Organoselenium-Catalyzed Baeyer-Villiger Oxidation of α,β-Unsaturated Ketones by Hydrogen Peroxide to Access Vinyl Esters

Practical and scalable enantioselective synthesis of (+)-majoranolide from Cyrene

A two-step enantioselective gram scale synthesis of the Persea derived γ-lactones (+)-majoranolide and (+)-majoranolide B has been achieved. The sequence uses the amine promoted crossed condensation of the biorenewable synthon Cyrene with aliphatic aldehydes followed by a Baeyer-Villiger oxidation. Comparison of optical rotation data with the natural products established the absolute configuration of the natural product series, and this work represents the first synthesis of these alkylidene natural products.

CuBr2-Catalyzed Annulation of 2-Bromo-N-Arylbenzimidamide with Se/S8 Powder for the Synthesis of Benzo[d]isoselenazole and Benzo[d]isothiazole

A CuBr₂-catalyzed annulation of 2-bromo-N-arylbenzimidamide with selenium/sulfur powder for the synthesis of benzo[d]isoselenazole and benzo[d]isothiazole in generally good yields was investigated. This synthetic strategy features good substrate scope and functional group tolerance. Furthermore, the corresponding products could be converted into N-aryl indoles via rhodium^III-catalyzed ortho C-H activation of the N-phenyl ring, providing an efficient approach for axial aromatic molecules.

Recent Advances in Organoselenium Catalysis

Abstract:

: Organoselenium chemistry has developed as an important tool in the field of synthetic and medicinal chemistry. Various organoselenium reagents have been developed and used successfully to achieve different organic transformations such as the selenocyclizations, oxyselenenylations and selenoxide eliminations etc. Additionally, the potential of organoselenium reagents is not limited their use as stoichiometric reagents but they have successfully used as organocatalyst in number of synthetic transformations. Various organic and inorganic oxidants have been identified as terminal oxidants to regenerate the active catalytic specie. In this review article, the recent progress of organoselenium reagents in catalysis is being highlighted along with their asymmetric variants.

Highly crystalline K-intercalated Se/C: An easily accessible mesoporous material catalyzing the epoxidation of β-ionone

Highly crystalline K-intercalated Se/C was fabricated by calcining the commercially available methylselenized glucose with KBr being followed by the subsequent water washing. The corrosion of water to KBr led to...

Selenium-catalyzed oxidation of alkenes: insight into the mechanisms and developing trend

Recent progresses of the selenium-catalyzed oxidation of alkenes are summarized at the mechanism level. It may be beneficial for designing novel selenium-containing catalysts and alkene oxidation protocols for the next phase of studies.

Dumbbell-like Pt-Fe3O4 Nanoparticles Encapsulated in N-Doped Carbon Hollow Nanospheres as a Novel Yolk@Shell Nanostructure toward High-Performance Nanocatalysis

Noble metal-Fe₃O₄ dumbbell-like nanoparticles have aroused considerable attention because of their high potential as heterogeneous nanocatalysts. The designed synthesis of the advanced architecture of noble metal-Fe₃O₄ dumbbell-like nanoparticles with both improved catalytic activity and stability is still a challenge. Herein, through the combination of yolk@shell and dumbbell-like nanostructures, dumbbell-like Pt-Fe₃O₄ nanoparticles encapsulated in N-doped carbon hollow nanospheres (Pt-Fe₃O₄@N-carbon) as a special yolk@shell nanostructure were developed. In comparison with Pt-Fe₃O₄ dumbbell-like nanoparticles, Pt-Fe₃O₄@N-carbon yolk@shell nanoparticles showed improved catalytic activity and stability toward the liquid-phase 4-nitrophenol reduction and β-ionone oxidation, making them a promising candidate for catalysis applications.

Organoselenium small molecules as catalysts for the oxidative functionalization of organic molecules

This perspective highlights the critical analysis of the challenges, in the past decade, which led to the development of organoselenium compounds and their use as versatile catalysts in organic synthesis towards the oxidation of olefins and C–H bonds. Furthermore, the emphasis here differs from previous reviews of the field by classifying the various types of catalyses and the diverse strategies.

Selenium reagents as catalysts

Organoselenium chemistry has become an important tool in synthetic and medicinal chemistry.

Fabrication of Se/C using carbohydrates as biomass starting materials: an efficient catalyst for regiospecific epoxidation of β-ionone with ultrahigh turnover numbers

Fabrication of Se/C catalyst from glucose as the biomass starting materials was reported for the first time, affording an efficient and regiospecific epoxidation of β-ionone.

Easily fabricated and recyclable Pd&Cu@Al catalyst for gram-scale phosphine-free Heck reactions with high TON

A unique Pd&Cu@Al catalyst was easily fabricated just by immersing commercial aluminum foil in a mixed xylene solution of PdCl₂ and CuCl₂. The catalyst fabrication process led to aluminum oxide coatings in situ, which supported the metal nanoparticles and enhanced their catalytic activities for the phosphine-free Heck reaction of aryl halides and styrenes with high turnover number (TON) up to 3.9×10⁵. The reaction can be scaled up to at least 100mmol and has been applied in modification of drug Lapatinib's intermediate with low metal residue. This novel catalyst is of good application potential in industrial production because it was extremely easy to be recycled, in regardless of the generation of the insoluble impurities or tars during the reaction processes.

