Symmetrical ammonium dibromide as an efficient promoter for the ultrasonic irradiation multi-component preparation of pyrrolidine derivatives

In this work, a method has been developed for the formal, multi-component reaction of cyclopropyl dicarboxylates, aldehydes, and amines under ultrasonic irradiation. The symmetrical dibromide salt (A) was prepared from the reaction of 1,2-bis(2-bromoethoxy)ethane with 2,3,4,6,7,8-hexahydropyrrolo[1,2-a]pyrimidine in toluene under reflux condition. CeCl3 and compound (A) were used as catalyst and promoter and showed a good potential for application in the synthesis of a range of structurally diverse pyrrolidine rings in short reaction times (3-5h) and excellent yields (89-97%).