Baeyer-Villiger Oxidation Reaction Research Articles

In Situ Synthesis of Iron-Based Porphyrin Metal-Organic Frameworks for the Baeyer-Villiger Oxidation Using Air as an Oxidant.

Iron-based porphyrin metal-organic frameworks (PMOFs) are a new type of material with good stability, catalytic activities, and reusability, which have broad application prospects. However, the synthesis of iron-based PMOFs with different metalloporphyrin units requires a considerable amount of reagents and time. Herein, an in situ synthesis method was developed to simplify the synthetic process of iron-based PMOFs. A series of highly stable iron-based PMOFs (Msitu-PMOF-3(Fe) (M = Fe, Co, Ni, Cu, Pd)) were synthesized in one pot without the preparation of metalloporphyrin ligands in advance. This synthesis method is simpler and more efficient, saving considerable time and material costs. The resultant Msitu-PMOF-3(Fe) exhibits a high tolerance to aqueous solutions with pH ranging from 0 to 11, as well as various organic solvents. The catalytic experiments show that both Fesitu-PMOF-3(Fe) and Cositu-PMOF-3(Fe) can catalyze the Baeyer-Villiger oxidation of cyclohexanone using air as an oxidant at 35 °C. Moreover, when the mixtures of Fesitu-PMOF-3(Fe) and Cositu-PMOF-3(Fe) were employed as catalyst, they can exert a cooperative catalysis effect, resulting in a significantly enhanced catalytic activity compared to a single component. The mild reaction condition, high catalytic efficiency, and excellent selectivity endow this catalytic system with a good application prospect. This work not only provides a new approach for the synthesis of iron-based PMOFs but also offers guidance for the Baeyer-Villiger oxidation reactions using air under mild conditions.

Efficient catalysis for the Baeyer-Villiger oxidation reaction of 2-adamantone in acidic deep eutectic solvents

A deep eutectic solvent (DES) comprising p-toluenesulfonic acid (PTSA) and polyethylene glycol 200 (PEG200) was synthesized and applied to the Baeyer-Villiger (B-V) oxidation reaction of 2-adamantanone, which exhibited good catalytic effect and cyclic stability under relatively mild conditions. It was found that the hydrogen bond of DESs not only governed their physical properties, such as viscosity and electrical conductivity, but also influenced their chemical behavior, including the catalytic effect in B-V oxidation reaction. By adjusting the composition, the hydrogen bond properties can be optimized. This study aims to elucidate the intricate relationship between composition, hydrogen bond strength, and physicochemical properties of DESs, thereby establishing a preliminary theoretical foundation for a comprehensive understanding and construction of DESs systems. This provides a novel and promising environmentally friendly approach for the B-V oxidation reaction.

3D Hierarchical Composites of Hydrotalcite-Coated Carbon Microspheres as Catalysts in Baeyer–Villiger Oxidation Reactions

The use of heterogeneous catalysts is fundamental in the search for sustainable chemical processes. Research on hierarchical materials is a growing field aimed at optimizing the synthesis of catalysts. In this work, layered materials with metals of different cationic ratios and three-dimensional hierarchical structures have been synthesized in a simple and easy way using carbon spheres as support. All materials were characterized with various techniques such as XRF, elemental analysis XRD, FT-IR, SEM, and TEM to study their composition and structure. Finally, these materials were used in the Baeyer–Villiger reaction, which was carried out under optimized conditions. The results showed that the metal ratio was an important factor in the coating process, affecting the catalytic capacity of the materials.

