Opening of Tartrate Acetals Using Dialkylboron Bromide: Evidence for Stereoselectivity Downstream from Ring Fission
作者:Yvan Guindon、William W. Ogilvie、Josée Bordeleau、Wei Li Cui、Kathy Durkin、Vida Gorys、Hélène Juteau、René Lemieux、Dennis Liotta、Bruno Simoneau、Christiane Yoakim
DOI:10.1021/ja012530g
日期:2003.1.1
Johnson-type acetals derived from dimethyl tartrate give, after opening with Me(2)BBr and cuprate displacement, secondary alcohols with high diastereoselectivity (>30:1). The mechanism proposed for the induction of diastereoselectivity is downstream from the ring fission. It implies a direct participation of the Lewis acid as a source of nucleophile and the stereospecific transformation of the resulting
由酒石酸二甲酯衍生的约翰逊型缩醛,在用 Me(2)BBr 和铜酸盐置换后,产生具有高非对映选择性 (>30:1) 的仲醇。用于诱导非对映选择性的机制是环裂变的下游。这意味着路易斯酸作为亲核试剂来源的直接参与以及所得溴缩醛的立体有择转化通过反转和温度依赖性过程。通过所需醛与酒石酸二甲酯反应制备缩醛。助剂的去除是通过 SmI(2) 还原或通过使用甲醇盐的加成消除协议来完成的。