Linear Well-Defined Polyamines via Anionic Ring-Opening Polymerization of Activated Aziridines: From Mild Desulfonylation to Cell Transfection

Linear polyethylenimine (L-PEI), a standard for nonviral gene delivery, is usually prepared by hydrolysis from poly(2-oxazoline)s. Lately, anionic polymerization of sulfonamide-activated aziridines had been reported as an alternative pathway toward well-defined L-PEI and linear polyamines. However, desulfonylation of the poly(sulfonyl aziridine)s typically relied on harsh conditions (acid, microwave) or used a toxic solvent (e.g., hexamethylphosphoramide). In addition, the drastic change of polarity requires solvents, which keep poly(sulfonyl aziridine)s as well as L-PEI in solution, and only a limited number of strategies were reported. Herein, we prepared 1-(4-cyanobenzenesulfonyl) 2-methyl-aziridine (1) as a monomer for the anionic ring-opening polymerization. It was polymerized to well-defined and linear poly(sulfonyl aziridine)s. The 4-cyanobenzenesulfonyl-activating groups were removed under mild conditions to linear polypropylenimine (L-PPI). Using dodecanethiol and diazabicyclo-undecene (DBU) allo...