Lewis Base Activation of Lewis Acids: Catalytic, Enantioselective Addition of Glycolate-Derived Silyl Ketene Acetals to Aldehydes
作者:Scott E. Denmark、Won-jin Chung
DOI:10.1021/jo8006539
日期:2008.6.1
A catalytic system involving silicon tetrachloride and a chiral, Lewis basic bisphosphoramide catalyst is effective for the addition of glycolate-derived silyl ketene acetals to aldehydes. It was found that the sense of diastereoselectivity could be modulated by changing the size of the substituents on the silyl ketene acetals. In general, the trimethylsilyl ketene acetals derived from methyl glycolates
涉及四氯化硅和手性路易斯碱性双磷酰胺催化剂的催化体系可有效地将乙醇酸衍生的甲硅烷基烯酮缩醛添加到醛中。发现可以通过改变甲硅烷基烯酮缩醛上取代基的大小来调节非对映选择性。一般情况下,三甲基甲硅烷烯酮缩醛选自甲基甘醇酸酯衍生的与α-氧气的大型保护基提供对映体富集的α,β二羟基酯具有高顺式-diastereoselectivity,而叔丁基二烯酮缩醛从α-笨重的酯衍生的甲氧基乙酸提供对映体富集的α,高β二羟基酯抗-diastereoselecitvity。