Abstract
Oxidative free-radical cyclization of 11a or 11b in the presence of Mn(III) and Cu(II) leads to the expected dienylcyclopentane 14 by rapid oxidation of the kinetically formed cyclopentanealkyl radical 13. Oxidative cyclization of 11a with Mn(III) only in ethanol or with benzoyl peroxide in cyclohexane affords a mixture of the stereoisomers of methylhydrindane 15. As expected, the first cyclization of the stabilized acyclic radical 12 is reversible. The second cyclization of the unstabilized cyclohexyl radical 17 leads to the hydrindanemethyl radical 16.