Solvent free Lewis acid catalyzed vinylogous condensation

(4Z)-4-(4-Methoxybenzylidene)-2-((E)-4-methoxystyryl)-1-phenyl-1,4-dihydro-5H-imidazolin-5-one and its analogues were synthesized via carbon - carbon bond formation in the presence of a variety of Lewis acids under essentially solvent free conditions. ZnCl2 was used as the prototype catalyst in these studies. Several other Lewis acids were also tested in this synthesis with AlCl3 giving very good yields. Protic acids also catalyzed the reaction albeit at much higher mole percents. All 2-methyl substituted imidazolin-5-one starting materials resulted in the formation of the pi-conjugated product on reaction with aromatic aldehydes. The mechanism of this reaction has also been elucidated.