Regioselective Synthesis of Substituted Cyclopenta[l]phenanthrenes

A simple and efficient synthesis of cyclopenta­[l]­phenanthrenes from substituted acetophenones provides access to polycyclic aromatics with a variety of substitution patterns. The synthesis requires only three steps from a silyl enol ether: a Mukaiyama aldol reaction followed by McMurry coupling and then Mallory photocyclooxidation to give the target phenanthrenes. Photocyclization conditions have been found that give regioselective formation of 2,7-phenanthrenes from bis­(meta-substituted) stilbenes.