Stereoselective Radical Carbon−Carbon Bond Forming Reactions of β-Alkoxy Esters:  Atom and Group Transfer Allylations under Bidentate Chelation Controlled Conditions

The radical allylation of a series of β-alkoxy esters using allyltrimethylsilane in the presence of MgBr2· OEt2 is described. Under bidentate chelation-controlled conditions, allyltrimethylsilane rivals allyltributyltin in efficiency and is a superior reagent from ecological and practical perspectives. The reactions work with iodides and bromides as well as phenylselenides. The isolation of γ-phenylseleno intermediates indicates that the reaction proceeds by an atom transfer process. These reactions require initiation with Et3B and can be inhibited by galvinoxyl, m- and p-dinitrobenzene indicating that this atom transfer sequence involves the intermediacy of radicals.