The catalytic enantioselective meso-epoxide ring opening reaction with phenolic oxygen nucleophile (4-methoxyphenol) is described for the first time herein. This reaction was first found to be promoted by (R)-GaLB (Ga ) gallium, L ) lithium, B ) (R)-BINOL), giving a variety of epoxide opening products in good to high ee (67-93% ee). However, chemical yield was only modest (yield 31-75%), despite the use of more than 20 mol % GaLB. This was due to the undesired ligand exchange between BINOL and 4-methoxyphenol, which resulted in the decomplexation of GaLB. Application of various known chiral ligands such as 6,6′-bis((triethylsilyl)ethynyl)-BINOL and H 8 -BINOL were examined, but satisfactory results were not obtained. To overcome this problem a novel linked-BINOL containing coordinative oxygen atom in the linker has been developed. By linking two BINOL units in GaLB, the stability of the Ga-complex was greatly improved. Using 3-10 mol % (R,R)-Ga-Li-linked-BINOL complex, a variety of epoxide opening reactions were found to proceed smoothly, affording products in analogous ee (66-96% ee) and in much higher yield (yield 67-94%) compared to (R)-GaLB. The structure of the LiCl free Ga-Li-linked-BINOL complex was elucidated by X-ray analysis. This is the first X-ray data for an asymmetric catalyst containing gallium. The possible mechanism of the entitled reaction is also discussed, based on the X-ray structure of the Ga-complex.

Heterobimetallic asymmetric catalysts, such as the lanthanum-lithium-binaphthol complex (LaLi-BINOL), the aluminum -lithium -binaphthol complex (AlLi-BINOL), and a newly prepared gallium -sodium -binaphthol complex (Ga Na -BINOL), have been selfassembled with reactive nucleophiles, such as lithium nitronates and sodium malonates, to generate more efficient catalysts than the parent heterobimetallic catalysts. For example, by the combined use of LaLi-BINOL (1 mol%; contains one H,O molecule) and BuLi (0.9 mol%) as the catalyst system, asymmetric nitroaldo1 reactions are greatly accelerated in all cases without a decrease in the optical purity of the nitroaldol products. Kinetic analyses have also been carried out on the Ga Na -BINOL-catalyzed Michael reaction of dibenzyl malonate with cyclohexenone, with or without NaOtBu. The calculated rate constants show that the combined use of GaNa-BINOL and NaOtBu as the catalyst gives reaction rates that are about 50 times faster than with GaNa-BINOL alone. This activation method should be useful for other asymmetric reactions catalyzed by heterobimetallic complexes.

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