Accelerated Growth of Dendrimers via Thiol−Ene and Esterification Reactions

By taking advantage of the orthogonal nature of thiol−ene coupling and anhydride based esterification reactions, a facile and chemoselective strategy to dendritic macromolecules has been developed. The ability to interchange growth steps based on thiol−ene and anhydride chemistry allows the synthesis of fifth-generation dendrimers in only five steps and under benign reaction conditions. In addition, the presented coupling chemistries eliminate the traditional need for protection/deprotection steps and afford dendrimers in high yield and purity. The modularity of this strategy coupled with the latent reactivity of the alkene/hydroxyl chain ends was demonstrated by using different cores (alkene and hydroxyl functional), various AB2 and CD2 monomers and a range of chain end groups. As a result, three dendritic libraries were prepared which exhibited tunability of both the chemical functionality and physical properties including the fabrication of PEG hydrogels.