Unprecedented nor-seco-diterpene lactones inhibited osteogenic differentiation of valve interstitial cells

The first examples of ent-atisane and ent-isopimarane diterpene lactones with an unusual 2,3-seco-2-nor-tetrahydro-2H-pyran-2-one nucleus, eufislactones A (1) and B (2), were isolated from the roots of Euphorbia fischeriana, together with a new (3) and fifteen known biosynthetic congeners (4–18). Their structures incorporating absolute configurations were elucidated via the comprehensive spectroscopic analyses, electronic circular dichroism (ECD) calculation, and single-crystal X-ray diffraction analyses. Biogenetically, compounds 1 and 2 were constructed by the plausible monomeric precursors, ent-atis-16-ene-3,14-dione (6) and ent-isopimara-8(14),15-dien-3-one (17), respectively, via key Baeyer-Villiger oxidation, decarboxylation, and semi-acetalization reactions to create a unique 2,3-seco-2-nor-tetrahydro-2H-pyran-2-one core. Our bioassays have revealed that eufislactone A (EFA, 1) displayed significant inhibitory effect on the osteogenic differentiation of human valvular interstitial cells (VICs), highlighting its potential as a preventive agent against the progression of human calcific aortic valve disease (CAVD).

Enhanced Photoinduced Baeyer–Villiger Oxidation of Ketones by Introducing Trinuclear Ruthenium Clusters into Polyoxometalate-Based Metal–Organic Frameworks

The development of solar-driven organic synthesis processes as an alternative to conventional thermo-catalytic technologies is of great research significance in academia and industry. Herein, we looked into the photoinduced Baeyer–Villiger oxidation of cyclohexanone based on the Mukaiyama method for the first time. We fabricated a crystalline polyoxometalate-based metal–organic framework photocatalyst, CR-SiW12, which represents the first example of trinuclear ruthenium clusters involved in the construction of polyoxometalate-based metal–organic frameworks. The cyclohexanone was efficiently converted to ε-caprolactone under visible light (>400 nm) irradiation with CR-SiW12 as the catalyst, with a reaction turnover number and turnover frequency recorded as 941 and 274.5 h–1, respectively, and the apparent quantum yield at 465 nm was measured to be 8.4%. Moreover, CR-SiW12 exhibited high structural stability and reaction reusability where reaction yield remained high at 91.3% after five consecutive reaction cycles. This work offers a promising strategy for accomplishing Baeyer–Villiger oxidation reactions under green conditions.

Fe@g-C3N4: an effective photocatalyst for Baeyer–Villiger oxidation under visible light condition

We fabricated peculiar, highly cogent Fe@g-C3N4 catalysts. Under visible light conditions, Fe@g-C3N4 (1 : 1) catalyst achieved 100% cyclohexanone conversion with 99.85% 2-oxepanone selectivity in the Baeyer–Villiger oxidation reaction.

Three-Dimensional Hierarchical Hydrotalcite–Silica Sphere Composites as Catalysts for Baeyer–Villiger Oxidation Reactions Using Hydrogen Peroxide

The development of effective, environmentally friendly catalysts for the Baeyer–Villiger reaction is becoming increasingly important in applied catalysis. In this work, we synthesized a 3D composite consisting of silica spheres coated with Mg/Al hydrotalcite with much better textural properties than its 2D counterparts. In fact, the 3D solid outperformed a 2D-layered hydrotalcite as catalyst in the Baeyer–Villiger reaction of cyclic ketones with H2O2/benzonitrile as oxidant. The 3D catalyst provided excellent conversion and selectivity; it was also readily filtered off the reaction mixture. The proposed reaction mechanism, which involves adsorption of the reactants on the hydrotalcite surface, is consistent with the catalytic activity results.

Electrochemical Formation and Activation of Hydrogen Peroxide from Water on Fluorinated Tin Oxide for Baeyer–Villiger Oxidation Reactions

