Optical resolution of DL-2,2′-bipiperidine through its cobalt(III) complex

Abstract

The separation of racemic 2,2′-bipiperidine and the meso form has been performed through the dihydrochloride salt of the diamine. The reaction of racemic 2,2′-bipiperidine with [Co(NO₂)₆]^3– has been shown to yield only one DL pair of trans-bis(2,2′-bipiperidine)dinitrocobalt(III) complexion. The dinitro-complex has been characterized and optically resolved using ammonium D-2- bromo-4,7-dimethyl-3-oxobicyclo[2.2.1]heptane-7-methanesulphonate. Optically pure (–)₅₈₉-2,2′-bipiperidine was recovered from the less soluble diastereoisomer and shows a specific rotation of –12.2°. The stereoselective formation of the trans-dinitro-complex is discussed in relation to the predictions of strain energy minimization calculations.