A variety of linear tetrapyrrolic systems is described, all of which fail to yield macrocyclic compounds under conditions in which porphyrins are obtained from the appropriate 1,19-dideoxybiladienes-ac. The tetrapyrrolic compounds prepared include 5,5-bi-(dipyrromethenyls) for which several new synthetical routes are described, 1,19-dideoxy-10,10-dimethylbiladienes-ac and 1,2-bis(dipyrromethen-5-yl)-ethanes.