- Highly regio- and diastereoselective chromium(0)-catalysed cyclopropanation of 1-alkoxy-1,3-dienes with diazo compounds
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Pentacarbonyl(η2-cis-cyclooctene)chromium(0) (1) is an efficient catalyst for diazo decomposition and selective [2+1]-cycloaddition reactions of the resulting carbene intermediates with electron-rich dienes. The cyclopropanation of 1-alkoxy-1,3
- Hahn, Norbert D.,Nieger, Martin,Doetz, Karl Heinz
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Read Online
- Solvent and excitation wavelength effects on photocleavage of N-(9-anthroyloxy)-9-fluorenylideneamine as a precursor of 9-anthroyloxyl radicals. A mechanistic study
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Photocleavage of the N-O bond of N-(9-anthroyloxy)-9-fluorenylideneamine takes place efficiently in acetonitrile in the excited singlet state attributed to the fluorenylidene moiety. This made it possible for the first time to directly observe 9-anthroyloxyl radicals. However, the efficiency decreases remarkably in benzene in which the lowest excited singlet state is attributed to the anthroate moiety. (C) 2000 Elsevier Science Ltd.
- Saitoh,Segawa,Itoh,Sakuragi
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Read Online
- (PNP)Cobalt-Catalyzed Olefination of Diazoalkanes
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Addition of excess diazoalkane to the pincer-supported cobalt(I) dinitrogen complex (tBumPNP)CoN2 (tBumPNP = modified 2,6-bis[(ditert-butylphosphino)methyl]pyridine) resulted in the catalytic formation of the homocoupled alkene product with concomitant loss of N2. Monosubstituted diazoalkanes, trimethylsilyldiazomethane and tolyldiazomethane, generated the olefin product in quantitative yield with exclusive (E)-stereoselectivity. Disubstituted diazoalkanes, diphenyldiazomethane and 9-diazofluorene, also yielded the olefin as the major product along with minor azine coupling. Investigations into the nature of the diazoalkane-cobalt interaction by multinuclear NMR spectroscopy and X-ray diffraction established end-on diazoalkane cobalt complexes as the resting states. The isolated four-coordinate cobalt diazoalkane complexes promoted conversion to the corresponding olefin. The reaction of (tBumPNP)CoN2 with an α-diazo-β-ketoester resulted in the formation of a five-coordinate Co(I)-diazoalkane complex with a chelating ester unit that was unreactive for olefination.
- Chirik, Paul J.,Semproni, Scott P.,Yruegas, Sam
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supporting information
(2022/03/17)
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- Reactions of hydrazones and hydrazides with Lewis acidic boranes
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The reaction of (diphenylmethylene)hydrazone or 1,4-bis-hydrazone-ylidene(phenylmethyl)benzene with Lewis acidic boranes B(2,4,6-F3C6H2)3 or B(3,4,5-F3C6H2)3 generates the Lewis acid-base adducts. Alternatively, when (9H-fluoren-9-ylidene)hydrazone is employed several products were isolated including 1,2-di(9H-fluoren-9-ylidene)hydrazone, the 2:1 borane adduct of NH2-NH2 and the 1-(diarylboraneyl)-2-(9H-fluoren-9-ylidene)hydrazone in which one ArH group has been eliminated. The benzhydrazide starting material also initially gives an adduct when reacted with Lewis acidic boranes which upon heating eliminates ArH generating a CON2B heterocycle.
- Gazis, Theodore A.,Dasgupta, Ayan,Hill, Michael S.,Rawson, Jeremy M.,Wirth, Thomas,Melen, Rebecca L.
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p. 12391 - 12395
(2019/08/26)
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- Substituent Effects on Reactions of [RhCl(COD)]2 with Diazoalkanes
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The reactions of [RhCl(COD)]2 with a series of diazoalkanes with different substitutents were investigated. The outcomes of the reactions were found to be substituent-dependent via four different pathways. (1) The reactions with diazoindenes produced ??5-cyclopentadienyl complexes. (2) The reaction with diazofluorene produced a mixture of olefin and azine compounds. (3) The reactions with monosubstituted diazoalkanes RCHN2 (R = Ph, MeO2C) produced olefins RCHa?CHR. (4) The reaction with the disubstituted diazoalkane Ph2CN2 produced the azine Ph2Ca?N-Na?CPh2 only. Computational studies have been carried out to understand the interesting substituent effect by comparing the kinetics and thermodynamics of the reaction pathways. It was found that the reactions with diazocyclopentadiene, diazoindene, and Ph2CN2 are kinetically controlled, while the reactions with RCHN2 and diazofluorene are both thermodynamically and kinetically controlled.
