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Updated: Oct 9, 2025

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes
Published on: November 21, 2017
Ring Opening Reactions of β-Propiolactam in Superacidic Media
Stefanie Beck1,2, Vanessa Rück1, Lea-Viktoria Pietsch1
1Department of Chemistry, Ludwig-Maximilian University of Munich, Butenandtstr. 5-13, 81377, München, Germany.
Abstract:
The reaction of β-propiolactam in the superacidic systems HF/MF5 (M=Sb, As) led to the formation of monoprotonated 3-aminopropanoyl fluoride in the form of [C(O)F(CH2 )2 NH3 ][SbF6 ] and [C(O)F(CH2 )2 NH3 ][AsF6 ]. In the presence of traces of water, the diprotonated species β-alanine [C(OH)2 (CH2 )2 NH3 ][AsF6 ]2 was synthesized for the first time. All salts were characterized by low-temperature infrared and Raman spectroscopy. Additionally, single-crystal X-ray analyses were conducted in the case of [C(O)F(CH2 )2 NH3 ][SbF6 ] and [C(OH)2 (CH2 )2 NH3 ][AsF6 ]2 . By using SO2 instead of HF as the solvent, the salt [C(OH)2 (CH2 )2 NHSO][SbF6 ]2 was obtained, and single-crystal X-ray analysis of this salt containing a thionylimide moiety was conducted. For the formation of these open-chain compounds, an acyl cationic species as intermediate is assumed, which is formed from N-protonated β-propiolactam. Quantum chemical calculations at the B3LYP/aug-cc-pVTZ and MP2/aug-cc-pVTZ levels of theory were carried out to gain a better understanding of the formation and the structural properties of protonated β-propiolactam.
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