Low temperature solvent-free allylic oxidation of cyclohexene using graphitic oxide catalysts

Abstract

A range of graphitic oxides have been utilised as metal free carbocatalysts for the low temperature oxidation of cyclohexene. The activity of the catalysts was correlated with the amount of surface oxygen on the graphitic oxide. In the case of cyclohexene oxidation, major selectivity is observed to allylic oxidation products. This is in contrast to the epoxide being the major product in linear alkene oxidation. This selectivity was maintained over long reaction times and at a conversion of above 50 %. Only small amounts of epoxide were observed, which eventually decreases at higher conversion due to hydrolysis to cyclohexane diol. The similarity between the non-catalysed and the catalysed product distribution suggests that these catalysts act as a solid initiator, and the role of the graphitic oxide is to decrease the lengthy induction period observed in the blank non-catalysed reaction.

Mesoporous Nitrogen-Doped Graphitized Carbon for Recyclable Oxidation of Cyclohexene

“…The comparison of the reaction atmosphere shows that new active intermediates will be produced under O 2 , which not only improves the allylic oxidation but also increases the possibility of epoxidation. According to relevant literature reports, , the remaining water of TBHP and the temperature exceeding 60 °C will be sufficient to hydrolyze the epoxides. Through the comparison experiments, it is found that despite the presence of water at 75 °C, the hydrolyzation of epoxides to cyclohexanediol could not occur with the existence of MNC-10 (Table S4).…”

“…They took the lead in developing metal-free catalysts in cyclohexene oxidation with the application of carbon nanotubes (CNTs) and nitrogen-doped CNTs using molecular oxygen as the oxidant. , The N-doped CNTs show significant improvement in activity for the nitrogen dopants and enhance the interaction between radicals and carbons. Metal-free catalysts represented by carbon materials have the advantages of high specific surface area, corrosion resistance, and low cost, which is preferred as a catalytic material in oxidation reaction . Defects, surface groups, types of nitrogen atoms, and graphitization degree play a regulatory role in the catalytic performance of these materials. , …”

“…Metal-free catalysts represented by carbon materials have the advantages of high specific surface area, corrosion resistance, and low cost, which is preferred as a catalytic material in oxidation reaction. 30 Defects, surface groups, types of nitrogen atoms, and graphitization degree play a regulatory role in the catalytic performance of these materials. 31,32 In this work, the melamine−formaldehyde-resin (MF) is used as the precursor, and silica is used as the template to synthesize nitrogen-doped graphitized carbon materials with a mesoporous structure (MNC).…”

Lowering the Operating Temperature of Gold Acetylene Hydrochlorination Catalysts Using Oxidized Carbon Supports

“…Further increasing the level of oxidation has a detrimental effect on the activity of the final catalyst, with the lowest initial activity of the set achieved using 10 g of KMnO 4 per 5 g of carbon. X-ray photoelectron spectroscopy (XPS) analysis of the range of oxidized carbon supported catalysts demonstrated that the trend in atomic percentage of oxygen (O at %) is nonlinear with respect to the amount of KMnO 4 used per 5 g of carbon (Figure c), a similar trend to that observed in our previous work. , Therefore, the comparison of maximum activities as a function of O at % is more appropriate than the amount of oxidant used (Figure d). This clearly demonstrates the effect of oxidation of the support, with an optimum of ca.…”

The Over-Riding Role of Autocatalysis in Allylic Oxidation

“…The catalyst is required for this initial reaction and in its absence the overall reaction is much slower, but in effect the catalyst is acting as an initiator. Most recently we have studied the allylic oxidation of cyclic alkenes with graphitic oxide [15]. While the presence of graphitic oxide increases the conversion compared with the blank reaction, both blank and catalysed reaction followed the same conversion verses selectivity trend, indicating that in this case the graphitic oxide is acting as an initiator for the allylic oxidation reaction.…”