Abstract
The chemistry of azetidin-2-ones has attracted considerable interest over the last decades, as compounds of this family (β-lactams) are associated with important biological activities. In addition, azetidin-2-ones can be used as building blocks in organic synthesis, by exploiting the possibilities of cleavage at any of the single bonds of the four-membered ring. By contrast, their photoreactivity has received much less attention. Specifically, the behavior of radical anions of azetidin-2-ones remains unexplored, in spite of their potential to exhibit new chemistry; in fact, injection of one electron to the ring system constitutes a different (and complementary) activation strategy. With this background, the aim of the present work is to use triethylamine as donor for the generation of the radical anions of azetidin-2-ones upon UV-excitation. Product studies show that the most general result is β-cleavage, leading to open-chain amides. This reactivity diverges from that found for the neutral excited states, which is characterized by β-cleavage. The experimental results are fully supported by DFT calculations on the course of the reaction at the UB3LYP/6-31+G(d) level of theory.
