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

摘要

The radical allylation of a series of beta-alkoxy esters using allyhrimethylsilane in the presence of MgBrr 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 gamma-phenylseleno intermediates indicates that the reaction proceeds by an atom transfer process. These reactions require initiation with Et_3B and can be inhibited by galvinoxyl, m- and p-dinitrobenzene indicating that' this atom transfer sequence involves the intenpediacy of radicals.