Cross-linked glycerol dendrimers and hyperbranched polymers as ionophoric, organic nanoparticles soluble in water and organic solvents.
Cross-linked glycerol dendrimers and hyperbranched polymers as ionophoric, organic nanoparticles soluble in water and organic solvents.
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DOI：
10.1002/anie.200702580
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发表时间：
2007-11
影响因子：
--
通讯作者：
S. Zimmerman;J. Quinn;E. Burakowska;R. Haag
中科院分区：
文献类型：
--
作者：
S. Zimmerman;J. Quinn;E. Burakowska;R. Haag
The usefulness of dendrimers and hyperbranched polymers in specific applications depends on the ability to tune their properties in a predictable fashion. We recently showed that allyl and homoallyl ether end groups of dendrimers can be covalently linked using the ring-closing metathesis (RCM) reaction. In addition to creating molecularly imprinted dendrimers and organic nanotubes, cross-linking of the end-groups was shown to produce a significant decrease in the size of the dendrimer. At the same time, these organic nanoparticles became more rigid. The extent of cross-linking could be controlled, thus allowing the dendrimer size and rigidity to be finely and independently modulated. However, attempts to functionalize the cross-linked dendrimers, particularly with an eye toward water-soluble analogues, were unsuccessful. Herein we report the ring-closing metathesis of polyallyl glycerol (Haag-type) dendrimers and the analogous hyperbranched polymers. The synthesis of these non-absorbing, organic nanoparticles is straightforward and readily scalable. Furthermore, the crosslinked dendrimers and hyperbranched polymers act as weak ionophores in organic solvents and can be readily dihydroxylated to make fully water-soluble nanoparticles. Generation 3.5 (G-3.5) polyallylated glycerol dendrimer 1 was prepared in seven steps (45% overall yield) from tris(hydroxymethyl)propane using an iterative process of Williamson etherification and catalytic dihydroxylation. Dendrimer 1 contains a mixture of many diastereomers, but its purity could be estimated by H NMR spectroscopy, MALDI-MS, and analytical size-exclusion chromatography (SEC) to be higher than 97%. Initial cross-linking studies were performed using the Grubbs catalyst 2 in benzene at room temperature (Scheme 1). The reaction typically required at least 24 h for near-complete conversion. The progress was monitored by
