Stilbene Oxide Research Articles

Cooperative Iodine and Nitrate Catalyzed Oxidation of Stilbenes to α-Diketones in Water.

An efficient oxidation of stilbenes to α-diketones co-catalyzed by bismuth nitrate and iodine is reported. The utilization of molecular oxygen as a terminal oxidant and water as the reaction solvent provides a low-cost and environmentally friendly approach to preparing the α-diketone derivatives from readily available stilbenes. Isotope labeling experiments suggest that the two oxygen atoms of the α- diketone products mainly originate from water. The method displays high functional group tolerance and we have demonstrated a concise route for preparing trifenagrel and HIV-1 integrase inhibitors from 1,2-diphenylethene.

Sintering of Platinum-Containing Conjugated Polymers: Gas Adsorption and Catalysis of the Formed Pt-Carbon Composites.

Pt-containing meta- and para-linked poly(phenyleneethynylene)s were synthesized by the dehydrochlorination coupling polymerization of PtCl2(PBu3)2 with m- and p-diethynylbenzenes. The formed polymers were sintered at 900 °C to obtain Pt-graphene hybrids, whose structures were examined by Raman scattering spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) measurements. Shapes─facets, terraces, and steps─with average diameters of 2.0-3.4 μm were observed by field emission scanning electron microscopy (FE-SEM). The Pt-graphene hybrids moderately adsorbed CO2 and O2 and slightly adsorbed ethylene and methane. Epoxidation of stilbene was carried out using Pt-graphene hybrids as catalysts to obtain stilbene oxide.

Stilbenes-enriched peanut sprouts alleviated physical fatigue via regulating interactions of nutrients-microbiota-metabolites revealed by multi-omics analysis.

In this study, the antifatigue effect and mechanism of peanut sprouts were explored. BALB/c mice divided into three groups (control, dark and UV-C) were respectively supplemented with a normal diet, peanut sprouts (dark germination) added diet and stilbenes-enriched peanut sprouts (UV-C radiated germination) added diet. Results showed that swimming time and levels of blood glucose and antioxidant enzymes significantly increased, while contents of triglyceride and malondialdehyde notably decreased by peanut sprout supplementation. Besides, combined analysis of gut microbiota gene sequencing and targeted metabolomics of fecal metabolites revealed that peanut sprout supplementation up-regulated abundances and metabolic transformations of Catenibacillus, Odoribacter, Prevotellaceae-UCG-001 and Butyricicoccus while it down-regulated the abundance of Parabacteroides. Consequently, contents of sebacic acid, azelaic acid, suberic acid, heptanoic acid, pimelic acid, aminoadipic acid and mono-phenolics notably increased, which were markedly correlated with the antifatigue effect. Compared with the dark group, the swimming time, glutathione peroxidase activity, methylmalonylcarnitine content and abundances of Butyricicoccus, Catenibacillus and Lachnospiraceae NK4A136 were higher in the UV-C group, while opposite results were obtained for the levels of triglyceride, malondialdehyde, alpha-linolenic acid, gamma-linolenic acid, 10Z-heptadecenoic acid and palmitelaidic acid. Overall, peanut sprout supplementation could alleviate fatigue by modulating gut microbiota composition to promote fatty acid oxidation and lysine and stilbene catabolism to increase energy supply and regulate redox balance. UV-C-radiated peanut sprout supplementation could alleviate fatigue more effectively by up-regulating abundances of Butyricicoccus, Catenibacillus and Lachnospiraceae NK4A136 to promote long-chain fatty acid oxidation and catabolism of flavonoids and stilbenes efficiently.

Efficient olefin epoxidation with high turnover rates over ordered mesoporous silica nanoparticles with uniform manganese sites

Olefin epoxidation has been studied over a series of mesoporous manganese silicate nanoparticles and tBuOOH. Partial substitution of Si by Mn in silica framework leads to highly dispersed, distorted Mn(III) sites, confirmed by various physicochemical analyses. High conversion and stable styrene oxide, stilbene oxide and epoxy cyclohexane yield have been achieved with MS75 with 1:1.5 ratio of olefin: oxidant. However, at faster reaction rates lower styrene oxide yield is observed at lower Mn-containing catalyst (MS100). High TON, TOF over manganese sites shows accessible monomeric Mn sites. Attributed to high reactant density at redox-active Mn silicate sites due to facile diffusion across shallow pore depth channels of nanoparticulate om-MSx and surface hydrophobic characteristics. The catalysts were found to be stable under recycling and filtration experiments. The excellent stability against leaching of active manganese species indicates stable sites and good textural properties in om-MSx, essential for extended activity.

