N,N’-Carbonyldiimidazole as a reagent of choice for the synthesis of thienyl-substituted pyrrolidine-2,5-diones

N-tert-Butyloxycarbonylamino-3-[Z-α-(2,5-dimethyl-3-thienyl)ethylidene]-4-isopropylidenepyrrolidine-2,5-dione was prepared in 80% yield from the corresponding isomeric hydrazidic acids using N,N’-carbonyldiimidazole, whereas a number of other cyclisation reagents were ineffective.