Xanthenone containing macromolecular photosensitizers as heterogeneous photocatalysts for visible light-promoted synthesis of urea and imine fine chemicals

Abstract

Visible light-mediated photocatalysis is an attractive strategy for synthesizing high-value-added fine chemicals. As heterogeneous photocatalysts, macromolecular photocatalysts can effectively overcome the disadvantages of small-molecule photosensitizers that are difficult to recycle. In this work, a novel macromolecular photocatalyst was designed and synthesized for the visible-light-promoted synthesis of urea and imine fine chemicals. Through a modified Mitsunobu reaction, the precursor poly(2-hydroxyethyl methacrylate) (PHEMA) was combined with the functional small molecule photosensitizer 3-hydroxyl-9H-xanthine-9-one to prepare macromolecular photosensitizer PHEMA-XT. Visible light-mediated synthesis of ureas and imines using PHEMA-XT as the photocatalyst was systematically investigated with various organic amines containing aryl, alkyl, cycloalkyl and heterocycle groups. The results indicated that all the reactions proceeded smoothly under LED irradiation. Notably, the photocatalyst PHEMA-XT could be easily separated, recovered, and reused for ten consecutive cycles without significant loss of catalytic activity. The developed macromolecular photosensitizer exhibited outstanding photocatalytic performance in visible-light-promoted synthesis of urea and imine fine chemicals, demonstrating promising potential for sustainable applications.