Polymeric Sulfonated Phenylamine as an Efficient Solid Catalyst for Photochromic Naphthopyrans Production

Abstract

Naphthopyran (NP) compounds, known for their photochromic properties, hold considerable promise across various applications. Nevertheless, synthesizing these compounds remains a significant challenge. In this research, sulfonated aniline was reacted with 1,4-dichlorobenzene via Friedel-Crafts alkylation polymerization to create a novel polymeric sulfonated phenylamine (PSP) solid acid catalyst. This catalyst was employed in the condensation reaction between naphthol and bisphenyl-2-propynyl-1-alcohol, resulting in high yields of NP and demonstrating excellent versatility in synthesizing various photochromic NPs. Remarkably, the catalyst can be easily recovered and reused without significant loss of performance. The study revealed that the appropriate acid strength of PSP is crucial for producing NP with high activity and selectivity. A possible mechanism explaining the enhanced catalytic activity of this novel PSP has been proposed.