- Reduction of Dioxygen by Radical/B(p-C6F4X)3 Pairs to Give Isolable Bis(borane)superoxide Compounds
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Triplet dioxygen was reduced by TEMPO or trityl radicals in the presence of two molar equivalents of the strong B(p-C6F4X)3 (X: F or H) boron Lewis acids under mild conditions to give the bis(borane)superoxide systems 2. T
- Tao, Xin,Daniliuc, Constantin G.,Janka, Oliver,P?ttgen, Rainer,Knitsch, Robert,Hansen, Michael Ryan,Eckert, Hellmut,Lübbesmeyer, Maximilian,Studer, Armido,Kehr, Gerald,Erker, Gerhard
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supporting information
p. 16641 - 16644
(2017/12/13)
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- The rearrangement of the trityloxy radical: Sherlock holmes' most recent case
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Reopening the case: One hundred years after Wieland's original publication, the rearrangement of the trityloxy radical was studied by K. Ingold et al., who investigated the title reaction with the logical reasoning and intellectual prowess of true detecti
- Bucher, Goetz
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body text
p. 6934 - 6935
(2010/12/18)
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- Reactions of titanium alcoholates Ti(OR)4 (R = n-Bu, t-Bu) with tertiary organic and organometallic hydroperoxides
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tert-Butyl and cumyl hydroperoxides in the reactions with Ti(OR) 4 are reduced to alcohols with the evolution of oxygen via formation of titanium-containing peroxides and trioxides. The pathways of the reactions of Ti(OR)4 with triphenylelement hydroperoxides R3EOOH (E = C, Si, Ge) depend on element E and on the structure of R; the reactions involve the rearrangement of the peroxides, and with (n-BuO)4Ti the alkoxy group is oxidized either with preservation or with breakdown of the hydrocarbon skeleton. Pleiades Publishing, Inc., 2006.
- Stepovik,Gulenova
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p. 235 - 244
(2008/02/09)
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- Thermolysis of N-tetramethylpiperidinyl triphenylacetate: Homolytic fragmentation of a TEMPO ester
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Thermolysis of N-tetramethylpiperidinyl triphenylacetate (7, Ph 3CCO2T, T = 2,2,6,6-tetramethylpiperidinyl) in benzene at 146 °C leads to the formation of triphenylmethane (Ph3CH, 80%), tetramethylpiperidine (TH, 91%), and tetraphenylmethane (Ph4C, 9%). First-order rate constants for the decomposition at 132.8 and 150.0 °C were 2.20 × 10-6 and 2.88 × 10-5 s-1, respectively. In benzene-d6 solvent the triphenylmethane was formed as Ph3CD to the extent of 20%, as determined by 1H NMR and mass spectrometry. The results are interpreted as showing that Ph 3CCC2T undergoes thermolysis by concerted two-bond scission with formation of Ph3C., tetramethylpiperidinyl radicals and CO2. The formation of Ph4C occurs by addition of Ph3C. to benzene, followed by hydrogen atom abstraction from the resulting adduct. Calculations using DFT methods at the B3LYP/6-311++G** level were used to elucidate the bond fission of HCO2T (2), and indicate that cleavage to HCO2. and T. is favored by 7.8 kcal mol-1 relative to cleavage to HC(·)=O and TO., in agreement with the experimental results. Copyright
- Henry-Riyad, Huda,Tidwell, Thomas T.
