Stereoselective Radical Allylation of α-Iodo-β-Alkoxy Esters: Reversal of Facial Selectivity by Lewis Acid Complexation

Y. Guindon; B. Guérin; C. Chabot; N. Mackintosh; W. W. Ogilvie

doi:10.1055/s-1995-4995

Synlett 1995; 1995(5): 449-451
DOI: 10.1055/s-1995-4995

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Stereoselective Radical Allylation of α-Iodo-β-Alkoxy Esters: Reversal of Facial Selectivity by Lewis Acid Complexation

Y. Guindon^* , B. Guérin, C. Chabot, N. Mackintosh, W. W. Ogilvie

^*Department of Chemistry, Université de Montréal, Montréal, Québec, Canada H3C 3J7; Bio-Méga/Boehringer Ingelheim Research, Inc., 2100 Cunard Street, Laval, Québec, Canada H7S 2G5

Abstract

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The radical allylation of a series of α-iodo-β-alkoxy esters under bidentate chelation-controlled conditions is reported and compared with the analogous reactions under non-chelating conditions. The addition of MgBr₂⋅OEt₂ is shown to give excellent selectivity for the anti products, in some cases ratios greater than 100:1 are obtained. The reactions require initiation with Et₃B and can be inhibited by m- and p-dinitrobenzene, implying a radical based mechanism. Iodides, bromides and phenyl selenides all are suitable substrates.

1,2-Asymmetric Induction - Chelation control - Radical reaction - Allylation - Quaternary Carbon

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