walton, David J.
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experimental part
p. 173 - 180
(2009/05/07)
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- Iron (III) perchlorate adsorbed on silica gel: A reagent for organic functional group transformations
-
Adsorption of Fe(ClO4)3(H2O)6 onto chromatographic-grade silica gel in the presence of organic solvents (S=water, acetonitrile, or lower fatty acids) produces a supported reagent, Fe(ClO4)3(S)6/SiO2. This reagent has been found to be effective for the rapid organic functional group transformations such as dimerization of alkynes, aromatic hydrocarbons, selective oxidation of thiols to disulfides, and transannular reactions in 1,5-cyclooctadienes on grinding using pestle and mortar in the solid state. Copyright Taylor & Francis Group, LLC.
- Parmar, Anupama,Kumar, Harish
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p. 2301 - 2308
(2008/02/10)
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- Sm/TiCl4 system induced reductive coupling reactions: Synthesis of tetraarylfurans
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Induced by low valent titanium, tetraarylfurans have been synthesized in good yields starting from aroyl chlorides under mild and neutral conditions.
- Li,Zhang,Liu
-
p. 188 - 189
(2007/10/03)
-
- Calcium peroxide diperoxohydrate as a storable chemical generator of singlet oxygen for organic synthesis
-
Calcium peroxide diperoxohydrate (CaO2·2H2O2) is an environmentally friendly generator of singlet oxygen (1O2, 1Δg) that can be used in organic synthesis as an alternative to the regular photochemical method. This compound produces 1O2 in various solvents and can be easily recovered by filtration for further regeneration. Both monitoring of 1O2 luminescence at 1270 nm and specific trapping have shown that CaO2·2H2O2 can be stored for several days at -80 °C and that the yield of 1O2 is equal to 25%. Oxidation of typical organic substrates in methanol or THF through [4 + 2] or [2 + 2] cycloaddition and ene reaction have been carried out on a preparative scale with total conversion and selectivity.
- Pierlot, Christel,Nardello, Veronique,Schrive, Jordane,Mabille, Caroline,Barbillat, Jacques,Sombret, Bernard,Aubry, Jean-Marie
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p. 2418 - 2423
(2007/10/03)
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- A novel oxidative dimerization of acetylenes to conjugated dicarbonyl systems using iron (III) perchlorate
-
Acetylenes 1a-e, terminal as well as substituted, have been converted into α,β- unsaturated dicarbonyl systems 2a-e in good to excellent yields when reacted with Iron (III) perchlorate (ITP) using acetonitrile as the solvent.
- Rana,Kaur,Kumar,Kumar,Anand
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p. 1170 - 1171
(2007/10/03)
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- Iron (III) perchlorate: A novel reagent for functional group as well as ring transformations in organic synthesis
-
Oxidative dimerization of some aromatic hydrocarbons, diphenylacetylene and diphenyl amine, selective oxidation of thiols to disulfides, and transformation of 1,5-cyclooctadiene to the corresponding bicyclooctane derivatives through trans-annular reactions have been achieved using iron (III) perchlorate(ITP).
- Kumar, Baldev,Parmar, Anupama,Rajpal, Anita,Kumar, Harish
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p. 593 - 595
(2007/10/03)
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- Thermolysis of selenophene 1,1-dioxides
-
Selenophene 1,1-dioxides are thermally far labile than the corresponding thiophene 1,1-dioxides. Even heavily substituted tetraphenylselenophene 1,1-dioxide (1a) decomposed, by a process not involving cyclodimerization, when heated above its melting point or heated in refluxing toluene. Thus, the thermolysis of la in refluxing toluene afforded tetraphenylselenophene (2a, 6%), tetraphenylfuran (3a, 71%), (Z)-l,2,3,4-tetraphenyl-2-butene-l,4-dione (Z-4a, 19%), (E)-1,2,3,4-tetraphenyl-2-butene-1,4-dione (E-4a, 4%), SeO2 (23%), and Se (22%), while that of the neat sample gave 2a (5%), Z-4a (78%), E-4a (17%), SeO2 (17%), and Se (29%). Similar results were also obtained on thermolyses of a series of selenophene 1,1-dioxides. The experimental observations (influence of solvents, oxygen, and additive such as diene to the decomposition rate and the presence of induction period) revealed that the mechanism of the decomposition is highly complex. A tentative mechanism that can explain the observed products is presented.
