Metal complexes nucleophilic addition, stereocontrol

We reasoned that some cyclic enone sulfoxides should form an even more rigid chelate than that formed from the corresponding acyclic alkenyl sulfoxides when complexed with metal ions model exemplifies the case for a cyclopentenone sulfoxide and suggests a high degree of stereocontrol during the nucleophilic addition reaction. 

Nucleophiles add to the face of the ligand opposite to that which bears the metal when reactions occur by a direct addition pathway and under kinetic control ([2]). This stereocontrol effect is very strong (100% diastereo-selective), so the planar chirality of the metal complex can dominate other stereodirecting influences. There are no conventional stoichiometric control systems that can match the generality, versatility and reliability of this metal-mediated strategy for asymmetric induction. In the case of stoichiometric-control methods, it is essential that the multiple use is made of the control group (otherwise... 

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