- Cui, Mingxu,Lin, Shujuan,Sung, Herman H. Y.,Williams, Ian D.,Lin, Zhenyang,Jia, Guochen
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p. 905 - 915
(2019/03/04)
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- Metal-free and fecl3-catalyzed synthesis of azines and 3,5-diphenyl-1H-pyrazole from hydrazones and/or ketones monitored by high resolution ESI+-MS
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9-Fluorenone azine 2a or benzophenone azine 2b have been synthesized, respectively, by treatment of 9-fluorenone hydrazone la or benzophenone hydrazone lb with FeCl3 Lewis acid catalyst in CHCb. Treatment of la and lb with FeCb affords the asymmetrical azine l-(diphenylmethylene)-2-(9H-fluoren-9-ylidene)hydrazine 2c. l,3-Diphenyl-2-propenone 3 reacts with hydrazine to produce l-((E)-l,3-diphenylallylidene)hydrazine 3a. Under prolonged heating, 3a undergoes a cyclization to yield 3,5-diphenyl-lH-pyrazoIe 4. Chalcone 3 reacts with la or lb to produce a mixture of 4 and 2a or 4 and 2b, respectively. The reaction of cyclohexanone 5 with hydrazine leads to the formation of 1,2-dicyclohexylidene hydrazine 6. Ketone 5 reacts with la or lb to give the asymmetrical azine product 6a or 6b, respectively. The progress of the reactions has been monitored by electrospray ionization mass spectrometry (ESI-MS), and the compounds have been characterized by elemental analyses, IR,1H,13C and DEPT-135 NMR spectroscopy and also by high resolution ESI+-MS.
- Lasri, Jamal,Ismail, Ali I.
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p. 362 - 373
(2019/05/21)
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- Cyclopropanespiro-β-lactones derived from 4-[(Z)-ethylidene]-3- methyloxetan-2-one: Diastereoselective formation and rearrangement reactions
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The metal catalysed reaction of monosubstituted diazo esters and ketones with 4-[(Z)-ethylidene]-3-methyloxetan-2-one results in the formation of cyclopropanespiro-β-lactones. In contrast to most alkene cyclopropanations, including those involving diketene, the reaction occurs diastereoselectively. A computational model of the reaction has been developed that accounts for the observed stereochemistry. The metal promoted thermal rearrangement of these spiro compounds is also unusual in that it affords pyranones, rather than the decarboxylation products characteristic of β-lactones in general, or the furanones formed from diketene derived cyclopropanespiro-β-lactones.
- Geraghty, Niall W.A.,McArdle, Patrick,Mullen, Laverne M.A.
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experimental part
p. 3546 - 3552
(2011/06/11)
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- The decomposition of diazo-compounds induced by nucleophiles. The decomposition of 9-diazofluorene in the presence of hydroxide or alkoxide ions
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9-Diazofluorene, on treatment with stoichiometric or substoichiometric amounts of quaternary ammonium hydroxide or methoxide or of potassium t-butoxide in solution in aqueous or alcoholic dimethyl sulfoxide or acetonitrile at 30°C, decomposes with evolution of nitrogen to yield fluorenone azine [bis(fluorenylidene)hydrazine] in almost quantitative yield. Studies are reported of the identity of the minor by-products, together with an examination of the kinetics of the reactions and additional spectroscopic experiments. The general rate equation is v = k[FIN2]3/2[Nu-]1/2, where Nu- represents the nucleophile. It is concluded that the oxyanions, most probably after nucleophilic attack on 9-diazofluorene under these basic conditions to generate a new anionic species, are capable of transferring an electron to the diazo-compound. This initiates decomposition of further diazo-molecules in a process of electron-transfer chain catalysis that bears some similarities to, but has also some differences from, that encountered using cathodic initiation. In support of this interpretation it is found that reactions can be accelerated by the introduction of carbon acids (fluorene, 9-phenylfluorene) into the reaction mixtures. The nature of the initiation, propagation and termination steps of the chain mechanism are discussed.
