- Triphenylsulfonium Salt Photochemistry. New Evidence for Triplet Excited State Reactions
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Direct and sensitized photolysis of triphenylsulfonium salts can generate the triplet state which yields diphenyl sulfide as the major photoproduct.Triplet sensitization is observed in the presence of ketones with ET > 74 kcal/mol, and the efficiency of sensitization correlates qualitatively with increasing ET of the sensitizer.In contrast, the singlet excited state yields mainly (phenylthio)biphenyls in addition to diphenyl sulfide.
- Dektar, John L.,Hacker, Nigel P.
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- A novel electron beam-induced reaction of sulfonium salt in the crystalline state
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The electron beam irradiation of triphenylsulfonium methanesulfonate in the crystalline state provides a new benzene-substituted sulfonium salt. This product has not been observed either by photolysis in the crystalline state nor by electron beam irradiation in a solution. The formation of the substitution product was confirmed by GC-MS analysis.
- Moon, Seongyun,Maekawa, Yasunari,Yoshida, Masaru
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- Photochemical reaction of onium salts with N,N-dimethylaniline: Evidence for photoinduced electron transfer
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Direct photolysis of diphenyliodonium salts gives significantly more iodobiphenyls than in the presence of dimethylaniline. An electron transfer reaction from the singlet excited state of dimethylaniline is proposed.
- Buijsen,Hacker
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- A New Mechanism for Photodecomposition and Acid Formation from Triphenylsulphonium Salts
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A new photodecomposition pathway for triphenylsulphonium salts yields phenylthiobiphenyls by a cage fragmentation-recombination process as major products, in addition to diphenyl sulphide; a new mechanism for acid formation is described.
- Dektar, John L.,Hacker, Nigel P.
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- Triphenylsulfonium topophotochemistry
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The products from the 193 nm irradiation of triphenylsulfonium nonaflate (TPS) embedded in a poly(methyl methacrylate) (PMMA) film have been characterized. The analysis of the photoproduct formation was performed using chromatographic techniques including HPLC, GPC and GC-MS as well as UV-vis and NMR spectroscopic methods. Two previously unreported TPS photoproducts, triphenylene and dibenzothiophene, were detected; additionally, GPC and DOSY-NMR spectroscopic analyses after irradiation suggested that TPS fragments had been incorporated into the polymer film. The irradiation of acetonitrile solutions containing 10% w/v PMMA and 1% w/v TPS in a 1 cm-path-length cuvette showed only a trace amount of triphenylene or dibenzothiophene, indicating that topochemical factors were important for the formation of these molecules. The accumulated evidence indicates that both products were formed by in-cage, secondary photochemical reactions: 2-(phenylthio)biphenyl to triphenylene, and diphenylsulfide to dibenzothiophene.
- Despagnet-Ayoub,Kramer,Sattler,Sattler,Labeaume,Thackeray,Cameron,Cardolaccia,Rachford,Winkler,Gray
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- A benzannulation protocol to prepare substituted aryl amines using a michael-aldol reaction of β-keto sulfones
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(Chemical Equation Presented) A practical benzannulation method to prepare variously substituted aryl amines and sulfides was developed. The approach involves a Michael-aldol reaction of β-keto sulfones with enones followed by a subsequent condensation of the initial adduct with various amines. The base-induced Michaelaldol cascade proceeds smoothly with a number of different β-keto sulfones, affording the adducts as single diastereomers. Heating the resulting Michael-aldol product with an amine in toluene at 120°C results in the formation of a transient enamine, which then undergoes loss of phenyl sulfenic acid to furnish the aromatized amine in good yield. A related reaction also occurred when the Michael-aldol product was heated with thiols or alcohols, giving rise to aryl-substituted sulfides or ethers.
