Cascade Polyannulation of Diyne and Benzoylacetonitrile: A New Strategy for Synthesizing Functional Substituted Poly(naphthopyran)s

A new strategy for synthesizing multisubstituted poly­(naphthopyran)­s (PNPs) with novel functionalities was described. The cascade oxidative polyannulation of benzoylacetonitrile and internal diynes are catalyzed by [RhCp*Cl₂]₂ and Cu­(II) acetate in dimethylformamide at 90 °C, generating PNPs with high molecular weight of up to 19 300 in excellent yields (isolation yield up to 96.4%). This polymerization method enjoys the remarkable advantages of high reaction rate, high efficiency, and atom-economy. All of the polymers show good solubility in common organic solvents and high thermal stability (degradation temperature up to 431 °C). The thin films of PNPs display high refractive indices (1.5137–1.7524) in a wide wavelength range of 450–1600 nm. PNP containing tetraphenylethene units can be utilized to generate a well-resolved nanoscale photopattern by UV irradiation of its film through a copper mask. The PNPs exhibit the phenomena of mechanochromism and vapochromism: their emission is turned on upon scratching and solvent fuming their solid powders. Such attributes allow the polymers to be used as security materials or fluorescent indicators in various fields.