Synthesis and Self‐Association of First‐Generation 1,3,4‐Oxadiazole‐Containing Dendrimers

Two 1,3,4‐oxadiazole‐containing dendrimers, 14 and 15 , have been prepared employing a palladium‐catalyzed carbonylation reaction as the key step of the synthesis. In order to shorten the reaction sequence, a new oxadiazole synthesis has been developed based on the coupling of aryl iodides with aryl tetrazoles in the presence of a Pd(0) catalyst and carbon monoxide, and has been applied to the preparation of dendrimer 14 . Both new dendrimers are highly soluble in chlorinated solvents, but 14 , with fewer solubilizing tert ‐butyl groups at its periphery, self‐associates in solution by π‐π interactions and possibly due to solvophobic effects. Considerable upfield shifts of the 1 H‐NMR signals of the protons in the centre of the molecule indicate the formation of π‐stacks in solution. Vapour‐pressure osmometry studies allow a degree of association of ⩾3 to be estimated.