- McDowell, Linda J.,Khodaei, M. Mehdi,Bethell, Donald
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p. 995 - 1003
(2007/10/03)
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- Mechanism for photocleavage of N-(anthroyloxy)-9-fluorenylideneamines and dynamic behavior of anthroyloxyl radicals
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Photocleavage of the N-O bond of N-(9-anthroyloxy)-9-fluorenylideneamine and its 1-and 2-anthroyloxy derivatives takes place efficiently in acetonitrile in the excited singlet state attributed to the fluorenylidene moiety. This made it possible for the first time to directly observe anthroyloxyl radicals by the transient absorption method. The quantum efficiency for photocleavage decreases remarkably in benzene, in which the lowest excited singlet state is attributed to the anthroate moiety. All the three kinds of anthroyloxyl radicals are much less reactive in decarboxylation, addition to olefins, and hydrogen-atom abstraction than benzoyloxyl and 1- and 2-naphthoyloxyl radicals; 9-anthroyloxyl radicals supposedly undergo intramolecular addition-elimination in the ipso-position in equilibrium with α-lactonic spirodihydroanthryl radicals, as indicated by one-color and two-color laser photolyses.
- Saitoh, Yasuo,Kaneko, Makoto,Segawa, Katsunori,Itoh, Hiroki,Sakuragi, Hirochika
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p. 2013 - 2023
(2007/10/03)
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- Chromium complex catalyzed synthesis of spirocyclopropanes from diaryl diazo compounds - Direct NMR-spectroscopic observation of a carbene complex intermediate
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The [2 + 1] cycloaddition reaction of electron-rich alkenes such as enol ethers with 9-diazo-9H-fluorene (1) is efficiently catalyzed by pentacarbonyl(η2-cis-cyclooctene)chromium(0) (2). This cyclopropanation reaction shows a pronounced prefere
- Pfeiffer, Juergen,Nieger, Martin,Doetz, Karl Heinz
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p. 1011 - 1022
(2007/10/03)
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- Synthesis and Properties of 9-(Tropylidenehydrazono)fluorene and Related Compounds
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9-(Tropylidenehydrazono)fluorene (1) was obtained by a reaction between 9-fluorenone hydrazone and tropylium tetrafluoroborate. ccompanied by 9-fluorenone azine, 9-(benzylidenehydrazono)fluorene, and 9,9-ditropylfluorene. The amination of 1 occurred at the 2-position of the tropylidene moiety. The addition of tosyl isocyanate to 1 gave the [8 +2] cycloadduct at the 2,4,6-cydoheptatrien-1-imine structure.
- Minabe, Masahiro,Nozawa, Toshiya,Kurose, Tomoko,Kimura, Takao,Tsubota, Motohiro
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p. 693 - 697
(2007/10/03)
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- Laser flash photolysis of carbamates derived from 9-fluorenone oxime
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The photochemistry of carbamates derived from 9-fluorenone oxime was investigated by laser flash photolysis and by product studies. Primary photocleavage of the excited carbamates leads to decarboxylation and concomitant generation of the 9-fluorenone ketimine-N-yl radical and an amino radical. In the case of 9-fluorenylideneamino N-(2,5-dimethoxyphenyl)carbamate the presence of 1,4-dimethoxybenzene in the product mixture as well as spectroscopic and kinetic evidence points to the intermediary formation of triplet (2,5-dimethoxyphenyl)nitrene, which in acetonitrile dimerizes to the corresponding azo compound. Analogously, the formation of trans-azobenzene upon photolysis of 9-fluorenylideneamino N-phenylcarbamate indicates the intermediacy of parent triplet phenylnitrene, which, until now, had not been observed in solution at ambient temperature.
- Bucher, G?tz,Scaiano,Sinta,Barclay,Cameron
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p. 3848 - 3855
(2007/10/02)
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- A GENERAL METHOD FOR PREPARING DIPHOSPHIRANES
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Diphosphiranes 3a-3f are obtained by action of diazo derivatives and carbenes on the trans-diphosphene 1.The structures are elucidated by spectroscopic methods.In all cases the cycloaddition reaction is stereoselective.
