SYNTHESIS OF 4 GENERATIONS OF MONODISPERSE ARYL ESTER DENDRIMERS BASED ON 1,3,5-BENZENETRICARBOXYLIC ACID

The convergent synthesis of a series of monodisperse dendrimers based upon symmetrically substituted benzenetricarboxylic acid esters is described. These materials consist of 4, 10, 22, and 46 benzene rings connected symmetrically and have molecular diameters of up to 45 angstrom. The synthesis proceeds in a stepwise convergent manner, building dendritic arms, three of which are subsequently attached to a molecular core. The critical intermediate for the dendrimer arm synthesis is 5-(tert-butyldimethylsiloxy)isophthaloyl dichloride, obtainable in three steps from 5-hydroxyisophthalic acid. Reaction of the diacid chloride with phenol, followed by removal of the silyl protecting group, gives a new substituted phenol. Two moles of the latter are further reacted with 5-(tert-butyldimethylsiloxy)isophthaloyl dichloride. This process is repeated several times. The dendrimer arms formed by these reactions are coupled to 1,3,5-benzenetricarbonyl trichloride yielding dendrimers. Kinetic results suggest that the rate of reaction of the first dendrimer arm with the core is independent of the size of the dendrimer arm. These materials are stable up to 500-degrees-C under N2 and are highly soluble in typical organic solvents. Possible applications for these materials include molecular weight standards, polymer rheology modifiers, or molecular inclusion hosts.