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p. 559 - 563
(2007/10/03)
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- Chemiluminescence during thermolysis of the (Ph3COOCPh3)n-Ph3C. peroxide containing captured triphenylmethyl radical
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Chemiluminescence (CL) in the thermolysis of (Ph3COOCPh3)n-Ph3C. containing the triphenylmethyl radical captured during the synthesis of Gomberg's peroxide was found. Two CL emitters were identified: the triplet state of benzophenone (3Ph2CO*) and Ph3C.*. Ph3C.* is formed due to the energy transfer from the excited 3Ph2CO* generated in the disproportion of thermolysis intermediates, Ph3CO. radicals. This Ph3C.* luminescence is the first example of CL activation by an organic radical. Chemiluminescence during the thermolysis of Ph3COOCPh3 containing no Ph3C. is resulted from the emission of one emitter, 3Ph2CO*. The solid-phase CL was found during the oxidation of Ph3C. with dioxygen after the destruction of the crystalline lattice as a result of the thermolysis of the (Ph3COOCPh3)n-Ph3C. peroxide.
- Bulgakov,Kuleshov,Sharapova,Sadykov,Khursan
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p. 1194 - 1197
(2007/10/03)
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- Novel Transformations of 1,2-Dioxetanes: β-Hydroxy Ethers by Addition of Alkyllithium Reagents
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The reaction of 1,2-dioxetanes with alkyllithium reagents was investigated.The 3,3-disubstituted dioxetanes 2a,d and their halogen-substituted analogues 2b,c, which were used as probes to differentiate between the mechanistic alternatives (SN2 reactivity vs. single-electron transfer), reacted with n-BuLi to afford the β-hydroxy ethers 3a-d.Additionally, the epoxide 4 was obtained from dioxetanes 2b,c.The epoxide 5 and a small amount of acetophenone were found in the reaction of dioxetane 2c with triphenylmethyllithium, but only the minor part of the dioxetane-derived products could be identified.The observation of the epoxides 4 and 5 led to the mechanistic conclusion that nucleophilic attack (SN2 reactivity) is the most prominent process in this reaction.Key Words: Dioxetanes / Single electron transfer vs. nucleophilic attack / Ethers, β-hydroxy / Alkyllithium reagents
- Adam, Waldemar,Heil, Markus
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p. 235 - 241
(2007/10/02)
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- Arene Hydrides, 8. - SET vs. Nucleophilic Attack in Reactions of α-Bromoisobutyrophenone with Carbanions. Fragmentation of the Anion of Tetrahydrobianthracene
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SET is the main reaction pathway between α-bromoisobutyrophenone (1) and the carbanions 7a-j- of diarylmethanes or disubstituted acetonitriles: 7- 7. + e and e + 1 Br- PhCOCMe2. (3).Main secon
- Werry, Juergen,Stamm, Helmut,Sommer, Andreas
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p. 1553 - 1562
(2007/10/02)
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- The Reaction of Triphenylmethyl Bromide with Potassium O-Ethyl Dithiocarbonate (Potassium Xanthate) in Benzene and Cumene. A Note of Caution on the Application of the Radical Trap Dicyclohexylphosphine as a Probe for Electron-transfer-initiated Reactions of Triphenylmethyl Halides
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The title reaction was studied under conditions where homolysis of the triphenylmethyl-to-sulphur bond of the dithiocarbonate 1d, its main product does not take place, or is negligible.Triphenylmethane 1c, triphenylmethanol 1g and benzophenone were obtained as further products under argon in cumene and in the presence of oxygen in benzene, respectively.This, together with ESR studies, indicates that part of the dithiocarbonate 1d results from single-electron transfer from O-ethyl dithiocarbonate anion to triphenylmethyl bromide 1a and out-of-cage recombination of triphenylmethyl and xanthyl radicals 6a.The main pathways leading to dithiocarbonate 1d appear, under the conditions studied, to be either a polar pathway consisting of two successive SN2'-type steps and/or an SET-type reaction with rapid in-cage recombination of triphenylmethyl and xanthyl radicals 6a.The hydrogen-atom donor dicyclohexylphosphine (DCPH) may not be used for trapping of the triphenyl radicals formed in the title reaction because DCPH acts as a single-electron donor towards bromide 1a, i.e. it itself generates triphenylmethyl radicals from the bromide.
