Phenylenebis(ethynyl)-tethered bis-BINOL ligands for enantioselective catalyst based on dimeric TiIV aggregate.
Bis-BINOLs 7a-c in which two BINOL units are tethered by phenylenebis(ethynyl) groups react with titanium tetraisopropoxide (2 equiv) to form intramolecular dimeric titanium(IV) aggregates 2a-c. Of these, 2a,b with an o-phenylenebis(ethynyl) tether are stable in the presence of excess titanium tetraisopropoxide. Complex 2a exhibits a relatively high enantioselectivity in asymmetric addition of diethylzinc to an aldehyde. [structure: see text]
Harada
Toshiro
T
Department of Chemistry and Materials Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan. harada@chem.kit.ac.jp
Hiraoka
Yuki
Y
Kusukawa
Takahiro
T
Marutani
Yasuhisa
Y
Matsui
Shinichiro
S
Nakatsugawa
Masashi
M
Kanda
Koso
K