The synthesis of perfectly defined, monodisperse macromolecules is one of the challenges faced by polymer chemists today. Such precision synthesis requires a fundamentally different approach to conventional polymer synthesis, but in turn can unlock the door to many new applications. Therefore, we introduce here the combination of ultra-fast “click” reactions using 1,2,4-triazoline-3,5-diones (TAD) with the highly efficient and versatile Passerini three-component reaction. This new approach not only resulted in the synthesis of monodisperse, sequence-defined macromolecules of high purity and molecular weight (>7000 Da), but also offered new insights into the iterative synthesis of sequence-defined macromolecules in general, as we present a detailed comparative study of the same chemistry protocols carried out on solid phase as well as in solution.