ISSN:
0947-6539
Keywords:
heterobimetallic catalysts
;
Michael additions
;
multifunctional catalysts
;
nitroaldol reactions
;
self-assembly
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Heterobimetallic asymmetric catalysts, such as the lanthanum-lithium-binaphthol complex (La Li-BINOL), the aluminum-lithium-binaphthol complex (AlLi-BINOL), and a newly prepared gallium-sodium-binaphthol complex (Ga Na-BINOL), have been self-assembled 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 La Li-BINOL (1 mol%; contains one H2O molecule) and BuLi (0.9 mol%) as the catalyst system, asymmetric nitroaldol 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 Ga Na-BINOL and NaOtBu as the catalyst gives reaction rates that are about 50 times faster than with Ga Na-BINOL alone. This activation method should be useful for other asymmetric reactions catalyzed by heterobimetallic complexes.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/chem.19960021107