The two-electron oxidation of water (2e-WOR) has been studied in the past as a possible method for the alternative preparation of hydrogen peroxide. Often, fluorinated tin oxide (FTO) is used as an anode and FTO itself was found also to be active for 2e-WOR. Because one use of H2O2 is as an oxygen donor for Baeyer–Villiger oxidation of ketones catalyzed by tin compounds and materials, presently we were interested in studying the use of in situ formed H2O2 for these reactions. First, the formation of H2O2 was verified in an acetonitrile/water solvent in a 2e-WOR reaction, which is more efficient than a comparable reaction in water in terms of the H2O2 concentration attained and faradaic efficiency at comparable potentials, that is, ∼3 V vs SHE. Second, initial studies on oxygenation of reactive substrates such as sulfides showed normalized reaction rates (NRRs) for two-electron oxidation reactions that were about 3 times higher than the NRR for H2O2 formation, indicating the formation of an active oxygen-donating or oxidizing species on the electrode surface prior to the formation and release of H2O2 into solution. Third, the Baeyer–Villiger oxygenation of 2-adamantanone at 2.1 V versus SHE in acetonitrile/water showed both the formation of the expected lactone product and hydroxylation at both tertiary and secondary C–H bonds. Hydroxylation is most easily explained by the presence of hydroxyl radical species as supported by the formation of a spin adduct and its identification by electron paramagnetic resonance. However, the potential used, 2.1 V versus SHE, is an underpotential for the formation of a solvated hydroxyl radical in solution, thereby leading to the conclusion that surface-bound hydroxyl species, OH*, are those that are reactive for the apparent one-electron water oxygenation reaction. Fourth, it was shown that although H2O2 can be thermally activated on FTO as a catalyst to a minor degree, electrochemical activation is by far more significant, leading to the use of FTO as an electrochemical catalyst for activation of H2O2 for the Baeyer–Villiger oxygenation and also alkene epoxidation.

A graph-convolutional neural network for addressing small-scale reaction prediction.

We describe a graph-convolutional neural network (GCN) model, the reaction prediction capabilities of which are as potent as those of the transformer model based on sufficient data, and we adopt the Baeyer-Villiger oxidation reaction to explore their performance differences based on limited data. The top-1 accuracy of the GCN model (90.4%) is higher than that of the transformer model (58.4%).

H2O2/HCl system: Oxidation-chlorination of secondary alcohols to α,α′-dichloro ketones

The one-pot oxidation-chlorination of secondary alcohols to give α,α′-dichloro ketones in 62–80% yields is reported. The convenient and readily available H2O2/HCl system acts on secondary alcohols (C5-C17) with the formation of α,α′-dichloro ketones. The reaction proceeds with high selectivity under the reported conditions; during this process peroxide formation and the Baeyer-Villiger oxidation reactions are not observed.

Organocatalytic Ring-Opening Polymerization of N-Acylated-1,4-oxazepan-7-ones Toward Well-Defined Poly(ester amide)s: Biodegradable Alternatives to Poly(2-oxazoline)s.

We report a series of poly(ester amide)s (PEAs) synthesized by organocatalytic ring-opening polymerization (ROP) of N-acylated-1,4-oxazepan-7-one (OxP) monomers, produced from N-acylated-4-piperidones using the Baeyer-Villiger oxidation reaction. The ROP of OxPs, conducted in CH2Cl2 at room temperature with benzyl alcohol as initiator and TBD/TU (1,5,7-triazabicyclo[4.4.0]dec-5-ene/thiourea) as a binary organocatalytic system, revealed a controlled/living character. The thermodynamics of the ROP highly depends on the N-acylated substituent of monomers, with the following reactivity order: OxPPh > OxPMe > OxPPr > OxPBn. Based on NMR results, it seems that our system follows the hydrogen bonding bifunctional activation mechanism. All intermediates and final products were characterized by NMR, MALDI-TOF MS, SEC, and DSC techniques. All poly(N-acylated-1,4-oxazepan-7-one) (POxP) polymers are amorphous with different glass transition temperatures (Tg), depending on the N-acylated substituent (Tg: -2.90 to 43.75 °C). Among the synthesized polymers, only POxPMe was water-soluble and it degraded much faster than polycaprolactone in an aqueous phosphate buffer saline solution (pH = 7.4). Therefore, poly(N-acylated-1,4-oxazepan-7-one)s are potential biodegradable alternatives to poly(2-oxazoline)s.

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.

Hydrothermal synthesis of boron-free Zr-MWW and Sn-MWW zeolites as robust Lewis acid catalysts.

An innovative strategy based on dual structure-directing agent-facilitated crystallization was proposed to hydrothermally synthesize boron-free Zr-MWW and Sn-MWW metallosilicates that bear great structural diversity for potential pore engineering. The metallosilicates show distinctive features in Lewis acid-catalyzed reactions as efficient heterogeneous solid catalysts.

