Stereoselective Radical Carbon−Carbon Bond Forming Reactions of β-Alkoxy Esters: Atom and Group Transfer Allylations under Bidentate Chelation Controlled Conditions
摘要:
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.
Comparative study of the vicinal functionalization of olefins with 2:1 bromide/bromate and iodide/iodate reagents
作者:Manoj K. Agrawal、Subbarayappa Adimurthy、Bishwajit Ganguly、Pushpito K. Ghosh
DOI:10.1016/j.tet.2009.01.095
日期:2009.4
halohydrins, halo methyl ethers, and halo acetates from olefins using 2:1 Br−/BrO3− and I−/IO3− reagents. In many cases both reagents afforded products selectively in high yields. The highest halogen atom efficiencies attained were 97% and 93% for Br−/BrO3− and I−/IO3−, respectively. Of the two reagents, I−/IO3− was established to be the preferred reagent for vicinal functionalization of linear alkenes and