Catalytic asymmetric alpha-iminol rearrangement by vanol zirconium complex

Catalytic asymmetric &agr;-iminol rearrangement to the corresponding &agr;-amino ketone is developed that is based on a chiral zirconium complex generated from the vaulted biaryl ligand VANOL. As many as 19 different asymmetric catalysts were examined to identify the first chiral catalyst for the asymmetric &agr;-iminol rearrangement. Aluminate complexes of VANOL, VAPOL and 7,7'-tBu 2VANOL were found very effective for this reaction giving up to 88% ee. The ne plus ultra catalyst for this reaction was discovered to be the VANOL zirconium complex, and for the majority of the substrates it gave 97% to >99% ee. An X-ray analysis of the crystal that was grown from the catalyst solution revealed that the zirconium has bonded to three VANOL molecules and this is also the first structure reported for zirconium with three bis-phenol ligands.