On the solvent versatility in immobilized amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phase in high performance liquid chromatography: Application to the asymmetric cyclopropanation of olefins

The enantioseparation of a set of cyclopropanes derived from Meldrum's acid and 3,3,3-trifluoro-2-diazopropionate has been achieved on the new immobilized amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phase (Chiralpak IA) in high performance liquid chromatography (HPLC) using a mixture of n-hexane–2-propanol (90:10, or 99:1, v/v) as mobile phase with a flow-rate of 0.5 ml/min and UV detection at 254 nm. Due to its ability to withstand prohibited HPLC solvents like dichloromethane, an online HPLC equipped with a sensitive optical rotation detector for monitoring the optical activity of the racemic and enantioenriched cyclopropanes prepared via the Rh(II)-catalyzed asymmetric inter- and intramolecular cyclopropanations in dichloromethane is demonstrated. Direct analysis techniques without further purification, workup or removal of dichloromethane were summarized. The method provides an easy and direct determination of the enantiomeric excess of the cyclopropanes and selectivity of the catalyst used without any further work up.