Chiral iminophosphoranes organocatalyzed asymmetric hydroxylation of 3-substituted oxindoles with oxaziridines
作者:Baocheng Li、Zhen-Jiang Xu、Jianwei Han
DOI:10.1016/j.tetlet.2018.05.018
日期:2018.6
Enantioselective hydroxylation of N-protected 3-substituted oxindoles has been developed via chiral iminophosphorane catalysis with oxaziridines as oxidants. As such, a variety of optically active 3-substituted-3-hydroxy-2-oxindoles were obtained in excellent yields (91–99%) and moderate to excellent level of enantiomeric excess (up to 94% ee).
Cu(<scp>ii</scp>)-catalyzed enantioselective oxygen atom transfer from oxaziridine to oxindole derivatives with chiral phenanthroline
作者:Yuki Naganawa、Tomotaka Aoyama、Hisao Nishiyama
DOI:10.1039/c5ob01840d
日期:——
In the presence of a Cu(II) complex of axially chiral, N,N,O-tridentate phenanthroline ligand (S)-2, asymmetric oxygen atom transfer of oxindole derivatives (3) using Davis’ oxaziridine (4) occurred to give the corresponding 3-aryl-3-hydroxy-2-oxindole derivatives (1) with excellent enantioselectivity (up to 96% ee). The X-ray crystallographic analysis of the isolated Cu(II) complex disclosed its N
Asymmetric Rubottom‐Type Oxidation Catalyzed by Chiral Calcium Phosphates
作者:Hualing He、K. S. Satyanarayana Tummalapalli、Linfei Zhu、Minglei Chen、Suvratha Krishnamurthy、Jon C. Antilla
DOI:10.1002/chem.202203720
日期:2023.2.16
A highly efficient catalytic asymmetric Rubottom-type oxidation is described. Using meta-chloroperbenzoic acid (m-CPBA) as the oxidant and chiral calcium phosphate as the catalyst, the facile transformation enables direct hydroxylation of N-Boc oxindoles and β-ketoesters in high yields (up to 99 %) and in a highly enantioenriched fashion (up to >99 % ee).
A direct transition-metal-free asymmetric hydroxylation using commercially available enantiopure Davis oxaziridine as an efficient oxidant is disclosed. An array of medicinally and optically active 3-aryl/alkyl-3-hydroxy-2-oxindoles with a tetrasubstituted stereocenter were obtained in good yields and enantioselectivities. The protocol features ease of operation, scalability, and good functional-group