The exocyclic effect: Protecting group strategy to enhance stereoselectivity in hydrogen transfer reactions of acyclic free radicals

被引:34
作者
Guindon, Y
Faucher, AM
Bourque, E
Caron, V
Jung, G
Landry, SR
机构
[1] Inst Rech Clin Montreal, Bioorgan Chem Lab, Montreal, PQ H2W 1R7, Canada
[2] Univ Montreal, Dept Biochem, Montreal, PQ H3C 3J7, Canada
[3] Univ Montreal, Dept Chem, Montreal, PQ H3C 3J7, Canada
[4] Univ Montreal, Fac Pharm, Montreal, PQ H3C 3J7, Canada
[5] Boehringer Ingelheim Canada Ltd, Biomega Res Div, Laval, PQ H7S 2G5, Canada
关键词
D O I
10.1021/jo971595s
中图分类号
O62 [有机化学];
学科分类号
070303 ; 081704 ;
摘要
To enhance the diastereoselectivity of the hydrogen transfer reaction of acyclic substrates bearing 1,2- or 1,3-diols, the feasibility of a strategy employing bifunctional protecting groups has been demonstrated. This strategy is based upon the "exocyclic effect" or the significant improvement of anti-selectivity exhibited by the reductions of substrates in which the two substituents (R-1 and Y) at the stereogenic center alpha to the radical center are linked together. A rationale for the excellent facial discrimination of these exocyclic radicals is offered based on an analysis of transition state models, which considers both steric and electronic factors.
引用
收藏
页码:9276 / 9283
页数:8
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