Piperidinylpyrroles: Design, synthesis and binding properties of novel and selective dopamine D4 receptor ligands

Piperidinylpyrroles of type 3 were synthesized through a modified Paal-Knorr reaction. For the introduction of pyrrole-substituents high yielding transformations including Sonogashira cross-coupling reactions were utilized. Employment of the reagent TosMIC gave access to the regioisomeric oxazolyl derivatives 7 and 11 which showed the highest dopamine D4 receptor binding of the series investigated.