3.6.1.4.  Asymmetric Catalysis

The Lewis acidity of titanium has been used in asymmetric catalysis. Due to its strong Lewis acidity, it can easily coordinate with heteroatoms like oxygen and nitrogen. Now if the environment of the titanium centre is so modified such that the heteroatom containing substrate can find stereoselectively, then asymmetric induction is possible. This is achieved by attaching suitable chiral ligands to titanium centre which also tailors the Lewis acidity of titanium. For examples, asymmetric ene and Diels-Alder reactions have been demonstrated with excellent enantioselectivity in the presence of chiral titanium complexes as chiral Lewis acid catalysts (Scheme 8-9).

 

Scheme 8

Scheme 9