ABSTRACT
Interest in the area of pyridinium salt photochemistry dates back to the 1960s, a time when intense efforts were underway to probe the mechanistic details of photoinduced, benzene valence bond isomerization reactions. Amid this flurry of activity is found a single report in 1972 by Kaplan, Pavlik, and Wilzbach
, describing the novel, bicyclic aziridine forming, photohydration reaction of N-methylpyridinium chloride. Many years passed before another study, in 1983 and focused on pyridinium salt single electron transfer photochemistry, led to the tangential observation that the bicyclic aziridines, arising by excitedstate cyclizations of pyridinium salts, participate in acid catalyzed ring opening reactions to produce functionalized aminocyclopentenes. This area again remained uncultivated for many years until the pyridinium salt photocyclization and bicyclic aziridine ring-opening processes were finally investigated in a more thorough manner. The more recent efforts, starting in the mid-1990s, have finally uncovered the unique synthetic value of this chemistry.
