Chemistry

Flexible Dendrimer Synthesis

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Science  15 Apr 2005:
Vol. 308, Issue 5720, pp. 326
DOI: 10.1126/science.308.5720.326b

The formation of dendrimers, in which branching polymer chains extend from a central core, normally involves the covalent attachment of the dendrons to a central core. Leung et al. report a dynamic covalent chemistry strategy for the mechanical attachment of dendrons to a core; this pathway, unlike earlier forays, proceeds in high yield. The core bears −CH2NH2+CH2-centers on each arm that act as binding sites for crown ether groups terminated with two primary amines. These amines are then bridged by a dialdehyde-bearing dendron, producing two imine linkages and forming the ring that locks the macrocycle-dendrimer onto the core. These kinetically stable dendrimers form in >90% yields and can be fixed in place by reduction of the C=N bonds with BH3 in tetrahydrofuran and subsequent deprotonation with aqueous NaOH. The formation of each generation (0, 1, and 2) of dendrimer products, which reach molecular weights of up to ∼5000, was verified by mass spectrometry. — PDS

J. Am. Chem. Soc. 10.1021/ja0501363.

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