- Huszthy, Peter,Izso, Gyoengyi,Lempert, Karoly,Gyoer, Miklos,Rockenbauer, Antal
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p. 2009 - 2015
(2007/10/02)
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- The Reaction of Triphenylmethyl Halides with Tributylphosphine and Tributylamine in Apolar Solvents
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Triphenylmethyl bromide (1a) and chloride (1b) react with tributylphosphine and tributylamine in aromatic hydrocarbons by single electron transfer.The triphenylmethyl radicals produced (which may be detected by e.s.r. spectroscopy) abstract hydrogen from the solvent or the radical cations of the reagents to give triphenylmethane (1c), and are trapped by oxygen to give triphenylmethylperoxy radicals and subsequently benzophenone, triphenylmethanol (1d), and phenol.Tributylphosphine and tributylamine may act as hydrogen donors in the hydrogen-transfer processes involved in the formation of these oxygenation products.The halides (1a, b) and tributylphosphine furnish, in the absence of oxygen, in addition to triphenylmethane (1c) the tele substitution products (2a) and (2b), respectively.There is some evidence that the phosphonium salt (2a) is formed by an S'ET process, i.e. out-of-cage recombination of triphenylmethyl radicals and tributylphosphine radical cations or tributylphosphine.
- Huszthy, Peter,Izso, (nee Gergacz) Gyoengyi,Lempert, Karoly,Kajtar-Peredy, Maria,Gyoer, Miklos,et al.
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p. 1513 - 1520
(2007/10/02)
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- THE REACTION OF IMIDOYL RADICALS WITH MULTIPLE CARBON-CARBON BONDS
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A general view on the reaction between imidoyl radicals and carbon-carbon double or triple bonds is given; the synthesis of substituted quinolines starting from imines and alkenes is described, pointing out the differences with respect to the analogous reaction performed with alkynes.
- Leardini, Rino,Nanni, Daniele,Tundo, Antonio,Zanardi, Giuseppe
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p. 637 - 642
(2007/10/02)
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- Photoinduced Electron Transfer Oxygenation of Triphenylcarbenium Ion
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Photooxidation of triphenylcarbenium ion in the presence of an electron donor affords bis(triphenylmethyl) peroxide via one electron transfer from the electron donor to the excited singlet state of triphenylcarbenium ion.
- Futamura, Shigeru,Kamiya, Yoshio
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p. 1703 - 1706
(2007/10/02)
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- Triphenylmethyl Phenylcyanomethylenenitronate: Formation and Thermolysis
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The previously reported formation of carbon dioxide, α,α'-bis(tritylazo)stilbene (4), benzonitrile N-oxide (5), trityl isocyanate (6), and C33H25N3O (11) from a mixture ot trityl chloride and silver phenylcyanomethylenenitronate in toluene is now attributed to the initial formation at -20 deg C of trityl phenylcyanomethylenenitronate (3) and its dissociations at 5 deg C.The ester (3) was characterized by conversion into bromonitrophenylacetonitrile (7) by treatment with bromine, to p-nitrobenzoyl cyanide (8) by treatment with dinitrogen tetraoxide, to trityl alcohol by hydrolysis, and to a mixture of trityl alcohol and trityl peroxide by exposure to the atmosphere.The bisazostilbene (4) (18percent) and C33H25N3O, identified by X-ray crystallographic analysis to be 4,5-diphenyl-1-triphenylmethoxy-1,2,3-triazole (11) (24percent), were obtained from the nitronate ester (3) in toluene at 5 deg C; the nitrile oxide (5) and the isocyanate (6) were obtained in low yields from the ester (3) in dimethyl sulphoxide at 25 deg C.Hydrolysis converted the triazole (11) into 1-hydroxy-4,5-diphenyl-1,2,3-triazole (12) and trityl alcohol.Silver p-bromophenylcyanomethylenenitronate and trityl chloride afforded α,α'-bis-(tritylazo)-p,p'-dibromostilbene and its thermolysis product, p,p'-dibromodiphenylacetylene.Fragmentation of the ester (3) in presence of added phenyl isocyanate gave the bisazo compound (4) and 3,4-diphenyl-1,2,4-oxodiazol-5-one (18).A similar mixture stored at -20 deg C gave the triazole (11) and the oxadiazolone (18).Aroyl nitrile oxides as well as phenyl isocyanate suppressed the formation of the red bisazostilbene (4).The intermediacy of the N-trityl imine (14) of 4H-3-phenyl-1,2-oxazet-4-one-2-oxide in the thermolysis of the nitronate (3) was discussed.