- Etemad-Moghadam, Guita,Bellan, Jacques,Tachon, Christine,Koenig, Max
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p. 1793 - 1798
(2007/10/02)
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- Organic Reactive Intermediates: Part IX-Radical Ions as Reactive Intermediates in Redox Reactions of Triphenylphosphazines
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Two representative phosphazines namely, fluorenylidenetriphenylphosphazine (1) and diphenylmethylenetriphenylphosphazine (2) are shown to undergo oxidation and reduction involving single electron transfer to yield the corresponding cation and anion radicals, respectively.These ion radicals are unstable and decompose to give rise to a blend of other intermediates.Those which act almost certainly as principal intermediates in oxidation and reduction are carbenes and diazoalkane radical anions respectively.
- Handoo, Kishan L.,Gadru, Kanchan
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p. 412 - 417
(2007/10/02)
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- Reactivity of Carbenes and Related Compounds towards Molecular Nitrogen
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The thermal N2 exchange of a number of 15N-labelled diazo compounds was studied in solution.The compounds involved were 3-diazo-1-methylindolin-2-one (1), 9-diazafluorene (2), 5-diazo-1,3-cyclopentadiene-1,2,3,4-tetracarbonitrile (3), 2-diazo-2H-imidazole-4,5-dicarbonitrile (4), 4-diazocyclohexa-2,5-dienone (5), and the conjugate acids of 4 and 5, namely 4,5-dicyano-1H-imidazole-2-diazonium ion (6) and 4-hydroxybenzenediazonium ion (7).Only 1, 4, 6, and 7 exchange their diazo group with 'external' molecular N2.The results are explained on the hypothesis that only organic species which have an empty ? orbital and which are effective in ? electron back-donation are able to react with N2.Thus, reaction with carbenes is likely to occur only if the carbene is in the 1A2 singlet state and if its electrophilicity is high.
- Grieve, Duncan M. A.,Lewis, Graham E.,Ravenscroft, Michael D.,Skrabal, Peter,Sonoda, Takaaki,et al.
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p. 1427 - 1443
(2007/10/02)
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- INTERMEDIATES IN THE DECOMPOSITION OF ALIPHATIC DIAZO-COMPOUNDS. PART 20. KINETIC STUDIES ON REDUCTIVELY INITIATED ELECTRON TRANSFER CHAIN CATALYSIS OF THE DECOMPOSITION OF 9-DIAZOFLUORENE
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The method of constant-current electrolysis (c.c.e.) at a platinum cathode has been used to investigate the kinetics of the electron transfer chain catalysis of the decomposition of 9-diazofluorene (FlN2) in CH3CN solution.Equations have been derived for various possible kinetic forms of both chain propagation and termination, and comparision with observation indicates that the chain carrier reacts with a molecule of FlN2 to propagate the chain and reacts with the solvent, or other additive such as oxygen or diethyl malonate, to terminate the chain.Interruption of the current in the experiments (i.c.c.e.) leads to a different set of equations from which it is possible to evaluate separately the rate constants for propagation and termination.The identity of the chain carrier is discussed.It is established that this is unlikely to be the diazoalkane anion radical, FlN2(-.), as previously thought.Anion-radicals derived from the product fluorenone azine are the likeliest candidates under the reaction conditions used.
- Bethell, Donald,McDowall, Linda J.,Parker, Vernon D.
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p. 1531 - 1536
(2007/10/02)
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- INTERMEDIATES IN THE DECOMPOSITION OF ALIPHATIC DIAZO-COMPOUNDS. PART 19. KINETICS AND MECHANISM OF THE REACTIONS OF 9-DIAZOFLUORENE CATION RADICAL
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The decomposition of 9-diazofluorene (FlN2) brought about at a platinum anode or by chemical oxidants, Cu(BF4)2 or (p-BrC6H4)3N(+.)SbCl6(1-), in CH3CN solution leads to formation of mixtures of bifluorenylidene and flourenone azine in high yield.The reactions have been studied kinetically by conventional means and using the transient electrochemical techniques derivative linear sweep voltammetry (l.s.v.) and derivative cyclic voltammetry (d.c.v.).Constant-current electrolysis of FlN2 shows the characteristics of a chain process.The chemical oxidants give rise to a rate law -d/dt = k above a critical oxidant level, and the value of k is the same for both oxidants, even though their oxidation potentials are substantially different.It is inferred that the process studied is the chain propagation step in which the chain carrier reacts with a molecule of FlN2.Under the conditions of l.s.v. and d.c.v. experiments, it is shown that the instantaneously formed FlN2(+.) is consumed in a rapid process which is second order with respect to the cation radical and has a rate constant of 1.9 x 1E8 l mol-1 s-1; it is suggested that this process is cation radical dimerisation.Since the product of this step rapidly yields bifluorenylidene, it is argued that the slower macroscopic chain reactions do not involve dimerisation, but rather that FlN2(+.) rapidly attacks a further FlN2 molecule to generate the chain carrier which must have a lower oxidation potential than FlN2(+.).Possible structures for the chain carrier are considered in the light of earlier e.s.r. evidence for a radical intermediate.
