Design of Synergistic Function and Dynamic Stereocontrol of Hetero multi-metal complexes

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While non-racemic catalysts can generate non-racemic products with or without the "non-linear relationship" in enantiomeric excesses between catalysts and products, racemic catalysts inherently give only a racemic mixture of chiral products. Asymmetric catalysts can be further evolved into highly activated catalysts by association with chiral activators. This asymmetric activation process is particularly useful in racemic catalysis through selective activation of the one enantiomer of the racemic catalysts. Recently, a strategy whereby a racemic catalyst is selectively deactivated by a chiral additive has been reported as "chiral poisoning" to yield non-racemic products. 'Asymmetric activation' is an alternative but conceptually opposite strategy to asymmetric catalysts in which a chiral activator selectively activates rather than deactivates one enantiomer of a racemic chiral catalyst. The advantage of this activation strategy over the deactivation counterpart is that the activated catalyst can produce a greater enantiomeric excess (x_<act>% ee) in the products, even when using a catalytic amount of activator per chiral catalyst, than the ee attained by the enantiomerically pure catalyst on its own.Therefore, 'asymmetric activation' could provide a general and powerful strategy for the use of not only chirally rigid, racemic ligands but also chirally flexible ligands without enantiomeric resolution!