0000000000354708
AUTHOR
M. Consuelo Jiménez
Ring splitting of azetidin-2-ones via radical anions
The radical anions of azetidin-2-ones, generated by UV-irradiation in the presence of triethylamine, undergo ring-splitting via N-C4 or C3-C4 bond breaking, leading to open-chain amides. This reactivity diverges from that found for the neutral excited states, which is characterised by alpha-cleavage. The preference for beta-cleavage is supported by DFT theoretical calculations on the energy barriers associated with the involved transition states. Thus, injection of one electron into the azetidin-2-one moiety constitutes a complementary activation strategy which may be exploited to produce new chemistry.
Photocyclization of a bichromophoric phenol/olefi system substituted at the methylene spacer - Zwitterions versus H-bridged intermediates in the excited state proton transfer
Photolysis of (E)- and (Z)-2-(1-ethyl-3-phenylpropenyl)phenol (1 and 2) under a variety of conditions produces a mixture of dihydrobenzopyrans 3 and 4, dihydrobenzofuran 5, cyclopropanes 6 and 7, and rearranged olefin 8. Acidic treatment of 1 and 2 gives a mixture of the six-membered ring products 3 and 4. Remarkable differences, associated with the nature of the precursor and the reaction conditions, are observed in the regiochemistry of cyclization and in the stereochemistry of the dihydrobenzopyrans (3/4 ratio). This points in favour of an H-bridged intermediate, rather than a fully zwitterionic species, as the direct precursor of the photocyclized products.