Intramolecular Conjugate Addition ofα,β-Unsaturated Lactones Having an Alkanenitrile Side Chain : Stereocontrolled Construction of Carbocycles with Quaternary Carbon Atoms
Intramolecular Conjugate Addition ofα,β-Unsaturated Lactones Having an Alkanenitrile Side Chain : Stereocontrolled Construction of Carbocycles with Quaternary Carbon Atoms
复制标题
具有烷腈侧链的α,β-不饱和内酯的分子内共轭加成：季碳原子碳环的立体控制结构
作者：
Yoshimura;F.; Torizuka;M.; Mori;G.; Tanino;K.
基于α，β-不饱和内酯与链腈侧链的立体选择性环化反应，发展了一种有效的合成具有全碳季中心的碳环的方法。在三异丙基氯硅烷（TIPSCl）存在下，用六甲基二硅基氨基锂（LiHMDS）处理底物，生成相应的α-氰基碳负离子，这些碳负离子易于进行分子内共轭加成反应。发现三氟甲磺酸三甲基甲硅烷基酯（TMSOTf）和三乙胺的组合使用对于环化反应也是有效的，而不使用强碱。有趣的是，在两种环化方法中观察到不同的立体化学结果。
An efficient method for constructing carbocycles with all-carbon quaternary stereocenters has been developed on the basis of a stereoselective cyclization reaction of α, β-unsaturated lactones having an alkanenitrile side chain. Treatment of the substrate with lithium hexamethyldisilazide (LiHMDS) in the presence of triisopropylsilyl chloride (TIPSCl) led to the generation of the corresponding α-cyano carbanion species which readily underwent an intramolecular conjugate addition reaction. It was found that the combined use of trimethylsilyl trifluoromethanesulfonate (TMSOTf) and triethylamine is also effective for the cyclization reaction without using a strong base. Interestingly, different stereochemical outcomes were observed in the two cyclization methods.