Selectivity of Intramolecular Radical Addition Reactions Cyclization of ω-Alkenyl Radicals

Small ω-alkenyl radicals are known to cyclize exclusively via the unexpected Anti-Markownikow pathway which leads to cycloalkyl-methyl radicals as the observed reaction products. The strong kinetic preference diminishes, as the linking methylene chain becomes larger. Semiempirical calculations using MINDO/3-UHF allow to classify the observed reaction pathways as individual probes between allowed (n = 1, route A ) and electronically favourable (n = ∞, route M ) routes of reactions.