A Model for Late-Stage Modification of Polyurethane Dendrimers Using Thiol-Ene Click Chemistry.

Area of Science:

• Polymer Chemistry
• Organic Synthesis
• Materials Science

Background:

• Dendritic materials with urethane linkages exhibit superior stability compared to those with ether, ester, amide, or carbosilane groups.
• The high reactivity of isocyanates presents challenges in constructing well-defined polyurethane dendrimers.

Purpose of the Study:

• To develop a protecting group-free, one-pot multicomponent Curtius reaction for synthesizing AB2-type dendrons.
• To enable late-stage modification of dendrons and dendritic macromolecules for surface functionalization.
• To create a versatile strategy for synthesizing symmetrical and unsymmetrical (Janus) dendrimers.

Main Methods:

• A one-pot multicomponent Curtius reaction using 5-hydroxyisophthalic acid, 11-bromoundecanol, and 4-penten-1-ol.
• Late-stage modification via thiol-ene click chemistry.
• Characterization using 1D and 2D NMR and high-resolution MALDI-TOF mass spectrometry.

Main Results:

• Successful synthesis of a robust and versatile AB2-type dendron.
• Demonstration of facile late-stage functionalization of the synthesized dendron and resulting polyurethane dendrimer.
• Characterization confirmed the structure and purity of novel dendrons and dendrimers.

Conclusions:

• The developed Curtius reaction strategy offers a robust and efficient route to polyurethane dendrimers.
• The protecting group-free, one-pot approach simplifies dendrimer synthesis and allows for versatile late-stage modifications.
• This methodology is highly applicable for creating both symmetrical and asymmetrical (Janus) dendritic architectures.