Polyannulation of internal alkynes and O-acyloxime derivatives to synthesize functional poly(isoquinoline)s

Abstract

A novel polymerization route for the synthesis of multi-substituted poly(isoquinoline)s is introduced. The polyannulations of internal diynes and O-acyloxime derivatives are catalyzed by [Cp*RhCl₂]₂ with Cu(OAc)₂·H₂O as the oxidant in a methanol/THF mixture at 105 °C for 12 h, generating poly(isoquinoline)s containing fused heterocyclic rings with high molecular weights (up to 18 340) in almost quantitative yields. This polymerization is tolerant to stoichiometric imbalance and various functional groups, and is environmentally friendly with acetic acid as the only by-product. Most of the polymers are soluble and transparent in the visible light region (400–800 nm). Their thin films exhibit high refractive indices (RI = 1.832–1.571) in a wide wavelength region of 400–1000 nm. The poly(isoquinoline) carrying tetraphenylethene units is highly emissive in the aggregated state, and can generate discernible photopatterns upon UV irradiation. It can also function as a sensitive fluorescent chemosensor for detecting nitro-aromatic explosives such as picric acid in a superamplification manner.