Radical Migration–Addition of <i>N</i>-<i>tert-</i>Butanesulfinyl Imines with Organozinc Reagents
作者:Wei Huang、Jian-Liang Ye、Wei Zheng、Han-Qing Dong、Bang-Guo Wei
DOI:10.1021/jo401640c
日期:2013.11.15
A novel migration-addition sequence was discovered for the reaction of enantioenriched N-tert-butanesulfinyl with iminoacetate la functionalized benzylzinc bromide reagents, producing tert-leucine derivatives in excellent diastereoselectivity (dr 98:2). The absolute configurations of two new chiral centers were unambiguously assigned by chemical transformations and X-ray crystallography. In addition, the regio- and diastereoselectivities of this novel reaction were both explained through the key N-sulfinamine intermediate M6 generated by the tert-butyl radical attack on the imine. Computational analysis of this reaction process, which was performed at the B3LYP/6-311++G(3df,2p)//B3LYP/6-31G*-LANL2DZ level, also supported our proposed two-stage mechanism.