The Anionic Polymerization of a tert -Butyl-Carboxylate-Activated Aziridine.

N -Sulfonyl-activated aziridines are known to undergo anionic-ring-opening polymerizations (AROP) to form polysulfonyllaziridines. However, the post-polymerization deprotection of the sulfonyl groups from polysulfonyllaziridines remains challenging. In this report, the polymerization of tert -butyl aziridine-1-carboxylate ( BocAz ) is reported. BocAz has an electron-withdrawing tert-butyloxycarbonyl (BOC) group on the aziridine nitrogen. The BOC group activates the aziridine for AROP and allows the synthesis of low-molecular-weight poly( BocAz ) chains. A 13 C NMR spectroscopic analysis of poly( BocAz ) suggested that the polymer is linear. The attainable molecular weight of poly( BocAz ) is limited by the poor solubility of poly( BocAz ) in AROP-compatible solvents. The deprotection of poly( BocAz ) using trifluoroacetic acid (TFA) cleanly produces linear polyethyleneimine. Overall, these results suggest that carbonyl groups, such as BOC, can play a larger role in the in the activation of aziridines in anionic polymerization and in the synthesis of polyimines.