Stereospecific photochemistry of Delta(2)-1,2,3-triazo-lines in solution and in the solid state: scope and mechanistic studies

摘要

The stereospecific photochemistry of ten N-aryl-substituted cis-or trans-Delta(2)-1,2,3-triazolines to form the corresponding cis- or trans-aziridines was investigated both in solution and in the solid-state. We found that photochemical reactions in the solid state are more stereospecific than in solution for the 8 crystalline Delta(2)-1,2,3-triazolines. Additionally, triplet sensitization for some triazolines results in triplet biradicals, which provide the more thermodynamically favored trans-aziridine regardless of the starting triazoline stereochemistry. Product analyses as a function of temperature and solvent polarity suggest that the electronic excitation of the Delta(2)-1,2,3-triazolines results in the formation of a 1,3-biradical intermediate.