Catalytic Asymmetric Arylation of 3-Indolylmethanols: Enantioselective Synthesis of 3,3′-Bis(indolyl)oxindoles with High Atom Economy

The catalytic enantioselective arylation of 3-indolylmethanols has been established in an atom-economic fashion, which assembles isatin-derived 3-indolylmethanols and 3-methylindoles into biologically important 3,3-bis(indolyl)oxindoles bearing a quaternary stereogenic center in high yields and good enantioselectivities (approximate to 99% yield and 91:9 enantiomeric ratio). This reaction also represents the catalytic enantioselective synthesis of 3,3-bis(indolyl)oxindoles, which is applicable to a wide range of substrates, yielding a series of chiral 3,3-bis- (indolyl)oxindoles with structural diversity. Control experiments demonstrated that the NH group in the indole moiety of 3-indolylmethanol is important in obtaining good enantioselectivity, whereas the NH group of 3-methylindole plays a crucial role in the reactivity via the hydrogen bonding interaction with the catalyst.