Rigid tertiary amine/saccharin adduct as halide-free organocatalyst for the cycloaddition of CO2 into epoxides

Metal- and halide-free catalyst DABCO·HSac, i.e., the binary adduct of 1,4-diazabicyclo[2.2.2]octane (DABCO) and saccharin (HSac), in an ionic pair structure of DABCO-H+·Sac- is shown mild and efficient in promoting the cycloaddition of CO2 into epoxides (CCE) reactions. Under comparatively low temperature of 60 °C, ambient pressure of 0.1 MPa, and 10 mol% catalyst loading, DABCO·HSac catalyzed the cycloaddition of epichlorohydrin into CO2 with the conversion of 96% in 24 h. Terminal epoxides including epibromohydrin, glycidyl ethers, and alkylene oxides received 83–99% conversions, however, cyclohexene oxide and stilbene oxide were not viable under these mild reaction conditions. A catalytic cycle initiated by the saccharinate anion of its nucleophilic attack on methylene carbon of an epoxide ring with the iminolate oxygen was proposed as the key step, in which the Sac- anion functioned similarly to halide X- in other ring-opening mechanisms. The tertiary amine DABCO was protonated into an onium cation DABCO-H+ that worked as a hydrogen-bond donor in coordinating and activating the epoxide. A cocatalysis mechanism was suggested and validated by NMR titrations. Further control experiments by switch cation or anion of DABCO-H+·Sac- in structural analog cocatalysts certified both the onium DABCO-H+ and the saccharinate Sac- was indispensable in the catalytic cycle. The design of ionic pair organocatalysts illustrated the possibility of non-halide anions as the nucleophiles in wider halide-free catalyst discovery.

Cover Feature: Acid and Base Water Coexists in a Micro‐Structured Ionic Liquid and Catalyzes Organic Reactions in One‐Pot (ChemCatChem 19/2022)

The Cover Feature artistically shows that when 5 wt% acid water is added to a conventional ionic liquid, such as 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), with a simple pipette, water microdroplets of ∼1 μm spontaneously form at room temperature. In their Research Article, A. Leyva-Pérez and co-workers describe that the same effect occurs when basic water is added, and also when both acidic and basic water are added sequentially. The microdroplets form without mixing. The microstructured acid/base liquid system performs as a catalyst/solvent system for one-pot organic reactions, such as the rearrangement of stilbene oxide, one-pot ketal hydrolysis/Knoevenagel condensation, or Pd/Cu-catalysed one-pot Sonogashira coupling/silane deprotection/Au-catalysed alkyne hydration. This extremely simple acid/base system is a rare example of co-existing simple acids (i.e., HCl) and bases (i.e., KOH). More information can be found in the Research Article by A. Leyva-Pérez and co-workers.

Ultrafast Photo-ion Probing of the Ring-Opening Process in Trans-Stilbene Oxide.

The ultrafast photo‐induced ring opening of the oxirane derivative trans‐stilbene oxide has been studied through the use of ultrafast UV/UV pump‐probe spectroscopy by using photo‐ion detection. Single‐ and multiphoton probe paths and final states were identified through comparisons between UV power studies and synchrotron‐based vacuum ultraviolet (VUV) single‐photon ionization studies. Three major time‐dependent features of the parent ion (sub‐450 fs decay, (1.5±0.2) ps, and >100 ps) were observed. These decays are discussed in conjunction with the primary ring‐opening mechanism of stilbene oxide, which occurs through C−C dissociation in the oxirane ring. The appearance of fragments relating to the masses of dehydrogenated diphenylmethane (167 amu) and dehydrogenated methylbenzene (90 amu) were also investigated. The appearance of the 167 amu fragment could suggest an alternative ultrafast ring‐opening pathway via the dissociation of one of the C−O bonds within the oxirane ring.

Ruthenium/dendrimer complex immobilized on silica‐functionalized magnetite nanoparticles catalyzed oxidation of stilbenes to benzil derivatives at room temperature

A new ruthenium/dendrimer complex stabilized on the surface of silica‐functionalized nano‐magnetite was fabricated and well characterized. The nano‐catalyst showed good activity in the synthesis of benzil derivatives via the oxidation of stilbenes with high turnover frequency (TOF) at room temperature. Moreover, the catalyst could also be reused up to fifteen times without any loss of its activity.

Controlled Exchange of Achiral Linkers with Chiral Linkers in Zr-Based UiO-68 Metal-Organic Framework.

