Thioether bridged cationic cyclodextrin stationary phases: Effect of spacer length, selector concentration and rim functionalities on the enantioseparation

- Four single thioether bridged cationic CD-CSPs are fabricated by mild thiol-ene click chemistry.
- p-Methylphenylcarbamoylated CD-CSP can be readily prepared by a post-synthetic carbamoylation approach with a high surface loading.
- The complementarity between native and phenylcarbamoyl CD significantly broadens the separation profile of CD-CSPs.
- CD-CSPs with well-defined structures afford better enantioseparation ability.

The preparation and evaluation of four single thioether bridged cationic cyclodextrin (CD) chiral stationary phases (CSPs) with different spacer length, selector concentration and rim functionalities are reported. Mono-6-(1-vinyl/allyl/butenylimidazolium)-β-CDs chloride were synthesized and clicked onto thiol silica to form three novel cationic native-CD-CSPs (CSP1, CSP2 and CSP3) and a post-synthetic phenylcarbamoylation of CSP2 was performed affording CSP4. The enantioseparation ability of the as-prepared CSPs were evaluated in high performance liquid chromatography (HPLC) by separating over forty enantiomers including isoxazolines, dansyl amino acids, flavonoids, tröger's base, 4-chromanol, bendroflumethiazide and styrene oxide. Most of the enantiomers were well resolved with the resolution (Rs) of 4NPh-OPr reaching 12.68. The effects of spacer length, selector concentration and rim functionalities on the enantioseparation were investigated. A comparison of the current CSP with a commercial column (Cyclobond I 2000) was also conducted to reveal the superiors enantioselectivity of the as-prepared CSPs.