1227411-38-2Relevant articles and documents
Catalytic asymmetric synthesis of 3-(α-hydroxy-ss-carbonyl) oxindoles by a ScIII-catalyzed direct aldol-type reaction
Shen, Ke,Liu, Xiaohua,Zheng, Ke,Li, Wei,Hu, Xiaolei,Lin, Lili,Feng, Xiaoming
supporting information; experimental part, p. 3736 - 3742 (2010/07/13)
A direct catalytic asymmetric aldol-type reaction of 3-substituted- 2oxindoles 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), and > 99 % enantiomeric excess (ee)) under mild conditions, to deliver 3-(α-hydroxy-ss-carbonyl) oxindoles with vicinal quaternary-tertiary or quaternaryquaternary stereocenters. Even with 1 mol% catalyst loading or on scaleup (10 mmol of starting material), maintenance of ee was observed, which showed the potential value of the catalyst system. In studies probing the reaction mechanism, a positive nonlinear effect was observed and ScIII-based enolate intermediates were detected by using ESIMS. On the basis of the experimental results and previous reports, a possible catalytic cycle was assumed.