- Umezawa, Takashi,Matsui, Tomoki,Sugihara, Yoshiaki,Ishii, Akihiko,Nakayama, Juzo
-
-
- Preparative oxidation of organic compounds in microemulsions with singlet oxygen generated chemically by the sodium molybdate/hydrogen peroxide system
-
A reverse (water in oil) microemulsion has been designed to oxidize hydrophobic organic substrates with singlet oxygen (1O2, 1Δ(g)) generated from the disproportionation of hydrogen peroxide catalyzed by molybdate ions. The microemulsion was prepared by mixing methylene chloride, sodium dodecylsulfate, n-butanol, and aqueous molybdate. Flash photolysis studies have shown that in such media singlet oxygen exhibits a similar kinetic behavior that under homogeneous conditions (τ(Δ) ? 42 μs). Various typical organic substrates have been oxidized on the preparative scale with this chemically generated singlet oxygen, and the expected oxidation products have been isolated in high yields.
- Aubry, Jean-Marie,Bouttemy, Sabine
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p. 5286 - 5294
(2007/10/03)
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- Oxidation of Aromatic Compounds. IV. Oxidation of Symmetrical Diarylacetylenes in the CF3COOH-CH2Cl2-PbO2 System. A New One-Pot Synthesis of 1,2,3,4-Tetraaryl-2-butene-1,4-diones
-
Oxidation of symmetrical diarylacetylenes in the CF3COOH-CH2Cl2-PbO2 system (0-20 deg C, 1-3 h) yields 1,2,3,4-tetraaryl-2-butene-1,4-diones.According to (1)H NMR and GC-MS data the compounds synthesized have Z configuration.
- Rudenko, A. P.,Vasil'ev, A. V.
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p. 1360 - 1379
(2007/10/03)
-
- Oxidation of Tetraarylselenophenes and Benzoselenophene with m-Chloroperbenzoic Acid
-
Oxidation of tetraarylselenophenes with m-chloroperbenzoic acid produces cis-1,2-diaroyl-1,2-diarylethylenes and SeO2 as the principal product, while the oxidation of benzoselenophene affords benzoselenophene 1-oxide.
- Nakayama, Juzo,Matsui, Tomoki,Sato, Noriko
-
p. 485 - 486
(2007/10/03)
-
- Superoxide-Mediated Base-Catalyzed Autoxidation of Tetraphenylcyclopentadiene
-
The superoxide (KO2/18-crown-6)-mediated oxidation of tetraphenylcyclopentadiene (1) in aprotic media generated a variety of products following aqueous workup, including 2-hydroxy-2,4,5-triphenylfuranone (3), 2,3,4,5-tetraphenylfuran (4), cis-dibenzoylsti
- Frimer, Aryeh A.,Strul, Gila,Gottlieb, Hugo E.
-
p. 4521 - 4524
(2007/10/02)
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- ANODIC OXIDATION OF DIARYLACETYLENES AND DIARYLDIACETYLENES: ELECTROSYNTHESIS OF DIAROYL-STILBENES AND ACETYLENIC α- AND γ-DIKETONES
-
Diarylacetylenes and diaryldiacetylenes have been electrooxidized in acetonitrile through the use of a graphite plate anode, thus overcoming a very high passivation.Diarylacetylenes led mainly to 1,2-diaroyl-1,2-diaryl-ethylenes.Anodic oxidation of conjugated diaryldiacetylenes, at the same anode, led to a mixture of acetylenic α- and γ-diketones.This represents the very first synthesis of acetylenic α-diketones Ar-CO-CO-CC-Ar.
- Cariou, Michel
-
p. 799 - 808
(2007/10/02)
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- Triplet Ground-State Benzoylphenylmethylene and Its Quintet Ground-State Triplet-Triplet Radical Pair
-
Photolysis of crystalline azibenzil powder at 77 K and λ >/= 345 nm generates a complex ESR spectrum consisting of four components, namely a strong triplet, a weak triplet, a quintet, and a doublet.The strong triplet has been previously assigned to ground-state benzoylphenylmethylene and the quintet to the ground state of a radical pair formed between two triplet benzoylphenylmethylenes.On the basis of the similar values exhibited by the zero-field splitting parameters, the strong and weak triplet signals are assigned here to the s-Z and s-E isomers of the ground state of benzoylphenylmethylene, respectively.The s-Z conformer is more abundant and less stable than the s-E, and on annealing, the decay of both signals follows first-order kinetics.Above 90 K the quintet radical pair also decays with first-order kinetics to yield a new triplet diradical, which is stable at T 120 K but disappears with first-order kinetics above 120 K.The Arrhenius parameters have been determined for all decay reactions and utilized in their mechanistic interpretation.The carrier of the structureless, broad doublet signal observed appears to be generated from the secondary photolysis of the tiplet benzoylphenylmethylene.The assignment of the quintet spectrum to a radical pair is also supported by the absence of this spectrum in the photolysate of dilute azibenzil solutions in glassy matrices.Under such conditions, in addition to the spectrum of benzoylphenylmethylene and its doublet photolysis products, a new triplet diradical appears wiht a kinetics of formation suggesting that it is formed by the decay of the quintet.However, its identity has not been established.
