Synthesis, resolution and racemisation studies of new tridentate ligands for asymmetric catalysis

The high-yielding preparation of two tridentate, isoquinoline-derived ligands, involving successive Suzuki cross-coupling reactions, is described. The first ligand was resolved via molecular complexation with N-benzylcinchonidinium chloride, while the second was resolved by chromatographic separation of its epimeric camphorsulfonates. The barrier to rotation about the central biaryl axis was evaluated and the absolute configuration assigned by X-ray crystallography.