- Ahmad, Iftikhar,Bethell, Donald,Parker, Vernon D.
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p. 1527 - 1530
(2007/10/02)
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- Chemical Behavior of Cyclopropylmethyl Radicals: Relative Unimportance of Cyclopropylmethyl to 3-Butenyl Rearrangement in the Cycloaddition Reactions Proceeding via Allylically Stabilized Diradicals
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The reaction of cis-1-cyclopropyl-1,3-butadiene (1c) with fluorenylidene (Fl:), which was thermally generated from 9-diazofluorene (2), produced 3c in addition to fluorenone azine (4) and 9,9'-bifluorenylidene (5).The reaction of 1t with 2 gave a mixture of two adducts, 3t and 6, in which 6 was proved to be the secondary product derived from 3t.The addition of Fl: was thus regiospecific and gave 3, and the stereochemistry of the C1-C2 double bond in 1 was retained throughout the addition.The reaction of 1,1-dicyclopropyl-1,2-propadiene (7) with Fl: took place exclusively at the C1-C2 double bond to give 13.On being heated at 140 deg C, 13 underwent the anticipated skeletal isomerization to give 14.At 180 deg C, more extensive rearrangements took place to produce 15, 16Z, and 16E in a 2.9:1.0:3.7 ratio. 1,1-Dibromo-2,2-dicyclopropylcyclopropane (19), on the other hand, produced a mixture of 20Z and 20E on being heated at 140 deg C.In contrast to the results obtained in the Fl: addition reactions, the radical addition of bromotrichloromethane (22) to 1 yielded cyclopropane-cleaved 23 as the exclusive product.It may thus be concluded that the cyclopropylmethyl to 3-butenyl rearrangement in the diradicals, in which the cyclopropyl-substituted site is stabilized with allylic resonance, is unimportant relative to the intramolecular coupling of the two radicals sites at least at 140 deg C or below, whereas the intermolecular atom abstraction of the cyclopropyl-substituted allyl radical occurs relatively slowly and hence is accompanied by the cyclopropane cleavage.
- Nishida, Shinya,Komiya, Zen,Mizuno, Tetsuo,Mikuni, Akihiro,Fukui, Tadashi,et al.
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p. 495 - 502
(2007/10/02)
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- Fluorenylidene: Kinetics and Mechanism
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Laser irradiation of 9-diazafluorene in solution leads to the formation of a transient species with λmax=470 nm that has been characterized as the triplet carbene and is believed to be in thermal equilibrium with the singlet state, which lies within a few kcal/mol.The singlet carbene is frequently more reactive and tends to dominate the chemistry.For example, in hydrogen donors, the triplet state abstracts hydrogen leading to the 9-fluorenyl radical, which is the only species detected in the flash experiments.However, product studies demonstrate that the predominant reaction path is the insertion of the singlet into C-H bonds (e.g., in cyclohexane), a process that is transparent to the technique of nanosecond laser photolysis.Irradiation of 9-diazofluorene in nitrile solvents results in carbene addition to the nitrile function, leading to nitrile ylides that react rapidly with electron-deficient olefins and present a characteristic absorption band at ca. 400 nm.The singlet carbene has a lifetime of =5 ns and obeys the Skell-Woodworth rules.
- Griller, D.,Hadel, L.,Nazran, A. S.,Platz, M. S.,Wong, P. C.,et al.
