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The iodine–magnesium exchange reaction with i -PrMgCl allows a mild preparation of functionalized arylmagnesium compounds bearing a leaving group in the molecule. With the appropriate transition-metal catalyst (a copper or cobalt salt), cyclization reactions occur leading to five- or six-membered ring systems in good yields.

In order to understand the heterolytic cleavage of 4′-DNA radical 1 and the regioselective attack of nucleophiles at the intermediate DNA radical cation 3, the chemistry of model radical 8 was studied. It turned out that the heterolytic cleavage in water is favored over homolysis because of the effective solvation of the ions 9 and 10. The regioselectivity of the nucleophilic attack at radical cation 10 can be explained with the valence bond configuration mixing (VBCM) model.

Anthracene (III) and the derivatives 9-methoxymethylanthracene (IV), 9-cyanoanthracene (V) and (E-3-phenyl-prop-2-ene-1-yl(anthracene-9-methyl)-ether) (I) were subjected to irradiation at inca347 nm in dilute deoxygenated acetonitrile solution at room temperature. With the aid of the flash photolysis method employing fluorescence, optical absorption and electrical conductivity measurements the monophotonic photoionization and the formation of free ions was evidenced for compounds III‐V. In the case of the bichromophoric compound I a photocurrent was not observed although a transient optical absorption attributable to the radical anion of the arthracene moiety was detected. Moreover, the fluorescence lifetime of I was found to be definitely shorter than that of IV (model compound). On this basis it was concluded that a certain fraction of electronically excited singlet states of I is deactivated via intramolecular electron transfer. The transient zwitter ions formed in this way, overwhelmingly undergo a self-reaction thus regenerating I, but a small portion undergoes an intramolecular Diels‐Alder reaction forming VI, the only photoproduct. The quantum yield is (VI)0.04. # 1999 Elsevier Science S.A. All rights reserved.

Stereoselective radical reactions are observed with chiral methacrylamides 3 and 7 . although the π-systems are twisted to a considerable extent.