Phenylboronic acid functionalized polyacrylonitrile fiber for efficient and green synthesis of bis(indolyl)methane derivatives

Abstract

The use of fiber as a catalyst carrier to construct heterogeneous catalysts with good catalytic activity and recycling performance has received wide attention. In this study, three phenylboronic acid functionalized polyacrylonitrile fiber (PANF) catalysts were synthesized by amination and quaternization. Fourier transform infrared spectroscopy, X-ray diffractometry, scanning electron microscopy, and X-ray photoelectron spectroscopy were used to verify the successful grafting of phenylboronic acid and the structural integrity of the fiber catalyst after recycling. The activity of the catalysts was explored with the Friedel–Crafts alkylation between indole and aromatic aldehydes. The results indicate that the synthesized catalyst (PAN p -BA F) in which the phenylboronic acid functional group was linked at the para position, exhibited the highest catalytic activity for the Friedel–Crafts alkylation. The substrate scope experiments confirmed that the catalyst has outstanding catalytic activity for most aromatic aldehydes, especially for those containing moderate electron donating groups. Moreover, the catalyst can be reused eight times in water without significant decrease in its catalytic activity. Further, the scale-up experiment confirmed that the fiber catalyst has a certain potential for industrial application.