Baeyer-Villiger Oxidation Of Cyclohexanone Research Articles

A Family of Hexacopper Phenylsilsesquioxane/Acetate Complexes: Synthesis, Solvent-Controlled Cage Structures, and Catalytic Activity.

Convenient self-assembly synthesis of copper(II) complexes via double (phenylsilsesquioxane and acetate) ligation allows to isolate a family of impressive sandwich-like cage compounds. An intriguing feature of these complexes is the difference in the structure of a pair of silsesquioxane ligands despite identical (Cu6) nuclearity and number (four) of acetate fragments. Formation of particular combination of silsesquioxane ligands (cyclic/cyclic vs condensed/condensed vs cyclic/condensed) was found to be dependent on the synthesis/crystallization media. A combination of Si4-cyclic and Si6-condensed silsesquioxane ligands is a brand new feature of cage metallasilsesquioxanes. A representative Cu6-complex (4) (with cyclic silsesquioxanes) exhibited high catalytic activity in the oxidation of alkanes and alcohols with peroxides. Maximum yield of the products of cyclohexane oxidation attained 30 %. The compound 4 was also tested as catalyst in the Baeyer-Villiger oxidation of cyclohexanone by m-chloroperoxybenzoic acid: maximum yields of 88 % and 100 % of ϵ-caprolactone were achieved upon conventional heating at 50 °C for 4 h and MW irradiation at 70 or 80 °C during 30 min, respectively. It was also possible to obtain the lactone (up to 16 % yield) directly from the cyclohexane via a tandem oxidation/Baeyer-Villiger oxidation reaction using the same oxidant.

Protecting Mg-sites from hydration by embedding magnesium-aluminium layered double hydroxide in halloysite and using as pickering catalysts in Baeyer-Villiger oxidation

A facile strategy was developed via thermal treatment to get hierarchically structured magnesium-aluminium layered double hydroxide (MgAl-LDH) selectively loaded on the inner and external surfaces of halloysite nanotubes, respectively. The loaded MgAl-LDH was found to have active centers for Baeyer-Villiger (BV) oxidation that was protected from hydration by embedding in halloysite lumens. The BV oxidation of cyclohexanone was observed to have better performance by using the halloysite impregnated MgAl-LDH (MgAl-LDH@Hal) as catalysts than that of external surface modified MgAl-LDH (MgAl-LDH@Hal600). A conversion 57.0% of cyclohexanone was achieved, and the yield of ε-caprolactone was 22.0% when the MgAl-LDH@Hal was used as catalysts. Density Functional Theory (DFT) calculations as well as high-resolution of X-ray photoelectron spectrum (XPS) measurements revealed the charge depletion occurred in the Mg-sites of sample MgAl-LDH@Hal in comparison with MgAl-LDH@Hal600, which benefited the activation of H2O2 oxidants, and thus assisting the BV reaction. The prepared composites were able to work as phase-transfer catalysts as Pickering emulsions in oxidation of cyclohexanone.

One-pot Baeyer–Villiger oxidation of cyclohexanone with in situ generated hydrogen peroxide over Sn-Beta zeolites

ε-Caprolactone is traditionally produced through Baeyer-Villiger oxidation of cyclohexanone oxidized by peracids in industry, which inevitably results in large discard acid and environmental pollution. To this end, a green route to ε-caprolactone was developed by coupling the direct generation of hydrogen peroxide from aerobic oxidation of benzhydrol catalyzed by NHPI and Baeyer-Villiger oxidation of cyclohexanone with the in situ hydrogen peroxide over Sn-Beta zeolites in one pot. Molecular oxygen was employed as the terminal oxidant, and the effects of several reaction factors were studied. Compared with one-step process, the one-pot two-step method noticeably improved the selectivity of ε-caprolactone. When the amount of in situ hydrogen peroxide was 0.72 equivalent, the selectivity of ε-caprolactone was obtained 94.8% with 39.2% conversion of cyclohexanone, and the efficiency of H2O2 was up to 51.5%. As compared to the commercial 30 wt% aqueous H2O2 added directly, in situ H2O2 dramatically improved the selectivity of ε-caprolactone and had higher efficiency. Additionally, the catalyst could be easily separated from the reaction solution and reused several times without the remarkable loss of activity.

Tin and copper species dispersed on a metal-organic framework as a new catalyst in aerobic Baeyer-Villiger oxidation: An insight into the mechanism

Metal-organic frameworks (MOF) containing tin and copper metal salts were used as catalysts in the Baeyer-Villiger oxidation of cyclohexanone. The outcome was a synergistic effect on the catalyst's efficiency, which resulted from the simultaneous presence of copper and tin species in the MOF. The catalyst with high metal content showed the intermolecular dehydration of benzoic acid and the formation of benzoic anhydride in a side reaction as well as the Baeyer-Villiger oxidation reaction with a decline in efficiency. The optimized catalyst promoted the Baeyer-Villiger reaction in a high yield without the formation of benzoic anhydride.

