Helical sense selective polymerization of bulky aryl isocyanide possessing chiral ester or amide groups initiated by arylrhodium complexes

Bulky aryl isocyanide monomers possessing tert-butyl groups at the ortho position and chiral ester or amide groups at the para position were prepared and polymerized by arylrhodium complex to give polyisocyanides with narrow polydispersity indexes in good yields. The large specific rotation and the intense Cotton effect at 347 nm suggest that the resulting polymers maintained predominantly one-handed helical conformation in solution. The chiroptical properties were increased with an increase in the polymerization degree and were fixed in the region of the polymerization degree more than 70. A positive nonlinear relationship was observed between the optical purity of the chiral monomer and the helical sense selectivity of the resulting polymers. The helical sense selectivity depends on the structure of the chiral ester groups such as the length of the alkyl chain and the position of the chiral carbon center.