- Kinetics of Intramolecular Alkyl Radical Attack on Sulfur in Disulfides and Thioesters
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The 4-(alkyldithio)butyl radicals 8a and c, and the 4-(phenyldithio)butyl radical 8b, generated from the corresponding esters of N-hydroxypyridine-2(1H)-thione, undergo fast exo-cyclisation by SHi attack at sulfur.Similarly, the 5-(alkyldithio)pentyl radical 8d undergoes 1,6-ring formation.The rate constants for cyclisation were determined by photolysis of the radical precursors in the presence of appropriate thiols.Butyl and pentyl radicals bearing ω-acetylthio or ω-benzoylthio substituents also undergo ring closure but much more slowly.The kinetics of these intramolecular SH2 reactions are discussed and compared with those for the intermolecular attack of hexyl radicals on diphenyl disulfide and on dibutyl disulfide.
- Beckwith, Athelstan L. J.,Duggan, Sandhya A. M.
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p. 1509 - 1518
(2007/10/02)
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- Synthesis of Disulfides via Sulfenylation of Alkyl and Aryldithiopyridine N-Oxides
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Alkyl and aryldithiopyridine N-oxides were prepared by reaction of 2,2'-dithiopyridine-1,1'-dioxide with various thiols in high yields.Some of the mixed disulfide products could in turn be used to sulfenylate efficiently other thiols.Therefore, practical and efficient synthetic methods for both symmetrical and unsymmetrical disulfides were developed.
- Barton, Derek H. R.,Chen, Chen,Wall, G. Michael
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p. 6127 - 6138
(2007/10/02)
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- A Convenient Method for Kinetic Studies of Fast Radical Rearrangements. Rate Constants and Arrhenius Function for the Cyclopropylcarbinyl Radical Ring Opening
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An indirect method for studying the kinetics of radical rearrangements employing N-hydroxypyridine-2-thione esters as radical precursors and hydrogen atom transfer from thiophenol as the basis trapping reaction is demonstrated in a study of an archetypal fast radical reaction, the cyclopropylcarbinyl radical ring opening.Rate constants measured over the temperature range -37 to 50 deg C gave a temperature-dependent function for the ring opening of log(k/s-1)=(13.0+/-0.14)-(6.8+/-0.2)/θ and a rate constant for ring opening at 25 deg C of 1.0E8 s-1.The kinetic values from this work were combined with rate data from low-temperature ESR studies and higher temperature nitroxyl radical trapping studies to give an Arrhenius function of log(k/s-1)=13.15-7.05/θ that is recommended for calculations of rate constants for the title ring opening.
- Newcomb, Martin,Glenn, Anne G.
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p. 275 - 277
(2007/10/02)
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