Visible Light-Emitting Diode Light-Driven Aerial Oxidation of Aldehydes under Catalyst and Solvent-Free Conditions

摘要

Background: Green and sustainable method for the oxidation of aldehydes into acids is now in demand as carboxylic acids are important and versatile intermediates. In this context, visible LED light-promoted aerial oxidation can be efficient and greener protocol. Objective: Herein, we have demonstrated a visible LED light-promoted efficient and greener protocol for the aerial oxidation of aromatic aldehydes into corresponding acids in the absence of any additives, base, catalyst, and oxidant. Methods: The oxidation of aromatic aldehydes was irradiated by an LED light at room temperature under an open atmosphere, monitored by TLC. The rate of oxidation was also monitored using different LED lights by UV-Vis studies. The products were purified by column chromatography using silica gel, and the mixture of ethyl acetate/petroleum ether as an eluting solvent and the pure products were confirmed by their melting point determination and NMR spectroscopic analysis. Results: The aldehydes were successfully converted into corresponding acids with good isolated yields (60-90 %) by this protocol, where blue LED light (l ~ 490 nm) was found to be the best choice. Conclusion: The present protocol of aerial oxidation of aromatic aldehydes into corresponding acids under visible LED light has been carried out in the absence of catalyst, oxidant, base, and any other additives. The higher isolated yields, no byproduct formation, and neat reaction conditions are the major advantages of the protocol.