The development of highly robust heterogeneous catalysts for broad asymmetric reactions has always been a subject of interest, but it remains a synthetic challenge. Here we demonstrated that highly stable metal-organic frameworks (MOFs) with potentially acid-labile chiral catalysts can be synthesized via postsynthetic exchange. Through a one- or two-step ligand exchange, a series of asymmetric metallosalen catalysts with the same or different metal centers are incorporated into a Zr-based UiO-68 MOF to form single- and mixed-M(salen) linker crystals, which cannot be accomplished by direct solvothermal synthesis. The resulting MOFs have been characterized by a variety of techniques including single-crystal X-ray diffraction,N2 sorption, CD, and SEM/TEM-EDS mapping. The single-M(salen) linker MOFs are active and efficient catalysts for asymmetric cyanosilylation of aldehydes, ring-opening of epoxides, oxidative kinetic resolution of secondary alcohols, and aminolysis of stilbene oxide, and the mixed-M(salen) linker variants are active for sequential asymmetric alkene epoxidation/epoxide ring-opening reactions. The chiral MOF catalysts are highly enantioselective and completely heterogeneous and recyclable, making them attractive catalysts for eco-friendly synthesis of fine chemicals. This work not only advances UiO-type MOFs as a new platform for heterogeneous asymmetric catalysis in a variety of syntheses but also provides an attractive strategy for designing robust and versatile heterogeneous catalysts.

ChemInform Abstract: Benzylic Ammonium Ylide Mediated Epoxidations.

A high yielding synthesis of stilbene oxides using ammonium ylides has been developed. It turned out that the amine leaving group plays a crucial role as trimethylamine gives higher yields than DABCO or quinuclidine. The amine group also influences the diastereoselectivity, and detailed DFT calculations to understand the key parameters of these reactions have been carried out.

Benzylic Ammonium Ylide Mediated Epoxidations.

A high yielding synthesis of stilbene oxides using ammonium ylides has been developed. It turned out that the amine leaving group plays a crucial role as trimethylamine gives higher yields than DABCO or quinuclidine. The amine group also influences the diastereoselectivity, and detailed DFT calculations to understand the key parameters of these reactions have been carried out.

ChemInform Abstract: Enantioselective Bio‐Hydrolysis of Various Racemic and meso Aromatic Epoxides Using the Recombinant Epoxide Hydrolase Kau2.

Epoxide hydrolase Kau2 overexpressed in Escherichia coli RE3 has been tested with ten different racemic and meso,-disubstituted aromatic epoxides. Some of the tested substrates were bi-functional, and most of them are very useful building blocks in synthetic chemistry applications. As a general trend Kau2 proved to be an extremely enantioselective biocatalyst, the diol products and remaining epoxides of the bioconversions being obtained – with two exceptions – in nearly enantiomerically pure form. Furthermore, the reaction times were usually very short (around 1 h, except when stilbene oxides were used), and the use of organic co-solvent was well tolerated, enabling very high substrate concentrations (up to 75 g/L) to be reached. Even extremely sterically demanding epoxides such as cis-and trans-stilbene oxides were transformed on a reasonable time scale. All reactions were successfully conducted on a 1-g preparative scale, generating diol-and epoxide-based chiral synthons with very high enantiomeric excesses and isolated yields close to the theoretical maximum. Thus we have here demonstrated the usefulness and versatility of lyophilizedEscherichia coli cells expressing Kau2 epoxide hydrolase as a highly enantioselective biocatalyst for accessing very valuable optically pure aromatic epoxides and diols through kinetic resolution of racemates or desymmetrization of meso epoxides.

Synthesis of Stilbene Derivatives: A Comparative Study of their Antioxidant Activities

A series of structurally simple compounds belonging to thestilbene family were synthesized by means of a Ti(III)-mediated methodology that allows access, in an efficient manner, to derivatives of dihydrostilbene, E-stilbene, and stilbene oxide, with high yields. The antioxidant activity of these compounds has been evaluated by means of two electrochemical assays, which provide complementary information, showing that the majority of these stilbene analogs exhibit significant antioxidant activity dependent on the electronic structure and functionalization of the molecule in each case.

Enantioselective Bio‐Hydrolysis of Various Racemic and meso Aromatic Epoxides Using the Recombinant Epoxide Hydrolase Kau2

AbstractEpoxide hydrolase Kau2 overexpressed in Escherichia coli RE3 has been tested with ten different racemic and meso α,β‐disubstituted aromatic epoxides. Some of the tested substrates were bi‐functional, and most of them are very useful building blocks in synthetic chemistry applications. As a general trend Kau2 proved to be an extremely enantioselective biocatalyst, the diol products and remaining epoxides of the bioconversions being obtained – with two exceptions – in nearly enantiomerically pure form. Furthermore, the reaction times were usually very short (around 1 h, except when stilbene oxides were used), and the use of organic co‐solvents was well tolerated, enabling very high substrate concentrations (up to 75 g/L) to be reached. Even extremely sterically demanding epoxides such as cis‐ and trans‐stilbene oxides were transformed on a reasonable time scale. All reactions were successfully conducted on a 1 g preparative scale, generating diol‐ and epoxide‐based chiral synthons with very high enantiomeric excesses and isolated yields close to the theoretical maximum. Thus we have here demonstrated the usefulness and versatility of lyophilized Escherichia coli cells expressing Kau2 epoxide hydrolase as a highly enantioselective biocatalyst for accessing very valuable optically pure aromatic epoxides and diols through kinetic resolution of racemates or desymmetrization of meso epoxides.magnified image

