Photochemical Ring Closure of 10,10′-Disubstituted 9,9′(10H,10′H)-Biacridinylidenes Followed by Dehyrogenation

The photolysis of 10,10′-disubstituted 9,9′(10H,10′H)-biacridinylidenes afforded the corresponding 7,16-dihydrobenzo[1,2,3-kl:6,5,4-k′l′]diacridines. The formation of photocyclized dihydrophenanthrene-type intermediates was confirmed spectroscopically.