Chiral N-Heterocyclic Carbene Ligands Bearing a Pyridine Moiety for the Copper-Catalyzed Alkylation of<i>N</i>-Sulfonylimines with Dialkylzinc Reagents
作者:Takahiro Soeta、Tomohiro Ishizaka、Yuta Tabatake、Yutaka Ukaji
DOI:10.1002/chem.201404241
日期:2014.12.8
Amino acid‐derived chiral imidazolium salts, each bearing a pyridine ring, were developed as N‐heterocyclic carbene ligands. The copper‐catalyzed asymmetric alkylation of various N‐sulfonylimines with dialkylzinc reagents in the presence of these chiral imidazolium salts afforded the corresponding alkylated products with high enantioselectivity (up to 99 % ee). The addition of HMPA to the reaction
氨基酸衍生的手性咪唑鎓盐(每个带有吡啶环)被开发为N杂环卡宾配体。在存在这些手性咪唑鎓盐的情况下,用二烷基锌试剂对各种N-磺酰亚胺类化合物进行铜催化的不对称烷基化反应,可得到具有高对映选择性(最高ee高达99%)的相应烷基化产物。就化学收率和对映选择性而言,将HMPA作为共溶剂添加到反应混合物中至关重要。发现广泛的N-磺酰亚胺碱和二烷基锌试剂适用于该反应。