- Murai, H.,Safarik, I.,Torres, M.,Strausz, O. P.
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p. 1025 - 1032
(2007/10/02)
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- ORGANIC CHEMISTRY OF SUBVALENT TRANSITION METAL COMPLEXES XI. OXIDATIVE ADDITIONS OF NICKEL(0) COMPLEXES TO CARBON-CARBON BONDS IN ALKYNES: NICKELIRENES AND NICKELOLES AS CATALYTIC CARRIERS IN THE OLIGOMERIZATION OF ALKYNES
-
The formation of 2,3,4,5-tetraphenylnickelole-bis(triphenylphosphine) (IIIa) and 2,3,4,5-tetraphenylnickelole-bis(1,2-diphenylphosphino)ethane (IIIb), either from (E,E)-1,2,3,4-tetraphenyl-1,3-butadien-1,4-ylidenedilithium (I) and the corresponding nickel(II) chloride-phosphine complexes (II) or from the reduction of η4-tetraphenylcyclobutadienenickel(II) bromide dimer (XII) in the presence of phosphines, proceeds in good yields.Nickelole IIIa displays physical and chemical properties consistent with its structure and is a catalyst for the trimerization of diphenylacetylene.Nickelole IIIb is a highly associated structure but in its chemical response to alkynes, HOAc, O2, Br2, NaAlEt2H2 and heat displays the properties of a nickelole, rather than a cyclobutadienenickel(0) complex.Attempts to generate IIIb photochemically from η4-1,5-cyclooctadiene(η4-tetraphenylcyclopentadienone)nickel and diphos failed, but it was shown that structural types, such as η4-tetraphenylcyclopentadienone(diphos)nickel (a model for the structure suggested by Hoberg and Richter for IIIb), are unstable.Oligomerizations of diphenylacetylene by bis(1,5-cyclooctadiene)nickel were retarded by conducting the reaction in THF or in the presence of diphos.This retardation permitted the interception of products (cis-stilbene and (E,E)-1,2,3,4-tetraphenyl-1,3-butadiene)diagnostic for the intermediacy of nickelirenes and nickeloles.Deuterium labeling verified the presence of carbo-nickel bonds.These trapping experiments, together with findings on the thermal behavior of nickeloles, are combined into a comprehensive view of the cyclotrimerization, cyclotetramerization and linear polymerization of alkynes by nickel(0).
- Eisch, John J.,Galle, James E.,Aradi, Allen A.,Boleslawski, Marek P.
