Free Radicals in Synthesis and Biology

Free-radical reactions have been for long time the domain of the physical chemists and the basic chemical industry (polymerization of vinyl monomers, oxidation by molecular oxygen, chlorination of methane etc.), where the use of simple molecules and the possibility of partial conversions without heavy problems of product separations makes less dramatic the aspects of regio and chemoselectivity. As synonym of unselectivity, free radical reactions were considered of poor use in the synthesis of fine chemicals or sophisticated molecules, where a high selectivity is an essential condition for the success, or in the involvement of biological processes. Within the last 15 years, however, an authentic explosion of synthetic applications of free radical reactions occurred; they have gained a remarkable position among the selective methods of synthesis. At the same time the great importance of free radical reactions in fundamental biological processes and in the metabolism of drugs has been recognized. Thus a specialized meeting on these topics was generally felt appropriate. I had the honour and the onus to organize this workshop because for more than 30 years I have been involved in the research of free radical reactions. Thanks to a generous grant from NATO Scientific Affairs Division and the financial support of CNR and chemical industry (Montedison, Enichem, Zambon) such a meeting among almost 50 specialists and 15 observers of sufficient standard to take advantage of the discussion, became possible at Bardolino (Italy).

Contenu

1. Captodative Substituent Effects in Synthesis.- 2. The Influence of gem-Substitution on the CC-Bond.- 3. Iodine Atom Transfer Reactions in Organic Synthesis.- 4. Alkyl Iodides as Source of Alkyl Radicals, Useful for Selective Syntheses.- 5. Introduction of a Single Electron-with-drawing Carbon Substituent into ? -Deficient N-Heteroarenes by Means of Free-Radical Reactions: Strategies and Synthetic Applications.- 6. Free Radical Syntheses of Pyridylderivatives: Influence of the Solvent.- 7. Photoinitiated Radical Reactions of 1-(4?-Pyridyl)-4-Pyridane and Its N-Protio and N-Methyl derivatives. Dimerization and Polymerization Reactions.- 8. Radical Reactions with Organocobalt Complexes.- 9. New Ways of Generating Stannyl Radicals for Organic Syntheses.- 10. Silanes as New Reducing Agents in Organic Synthesis.- 11. Acyl, Imidoyl and Other Hetero-substituted Free Radicals as Intermediates in the Synthesis of Cyclic Organic Compounds.- 12. Some Studies on Carbonyl Radical Cyclizations on the Synthesis of 2-Deoxy-?-D-glycosides by Stereoselective Radical Reactions.- 13. Stereoselective Formation of Linear Aza-Triquinanes by Three Consecutive Radical Ring Closures.- 14. Synthetic Applications of Substitution and Addition Reactions Promoted by Cerium (IV) Ammonium Nitrate.- 15. Use of Homolytic Redox Processes in Organic Syntheses.- 16. One-Electron Redox Reactions between Radicals and Molecules. Dominance of Inner-Sphere Mechanisms.- 17. Electron-Transfer Photosensitization in the Oxidation of Alkyl Aromatics and Heteroaromatics.- 18. Selenium Radical Ions in Organic Synthesis.- 19. A. Synthetically Useful Source of Alkyl and Acyl Radicals.- 20. Chlorination of Hypochlorous Acid. Free-Radical versus Electrophilic Reactions.- 21. Induced Decomposition of Peroxycompounds in Synthesis: Free Radical Functionalization of Crown Ethers.- 22. Unwanted Synthesis in Combustion and Pyrolysis: Soot and Dioxins.- 23. Polar Effects on Radical Addition Reactions: An Ambiphilic Radical.- 24. The Effect of Temperature in the Reactions of Arenesulphonyl Radicals.- 25. Synthesis of New 5-Nitroimidazoles Highly Active against Anaerobes by Substitution Reactions which Proceed via Radical and Radical-Anion Intermediates.- 26. Electron Spin Resonance Studies of the Reactions of .OH and SO4.- Radicals with DNA, Polynucleotides and Single Base Model Compounds.- 27. Detection of Free Radicals in Biochemistry by Electron Spin Resonance Spectroscopy.- 28. Error in Enzymic Stereospecificity as a Probe for the Occurence of Radical Intermediates.- 29. Kinetics of Peroxyl Radical Reactions in Model Biomembranes.- 30. Rearrangements of Optically Pure Hydroperoxides.- 31. In vivo Detection of Free Radical Metabolites.- 32. The Involvement of Free Radicals in the Metabolism of Drugs.- 33. The Formation of Fluorescent Pigments Due to Radicals in Biological Tissues.- 34. The Chemistry/Biochemistry Interface in Free Radical Reactions.