An efficient and scalable room temperature aerobic alcohol oxidation catalyzed by iron chloride hexahydrate/mesoporous silica supported TEMPO

An efficient room temperature catalytic system FeCl3·6H2O/SBA-15-TEMPO/NaNO2 for the oxidation of alcohols with dioxygen or air as terminal oxidant has been developed. Various alcohols were oxidized at a low catalyst loading (0.1-1 mol %) to the corresponding carbonyl compounds in good to excellent yields. For the oxidation of benzyl alcohol, the excellent turn-over frequency (TOF) of 81.4 h−1 was achieved (turn-over number (TON) up to 9770). The catalyst SBA-15-TEMPO can be reused for 10 reaction runs without significant loss of catalytic activity. In addition, the two components FeCl3·6H2O and SBA-15-TEMPO can also be reused for at least four reaction runs without appreciable loss of catalytic activity. In the case of large-scale experiment for the oxidation of benzyl alcohol, the desired product benzaldehyde was obtained in 94.5% yield.

An efficient and practical room temperature oxidation of alcohols catalytic system by using FeCl3·6H2O in conjugation with NaNO2 and a low catalytic amount of SBA-15-supported TEMPO (0.1-1 mol %) with dioxygen or air as terminal oxidant was developed. Various alcohols were smoothly oxidized to their corresponding carbonyl compounds with good to excellent yields, even in large-scale operations. The catalysts could be reused for at least four runs without significant loss of catalytic activity.