The development and application of a novel linked-1,1′-binaphthol (linked-BINOL) as an approach towards practical asymmetric multifunctional catalysis is described. Linked-BINOL was first designed to increase the stability of a Ga-Li-BINOL complex against ligand exchange with 4-methoxyphenol. An oxygen-containing linked-BINOL, which is a semi crown ether, was effective in both promoting the formation of a monomer complex and increasing the stability of the Ga-Li complex. A Ga-Li-linked-BINOL complex promoted the epoxide opening reaction in up to 96% enantiomeric excess (ee). Second, based on the X-ray structural information of the Ga-Li-linked-BINOL complex, we designed a more stable lanthanide linked-BINOL complex. An air-stable, storable, and reusable La-linked-BINOL complex promoted the Michael reaction in up to >99% ee. The catalyst activity remained unchanged after storage under air for 4 weeks. Calculations suggested that the linked-BINOL would function as a pentadentate ligand in a lanthanum complex, thus efficiently improving the stability of the complex. Finally, the linked-BINOL was applied to a new homobimetallic multifunctional catalysis. A dinuclear Zn-Zn-linked-BINOL complex promoted the enantio- and diastereoselective direct aldol reaction in up to 99% ee, where one Zn cation might function as a Lewis acid and the other Zn-phenoxide as a Brønsted base.
|Number of pages||13|
|Journal||Advanced Synthesis and Catalysis|
|Publication status||Published - Jan 2002|
All Science Journal Classification (ASJC) codes
- Organic Chemistry