Dendrimers commercially available

The data presented in Figure 8 graphically illustrate the tremendous and rapid growth in interest in FOSS chemistry, especially for patented applications. This looks set to continue with current applications in areas as diverse as dendrimers, composite materials, polymers, optical materials, liquid crystal materials, atom scavengers, and cosmetics, and, no doubt, many new areas to come. These many applications derive from the symmetrical nature of the FOSS cores which comprise relatively rigid, near-tetrahedral vertices connected by more flexible siloxane bonds. The compounds are usually thermally and chemically stable and can be modified by conventional synthetic methods and are amenable to the usual characterization techniques. The recent commercial availability of a wide range of simple monomers on a multigram scale will help to advance research in the area more rapidly. 

The history of dendrimer chemistry can be traced to the foundations laid down by Flory [34] over fifty years ago, particularly his studies concerning macro-molecular networks and branched polymers. More than two decades after Flory s initial groundwork (1978) Vogtle et al. [28] reported the synthesis and characterization of the first example of a cascade molecule. Michael-type addition of a primary amine to acrylonitrile (the linear monomer) afforded a tertiary amine with two arms. Subsequent reduction of the nitriles afforded a new diamine, which, upon repetition of this simple synthetic sequence, provided the desired tetraamine (1, Fig. 2) thus the advent of the iterative synthetic process and the construction of branched macromolecular architectures was at hand. Further growth of Vogtle s original dendrimer was impeded due to difficulties associated with nitrile reduction, which was later circumvented [35, 36]. This procedure eventually led to DSM s commercially available polypropylene imine) dendrimers. 

The addition of ammonia to excess methyl acrylate (a linear monomer), followed by amidation with excess ethylenediamine afforded the resultant cascade molecule, and thus Tomalia [37] created the commercially available PAMAM starburst series of dendrimers (2, Fig. 2). Related core molecules such as ethylenediamine and aminoalcohols and other functionalizable groups such as thiol moieties were used to prepare similar dendrimers [38]. This methodology is applicable to most primary amines, resulting in a 1 —> 2 branching pattern. Recently, examples of related Si-, [39] P-, [40] and metallo systems [41], which follow this linear monomer protocol have been reported. 

At present, improved methods of dendrimer construction have made possible the commercial availability of these macromolecules with a variety of molecular weight ranges and surface functional groups. Instead of testing the limits... 

RG. 66. Commercially available dendrimer scaffolds commonly used for glycodendrimer syntheses, and general synthetic strategies for synthesis of glycodendrimers. 

Another reaction performed in the dead-end reactor discussed before, is the allylic amination of 3-phenyl-2-propenyl-carbonic acid methyl ester with morpholine. [30] First and second generation commercially available DAB-dendrimers were functionalized with diphenylphosphine groups (Figure 4.13). Two different membranes were used, the Nadir UF-PA-5 (ultrafiltration) and the Koch MPF-50 (former SELRO) (nanofiltration), which gave retentions of 99.2% and 99.9% respectively for the second generation functionalized dendrimers. 

Two different dendrimer families are presently commercially available Starburst polyamidoamine (PAMAM) dendrimers from Dendritech Inc., Midland, Michigan, and ASTRAMOL polypropyleneimine (PPI) dendrimers from DSM, Geleen, the Netherlands. 

We thus obtain defined, monodisperse, defect-free functionalized dendrim-ers, which are easily purified due to the high mass differences between the cyclopentadienone and the final dendrimer. However, for each new functionality, an appropriate cyclopentadienone building unit has to be synthesized. This can be achieved via a double Knoevenagel reaction of an already functionalized benzil 35 and diphenylacetone 24. For example, 4,4 -dibromobenzil (35a) as well as 4,4 -dimethoxybenzil (35 b) are commercially available and give the cyclopentadienone building unit with two bromo- or methoxy substituents in high yields [30, 34]. Furthermore the bromo substituent of the dibromocyclopenta-dienone can be quantitatively converted into a cyano (37) or amino (38) function (Scheme 13) [52]. 

This chapter describes composite materials composed of dendrimers and metals or semiconductors. Three types of dendrimer/metal-ion composites are discussed dendrimers containing structural metal ions, nonstructimal exterior metal ions, and nonstructiu al interior metal ions. Nonstructural interior metal ions can be reduced to yield dendrimer-encapsulated metal and semiconductor nanoparticles. These materials are the principal focus of this chapter. Poly(amidoamine) (PAMAM) and poly(propylene imine) dendrimers, which are the two commercially available families of dendrimers, are in many cases monodisperse in size. Accordingly, they have a generation-dependent munber of interior tertiary amines. These are able to complex a range of metal ions including Pd +, and Pt +. The maximmn munber... 

Since the first report of the synthesis of dendrimers twenty years ago [1], there has been a remarkable increase in interest in these fascinating materials. For example, the number of publications relating to dendrimers was about 15 in 1990, but this number increased to 150 in 1995, and 420 in 1997. Until very recently emphasis in this field was placed on the synthesis of new families of dendrimers having novel architectures, but more recently there has been interest in finding technological applications for these materials [2-5]. The pursuit of applications has been greatly accelerated by the recent commercial availability of dendrimers through Dendritech, Inc. (Midland, MI), Dutch State Mines (DSM, The Netherlands), and the Aldrich Chemical Co. (Milwaukee, WI). 

PPI dendrimers are synthesized via the reaction sequence as shown in Fig. 2. This repetitive reaction sequence involves a Michael addition of two equivalents of acrylonitrile to a primary amine, followed by hydrogenation of the nitrile groups to primary amines. Commercially available PPI dendrimers are usually terminated with amine groups. 

In 1996, Kim and coworkers reported for the first time on the use of a polyami-doamine (PAMAM) dendrimer [Gl] as a soluble support for organic synthesis (Fig. 7.5) [37]. Advantages of PAMAM are its commercial availability and its high symmetry, which provides uniform site accessibility (in lower generations) and facilitates NMR interpretation. By attaching 4-hydroxymethylbenzoic acid (HMB) to... 

Commercially available dendrimers are polyamine dendrimers (Astramol ,... 

Recently another family of dendrimers has become commercially available. These polyamines were developed by Meijer and de Brabander-van den Berg of DSM Research and are based on Vogtle s initial synthesis [7]. In this case the troublesome reduction step was performed using a Raney cobalt hydrogenation catalyst and other process improvements have permitted this synthesis to be continued up to the fifth generation with multikilogram quantities available. 

Reetz et al. (16) functionalized commercially available DAB-dendrimers with diphenylphosphine groups at the periphery (1) via a double phosphination of the amines with diphenylphosphine and formaldehyde. The transition metal complexes la-le have been prepared in which the dendrimer-N-(CH2PPh2)2 groups act as bidentate ligands. 

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