Effect of chiral ligand

The effect of chiral ligands on the stereoselectivity of products is another considerable property which at this stage is very hard to deduce undoubtedly. In some cases the usage of them concluded to preferred stereoselectivity [48,54,67,68, 71,75], but in some other cases their usage did not reach any sensible preference on specific stereoisomer [16, 60]. This clearly shows the need of more investigation in this area to clear the parameters which determine the stereochemistry of the metal alkoxide organic reaction catalysis. 

Nakagawa, M. Nakao, H. Watanabe, K. I. (1985) Steric effects of chiral ligands in a new type of aldol condensations catalyzed by zinc(ll) complexes of a-amino acid esters, Chem. Lett., 391. ... 

Crystallographic data Determine preferred conformation of intermediate metal carbenes, and measure effect of chiral ligands 126 ... 

Osmium tetroxide oxidations can be highly enantioselective in the presence of chiral ligands. The most highly developed ligands are derived from the cinchona alkaloids dihydroquinine (DHQ) and dihydroquinidine (DHQD).45 The most effective... 

Ito et al.120 reported TADDOL 126 as a new type of chiral ligand in place of amino alcohol and examined the catalytic ligand effect of using various chiral diols in the presence of Ti(OPr )4. 

As described in the previous sections, asymmetric allylic alkylation of acyclic allylic esters proceeds smoothly and effectively by using various types of chiral ligands. In contrast, allylic alkylation of cyclic allylic esters remains yet to be investigated. Thus, only a few examples are described in this section. 

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