Enantioselective Organozinc Addition to Aldehydes Using Planar Chiral [2.2]Paracyclophane-Imidazoline N,O-Ligands.

We present an improved and convenient synthesis of [2.2]paracyclophane-imidazoline N,O-ligands with central and planar chirality in seven steps starting from [2.2]paracyclophane. The utility of these ligands in organozinc additions to aldehydes is described. The asymmetric ethylation of aldehydes proceeded with enantioselectivities of up to 97 % ee, while the asymmetric arylation of aldehydes gave up to 95 % ee (R) and 82 % ee (S) using (S,S,S)-UCD-Imphanol and (S,S,R)-UCD-Imphanol, respectively.