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p. 399 - 416
(2007/10/02)
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- Oxidative Addition of Nickel(0) Complexes to Carbon-Carbon Bonds in Cyclobutadiene. The Question of the Interconvertibility of Cyclobutadiene-nickel(0) Complexes and the Nickelaring Systems
-
Bis(triethylphosphine)(η4-tetraphenylcyclobutadiene)nickel (4) was synthesized by the reduction of (η4-tetraphenylcyclobutadiene)nickel(II)bromide (3) with t-butyllithium in the presence of Et3P, and its structure was determined by X-ray crystallography.Furthermore, its reactivity towards CO, CH3CO2H, PhCCPh, LiAlH4 and O2 were investigated. 1,1-Bis(triethylphosphine)-2,3,4,5-tetraphenylnickelole (14) was synthesized from (E,E)-1,4-dilithio-1,2,3,4-tetraphenyl-1,3-butadiene (15) and bis(triethylphosphine)nickel(II)bromide.Since the resulting crystals of the nickelole were not suitable for X-ray structure determination, the compound was characterized by elemental analyses, spectral data and carbonylation to yield tetraphenylcyclopentadienone (6).Analogous reductions of (η4-tetraphenylcyclobutadiene)nickel(II)bromide (3) in the presence of Ph3P or Ph2PCH2CH2PPh2, followed by carbonylation, led to 6 in 40percent yield, demonstrating that about half of the cyclobutadiene rings in 3 undergo cleavage upon reduction to give the nickelole.Reactions of the dilithium reagent 15 with NiBr2 complexed with Me2PCH2CH2PMe2, Ph3P or Et2PCH2CH2PEt2, led to the formation of thermolabile nickeloles, as demonstrated by carbonylation which yielded 6.Warming of the nickeloles and subsequent treatment with CH3CO2H led to the formation of 1,2,3,4,5,6,7,8-octaphenyl-1,3,5,7-octatetraene (8) and, in one case, octahenylcyclooctatetraene (5).The relevance of these findings to the mechanism of the Reppe nickel-catalyzed oligomerization of alkynes is discussed. - Key words: Insertion Reaction, Oxidative Addition, Cyclobutadiene-Nickel(0) Complexes, Nickelacyclopentadiene, Nickelole
- Eisch, John J.,Piotrowski, Andrzej M.,Aradi, Allen A.,Krueger, Carl,Romao, Maria J.
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p. 624 - 635
(2007/10/02)
-
- Studies on Singlet Oxygen in Aqueous Solution. Part 1. Formation of Singlet Oxygen from Hydrogen Peroxide with Two-electron Oxidants
-
Kinetic parameters are reported for the trapping of singlet oxygen by anthracene-9,10-bis(ethanesulphonate) (aes) in water and deuterium oxide solutions.The kinetics of the reactions of N-chlorosuccinimide, chloramine T (N-chlorotoluene-p-sulphonamide), N-chloromethanesulphonamide, and N,N-dichloromethanesulphonamide with hydrogen peroxide have been studied.For chloramine T and N-chloromethanesulphonamide the rate-determining step is formation of the corresponding dichloro-compounds, which are the reactive species.Using aes as a trap, it is shown that both chloramine T and N-chlorosuccinimide with H2O2 produce singlet oxygen in essentially quantitative yield.Iodylbenzene reacts with H2O2 to give, in the rate-determining step, iodosylbenzene and oxygen and then iodobenzene and oxygen; 47 percent of the oxygen produced is in the singlet state.For the corresponding reaction with 4-iodosylbenzene-1-sulphonic acid, the yield of singlet oxygen is 45 percent, i.e. indistinguishable within experimental error.Periodate and H2O2 give lower yields of singlet oxygen, and it is considered that two concomitant processes are involved.With hypobromite and H2O2 the yield of singlet oxygen is 76 percent.These variations in yield are briefly discussed.
- Evans, Dennis F.,Upton, Mark W.
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p. 1141 - 1145
(2007/10/02)
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- Ozonides de phosphite source d'oxygene singulet: rendement, mecanisme
-
The ozonides of several phosphites in solution in dichloromethane have been reacted with some scavengers of singlet oxygen (1O2) like rubrene (2), tetraphenylcyclopentadienone (4), and 9,10-diphenylanthracene (6).These ozonides react on the sca
- Caminade, Anne Marie,Khatib, Fayez El,Koenig, Max,Aubry, Jean Marie
-
p. 3203 - 3209
(2007/10/02)
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- NOUVEAUX TRIOXOPHOSPHETANES GENERATEURS D'OXYGENE SINGULET A BASSE TEMPERATURE
-
We have prepared phosphite ozonides 1b-3b which are efficient and clean singlet oxygene generators at low temperature.
- Khatib, Fayez El,Tachon, Christine,Caminade, Anne-Marie,Koenig, Max
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p. 3007 - 3010
(2007/10/02)
-
- Reactions of Monothiobenzil and its Dimer
-
In contrast to the usual formation of monothiobenzil from desyl thiosulfate in a two-phase system involving aqueous sodium hydroxide and methylene chloride, the dimer, 2,4-dibenzoyl-2,4-diphenyl-1,3-dithietane, is obtained in the absence of methylene chloride; and didesyl sulfide is obtained in ethanolic sodium hydroxide-methylene chloride.Thermolysis of monothiobenzil or monothioanisil gives 1,2,3,4-tetraaryl-2-butene-1,4-diones which may be accompanied by benzil or anisil.Monothiobenzil forms an unstable adduct with cyclopentadiene which can be converted to a stable dibromo derivative; it is converted to benzil by treatment with peracide or nitric acid.Dibenzoylstilbene is obtained by thermolysis of the dimer of monothiobenzil or by treatment of the dimer with triphenylphosphine.Treatment of the dimer with Cleland's reagent (2,3-dihydroxy-1,4-butanedithiol) gives didesyl sulfide, and treatment with cyanide ion gives 2-benzoyl-2,4,5-triphenyl-1,3-oxathiole.
