A Highly Flexible and Efficient Ugi-Type Multicomponent Synthesis of Versatile N-Fused Aminoimidazoles

A microwave-promoted highly flexible and efficient Ugi-type multicomponent reaction of heterocyclic amidines With aldehydes and isocyanides catalyzed by zirconium(IV) chloride was developed. The general protocol offered the very reliable synthesis of a library of medicinally important, widely versatile N-fused aminoimidazoles in excellent yields. Poorly reactive heterocyclic amidines, functionally and sterically hindered aldehydes, which suffer as troublesome reactants in earlier described methods, were rendered as feasible substrates in this process. The efficient catalysis by ZrCl4 in addition to the effect of microwave irradiation was found crucial for gaining Superior flexibility and efficiency of the protocol.