Iterative Synthesis of 1,3,5-Polyphenylene Dendrons via C−H Activation

An iterative synthesis of 1,3,5-polyphenylene dendrons via C−H activation/Suzuki−Miyaura coupling up to a third generation dendron is described. C−H bonds at the focal points of the dendrons are selectively borylated via iridium-catalyzed borylation, eliminating the need for reactive protecting groups. Sequential additions of low catalyst loadings efficiently borylate higher-generation dendrons, whereas higher initial catalyst loadings are less efficient.