COPPER TRIFLATE CATALYZED BAEYER- VILLIGER OXIDATION OF KETONES

A simple, efficient and eco-friendly method for Baeyer-Villiger oxidation reaction has been developed. The reaction employed m-CPBA as the oxidant with Cu(OTf)2 catalyst and was carried out in CH2Cl2 at room temperature. Nine lactones and ester were obtained in excellent yield (85-94%). Furthermore, the catalyst could be reused twice without considerable loss in activity.

Study on Synthesis of Acid-Washed Illite Supported Fe3O4 Nanometer Catalyst and Baeyer–Villiger Oxidation Reaction of Cyclohexanone

Baeyer–Villiger oxidation allows for effective control of the stereochemical structure of the product, which is a significant feature for functional group conversion and ring expansion in organic synthesis. In this study, Fe3O4 nanoparticles were loaded on acid-washed porous illite silicon slag (I-SR) using an in situ hydrothermal method to obtain the magnetic composite Fe3O4@I-SR. This composite was characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, N2 adsorption–desorption isotherm measurements, vibrating sample magnetometer analysis, etc. The results indicated that the Fe3O4 nanoparticles had a face-centered cubic lattice geometry with an average size of about 10 nm; the nanoparticles were uniformly dispersed on the surface of the carrier (I-SR) and exhibited strong paramagnetism. Fe3O4@I-SR composite was found to be a promising and efficient catalyst with high activity (> 99% cyclohexanone conversion and > 99% e-caprolactone selectivity) for the Baeyer–Villiger of cyclohexanone to e-caprolactone. The catalyst could be easily separated from the reaction mixture and reused many times. Thus, Fe3O4@I-SR is an attractive multiphase catalyst that is easy to handle and recycle under environmentally friendly reaction conditions.

Formation of novel disinfection by-products chlorinated benzoquinone, phenyl benzoquinones and polycyclic aromatic hydrocarbons during chlorination treatment on UV filter 2,4-dihydroxybenzophenone in swimming pool water.

2,4-Dihydroxybenzophenone (BP-1) is an important component and metabolite of benzophenone-type (BPs) UV filters, it is widely used in commercial products and frequently detected in environmental media and organism samples. The transformation characteristics and genotoxicity changes of BP-1 during chlorination disinfection process were explored. Nineteen transformation products were separated and tentatively identified, eleven of which were not previously reported. Most importantly, nine novel by-products including one chlorobenzoquinone, four phenyl benzoquinones, and four polycyclic aromatic hydrocarbons were formed during BP-1 chlorination. Plausible transformation pathways for BP-1 during chlorination treatment were proposed, in which chlorination substitution, Baeyer-Villiger oxidation, hydrolysis, and CC coupling reactions were involved. The CC coupling reaction is firstly observed in chlorination disinfection system. Higher pH values and chlorine doses would be a benefit for BP-1 transformation. The genotoxicity of the reaction mixture increased significantly with increasing chlorine dose under acid and neutral conditions due to the formation of benzoquinones and polycyclic aromatic hydrocarbons. It was noted that BP-1 and its chlorinated products were found in swimming pool water samples. This work inferred that BP-1 and its analogs are transformed during the chlorination disinfection process and may cause potential ecological and health risks.

Aqueous microdroplets containing only ketones or aldehydes undergo Dakin and Baeyer-Villiger reactions.

The Dakin and Baeyer-Villiger (BV) oxidation reactions require addition of peroxides as oxidants and an acid or a base as a catalyst. Reaction times range from hours to days to obtain target products. Previously, we reported that hydrogen peroxide (H2O2) is spontaneously generated in water microdroplets without any added chemicals or applied electrical potential. Here, we report that the Dakin and BV reactions occur in modest yields within milliseconds in aqueous microdroplets at room-temperature without the addition of external peroxides and catalysts. H2O2 generation is the result of the special environment of the microdroplet surface, which promotes water autoionization. We find that increasing the content of water and decreasing the droplet size improve the product yield of the Dakin and BV reactions, supporting the contention that the amount of H2O2 generated in aqueous microdroplets could induce the two reactions and the reactions occur at or near the air-water interface of the microdroplet surface.

