Selenium-modified microgels as interfacial catalysts for the heterophase oxidation of aromatic aldehydes†

Abstract

The use of selenium-modified microgels as interfacial catalysts offers a promising solution for the efficient and environmentally friendly oxidation of aromatic aldehydes. Our study highlights the use of mild reaction conditions (30–50 °C) and hydrogen peroxide as a green oxidant, taking advantage of a heterophase reaction system for the ease of product separation. The effectiveness of this system is demonstrated by the high yield of benzoic acid (95.6% with a selectivity of 96.6%) achieved in a toluene/water system at 50 °C and 8 hours reaction time. The versatility of this catalytic system is further highlighted by its successful application to various aldehydes – anisaldehyde (28.5% yield of anisic acid and 35.2% yield of mequinol), cinnamaldehyde (29.8% yield of cinnamic acid and 9.8% yield of hydrocoumarin), and veratraldehyde (39.0% yield of 3,4-dimethoxyphenol). Notably, the selenium-modified microgels exhibit excellent surfactant properties and interfacial catalytic activity in diverse heterophase organic/water solvent systems, such as chloroform/water (70.9% yield of benzoic acid), ethyl acetate/water (53.6% yield of benzoic acid), and 1-octanol/water (25.5% yield of benzoic acid and 23.3% yield of octylbenzoate). This adaptability expands the potential applications of these microgel catalysts. Moreover, the ease of catalyst recovery and good reusability of the microgel catalysts were confirmed over multiple reaction cycles, making them an attractive alternative for sustainable synthesis of aromatic acids and other oxidation processes.