- Quantum Yields in the Photochemically Induced Radical Chemistry of Acyl Derivatives of Thiohydroxamic Acids
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Acyl derivatives of N-hydroxyquinazoline-4-thiones are a novel source of disciplined carbon radicals.Quantum yield determination reveals that photolysis of these compounds initiates radical chains, resulting in quantum yields up to φ = 60.Comparative studies with acyl derivatives of N-hydroxy-2-thiopyridone show that the quinazoline derivatives are more light-sensitive than the thiopyridone compounds.The carbon radicals thus formed from the former can be trapped selectively, without the formation of rearranged products (i.e. without the competition of the radicophilic thiocarbonyl group of the starting material with the radical trap).
- Barton, Derek H. R.,Blundell, Paul,Jaszberenyi, Joseph Cs.
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p. 6937 - 6942
(2007/10/02)
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- Sonication-Induced Halogenative Decarboxylation of Thiohydroxamic Esters
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The sonication of primary, secondary, and tertiary thiohydroxamic esters in CCl4 has led to their synthetic transformation to alkyl chlorides, bromides, or iodides.The high yields were comparable to the previous thermal-or photoinduced version of this same reaction.This radical reaction calls attention to the utility of ultrasound in production of trichloromethyl radical, which was concluded to initiate decomposition of the thiohydroxamic esters.
- Dauben, William G.,Bridon, Dominique P.,Kowalczyk, Bruce A.
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p. 6101 - 6106
(2007/10/02)
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- LIGHT INDUCED HALOGENATIVE DECARBOXYLATION OF THIOHYDROXAMIC ESTERS
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The generality of lidht initiated halogenative decarboxylation of thiohydroxamic esters was studied.This method gave high yields of alkyl chlorides, bromides and iodides derived from primary, secondary and tertiairy substituted carboxylic acids.
- Dauben, William G.,Kowalczyk, Bruce A.,Bridon, Dominique P.
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p. 2461 - 2464
(2007/10/02)
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- THE INVENTION OF RADICAL REACTIONS. PART XV. SOME MECHANISTIC ASPECTS OF THE DECARBOXYLATIVE REARRANGEMENT OF THIOHYDROXAMIC ESTERS
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Esters (mixed anhydrides) derived from aliphatic or alicyclic carboxylic acids (RCO2H) and thiohydroxamic acids 2 or 3 undergo a thermally or photochemically induced radical chain reaction to give sulphides 4 with loss of carbon dioxide.On irradiation at low temperature however, the chain reaction is essentially suppressed.Under these conditions moderate to good yields of dimers R-R are obtained from primary acids.The mechanistic and synthetic implications of these observations are discussed.
- Barton, Derek H. R.,Bridon, Dominique,Fernandez-Picot, Isabel,Zard, Samir Z.
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p. 2733 - 2740
(2007/10/02)
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- The Invention of New Radical Chain Reactions. Part 12. Improved Methods for the Addition of Carbon Radicals to Substituted Allylic Groups
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Reagents for the allylation of carbon radicals derived from the esters (mixed anhydrides) of N-hydroxy-2-thiopyridone have been investigated.Because of competition between the background reaction of decarboxylative rearrangement and the desired allylation process, conventional allylation reagents give moderate yields of the desired adducts.Improved yields are secured if the β-position bears an electron withdrawing group.A concerted addition and elimination process can be postulated.
- Barton, Derek H. R.,Crich, David
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p. 1613 - 1620
(2007/10/02)
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