Improving the rate of the copper-catalyzed Henry reaction by surface plasmon excitation of gold nanoparticles

Abstract

Green LED plasmon excitation (525 nm) of colloidal gold nanoparticles (NPs), onto which a copper(II) complex was grafted, in the presence of nitrobenzaldehyde and nitromethane in DMF lead to the formation of the corresponding nitroaldol with high efficiency. Kinetic studies using ¹H NMR and Raman spectroscopies showed that the reaction was faster under irradiation with green light, especially when in close proximity to the NPs (ca. 100% conversion after 100 min). After reaction completion, it was possible to recover the nanocatalyst and run two subsequent reactions. Green LED excitation of plasmonic nanocatalyst is shown to be a straightforward and efficient method for accelerating the rate of the Henry reaction with a lower energy demand and over a shorter reaction time when compared to the reaction performed under classical conditions.