Manganese(III)-mediated oxidative free-radical cyclisations of allenyl malonates

The regioselective synthesis of alkenylcyclanones by the oxidative radical cyclisation of malonyl radicals onto both allenes and an allylsilane is reported, along with the diastereoselective formation of [3.3.0]-bicyclic gamma-lactones from two of these alkenylcyclanones. Furthermore, the cyclisation of 3-,4- and 5-allenyl malonates on exposure to manganese(III) acetate under both oxidative and reductive termination conditions is reported. (C) 2009 Elsevier Ltd. All rights reserved.