- Hartnedy, Richard C.,Dittmer, Donald C.
-
p. 4752 - 4754
(2007/10/02)
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- Reactions of Diphenylcyclopropenone and Tetracyclones with Potassium Superoxide
-
Reactions of diphenylcyclopropenone and various tetracyclones with potassium superoxide are reported.
- Neckers, Douglas C.,Hauck, Gerhard
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p. 4691 - 4695
(2007/10/02)
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- PHOTOOXYGENATION OF SILACYCLOPENTADIENES: A NOVEL OXYGENATION PRODUCT, 2,4-DIOXA-3-SILABICYCLOHEPT-6-ENE, AND ITS CYCLOREVERSION REACTIONS
-
Photooxygenation of 1,1-dimethyl-2,3,4,5-tetraphenyl-1-silacyclopentadiene afforded 2,4-dioxa-3-silabicyclohept-6-ene(III) together with dibenzoylstilbene.The former was converted to isodidesyl and didesyl by treatment on alumina.Valence bond isome
- Nakadaira, Yasuhiro,Nomura, Tamotsu,Kanouchi, Seiichi,Sato, Ryuji,Kabuto, Chizuko,Sakurai, Hideki
-
p. 209 - 212
(2007/10/02)
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- Reactions of low-valent titanium with various functional groups (phenyl derivatives)
-
Titanium slurries, prepared by reduction of titanium chlorides with LiAlH4, are not only effective in couplings of ketones and aldehydes to alkenes, but also in reductive couplings and reductions of other functional groups.
- Dams, Rudy,Malinowski, Marek,Giese, Herman J.
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p. 112 - 114
(2007/10/02)
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- Photochemical reactions of a cobaltacyclopentadiene and the molecular structure of (η5 Cyclopentadienyl)
-
Least-squre refinement on 177 variables led to a final value of the R index on of unique observations; the conventional R index on observations having bond.
- Trogler, Willam C.,Ibers, James A.
-
p. 536 - 542
(2008/10/08)
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- Bis(acetylacetonato)copper(II) Catalysed Dimerisation of Benzoylphenylcarbene
-
Bis(acetylacetonato)copper(II) catalysed thermal decomposition of 2-diazo-1,2-diphenylethanone (1) gives cis-1,2,3,4-tetraphenylbut-2-ene-1,4-dione (3) and N,N'-bis(2-oxo-1,2-diphenylethylidene)azine (4), characterised by analytical and spectral (UV, IR a
- Singh, S. B.
-
-
- Formation and Thermal Cleavage Reactions of the Cycloadduct of 9,10-Dimethylanthracene and Nitrosyl Cyanide
-
Nitrosyl cyanide and 9,10-dimethylanthracene (DMA) (2) reacted at -25 deg C to form the crystallyne cycloadduct, 9,10-dihydro-9,10-(N-cyanoepoxyimino)-9,10-dimethylanthracene (1).The adduct (1) decomposed in the presence of the conjugated diene thebaine (3), to form DMA(2) and the adduct (4) of nitrosyl cyanide and thebaine.First-order kinetics, k = 6.9E-5 s-1, were observed for the release of DMA in benzene at 40 deg C, consistent with slow dissociation of the adduct (1) followed by rapid capture of nitrosyl cyanide by thebain.A similar first-order rate, k = 6.8E-5 s-1, was observed for the reaction of the adduct (1) and triphenylphosphine (2 mol equiv.) under the same conditions, the products being DMA, triphenylphosphine oxide, and triphenylphosphine N-cyanoimide (5).The reactions of nitrosyl cyanide, generated thermally from the adduct (1), were studied with a range of dienes.The conjugated dienes, N-cyanomethyl-N-northebaine (3; NCH2CN replacing NMe), trans,trans-1,4-diphenylbuta-1,3-diene (6; R=H), and ergosteryl acetate (11) all gave the expected cycloadducts (3,6-dihydro-2H-1,2-oxazines).Norbornane gave the tetracyclic adduct (10) arising from 1,4-conjugate addition of nitrosyl cyanide.The reactions of the adduct (1) with tetraphenylcyclopentadienone (14), 1,3-diphenylisobenzofuran (18), 2-methyl-1,3-diphenylisoindole (23), diazofluorene (24), and diphenyldiazomethane all took a more complex course leading in each case to the formation of an N-cyano-ketimine (alkylidene-cyanamide)
- Horsewood, Peter,Kirby, Gordon W.,Sharma, Ram Prakash,Sweeny, James
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p. 1802 - 1806
(2007/10/02)
