In most cases, the yield and selectivity were moderate to good. The ligands with a free –NH group 3 and –NHCOPh group 5 were both ineffective in this reaction, while derivatives prepared from tert -leucine showed good selectivity. The amino oxazolines9 and 10showed consistent results with
both good conversion and enantioselectivity. As a result, these were then investigated for a few aromatic aldehydes substituted with electron withdrawing groups (Table 3).