Resolution and coupling of 1-(2′-hydroxy-1′-naphthyl)isoquinolines

The synthesis of bridged dimeric isoquinolylnaphthols has been developed. A simple method for the resolution of 1,1′-isoquinolyl-2′-naphthol permits measurement of the optical stability of the monomer, and in several cases slow racemisation at ambient temperature was observed. The enantiomeric stability is not greatly affected by steric buttressing. An unusual enhancement of the rate of atropisomerism is provided by the 3-bromomethylisoquinolines, and undermines the possibility of coupling pure enantiomeric components to provide a single stereoisomer of a tetradentate ligand.