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p. 2227 - 2235
(2007/10/02)
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- On the Importance of Indiscriminate Insertion for Photoactivable Reagents - Photolysis of Diazofluorene in Mixed Organic Solvents
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Photolysis of diazofluorene (I), a new fluorescent photoactivable reagent, in cyclohexane, cyclohexene, methanol and in mixtures of the solvents is reported.Quantitative analysis of products formed has been carried out.In bulk hydrophobic milieu diazofluorene does show some indiscriminateness in its insertion reactions.The importance of indiscriminate insertion in photoaffinity labeling studies has been dicussed.A simple method has thus been developed to test the indiscriminate properties of a photoactivable reagent by photolysing it first in simple organic solvents.Such studies should prove useful and photoactivable reagents can be tested before applying them directly to biological systems.
- Anjaneyulu, P. S. R.,Lala, Anil K.
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p. 802 - 807
(2007/10/02)
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- Ketene. Part 21. Reactions of Heterocumulenes with Nitrones
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Degradative and mass spectrometric evidence confirms the formation of the isoxazolidinones (2) from the reaction of cyano-t-butylketene with the N-alkyl nitrones (1), whilst the reaction with the N-phenyl nitrone (1d) gives the expected oxazolidinone (3b).Cyano-t-butylketene reacts with diphenyl nitrone to give the indolones (10a) and (10b).The reaction of phenyl isocyanate with diphenyl nitrone, and the N-alkyl nitrones (1a) and (1d) gives the normal 1,3-dipolar cycloadducts without rearrangement.Ethoxycarbonyl-t-butylketene reacts with the N-phenyl nitrone (1d) to give an oxazolidinone , but reaction with the N-alkyl nitrones (1) gives only fluorenone azine.This ketene reacts with diphenyl nitrone to give the anil (15) and the dihydroindole (16).
- Evans, Andrew R.,Hafiz, Mushtaq,Taylor, Giles A.
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p. 1241 - 1246
(2007/10/02)
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- Electrochemical Studies of the Reduction of Fluorenone Triphenylphosphazine. Formation of the Stable Dimeric Dianion, (FlN2)2(2-)
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The electrochemical reduction of fluorenone triphenylphosphazine (Fl=NN=PPh3) in N,N-dimethylformamide - 0.1 M (n-Bu)4NClO4 is initially a one-electron process which affords the corresponding anion radical.Fl=NN=PPh3(-*) is unstable on the cyclic voltammetric time scale, decomposing by nitrogen-phosphorus bond cleavage (k = 0.45 s-1 at T = 1 deg C) to give PPh3 and 9-diazofluorene anion radical (FlN2(-*)).The latter species then reacts rapidly with either FL=NN=PPh3 or FlN2(-*) to give a stable dimeric dianion.The dianion, which was shown from chronoamperometric and coulometric gas-pressure studies to have the empirical formula (FlN2)2(2-), is oxidized in successive one-electron steps to (FlN2)2 which slowly loses N2 on the cyclic voltammetric time scale to give fluorenone azine (Fl=NN=Fl).The structure of the dimeric species is considered to be the tetraazatriene Fl=NN=NN=Fl.No evidence was obtained for the formation of the carbene anion radical, Fl(-*), via the loss of N2 from FlN2(-*).
- Herbranson, Dale E.,Theisen, F. J.,Hawley, M. Dale,McDonald, Richard N.
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p. 2544 - 2549
(2007/10/02)
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- Organic Reactive Intermediates: Part VII - Radical Anion Intermediates in Reduction of Fluorenone Hydrazone
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The reaction of fluorenone hydrazone (1) with KOH in DMSO-MeOH affords fluorenone azine (12) via radical anion derived from a diazoalkane intermediate (7).In this regard 1 exhibits departure from the well known Wolff-Kishner reduction.
- Handoo, Kishan L.,Gadru, Kanchan
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p. 839 - 840
(2007/10/02)
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- A Kinetic Study of the Reactions of Carbonyl Ylides Formed by the Addition of Fluorenylidene to Ketones
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Fluorenylidene addds to aliphatic ketones to give carbonyl ylide intermediates.With acetone, for example, laser flash photolysis experiments showed that the rate constant for this reaction was 1 x 107 M-1 s-1 in acetonitrile solvent.The resulting carbonyl ylide had an absorption spectrum with λmax = 640 nm in the absence of quenchers underwent ring closure to the corresponding oxirane.The lifetimes, τy, for the ring closure reaction are described by the equation -log(τy/s) = (13.26 +/- 0.11) - (10.96 +/- 0.12) / θ where θ = 2.3RT kcal mol-1.The spectra of the carbonyl ylides could be quenched with rate constants of circa 107 M-1 s-1 by electron-deficient olefins or oxygen.
