Catalysis by Carbon Materials for the Aerobic Baeyer–Villiger Oxidation in the Presence of Aldehydes

Abstract

Aerobic Baeyer–Villiger oxidation of ketones to corresponding esters was performed using metal-free carbon as a solid catalyst and benzaldehyde as the sacrificing agent. Several carbon materials were tested for the oxidation of cyclohexanone to ε-caprolactone, and it was found that Ketjen Black showed the highest catalytic activity, over 90% of ε-caprolactone yield at 50 °C. A catalyst recycling test suggests that the catalyst has high durability under the reaction condition of oxygen atmosphere at 50 °C. Mechanistic study suggests that peracid species produced by a series of chain propagation reactions is the key intermediate, and the carbon catalyst contributes to high aldehyde efficiency by buffering the radical species, which are essential for the chain propagation reactions.

Nano silica boron sulfuric acid as a dual Brønsted/Lewis acid and a heterogeneous catalyst in Baeyer–Villiger oxidation of ketones with hydrogen peroxide

“…Compared with the others, although dioxygen/benzaldehyde is an interesting approach and supplies good yields and times, but this protocol needs at least two or three equivalents of aldehyde per one equivalent of starting ketone. In addition, this combination also produces a peracid in situ, and once again we encounter to the aforementioned drawbacks of peracids [12][13][14]. Moreover, according to our literature survey, though many of the reported oxidative catalytic system of ketones, are powerful and efficient in oxidation of cyclic ketones, but most of them are unsuccessful or very weak in the oxidation of aromatic or acyclic ketones, whereas this work is more successful and shows a good versatility [6,12,29,[32][33][34].…”

“…Consequently, a lot of efforts have been focused on finding out of less dangerous and greener alternatives such as oxygen/aldehydes, hydrogen peroxide/carboxylic acids, hydrogen peroxide/acids or bases and also bio-oxidants, etc. [6][7][8][9][10][11][12][13][14]. Hydrogen peroxide with a high content of oxygen (47 wt%) is a commercially available, inexpensive and environmentally benign reagent, which simplifies greatly the workup and, contrary to peracids, avoids the separation of the carboxylic acid salt as the by-product.…”

Aerobic Baeyer–Villiger oxidation of cyclic ketones over periodic mesoporous silica Cu/Fe/Ni/Co-HMS-X

“…From the results and literature reports it can be said that catalytic system is capable of giving good result in short time on stream. [1][2][3][4][5][6][7][8][9] The influence of flow rate of O 2 on the oxidation of cyclohexanone over Co-HMS-X at 50 o C has also been carried out. The cyclohexanone conversion was 84% when flow rate was 5 mL/min, and then slowly increased to 93.6% with the rise of flow rate of O 2 to 10 mL/min.…”

“…The Baeyer-Villiger type oxidation is a valuable reaction to oxidize ketone to an ester directly [1]. Catalytic versions of the Baeyer-Villiger oxidation are particularly attractive for practical applications as described earlier.…”

Efficient Baeyer-Villiger electro-oxidation of ketones with molecular oxygen using an activated carbon fiber electrode in ionic liquid [bmim][OTf]

“…Therefore, molecular oxygen-based protocols are powerful methods for the oxidation of ketones and attract a great attention, which make the reactions of choice in large and industrial scale applications. A number of catalytic oxidation processes based on the combination of transition metals or organocatalysts and O 2 have been developed for such a conversion [31][32][33][34]. However, these methods still suffered from environmental hazards, poor recovery of expensive metal catalysts and laborious workup procedures.…”