Dendrimers hydrovinylation, using

The use of soluble dendrimers with phospine ligands experienced a rapid growth and was also transferred to several other dendrimer scaffolds [64—66]. Many reactions, such as hydrogenation, hydrovinylation, Stille coupling, Knoeve-nagel condensation and Michael addition were reported (Tab. 7.2) [73, 74]. 

For some of them, the use of membrane reactors for their recovery or application in continuously operated reactors has been demonstrated. Examples include the use of dendrimer-bound nickel catalysts for the Kharasch addition [54, 59] and dendritic palladium catalysts for an allylic substitution [73, 60]. The membrane reactor concept has also been transferred to reactions at higher pressure, as shown for the hydrovinylation of styrene (cf. Section 3.3.3) [75]. Modem ultra-and nanofiltration membranes allow an effective recovery of the homogeneously soluble catalyst. However, in some cases the long-term stability of the catalyst under operating conditions has to be improved. 

Pd complexes of soluble P,0-fimctionalized carbosilane dendrimers (8) were used by Vogt and co-workers for the hydrovinylation reaction (codimerization of ethylene and styrene). This C-C coupling reaction is of great interest, because it opens an easy access to building blocks for fine chemicals as well as pharmaceuticals [Eq. (6)] [16]. 

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