- Wong, P. C.,Griller, D.,Scaiano, J. C.
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p. 6631 - 6635
(2007/10/02)
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- REGIOSELECTIVE MONOALKYLATION OF THE VICINAL cis-DIOL GROUP IN MANNOPYRANOSIDES USING DIARYLDIAZOALKANES-TIN(II) CHLORIDE
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Highly regioselective monoalkylations of the cis-2,3-diol group in mannopyranosides can be achieved with diaryldiazoalkanes in the presence of catalytic amounts of tin(II) chloride.With diazo(diphenyl)methane (1), its 4,4'-dimethyl (2) and 4,4'-dichloro (
- Petursson, Sigthor,wEbber, John M.
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- Organic Reactive Intermediates: Part V - Electron Transfer Oxidation of Hydrazones of Aromatic Ketones by Tris(p-bromophenyl)ammoniumyl Perchlorate and Cu(II) Perchlorate
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Stable radical cation salt, tris(p-bromophenyl)ammoniumyl perchlorate effects oxidation of some hydrazones of aromatic ketones by electron-transfer radical mechanism leading to azines as principal products.A strong parallelism exists when the oxidation is brought about by cupric perchlorate in acetonitrile.These electron transfer oxidants bring about the oxidation analogous to anodic oxidation.
- Hando, Kishan L.,Handoo, Sudesh K.
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p. 270 - 272
(2007/10/02)
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- Organic Reactive Intermediates: Part IV-Diazoalkane-mediated Oxidation of Fluoren-9-yl Anions in Oxygen Atmosphere, a Novel Redox Reaction
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A novel redox reaction between fluoren-9-yl anions and 9-diazofluorene is described.The electron-transfer from the carbanion brings about facile reduction of the diazoalkane via radical anion intermediates.In oxygen atmosphere, carbanion-derived radicals form oxygenated products in high yields.Other discernible pathways involve coupling of these radicals with diazoalkane molecules and radical coupling yielding azines and dimers respectively.
- Handoo, Kishan L.,Bahadur, Yogender
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p. 412 - 414
(2007/10/02)
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- Hypovalent Radicals. Chemical Trapping of Electrogenerated Diazoalkane Anion Radicals
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Diazoalkane anion radicals produced by electroreduction of diazodiphenylmethane (Ph2CN2) and 9-diazofluorene (FlN2) in the presence of certain proton donors yield the corresponding hydrazones (R2C=NNH2); formation of diphenylmethane from electroreduction of Ph2CN2 is shown to proceed by formation of the carbene anion radical Ph2C*-.
- Triebe, F. M.,Hawley, M. Dale,McDonald, Richard N.
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p. 574 - 575
(2007/10/02)
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- Syntheses and reactions of spirocyclopropaneanthrones. Part 2. Rearrangements and cyclopropyl ring-opening reactions of phenyl-substituted spirocyclopropaneanthrones and related compounds
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Diphenylspirocyclopropaneanthrones [(1c) and (1d)] thermally rearranged with ring expansion to 1,10b-dihydro-2H-aceanthrones (2), whereas the phenyl analogue (1b) did not rearrange under comparable conditions. Phenylspirocyclopropeneanthrone (3a), prepared by the carbenic reaction of 10-diazoanthrone (6) with phenylacetylene, thermally rearranged to 10bH-aceanthrone (11). By contrast, the diphenyl analogue (3b), from the reaction with diphenylacetylene, was thermally stable. The diazoketone (6) reacted with 9-methylenefluorene to give directly the rearrangement product (2g), instead of the dispirocyclopropaneanthrone (1g). Spirocyclopropane-and spirocyclopropene-anthrones [(1) and (3)] reacted under acidic conditions to yield cyclopropyl or cyclopropenyl ring-opened products. In these reactions, the ring was shown to open from the more substituted side. These reactions are discussed in mechanistic terms.
- Hirakawa, Kiyoichi,Nosaka, Toshikazu
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p. 2835 - 2841
(2007/10/02)
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