Journal of the American Chemical Society, Vol.118, No.50, 12528-12535, 1996
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 allyltrimethylsilane in the presence of MgBr2 . OEt(2) 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 gamma-phenylseleno intermediates indicates that the reaction proceeds by an atom transfer process. These reactions require initiation with Et(3)B and can be inhibited by galvinoxyl, m- and p-dinitrobenzene indicating that this atom transfer sequence involves the intermediacy of radicals.
Keywords:ALPHA-SULFINYL RADICALS;TRANSFER ADDITION-REACTIONS;LEWIS-ACID;1;2-ASYMMETRIC INDUCTION;ACYCLIC RADICALS;SUBSTITUTED RADICALS;DIMETHYLBORON BROMIDE;MEDIATED REDUCTION;CYCLIZATION;COMPLEXATION