Acid/Base-Co-catalyzed Formal Baeyer-Villiger Oxidation Reaction of Ketones: Using Molecular Oxygen as the Oxidant.

A novel acid/base-co-catalyzed formal Baeyer-Villiger oxidation of various ketones using O2 as the sole oxidant under metal-free conditions has been developed for the first time. The reaction tolerates a wide range of ketones and anilines and provides a simple and efficient method for the construction of various amides and isoquinolin-1-ones from the reactions of ketones with anilines in a single step.

Discovery of Two Native Baeyer-Villiger Monooxygenases for Asymmetric Synthesis of Bulky Chiral Sulfoxides.

Two Baeyer-Villiger monooxygenases (BVMOs), designated BoBVMO and AmBVMO, were discovered from Bradyrhizobium oligotrophicum and Aeromicrobium marinum, respectively. Both monooxygenases displayed novel features for catalyzing the asymmetric sulfoxidation of bulky and pharmaceutically relevant thioethers. Evolutionary relationship and sequence analysis revealed that the two BVMOs belong to the family of typical type I BVMOs and the subtype ethionamide monooxygenase. Both BVMOs are active toward medium- and long-chain aliphatic ketones as well as various thioether substrates but are ineffective toward cyclohexanone, aromatic ketones, and other typical BVMO substrates. BoBVMO and AmBVMO showed the highest activities (0.117 and 0.025 U/mg protein, respectively) toward thioanisole among the tested substrates. Furthermore, these BVMOs exhibited distinct activity and excellent stereoselectivity toward bulky and prochiral prazole thioethers, which is a unique feature of this family of BVMOs. No native enzyme has been reported for the asymmetric sulfoxidation of bulky prazole thioethers into chiral sulfoxides. The identification of BoBVMO and AmBVMO provides an important scaffold for discovering enzymes capable of asymmetrically oxidizing bulky thioether substrates by genome mining.IMPORTANCE Baeyer-Villiger monooxygenases (BVMOs) are valuable enzyme catalysts that are an alternative to the chemical Baeyer-Villiger oxidation reaction. Although BVMOs display broad substrate ranges, no native enzymes were reported to have activity toward the asymmetric oxidation of bulky prazole-like thioether substrates. Herein, we report the discovery of two type I BVMOs from Bradyrhizobium oligotrophicum (BoBVMO) and Aeromicrobium marinum (AmBVMO) which are able to catalyze the asymmetric sulfoxidation of bulky prazole thioethers (proton pump inhibitors [PPIs], a group of drugs whose main action is a pronounced and long-lasting reduction of gastric acid production). Efficient catalysis of omeprazole oxidation by BoBVMO was developed, indicating that this enzyme is a promising biocatalyst for the synthesis of bulky and pharmaceutically relevant chiral sulfoxide drugs. These results demonstrate that the newly identified enzymes are suitable templates for the discovery of more and better thioether-converting BVMOs.

Ionic liquid infiltrated within metal loaded zeolites for Baeyer–Villiger oxidation reaction under solvent-free condition

We demonstrate the infiltration of ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) skeleton within robust Co metal loaded mesoporous zeolites viz. Co/ZSM-5 and/or Co/HY to prepare the ([BMIM]BF4@Co/ZSM-5) and/or ([BMIM]BF4@Co/HY) host–guest systems and characterized by various physico–chemical techniques. The catalytic activity of these catalysts was investigated in the liquid phase Baeyer–Villiger (BV) oxidation of cyclohexanone under solvent-free condition. Amongst them, [BMIM]BF4@Co/HY was found to be potential candidate by showing excellent performance with 54.88% conversion of cyclohexanone and 86.36% e-caprolactone selectivity with elevated TOF and TON values of 4312.43 h−1 and 25874.58, respectively. In addition to this, the host–guest system could be successfully recycled six times without significant loss of activity.