Resolution of (+-)-nipecotic acid ((+-)-3-piperidinecarboxylic acid) by separation of palladium(II) diastereomers containing orthometallated (S)-(-)-1-[1-(dimethylamino)ethyl]naphthalene

An efficient resolution of (+-)-nipecotic acid has been achieved by the fractional crystallization of internally diastereomeric palladium(II) complexes containing the chelated carboxylate and orthometallated (S)-(-)-1-[1-(dimethylamino)ethyl]naphthalene. The configurationally pure enantiomers of the acid were recovered from the individual diastereomers of the complex by treatment with hydrochloric acid, which also regenerated the palladium(II) resolving agent. The crystal structure of the less-soluble diastereomer of the complex has been determined.