Facile Synthesis of Polyamide Dendrimers from Unprotected AB2 Building Blocks: Dumbbell-Shaped Dendrimer, Star-Shaped Dendrimer, and Dendrimer with a Carboxylic Acid at the Core

Abstract

A fast, inexpensive, and highly efficient synthesis of aromatic polyamide dendrimers, without the need for protection and deprotection steps, has been developed. Dendrons and various types of polyamide dendrimers were easily prepared by a convergent approach involving activation of a carboxylic acid at the focal point using a small excess of thionyl chloride as the activating agent, followed by condensation with an unprotected AB2 building block, 3,5-bis(4-aminophenoxy)benzoic acid. A third generation dendrimer with a molecular weight of 8197 Da was prepared in a high yield, using 1,3,5-tris[N-(4-aminophenyl)]benzenetricarboxamide as a core molecule. A dendrimer with a carboxylic acid group at its core (molecular weight: 10 700 Da) could be prepared from the third generation dendron with 3,5-bis(3,5-diaminobenzoylamino)benzoic acid as the core molecule. All the above products purified only by precipitation revealed a high purity, assessed using matrix assisted laser desorption ionization time-of-flight m...