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- Mechanism of Thermolysis of Endoperoxides of Aromatic Compounds. Activation Parameters, Magnetic Field, and Magnetic Isotope Effecs
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A mechanistic investigation has been made of the thermolysis of several endoperoxides of anthracenes and naphthalenes which produce molecular oxygen and the parent aromatic species quantitatively.Qualitative thermochemical measurements in the solid state indicate that in all cases studied, the reactions were endothermic.This situation appears to be valid in solution also.Clean first-order kinetics were observed for these thermolyses.Activation parameters were derived from the temparature dependence of the first-order rate constants.The primary yields of singlet oxygen (1O2) from the several endoperoxides were determined, and a correlation was discovered between the A factors (ΔS values) for thermolysis and the yield of 1O2.It was found that high A factors (positive ΔS values) correlated with relatively low yields of 1O2 and that low A factors (slightly negative or near zero ΔS values) correlated with nearly quantitative yields of 1O2.These two results are interpreted in terms of a diradical mechanism which leads to low yield of 1O2 and a concerted mechanism which leads to quantitative yields of 1O2.This interpretation is consistent with the observation of a magnetic field effect on the yield of 1O2 from endoperoxides whose thermolyses proceed with positive ΔS values and the absence of a magnetic field effect on the yield of 1Oi endoperoxides whose thermolyses proceed with near zero ΔS values.Further support for the occurrence of a diradical mechanism is available from the demonstration of a special 17O isotope effect on the thermolysis of an endoperoxide which is postulated to undergo thermolysis principally via a diradical intermediate.The thermolysis of endoperoxides which decompose mainly by a diradical mechanism yields triplet molecular oxygen that is selectively enriched in 17O.
- Turro, Nicholas J.,Chow, Ming-Fea,Rigaudy, Jean
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p. 7218 - 7224
(2007/10/02)
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- Lewis-Acid-Catalysed Reaction of Oxygen with 1,3-Diphenylisobenzofuran, Tetraphenylfuran and Tetraphenylcyclopentadiene
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1,3-Diphenylisobenzofuran is converted into o-dibenzoylbenzene (40-70percent) by oxygen, either in dichlorometane at -78 deg C in the presence of 1-2 equiv. of a variety of Lewis acids, or on silica gel at 20 deg C, in the dark.Tetraphenylfuran is converted into (Z)-dibenzoylstilbene (55-65percent) under the former conditions in the presence of 0.05 equiv. of I2 or SnI4 under irradiation from a tungsten lamp.The conversions, which correspond to a mono-oxygenation process, do not involve as intermediates the furan endoperoxides, which were independently generated from the furans by use of singlet oxygen. 2,5-Dimethylfuran and p-menthofuran do not react with oxygen in the presence of Lewis acids under the foregoing conditions.Tetraphenylcyclopentadiene is converted by oxygen into the corrsponding endoperoxide (70-85percent) in the presence of 0.05 equiv. of I2 and SnI4 or 0.1 equiv. of Ph3C+BF4- in dichloromethane at -78 deg C under irradiation.
- Haynes, Richard K.,Peters, Jennifer M.,Wilmot, Ian D.
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p. 2653 - 2661
(2007/10/02)
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- BIS(TETRAPHENYLCYCLOBUTADIEN)PALLADIUM(0)
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Tetraphenylcyclobutadienepalladium dichloride reacts with 1,2,3,4-tetraphenyl-1,4-dilithium butadiene or with sodium with abstraction of halide to give the sandwich compound bis(tetraphenylcyclobutadiene)palladium(0).The structure of the latter is elucida
- Hoberg, Heinz,Froehlich, Christian
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p. 105 - 110
(2007/10/02)
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