Arylidene imidazothiazoles. Synthesis, structure and benzodiazepine receptor binding

A series of arylidene imidazo[2,1-b]thiazoles was synthesized, in order to investigate the influence of different spatial arrangements of the arylidene substituent towards the bicyclic structure of imidazo[2,1-b]-thiazole on benzodiazepine receptor affinity. 1,2- And 2,3-cyclized derivatives of mono- and di-substituted Z-5-arylidene-2-thiohydantoins were investigated. As an example of E isomers E-5-benzylidene-2,3-dihydroimidazo[2,1-b]thiazol-6(5H)-one was obtained. The spatial arrangement of the arylidene sub stituent toward the bicyclic structure as well as the character of isomers had little influence on the benzo diazepine receptor affinity of the compounds. It seems that the greatest influence on biological activity has the nature and the number of substituents on the phenyl ring. All investigated imidazo[2,1-b]thiazoles were less active than previously described arylidene imidazo[2,1-b]thiazepinones.