Dendrimers polyether

Carbon/oxygen-based (and Fr chet) dendrimers 4.1.6.1 Polyether dendrimers 

Repetitive two-stage synthesis of Frechet dendrons is based in the first stage on the reaction of a 3,5-dihydroxybenzyl alcohol with benzyl bromide. Transformation of the lengthened benzyl alcohols into the corresponding lengthened benzyl bromide permits iteration of the reaction with the monomer [42]. 

Molecular recognition processes between amphiphilic biaryl dendrimers 2 (with carboxylic acid moieties) as host compounds and the protein chymotryp-sin as guest were compared with those involving corresponding benzyl ether dendrons 1 (Fig. 4.26) [44]. In the biaryl dendrimers both the carboxylic acid groups of the periphery and those located in the inner shells are available for 

---

Chiral //A(oxazolinc) ligands disubstituted at the carbon atom linking the two oxazolines by Frechet-type polyether dendrimers coordinated with copper(II) triflate were found to provide good yields and moderate enantioselectivities for Mukaiyama aldol reactions in water that are comparable with those resulting from the corresponding smaller catalysts.291 AgPF6-BINAP is very active in this reaction and the addition of a small amount of water enhanced the reactivity.292... 

Mourey, T.H., Turner, S.R., Rubenstein, M., Frechet, J.M.J., Hawker, C.J., and Wooley, K.L. (1992) Unique behavior of dendritic macromolecules Intrinsic viscosity of polyether dendrimers. Macromolecules 25, 2401-2406. 

PREPARATION OF POLYETHER DENDRIMERS BY ASSEMBLY OF FRECHET-TYPE DENDRONS AROUND A CORE... 

Fig. 7. Plot of absorption maximum vs generation number for polyether dendrimers labeled with a focal point solvatochromic group...

It is also possible to introduce polymerizable groups at the focal point of dendritic macromolecules and a number of authors have demonstrated the synthesis of novel hybrid dendritic-linear block copolymers by this methodology [69-73]. Initial experiments in the use of the dendritic macromonomers involved the preparation of a series of polyether dendrimers, such as the third generation derivative, 37, which contains a single styrene at its focal point [74]. Copolymerization of 37 with styrene then affords a hybrid block copolymer, 38, in which... 

One immediate effect of being able to construct dendritic macromolecules with a wide variety of different chain ends is that the solubihty characteristics of the dendrimer can be finely tuned. For example, polyether dendrimers based on 3,5-dihydroxybenzyl alcohol as the repeat unit can be prepared with dodecyl... 

Mouiey TH, Turner SR, Rubinstein M, Fiechet JMJ, Hawker CJ, Wooley KL. Unique behavior of dendritic macromolecules intrinsic viscosity of polyether dendrimers. Macromolecules 1992 25 2401-2406. 

Saville PM, Reynolds PA, White JW, Hawker CJ, Frechet JMJ, Wooley KL, Penfold J, Webster JRP. Neutron reflectivity and structure of polyether dendrimers as Langmuir films. J Phys Chem 1995 99 8283-8239. 

Fig. 4.25 Synthesis of polyether dendrimers starting from a hypercore (according to Wooley, Frechet et al.)...

Sharpless et al. noted an increase of the specific rotation with increasing generation number in the case of dendrimers having trimesic acid as achiral core unit and a completely chiral polyether dendrimer skeleton based on 1,2-diol branching units (Fig. 4.72) [27]. The observed molar optical rotations corresponded to... 

Fig. 6.42 Polyether dendrimer, functionalised with quaternary ammonium groups (according to Ford et ai.)...

Ford et al. functionalised polyether dendrimers with quaternary ammonium ions (1 in Fig. 6.42) [68, 69]. 

Dendrimers are hyperbranched polymers that emanate from a single core and ramify outward with each subsequent branching unit [1,2]. In the commonly employed divergent synthesis, dendrimers can be prepared through sequential, alternating reactions of two smaller units, one of which has a point of bifurcation. As is described elsewhere in this volume, several classes of dendrimers are known, including polypropyleneimine (PPI), polyamidoamine (PAMAM), and Frechet-type polyether dendrimers [1,2]. 

Characterization of the series included the standard 13C and H NMR spectroscopies and gel permeation chromatography. The melting point of the first tier ester (176-178 °C), was found not to differ greatly from that of the fourth tier ester (192-203 °C) even though the molecular weights differ by a factor of nearly 10. Haddle-ton et al have demonstrated the utility of MALDI MS on these aromatic polyether dendrimers. 

Gitsov I, Wu S, Ivanova PT, Modular building blocks for combinatorial construction of polyether dendrimers and their hybrids, Polym. Mater. Sci. Eng., 77 214-215, 1997. 

Fig. 29. Computer simulated molecular graphics (wireframe) using POLYGRAF for STAR-BURST (polyether) dendrimers of generations 1-4...

---