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.
Metachloropehoxybenzoic acid promoted stereoselective synthesis of 2,5-disubstituted tetrahydrofurans from α or γ-allyl-β-hydroxy esters: A formal synthesis of (±) methyl nonactate
作者:Javed Iqbal、Anu Pandey、Bhanu P.S Chauhan
DOI:10.1016/s0040-4020(01)86451-6
日期:1991.1
A one pot stereoselectivesynthesis of cis or trans 2,5-disubstituted tetrahydrofurans 3–8 can be achieved in high yields via electrophilic cyclisation of the corresponding cis or trans α or γ-allyl-β-hydroxyesters mediated by metachloroperoxybenzoic acid. The tetrahydrofurans 5 or 6 may be converted into (±) methylnonactate by procedures described earlier. The role of methoxycarbonyl group during