- Boyer, Joseph H.,Manimaran, Thankiavelu,Ramakrishnan, Vayalakkavoor T.
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p. 2163 - 2170
(2007/10/02)
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- Aromatic Annelation by Reaction of Arylimidoyl Radicals with Alkynes: Evidence for the Intervention of a Spirocyclohexadienyl Radical in the Synthesis of Substituted Quinolines
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Arylimidoyl radicals, generated by hydrogen abstraction from N-arylideneanilines with di-isopropyl peroxydicarbonate, react with alkynes to give quinolines in good yields.The reaction also involves an intermediate spirocyclohexadienyl radical; the proposed mechanism is discussed.
- Leardini, Rino,Nanni, Daniele,Pedulli, Gian Franco,Tundo, Antonio,Zanardi, Giuseppe
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p. 1591 - 1594
(2007/10/02)
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- Single-electron-transfer-initiated Thermal Reactions of Arylmethyl Halides. Part 11. The Reaction of Trityl Halides with Sodium Methoxide in 2,2-Dimethoxypropane
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Trityl chloride (1a) and bromide (1b) furnish with sodium methoxide in 2,2-dimethoxypropane, in addition to several minor products, mixtures of the substitution products methyl trityl ether (1c) and p-methoxytriphenylmethane (2a), and of the reduction products triphenylmethane (1f) and p-diphenylmethyltritylbenzene (3a) which are the products of competing SN and single-electron transfer-initiated processes.Compound (1c) is suggested to be formed via two successive SN' processes rather than by either the SN1 or Sn2 mechanisms which are both disfavoured under the experimental conditions applied.
- Huszthy, Peter,Lempert, Karoly,Simig, Gyula
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p. 1323 - 1330
(2007/10/02)
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- Electron spin resonance study of the hyperfine splitting constants of naturally abundant carbon-13 and nitrogen-15 in diphenylmethyl tert-butyl aminoxyl (nitroxide). Solvent and temperature effects.
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The β- 13C and 15N hyperfine splitting constants in the phenyl radical adduct of phenyl tert-butyl nitrone (PBN), diphenylmethyl tert-butyl aminoxyl, have been measured as a function of solvent and temperature.
- Janzen, Edward G.
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p. 1653 - 1658
(2007/10/02)
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- Studies on the Development of the Tritylsulfenyl Group as a Nitrogen Protecting Group and Application in a Synthesis of δ-Coniceine
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The (triphenylmethyl)sulfenyl (tritylsulfenyl, TRS) group was found to posses properties which should make it useful as a nitrogen protecting group.The almost instantaneous reaction of TrSCl (6) with amines produced the corresponding triphenylmethanesulfenamides.The TRS group was found to render the nitrogen atom nonbasic and relatively nonnucleophilic, was stable to aqueous acid, aqueous base, and various reducing agents, and was moderately stable to Moffat oxidation conditions.The TRS group could be cleaved under mild conditions, generating the amine with either CuCl2/EtOH-THF, HI/THF-H2O, or trimethylsilyl iodide (Me3SiI)/CH2Cl2.A synthesis of δ-coniceine (16) illustrates carbon-carbon bond formation with tritylsulfenimine methodology and the utility of the tritylsulfenyl group as a nitrogen protecting group.
- Branchaud, Bruce P.
