Frechet-type dendritic catalyst

Styryl-terminated Frechet-type dendrimers have been introduced as novel polymer crosslinkers by Seebach et al. [43-45]. They are constituted of four to 16 peripheral styryl units attached to aryl end branches of dendritic TADDOL, BINOL or Salen ligands and were copolymerised with styrene by suspension polymerisation. The catalytic performance of the polymer-bound catalyst was identical to that of the homogeneous analogues however, the supported catalysts could be used in many consecutive catalytic runs with only small loss in catalytic activity. A major drawback of fixing the catalytic unit in the core of the crosslinker is the poor loading capacity of the final polymer (0.13-0.20 mmol g 0> especially when high amounts of catalysts (10-20 mol%) are needed. 

The second approach involved the covalent attachment of Frechet-type monodendrons (i.e., G = 1-3) to appropriate polymerizable reagents such as styrenes [143,146] or methacrylates [144] (Fig. 24). Suitable radical catalysts were used to polymerize these dendritic macromonomers into structures that were observed to be cylindrical rodlike architectures [144,146,147]. 

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