A hexadentate Schiff base ligand which undergoes reversible, diastereoselective addition of methanol

Condensation of enantiopure (S)-(−)- or (R)-(+)-1,1′-binaphthyl-2,2′-diamine with 2,2′-bipyridine-6-carbaldehyde in dry toluene gives enantiopure (S)-2 and (R)-2, but in MeOH/CH2Cl2, diastereoselective addition of MeOH occurs across the imine bonds of (S)-2 to give (S,S,S)-3; in CH2Cl2, CHCl3 or CH3CN, (S,S,S)-3 eliminates MeOH, reverting to (S)-2.