Inside Cover: Design of Peptidyl Thiourea Derivatives as Organocatalysts for the Asymmetric Ring Opening ofmeso-Stilbene Oxides (Asian J. Org. Chem. 6/2014)

Organocatalysis Organocatalytic asymmetric ring opening of epoxides with aliphatic amines has always been a challenge. In their Communication on page 700 ff., Swapandeep Singh Chimni report the design and synthesis of chiral peptidyl thiourea organocatalysts for the asymmetric ring opening of epoxides with N-phenylpiperazines. A tripeptide scaffold with a β-turn nucleating element provides favorable stereochemistry by positioning the nucleophile close to the epoxide. Chiral β-amino alcohols were obtained with up to 95% ee after crystallization. The configuration at the N-terminal residue of the catalyst affects the stereochemical outcome of the reaction.

Design of Peptidyl Thiourea Derivatives as Organocatalysts for the Asymmetric Ring Opening of meso‐Stilbene Oxides

AbstractChiral peptidyl thiourea organocatalysts were designed and synthesized for asymmetric ring‐opening of cis‐stilbene oxides with N‐phenylpiperazines. Chiral β‐amino alcohols were obtained with up to 95 % ee after crystallization. The configuration at the N‐terminal residue stereogenic center of peptidyl thiourea organocatalyst was found to affect the stereochemical outcome of the reaction.

A structure–activity relationship study on the Wacker oxidation of stilbenes at ambient condition

To evaluate which structural elements of the stilbenes are responsible for their activity on the Wacker oxidation, a series of stilbenes with various functional moieties and substitution patterns were considered. In this regard, it is found that the oxidation rate of stilbenes strongly depends on their structures to give the corresponding carbonyl compounds. Consequently, the ortho position of alkene and methoxy groups plays a key role in the complexation with PdCl2. The oxidation process is clean with high selectivity of product and low percentage of byproducts.

Facile and highly chemoselective synthesis of benzil derivatives via oxidation of stilbenes in an I2–H2O system

A facile and highly chemoselective protocol for the synthesis of benzil derivatives has been developed by oxidation of stilbenes in an I2–H2O system under air. Notably, the method was applicable to 26 examples and provided up to 98% yield, avoiding the use of acid, metal catalysts and so on.

Salen‐Based Coordination Polymers of Manganese and the Rare‐Earth Elements: Synthesis and Catalytic Aerobic Epoxidation of Olefins

Treatment of N,N'-bis(4carboxysalicylidene)ethylenediamine (H(4)L), with MnCl(2)⋅(H(2)O)(4), and Ln(NO(3))(3)⋅(H(2)O)(m) (Ln = Nd, Eu, Gd, Dy, Tb), in the presence of N,N-dimethylformamide (DMF)/pyridine at elevated temperature resulted (after work up) in the formation of 1D coordination polymers {[Ln(2)(MnLCl)(2)(NO(3))(2)(dmf)(5)]⋅4 DMF}(n) (1-5). In these coordination polymers the rare earth ions are connected through carboxylate groups from Mn-salen units in a 1D chain structure. Thus, the Mn-salen complex acts as a "metalloligand" with open coordination sites. All compounds were used as catalysts in the liquid-phase epoxidation of trans-stilbene with molecular oxygen, which resulted in the formation of stilbene oxide. Since the choice of the lanthanide had virtually no influence on the performance of the catalyst, only the manganese-gadolinium was studied in detail. The influence of solvent, catalyst concentration, reaction temperature, oxidant, and oxidant flow rate on conversion, yield, and selectivity was analyzed. A conversion of up to 70%, the formation of 61% stilbene oxide (88% selectivity), and a TON of 84 were observed after 24 h. A hot filtration test confirmed that the reaction is mainly catalyzed through a heterogeneous pathway, although a minor contribution of homogeneous species could not be completely excluded. The catalyst could be reused without significant loss of activity.

Evaluation of injection conditions for preparative supercritical fluid chromatography

Preparative supercritical fluid chromatography (SFC) has become the preferred method for the rapid purification of drug candidates during the pharmaceutical discovery process. This paper will discuss the evaluation of injection techniques for preparative SFC. A thorough evaluation of mixed stream vs. modifier stream™ injection was performed. It was shown that for the majority of the compounds evaluated, modifier stream injection gave better resolution relative to mixed stream injection. The improvement in resolution with modifier stream injection increased as injection volume increased. In addition, a study evaluating the effect of dissolution solvent on chromatographic performance for the preparative resolution of enantiomers using SFC showed that dissolution solvent had minimal impact on preparative resolution for the preparative SFC separation of trans stilbene oxide.