Immobilization of a cellulose carbamate-type chiral selector onto silica gel by alkyne-azide click chemistry for the preparation of chiral stationary chromatography phases

A new synthesis strategy for the preparation of cellulose derivative-based chiral selectors and the subsequent mild immobilization onto pre-functionalized silica gel are introduced, utilizing Cu(I)-catalyzed alkyne-azide Huisgen cycloaddition (click) chemistry. A cellulose 3,5-dimethylphenyl carbamate derivative carrying propynyl carbamate groups was prepared by a combination of carbonate aminolysis and isocyanate chemistry. For immobilization, 3-azidopropyl-functionalized silica gel as an inert carrier was used, synthesized via a 3-chloropropyl intermediate. The chiral selector, as well as the inorganic/organic hybrid materials (silica gel/ chiral selector), were comprehensively characterized by ATR-FTIR, solid-state C-13 and Si-29 NMR, liquid-state NMR, GPC, TGA, and elemental analysis. The enantioseparation performance of the immobilizedtype chiral stationary phase was evaluated by HPLC with a set of representative chiral test analytes and different eluents and compared to a respective coated-type (=non-covalently bound) chiral stationary phase carrying the same selector quality and quantity on the same silica gel matrix. The immobilization did not adversely affect the chiral separation performance; on the contrary, in some chromatographic separations the immobilized-type chiral stationary phase surprisingly even surpassed the coated reference material. [GRAPHICS] .

Automated summary

A new synthesis strategy for cellulose derivative-based chiral selectors and their immobilization onto silica gel was introduced. The immobilization process did not affect the chiral separation performance, and in some cases, the immobilized chiral stationary phase showed better performance than the coated reference material.