Starburst conjugates

Tomalia etal, US Patent 6,177,414 (January 23, 2001) Assignee The Dow Chemical Company Utility Agricultural and Pharmaceutical Intermediate 

N-t-Butoxycarbonyl-l,4,8,ll-tetraazara-5,7-dioxoundecane (13mmol) was dissolved in 100 ml methyl alcohol, methyl acrylate (68 mmol) added, and the reaction stirred at ambient temperature 72 hours. Thereafter the solution was concentrated to 30% solids and methyl acrylate (32 mmol) again added. The mixture was stirred 24 hours at ambient temperature until no partially alkylated moieties were detected using HPLC (Spherisorb ODSl, acetonitrile/0.04 M NH4OAC, 40 60). The solvent was removed at 30°C by rotary evaporation pumping down to 1 mmHg for 24 hours and the product isolated in 7.81 g of a viscous oil. 

The product from Step 1(10.45 mmol) was dissolved in 75 ml methyl alcohol and added dropwise over 2 hours to a stirred solution of ethylenediamine (7.41 mol) dissolved in 50 ml methyl alcohol. The reaction stirred at ambient temperature and excess ethylenediamine and solvent removed. The residue was dissolved in 90 ml methyl alcohol and purified from residual ethylenediamine by reverse osmosis (Filmtec TC-30 membrane and AmiconTClR channel separator, methyl alcohol as solvent). After 48 hours no ethylenediamine could be detected by gas chromatography (Column, Tenax 60/80) and the product isolated in 6.72 g as a glassy solid. 

Subsequent generations were prepared following the aforelisted Steps. 

Multi-generation dentrimers were also prepared by the author using other initiators indicated below. The preparation of these initiators is provided by the author. 

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In view of recent reports, it seems prospective to use the reaction of trans sily-lation for the synthesis of other types of unsaturated compounds, particularly for the synthesis of novel organosilicon starburst compounds having a silicon-bridged -conjugated structure which is expected to have potential optoelectronic properties. The effective functionalization of l,3,5-tris(dimethylvinylsi-lyl)benzene by the respective reactions with 1,4-divinylbenzene leads to the formation of a dendrimer (Fig. la) [55]. 

Benefiting from its special propeller starburst molecular structure, amorphous materials with isotropic optical and charge-transporting properties could be expected when combining triphenylamine with linear TZ-conjugated systems. The synthesis is shown in Figure 2.36. 

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