Multiple use of soluble metallodendritic materials as catalysts and dyes.

Different sizes of core-functionalized metallodendritic wedges were prepared by anchoring sensor-active arylplatinum(II) sites at the focal point of Fréchet-type polyether dendritic wedges of various generations. The strong color of these metallodendrimers in the presence of SO2 was used to assess the permeability of nanofiltration membranes (molecular weight cut-off of 400 dalton) at ambient pressure. A primary result of these studies is that dendrimers do not have to be exceptionally large for successful retention. Hence, nanofiltration, membrane-capped. immersion vials were developed, which operate as sensor devices when loaded with metallodendrimers with good retention properties. Appropriate substitution of the dye site at the focal point of these metallodendritic wedges by a catalytically active group afforded dendritic catalysts that exhibit essentially the same physical properties (shape, retention) as the corresponding dyefunctionalized dendritic wedges. When this homogeneous catalyst is compartmentalized in membrane-capped vials, a unique and convenient method for its retrieval from product solutions is available. Moreover, such immobilized metallodendritic catalysts can be regenerated and stored for months without losing their activity; this provides access for the development of novel sustainable homogeneous catalysts.

Functionalized carbosilane dendritic species as soluble supports in organic synthesis.

A new methodology, which is compatible with the use of reactive organometallic reagents, has been developed for the use of carbosilane dendrimers as soluble supports in organic synthesis. Hydroxy-functionalized dendritic carbosilanes Si[CH2CH2CH2SiMe2(C6H4CH(R)OH)]4 (G0-OH, R = H or (S)-Me) and Si[CH2CH2CH2Si[CH2CH2CH2SiMe2(C6H4CH(R)OH)]3]4 (G1-OH, R = H or (S)-Me) were prepared and subsequently converted into the esters Si[CH2CH2CH2SiMe2(C6H4CH(R)OC(O)CH2Ph)]4 (R = H or (S)-Me) and Si[CH2CH2CH2Si[CH2CH2CH2SiMe2(C6H4CH(R)OC(O)CH2C6H4 R')]3]4 (R = H and R' = H or R = (S)-Me and R' = H or R = H and R' = Br). As an example the latter compound was functionalized under Suzuki conditions. The functionalized carboxylic acid was obtained in high yield after cleavage from the dendritic support. Moreover, the ester functionalized dendrimers were converted to the corresponding zinc enolates followed by a condensation reaction with an imine to a beta-lactam in excellent yield and purity. Furthermore, it was demonstrated that a small combinatorial library of beta-lactams could be prepared starting from a carbosilane dendrimer functionalized with different ester moieties. These results show that carbosilane dendrimers can be applied as soluble substrate carriers for the generation of low molecular weight organic molecules. In combination with nanofiltration techniques, separation and recycling of the dendrimers can be realized.