Catalytic Asymmetric Synthesis of 3-(α-Hydroxy-β-carbonyl) Oxindoles by a Sc<sup>III</sup>-Catalyzed Direct Aldol-Type Reaction
作者:Ke Shen、Xiaohua Liu、Ke Zheng、Wei Li、Xiaolei Hu、Lili Lin、Xiaoming Feng
DOI:10.1002/chem.200903471
日期:2010.3.22
A direct catalytic asymmetric aldol‐type reaction of 3‐substituted‐2‐oxindoles with glyoxal derivatives and ethyl trifluoropyruvate, catalyzed by a chiral N,N′‐dioxide–Sc(OTf)3 (Tf=trifluoromethanesulfonyl) complex, has been developed that tolerates a wide range of substrates. The reaction proceeds in good yields and excellent enantioselectivities (up to 93 % yield, 99:1 diastereomeric ratio (dr),
已开发出手性N,N'-二氧化物-Sc(OTf)3(Tf =三氟甲磺酰基)配合物催化的3-取代-2-氧吲哚与乙二醛衍生物和三氟丙酮酸乙酯的直接催化不对称醛醇型反应,耐受各种基材。在温和的条件下,反应以良好的收率和出色的对映选择性(高达93%的收率,99:1的非对映体比率(dr)和> 99%的对映体过量(ee))进行,以生成3-(α-羟基-β-羰基)的吲哚具有邻近的四级到三级或四级到四级立体中心。即使催化剂负载量为1 mol%或按比例放大(起始原料为10 mmol),也可保持ee观察到,这表明了催化剂体系的潜在价值。在研究反应机理的研究中,观察到了积极的非线性效应,并使用ESIMS检测了基于Sc III的烯醇酸酯中间体。根据实验结果和以前的报告,假定可能的催化循环。