CuO{001} as the Most Active Exposed Facet for Allylic Oxidation of Cyclohexene via a Greener Route

Abstract

AbstractAllylic oxidation of olefins to α,β‐unsaturated carbonyl compounds, especially2‐cyclohexen‐1‐one, by the oxidation of cyclohexene is a prime chemical transformation in the organic industry due to its immense application as an intermediate in the synthesis of fine chemicals, pharmaceutical products, and perfumery products. Herein, we demonstrate microstructured copper oxide (CuO) as an efficient catalyst to oxidize cyclohexene to 2‐cyclohexen‐1‐oneand other value‐added intermediates in the presence of aerobic molecular oxygen as oxidant at 80 °C with outstanding conversion of cyclohexene and high selectivity towards 2‐cyclohexen‐1‐one. CuO with diverse shapes was synthesized by a one‐step hydrothermal method. CuO plates (PLs) and flowers (FLs) were obtained by varying the ammonia and sodium hydroxide concentration, and CuO spheres (SPs) and hollow spheres (HSs) were prepared by varying the urea concentration. Under optimized conditions, the CuO FL2 catalyst shows the highest conversion of cyclohexene (97.6 %) due to its smaller size, higher surface charge, and high‐energy {001} exposed facets. Reaction parameters such as reaction temperature, reaction duration, and catalyst concentration were varied to obtain the optimal reaction conditions for cyclohexene oxidation. Moreover, the CuO FL2 catalyst was recycled several times without any significant loss of catalytic activity, which ascertains recyclability and high stability of the catalyst for industrial use.