STEREOCHEMICAL CONTROL IN RADICAL REACTIONS BY COMPLEXATION WITH LEWIS ACIDS

通过与路易斯酸络合实现自由基反应的立体化学控制

• 批准号: 07640786
• 负责人: NAGANO Hajime
• 金额: $ 0.96万
• 依托单位: OCHANOMIZU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07640786/
• 关键词: Radical reaction; Lewis acid; 1,2-Asymmetric induction; Allylation; Deuteration; Lanthanide; Chelation; ランタノイド

Stereoselectivity in the radical-mediated allylation of alpha-bromo-beta-silyloxy esters yielding alpha-allyl-beta-silyloxy esters was remarkably affected when the reaction was conducted in the presence of Ln(fod)_3. In the allylation of alpha-bromo-beta-silyloxysuccinate esters affording preferentially syn diastereomers through the chelated trasition states was required stoichiometric amount of the Lewis acid [Eu(fod)_3 or La(fod)_3] to maximize the stereoselectivities, whereas in the reaction of alpha-bromo-beta-silyloxybutanoateesters and alpha-bromo-beta-silyloxy-beta-phenylpropanoate ester the effect induced by the coordination of Eu(fod)_3 to the ester group was catalytic.Diastereoselectivity in the radical mediated allylation and deuteration reactions of beta-chiral beta-alkoxy-alpha-bromoaldehyde dimethyl acetals and a related alkoxy bromide were remarkably enhanced when the reactions were conducted in the presence of Lewis acid (MgBr_2-OEt_2 for allylation ; MgI_2 for deuteration).

Ln（fod）_3对α-溴代-β-硅氧基酯的烯丙基化反应的立体选择性有显著影响。在α-溴-β-甲硅烷基氧基琥珀酸酯的烯丙基化反应中，通过螯合过渡态优先得到顺式非对映异构体，需要化学计量量的刘易斯酸[Eu（fod）_3或La（fod）_3]以使立体选择性最大化，而在α-溴-β-硅氧基丁酸酯和α-溴-β-硅氧基-β-苯丙酸酯的反应中，Eu（fod）_在刘易斯酸（MgBr_2-OEt_2用于烯丙基化，MgI_2用于氘代）存在下，β-手性β-烷氧基-α-溴醛缩二甲缩醛和相应的溴代烷氧基的烯丙基化和氘代反应的非对映选择性显著提高。

项目成果

Hajime Nagano: "Highly Stereoselective Chelation-Controlled Allylation and Deuteration of α-Chiral α,α′-Dialkoxy Radicals" Chem.Lett.(10). 845-846 (1996)

Hajime Nagano：“高度立体选择性螯合控制的 α-手性 α,α-二烷氧基自由基的烯丙基化和氘化”Chem.Lett.(10)。