title: Asymmetric Hydrogenation of Unprotected Indoles Catalyzed by η(6)-Arene/N-Me-sulfonyldiamine-Ru(II) Complexes.
abstract: Protecting-group-free transformation is a challenging and important issue in atom-economical organic synthesis. The η(6)-arene/N-Me-sulfonyldiamine-Ru(II)-BF4 complex-catalyzed asymmetric hydrogenation of 2-substituted unprotected indoles in weakly acidic hexafluoroisopropanol gives optically active indoline compounds with up to >99% ee. Under mild reaction media, halogen atoms and synthetically important protecting groups (e.g., silyl ether, acetal, benzyl ether, and ester) on indoles are maintained, which is advantageous for the synthesis of further complex indoline molecules.
authors: Molecular Chirality Research Center, Department of Chemistry, Graduate School of Science, Chiba University , 1-33 Yayoi, Inage-Ku, Chiba 263-8522, Japan.|Corporate Research & Development Division, Takasago International Corporation , 1-4-11 Nishi-yawata, Hiratsuka City, Kanagawa 254-0073, Japan.
authors: Taichiro
authors: T
authors: Touge
authors: Molecular Chirality Research Center, Department of Chemistry, Graduate School of Science, Chiba University , 1-33 Yayoi, Inage-Ku, Chiba 263-8522, Japan.
authors: Takayoshi
authors: T
authors: Arai