Influence of Hydrophilicity on the Snβ‐Catalyzed Baeyer–Villiger Oxidation of Cyclohexanone with Aqueous Hydrogen Peroxide

AbstractSnβ zeolites are amongst the most effective heterogeneous catalysts for the Baeyer–Villiger (BV) oxidation of ketones with aqueous hydrogen peroxide (H2O2). The high selectivity is rooted in the activation of the carbonyl substrate through interaction with the isolated SnIV sites. However, these sites are also accessible to other molecules in the reaction mixture (in particular the co‐solvent and product). In this contribution, we report the impact of competitive adsorption on the Snβ‐catalyzed BV oxidation of cyclohexanone with aqueous H2O2. We furthermore prepared a series of Snβ zeolites with varying amounts of framework silanols and quantified their hydrophilicities with water adsorption and IR experiments. By correlating the results with catalytic data, we show that Snβ zeolites with an intermediate hydrophilicity achieve the highest activity. Our adaptable post‐synthetic synthesis allows us to tune the material synthesis, resulting in enhanced activity compared with conventional hydrothermal Snβ.

Enhanced production of ε-caprolactone by coexpression of bacterial hemoglobin gene in recombinant Escherichia coli expressing cyclohexanone monooxygenase gene.

Baeyer-Villiger (BV) oxidation of cyclohexanone to epsilon-caprolactone in a microbial system expressing cyclohexanone monooxygenase (CHMO) can be influenced by not only the efficient regeneration of NADPH but also a sufficient supply of oxygen. In this study, the bacterial hemoglobin gene from Vitreoscilla stercoraria (vhb) was introduced into the recombinant Escherichia coli expressing CHMO to investigate the effects of an oxygen-carrying protein on microbial BV oxidation of cyclohexanone. Coexpression of Vhb allowed the recombinant E. coli strain to produce a maximum epsilon-caprolactone concentration of 15.7 g/l in a fed-batch BV oxidation of cyclohexanone, which corresponded to a 43% improvement compared with the control strain expressing CHMO only under the same conditions.

Baeyer-Villiger Oxidation of Cyclohexanone Catalyzed by SBA-15 Supported Silicotungstic Acid

Silicotungstic acid (H4O40SiW12) was supported on SBA-15 with the content of 20% by impregnation. The structure and proper-ties of the catalyst were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, N2 adsorption-desorption, and transmis-sion electron microscopy. H4O40SiW12 was highly dispersed on SBA-15 without structural change. The material was applied as an efficient catalyst for the Baeyer-Villiger oxidation of cyclohexanone under different conditions such as the catalyst amount, reaction temperature, and reaction time. When 10 mg of catalyst was used, the cyclohexanone conversion and selectivity for lactone were up to 86% and 99%, respec-tively, at 70 oC for 8 h. The catalyst had moderate reusability in the oxidation system.

ChemInform Abstract: Bioreduction of (R)-Carvone and Regioselective Baeyer-Villiger Oxidations: Application to the Asymmetric Synthesis of Cryptophycin Fragment A.

Abstract Cryptophycin fragment A ( 1 ) was prepared in high enantiomeric purity in 10 steps from ( R )-carvone. A stereoselective bioreduction of ( R )-carvone to neodihydrocarveol and a regioselective Baeyer-Villiger oxidation of cyclohexanone 8 with pertrifluoroacetic acid were employed in this synthesis.

Hydrotalcites as Catalysts for the Baeyer—Villiger Oxidation of Cyclic Ketones with Hydrogen Peroxide/Benzonitrile.

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Hydrotalcites as catalysts for the Baeyer–Villiger oxidation of cyclic ketones with hydrogen peroxide/benzonitrile

Hydrotalcites (HTs) in variable Mg/Al ratios were used as catalysts for the Baeyer–Villiger (BV) oxidation of cyclic ketones with hydrogen peroxide. All HTs studied were found to be active in the BV oxidation of cyclohexanone, their activity increases with increasing Mg/Al ratio. The reaction, which was conducted under very mild conditions (viz. atmospheric pressure and a temperature of 70 °C), provided conversions above 70% with 100% selectivity only after 6 h. This outcome was found to require the presence of a nitrile in the reaction medium, so a mechanism involving adsorption of the nitrile and cyclohexanone onto the catalyst is proposed that is consistent with the experimental results. Based on the proposed mechanism, the presence of a surfactant should result in improved conversion and catalytic activity, as was indeed observed with sodium dodecylsulfate in the reaction medium. The best catalyst among those tested was used with other cyclic ketones and found to provide excellent conversion and selectivity results in most cases.