Alkene-allenecyclopropane radical cyclisations promoted by tris-(trimethylsilyl)silane

Treatment of the butenyl-substituted allenecyclopropanes 5 and 12 with tris-(trimethylsilyl)silane (TTMSS)–AIBN results in facile radical cyclisations into the cyclopropane-carbon centres of the allene moieties, followed by cyclopropane ring-opening and allene isomerisation, leading to the bicyclic 1,3-dienes 10 and 13, respectively. By contrast, treatment of the pentenyl-substituted allenecyclopropane 15a and the iodoethane 18 with TTMSS–AIBN, led to the alkylsilane 16, and the enyne 21, respectively. Desilylation of 10 and 13 gave the corresponding bicyclic hydrocarbons.