Manganese(III)-induced radical additions to 3,7-dimethylocta-1,6-diene

Abstract

The reactions of 3,7-dimethylocta-1,6-diene with organic radicals generated by oxidation with manganese(III) acetate of (i) acetic acid, ethyl acetoacetate, and pentane-2,4-dione, and (ii) dimethyl malonate, acetone, cyclopentanone, cyclohexanone, and acetophenone have been examined. Whereas addends in group (i) react mainly at the 6,7-bond, addends in group (ii) react at the 1,2-centre with ring closure to yield cyclopentane derivatives. In competition for the radical ·CH₂·CO·CH₃, 3,7-dimethyloct-1-ene, 2,6-dimethyloct-2-ene, and 3,7-dimethylocta-1,6-diene react in the ratio 4.8 : 21.4 : 73.8. Competition between acetone and [²H₆]acetone indicates a kinetic isotope effect of ca. 3 for the overall process of generation and addition of the radical. The possibility of reversible addition of a radical to an alkene is considered.