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p. 3538 - 3544
(2007/10/02)
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- Stereochemistry and Mechanisms of Reactions of Dioxygen Complexes with Organic Electophiles as Studied by Use of Chiral Reagents and Isotopic Labeling
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From reactions of PtO2L2 (L = PPh3, P(c-C6H11)3) with 1 mol of triphenylmethyl bromide or benzoyl bromide the corresponding (alkylperoxo)platinum(II) complexes L2PtBr(OOR) (1a, L = PPh3, R = CPh3; 1b, L = P(c-C6H11)3, R = CPh3; 2, L = PPh3, R = COPh) were isolated, which were well characterized by elemental analysis and IR spectroscopy.The complex 1a,b or 2 was treated with another mole of organic halides to give the corresponding dialkyl peroxides (Ph3COOCPh3, PhC(O)OOC(O)Ph) in good yields.Thus, the stepwise mechanism proposed previously for "metal-assisted peroxidations" was verified.A similar reaction of PtO2(PPh3)2 with an optically active (S)-(-)-α-phenethyl bromide produced a peroxoplatinum(II) complex, PtBr(OOCH(CH3)Ph)(PPh3)2 (3), which gave upon acidolysis (R)-(+)-α-phenethyl hydroperoxide.Reductive cleavage of 3 with NaBH4 gave (R)-(+)-α-phenethyl alcohol.Hence, it can be concluded that the reaction of PtO2L2 with organic halides proceeds via the SN2-type transition state.From the IR 18O isotopic shifts the O-O stretching band was assigned for the products from the reactions of PtO2L2 with acetone (4), benzophenone (5), 1,1-dicyano-2-methylpropene (8), and tetracyanoethylene (9).The 18O IR study also shows that the peroxy bond involved in these products is derived from PtO2L2.The reaction product (10a, L = PPh3; 10b, L = P(c-C6H11)3) obtained from PtO2L2 and CH3OOCCCCOOCH3 was also studied by 18O isotopic IR and 13C NMR spectra.Acidolysis of 10b gave dimethyl dihydroxymaleate ina good yield.Thus it was established that the reaction of an electrophilic acetylene with PtO2L2 results in the O-O bond cleavage.
- Tatsuno, Y.,Otsuka, Sei
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p. 5832 - 5839
(2007/10/02)
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- Chemiluminescence in the Reaction of a Sulfurane with Alkyl Hydroperoxides
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The reaction of Martin's sulfurane 1 with tert-butyl hydroperoxide, in the presence of 9,10-dibromoanthracene, emits light in two stages.The early stage, beginning on warming to about -40 deg C, coincides with the formation of olefin, and is intensified by degassing and quenched by oxygen or by organic sulfides.The later stage, seen on warming from -20 to -10 deg C, occurs during the formation of acetone from the hydroperoxide; this luminescence is eliminated by degassing and quenched by 2,6-di-tert-butyl-p-cresol and organic sulfides.Similar phenomena are observed with cumyl hydroperoxide.Relevant observations are reported on the NMR shifts produced in alcohol proton signals by diphenyl sulphoxide and dimethyl sulfoxide and on the CIDNP signals occurring during the reaction.Some conclusions are drawn concerning the mechanism of the luminescence.
- Bartlett, Paul D.,Aida, Tetsuo,Chu, Hsien-Kun,Fang, Tai-Shan
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p. 3515 - 3524
(2007/10/02)
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- Homosolvolysis
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Nitroxides, when used as solvents, promote the homolysis of a variety of weak bonds.Strong chemical evidence for the formation of free radicals is confirmed by e.s.r. studies in which the formation of free radicals has been monitored.This fission of single bonds of solute molecules dissolved in solvents with unpaired electrons is called homosolvolysis, in contrast to the common bond fission observed in polar solvents which is called heterosolvolysis.
- Scott, Alan C.,Tedder, John M.,Walton, John C.,Mhatre, Sushila
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p. 260 - 266
(2007/10/02)
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