Solid-State 77Se NMR of Organoselenium Compounds through Cross Polarization Magic Angle Spinning (CPMAS) Method

Characterization of selenium states by 77Se NMR is quite important to provide vital information for mechanism studies in organoselenium-catalyzed reactions. With the development of heterogeneous polymer-supported organoselenium catalysts, the solid state 77Se NMR comes to the spotlight. It is necessary to figure out an advanced protocol that provides good quality spectra within limited time because solid state 77Se NMR measurements are always time consuming due to the long relaxation time and the relatively low sensitivity. Studies on small molecules and several novel polymer-supported organoselenium materials in this article showed that cross polarization (CP) method with the assistance of magic angle spinning (MAS) was more efficient to get high quality spectra than the methods by using single pulse (SP) or high power 1H decoupling (HPHD) combined with MAS. These results lead to a good understanding of the effect of the molecular structure, the heteronuclear coupling, the long-range ordering of the solid (crystal or amorphous), and the symmetry of 77Se on quality of their spectra.

Poly(N-isopropylacrylamide-co-l-proline)-catalyzed Claisen–Schmidt and Knoevenagel condensations: unexpected enhanced catalytic activity of the polymer catalyst

The heterogeneous catalyst is more active than the homogeneous one! The abnormal phenomenon is probably caused by the polymer, which enriches the reactants around the reaction sites.

Rearrangements of organic peroxides and related processes

This review is the first to collate and summarize main data on named and unnamed rearrangement reactions of peroxides. It should be noted, that in the chemistry of peroxides two types of processes are considered under the term rearrangements. These are conventional rearrangements occurring with the retention of the molecular weight and transformations of one of the peroxide moieties after O-O-bond cleavage. Detailed information about the Baeyer-Villiger, Criegee, Hock, Kornblum-DeLaMare, Dakin, Elbs, Schenck, Smith, Wieland, and Story reactions is given. Unnamed rearrangements of organic peroxides and related processes are also analyzed. The rearrangements and related processes of important natural and synthetic peroxides are discussed separately.

Ca(OH)2-Catalyzed Condensation of Aldehydes with Methyl ketones in Dilute Aqueous Ethanol: A Comprehensive Access to α,β-Unsaturated Ketones

Cheap, abundant but seldom-employed Ca(OH)2 was found to be an excellent low-loading (5-10 mol%) catalyst for Claisen-Schmidt condensation of aldehydes with methyl ketones under mild conditions. It was interesting that dilute aqueous ethanol (20 v/v%) was unexpectedly discovered to be the optimal solvent. The reaction was scalable at least to 100 mmol and calcium could be precipitated by CO2 and removed by filtration. Evaporation of solvent directly afforded the product in the excellent 96% yield with high purity, as confirmed by its (1)H NMR spectrum.

Exceptional activity of gallium(iii) chloride and chlorogallate(iii) ionic liquids for Baeyer–Villiger oxidation

The extremely high activity of chlorogallate(iii) ionic liquids and GaCl₃ in promoting Baeyer–Villiger oxidation of cyclic ketones with H₂O₂ to lactones is reported.

Efficient synthesis of unsymmetrical heteroaryl thioethers and chalcogenides by alkali hydroxide-mediated SNAr reactions of heteroaryl halides and dichalcogenides

An efficient S_NAr reaction of heteroaryl halides and diorganyl dichalcogenides is developed for practical synthesis of the useful unsymmetrical heteroaryl thioethers and chalcogenides.

Promotional effect of iron oxide on the catalytic properties of Fe–MnOx/TiO2 (anatase) catalysts for the SCR reaction at low temperatures

The surface interaction of the iron-improved MnO_x/TiO₂ (anatase) catalyst for the selective catalytic reduction of nitric oxide was studied. The role of iron was investigated through detailed experiments.

Organoselenium-catalyzed selectivity-switchable oxidation of β-ionone

The selectivities of the oxidations of β-ionone 1 were switched by the organoselenium catalyst used. [3,5-(CF₃)₂C₆H₃Se]₂ led to (E)-5,6-epoxy-β-ionone (2, 72% yield), while (PhCH₂Se)₂ gave the major Baeyer–Villiger oxidation product 3 in excellent yield (91%).

Rhenium-promoted Pt/WO3/ZrO2: an efficient catalyst for aqueous glycerol hydrogenolysis under reduced H2 pressure

Re improved the dispersion of Pt in Pt/WO₃/ZrO₂ and enhanced the catalyst surface acidity. Pt–Re/WO₃/ZrO₂ afforded glycerol conversion >99% and C3 alcohol selectivity >95%. The reactions were performed under reduced H₂ pressure.