Synthesis of Dendrimer-Like Helical Poly(Phenyl Isocyanide)s Using Air-Stable Palladium Complexes with Double Arms

A new stepwise iterative method is developed for the synthesis of well-defined dendrimer-like helical poly(phenyl isocyanide)s (PPIs). The method mainly involves the following three reaction steps in an iterative process: 1) the polymerization of decyl 4-isocyanobenzoate (monomer 1) or 4-isocyanobenzoyl-2-aminoisobutyric acid decyl ester (monomer 2) to afford the polymer, 2) reacting one pentafluorophenyl (PFP) ester-functionalized phenyl isocyanide (monomer 3) at the end of the polymer, followed by the treating of PPh3 to remove the -Pd(PEt3)(2)Cl groups, and 3) the transesterification reaction of the PFP group with hydroxyl functionalized palladium catalyst (catalyst 1) to introduce two -Pd(PEt3)(2)Cl groups at the end of the polymer, which can be used as the next initiating site. Repeating the above three reaction steps, (1), (2) and (3), enables the synthesis of high-generation and high-molecular-weight dendrimer-like helical PPIs. In practice, a series of dendrimer-like helical poly-1(n)s and poly-2(m)s up to the fourth generation (4G) are successfully synthesized. The molecular weight (M-n) of the final 4G dendrimer-like poly-1(n)s and poly-2(m)s is 49.4 and 66.5 kDa, respectively and they are both with narrow molecular weight distribution.