STEREOSELECTIVE RADICAL CARBON-CARBON BOND-FORMING REACTIONS OF BETA-ALKOXY ESTERS - ATOM AND GROUP-TRANSFER ALLYLATIONS UNDER BIDENTATE CHELATION CONTROLLED CONDITIONS

The radical allylation of a series of beta-alkoxy esters using allyltr imethylsilane in the presence of MgBr2 . OEt(2) is described. Under bi dentate chelation-controlled conditions, allyltrimethylsilane rivals a llyltributyltin in efficiency and is a superior reagent from ecologica l and practical perspectives. The reactions work with iodides and brom ides as well as phenylselenides. The isolation of gamma-phenylseleno i ntermediates indicates that the reaction proceeds by an atom transfer process. These reactions require initiation with Et(3)B and can be inh ibited by galvinoxyl, m- and p-dinitrobenzene indicating that this ato m transfer sequence involves the intermediacy of radicals.