- Kiren, Sezgin,Padwa, Albert
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experimental part
p. 7781 - 7789
(2009/12/30)
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- One-step arylthiolation of aromatic compounds by disulfide radical cations generated from oxidation of diaryl disulfides with aluminium chloride
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Reactions of di(phenyl and 4-tolyl) disulfides 1a and 1b with PhX 3a-e (X = H, Me, Et, Ph and Cl) in the presence of AlCl3 at 25°C give diaryl sulfides 4-6 by aromatic arylthiolation via the disulfide radical cations 2, along with thiophenols 7 formed in the incomplete reactions. Competitive intramolecular reactions of 2a also yield diphenyl sulfide 4a or/and thianthrene 8. However, the reactions of bis(4-chlorophenyl and 4-fluorophenyl) disulfides 1c and 1d selectively lead to the aromatic arylthiolation in high yields. The Hammett ρ = -8.8 at 25°C for the phenylthiolation in the reactions of 1a is more negative than that (ρ = -7.0 at -30°C) using SbCl5 instead of AlCl3, and the value ρ = -8.0 for the arylthiolation using 1d is less negative than that using 1a. These and the other mechanistic aspects support the arylthiolations via 2.
- Takeuchi, Hiroshi,Suga, Keisuke
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p. 1803 - 1808
(2007/10/03)
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- Photochemistry of triarylsulfonium salts
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The photolysis of triphenylsulfonium, tris(4-methylphenyl)sulfonium, tris(4-chlorophenyl)sulfonium, several monosubstituted (4-F, 4-Cl, 4-Me, 4-MeO, 4-PhS, and 4-PhCO), and disubstituted (4,4′-Me2 and 4,4′-(MeO)2) triphenylsulfonium salts was examined in solution. It was found that direct irradiation of triphenylsulfonium salts produced new rearrangement products, phenylthiobiphenyls, along with diphenyl sulfide, which had been previously reported. Similarly, the triarylsulfonium salts, with the exception of the [4-(phenylthio)phenyl]diphenylsulfonium salts, gave the new rearrangement products. The mechanism for direct photolysis is proposed to occur from the singlet excited state to give a predominant heterolytic cleavage along with some homolytic cleavage. The heterolytic cleavage gives phenyl cation and diphenyl sulfide, whereas homolytic cleavage gives the singlet phenyl radical and diphenylsulfinyl radical cation pair. These pairs of intermediates then produce the observed photoproducts by an in-cage recombination mechanism and also by reactions with the solvent. The effect of solvent viscosity, solvent polarity, anion, and aryl substituent was examined. The triplet sensitization of the sulfonium salts was also investigated. In contrast to previous reports, the triplet state of the sulfonium salt is labile, leading to a triplet geminate radical pair of phenyl radical and diphenylsulfinyl radical cation. These species ultimately form benzene and diphenyl sulfide as products. Direct photolysis of the [4-(phenylthio)phenyl]diphenylsulfonium salt, gave exclusively diphenyl sulfide, benzene, and acid and decomposes via the triplet excited state.
- Dektar, John L.,Hacker, Nigel P.
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p. 6004 - 6015
(2007/10/02)
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- CATIONIC PHOTOINITIATORS: SOLID STATE PHOTOCHEMISTRY OF TRIPHENYLSULFONIUM SALTS
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Triphenylsulfonium bromide, triflate, tetrafluoroborate, hexafluoroarsenate, hexafluorophosphate and hexafluoroantimonate were irradiated in solution and in the solid state.The photoproducts, 2-, 3- and 4-phenylthiobiphenyl are formed by an in-cage fragmentation-recombination mechanism, whereas diphenylsulfide is formed by a cage-escape reaction.In dilute solution, the ratio of cage to escape products is approximately one for each salt.Also in concentrated solutions, an identical cage:escape ratio is observed for all salts except for the bromide, which favors the escape reaction.Photolysis of the salts in the solid state shows remarkable counter ion dependence and cage:escape ratios as high as 5:1 are observed.The mechanism for both in-cage and escape reactions is described.
- Hacker, Nigel P.,Leff, Daniel V.,Dektar, John L.
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p. 505 - 511
(2007/10/02)
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