Photocyclisation of some stilbene analogues. Synthesis of dibenzo[a,l]pyrene

Benzo[c]phenanthrene, benz[a]anthracene, benzo[g]chrysene, and benzo[g,h,i]perylene are obtained by photocyclisation of appropriate stilbene analogues. The synthesis of dibenzo[a,l]pyrene from methylbenzo[g]chrysene is described.