4-π-Photocyclization of 1,2-Dihydropyridazines: An Approach to Bicyclic 1,2-Diazetidines with Rich Synthetic Potential

The 4-pi-photocyclization of a range of 1,2-dihydropyridazines is described, generating bicyclic 1,2-diazetidines in high yields on multigram scale. The key bicyclic 1,2-diazetidines are versatile synthetic intermediates and were easily converted into a range of novel derivatives, including functionalized 1,2-diazetidines, cyclobutenes, cyclobutanes, and 1,3-dienes.