Abstract
Photolyses of various diazine N-ethoxycarbonylimides (3, 9, and 19), prepared from the corresponding diazines (1, 8, and 17), resulted in the formation of the pyrazole derivatives (4 and 10) from pyrazine and pyrimidine N-imides, and of the pyrrole derivatives (20) from pyridazine N-imides. These photolyses may proceed by rearrangement to diaziridine intermediates, followed by ring expansion to the corresponding 1, 2, 5-, 1, 2, 4-, or 1, 2, 3-triazepines (6, 12, or 22), which then undergo isomerization to the triaza[3.2.0]bicycloheptadienes (7, 13, and 23), followed by elimination to give the products (4, 10, and 20, respectively).
