The invention provides a new process for the manufacture of aromatic compounds which at least once contain a benzene ring of an aromatic carbocyclic ring system bonded by an ethylene double bond in conjugation with a further aromatic ring system, i.e. contain the stilbene skeleton or stilbene analogon as central structural element, as well as certain classes of new compounds of this type. The process is characterized by the reaction of a Schiff base of an aromatic aldehyde with an aromatic carbocyclic six-membered ring compound which contains one to four methyl groups bonded to ring carbon atoms of a benzene ring, which furthermore contains aromatic rings which are exclusively six-membered carbocyclic rings, and wherein those benzene rings whose methyl groups are to be caused to react are free of other substituents which contain atoms wich are replaceable by alkali metal. The reaction is carried out in the presence of (a) a strongly basic alkali compound and (b) an N-dialkyl-acylamide as solvent. The compounds obtainable according to this process show a marked fluorescence emission and therefore are suitable for all purposes where fluorescence properties are used, as for instance optical brighteners, scintillators fluorescence dyes, etc.