Chiral Amino Alcohol Accelerated and Stereocontrolled Allylboration of Iminoisatins: Highly Efficient Construction of Adjacent Quaternary Stereogenic Centers

摘要

We have developed a highly efficient asymmetric allylboration of ketimines with nonchiral gamma,gamma-disubstituted allylboronic acids by using a chiral amino alcohol as the directing group, which is otherwise challenging. The amino alcohol not only serves as a cheap source of nitrogen and chirality, but also dramatically enhances the reactivity. The versatility of this method was demonstrated by its ability to access all four stereoisomers with adjacent quaternary carbon centers. A reaction model was proposed to explain the diastereoselectivity and the rate-accelerating effect.