Unique Steric Effect of Geminal Bis(silane) To Control the High Exo-selectivity in Intermolecular Diels–Alder Reaction

详细信息    查看全文

• 作者：Zengjin Liu ; Xinglong Lin ; Na Yang ; Zhishan Su ; Changwei Hu ; Peihong Xiao ; Yanyang He ; Zhenlei Song
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：February 17, 2016
• 年：2016
• 卷：138
• 期：6
• 页码：1877-1883
• 全文大小：583K
• ISSN：1520-5126

文摘

The unique steric effect of geminal bis(silane) [(R₃Si)₂CH] allows an exo-selective intermolecular Diels–Alder reaction of geminal bis(silyl) dienes with α,β-unsaturated carbonyl compounds. The approach shows good generality to form ortho–trans cyclohexenes in good yields with high exo-selectivity and high enantioselectivity in some asymmetric cases. The excellent exo-stereocontrol aptitude of (R₃Si)₂CH group is highlighted by comparing with R₃SiCH₂ and R₃Si groups, which leads to endo-selectivity predominantly. The conformational analysis of dienes suggests that (R₃Si)₂CH group effectively shields both sides of the diene moiety, ensuring the desired exo-selectivity. Moreover, the geminal bis(silane) can be further functionalized to transform the resulting ortho–trans cycloadducts into useful synthons, which makes the approach hold great potential for organic synthesis.