6705-49-3Relevant articles and documents
Isocyano Enones: Addition-Cyclization Cascade to Oxazoles
Chao, Allen,Lujan-Montelongo, J. Armando,Fleming, Fraser F.
, p. 3062 - 3065 (2016)
Copper iodide catalyzes the conjugate addition of organometallic and heteroatom nucleophiles to isocyano enones to afford oxazoles. A range of enolates, metalated nitriles, amines, and thiols undergo catalyzed conjugate addition to cyclic and acyclic oxoalkene isocyanides. Mechanistic studies suggest that copper complexation facilitates the nucleophilic attack on the isocyano enone to generate an enolate that cyclizes onto the isocyanide leading to a variety of substituted acyclic or ring-fused oxazoles.
Trinuclear Dioxidomolybdenum(VI) Complexes of Tritopic Phloroglucinol-Based Ligands and Their Catalytic Applications for the Selective Epoxidation of Olefins
Maurya, Mannar R.,Tomar, Reshu,Rana, Lata,Avecilla, Fernando
, p. 2952 - 2964 (2018)
Four trinuclear dioxidomolybdenum(VI) complexes, [{MoVIO2(H2O)}3ptk(bhz)3] (1), [{MoVIO2(H2O)}3ptk(fah)3] (2), [{MoVIO2(H2O)}3ptk(inh)3] (3), and [{MoVIO2(H2O)}3ptk(nah)3] (4), based on the tritopic central 2,4,6-triacetylphloroglucinol (H3ptk) ligands H6ptk(bhz)3 (I), H6ptk(fah)3 (II), H6ptk(inh)3 (III) and H6ptk(nah)3 (IV) (Hbhz = benzoylhydrazide, Hfah = 2-furanoylhydrazide, Hinh = isonicotinoylhydrazide and Hnah = nicotinoylhydrazide), respectively, are presented. All of the synthesized ligands, as well as their complexes, have been characterized by elemental, thermal, and electrochemical analyses, spectroscopic techniques (FTIR, UV/Vis, 1H and 13C NMR), and single-crystal X-ray studies of [{MoVIO2(H2O)}{MoVIO2(MeOH)}2ptk(bhz)3]·2H2O·1.25MeOH (1a) and [{MoVIO2(EtOH)}3ptk(fah)3]·3EtOH (2a). Each pocket of the ligands coordinates in a dibasic tridentate fashion through two oxygen atoms and one nitrogen atom to each metal center. Due to the presence of tridentate binding pockets in the ligands, each metal center conserves its octahedral structure by coordinating with water molecules in the synthesized complexes or by other solvent(s) in the crystal structures. These complexes were evaluated for the epoxidation of terminal and internal alkenes in the presence of H2O2 using NaHCO3 as a promoter. Under the optimized reaction conditions, all alkenes were converted to the corresponding epoxides selectively in good yield and high turnover number.
The catalytic epoxidation of 2-cyclohexen-1-one over uncalcined layered double hydroxides using various solvents
Sipiczki,ádám,Anitics,Csendes,Peintler,Kukovecz,Kónya,Sipos,Pálinkó
, p. 231 - 236 (2015)
The epoxidation reaction of an α,β-unsaturated ketone (2-cyclohexen-1-one), that is, an electron deficient C=C bond was performed over as-prepared and calcined layered double hydroxides (LDHs) of both the hydrotalcite- and the hydrocalumite type. It was found that the as-prepared LDHs always performed better than the calcined derivatives. Among them, the CaFe-LDH was the most active. The optimum reaction temperature and the most suitable solvent were also found after performing several set of reactions.
Epoxidation of conjugated C=C-bonds and sulfur-oxidation of thioethers mediated by NADH:FMN-dependent oxidoreductases
Mueller, Nicole Jasmin,Stueckler, Clemens,Hall, Melanie,MacHeroux, Peter,Faber, Kurt
, p. 1115 - 1119 (2009)
Three FMN-dependent oxidoreductases, YcnD and YhdA from Bacillus subtilis and Lot6p from Saccharomyces cerevisiae, oxidised α,β-unsaturated carbonyl compounds and a thioether, respectively, to furnish the corresponding racemic epoxides or sulfoxide, respectively. The mechanism of this enzyme-mediated (rather than enzyme-catalysed) oxidation was shown to proceed via the NADH-dependent reduction of O2, forming H2O 2, which acted as oxidant in a spontaneous (non-enzymatic) fashion. The Royal Society of Chemistry 2009.
Iron-Catalyzed Epoxidation of Linear α-Olefins with Hydrogen Peroxide
Mao, Shuxin,Budweg, Svenja,Spannenberg, Anke,Wen, Xiaodong,Yang, Yong,Li, Yong-Wang,Junge, Kathrin,Beller, Matthias
, (2022/01/26)
The combination of Fe(OTf)2 with N-methyl bis(picolylamine) (Me-bpa) L7 enables epoxidation of linear olefins including terminal, internal, and cyclic ones, using hydrogen peroxide as terminal oxidant under mild conditions. In the presence of picolinic acid as additive improved yields of epoxides up to 75 % have been achieved.
Activation of H2O2over Zr(IV). Insights from Model Studies on Zr-Monosubstituted Lindqvist Tungstates
Abramov, Pavel A.,Carbó, Jorge J.,Chesalov, Yuriy A.,Eltsov, Ilia V.,Errington, R. John,Evtushok, Vasilii Yu.,Glazneva, Tatyana S.,Ivanchikova, Irina D.,Kholdeeva, Oxana A.,Maksimchuk, Nataliya V.,Maksimov, Gennadii M.,Poblet, Josep M.,Solé-Daura, Albert,Yanshole, Vadim V.,Zalomaeva, Olga V.
, p. 10589 - 10603 (2021/09/02)
Zr-monosubstituted Lindqvist-type polyoxometalates (Zr-POMs), (Bu4N)2[W5O18Zr(H2O)3] (1) and (Bu4N)6[{W5O18Zr(μ-OH)}2] (2), have been employed as molecular models to unravel the mechanism of hydrogen peroxide activation over Zr(IV) sites. Compounds 1 and 2 are hydrolytically stable and catalyze the epoxidation of C?C bonds in unfunctionalized alkenes and α,β-unsaturated ketones, as well as sulfoxidation of thioethers. Monomer 1 is more active than dimer 2. Acid additives greatly accelerate the oxygenation reactions and increase oxidant utilization efficiency up to >99%. Product distributions are indicative of a heterolytic oxygen transfer mechanism that involves electrophilic oxidizing species formed upon the interaction of Zr-POM and H2O2. The interaction of 1 and 2 with H2O2 and the resulting peroxo derivatives have been investigated by UV-vis, FTIR, Raman spectroscopy, HR-ESI-MS, and combined HPLC-ICP-atomic emission spectroscopy techniques. The interaction between an 17O-enriched dimer, (Bu4N)6[{W5O18Zr(μ-OCH3)}2] (2′), and H2O2 was also analyzed by 17O NMR spectroscopy. Combining these experimental studies with DFT calculations suggested the existence of dimeric peroxo species [(μ-?2:?2-O2){ZrW5O18}2]6- as well as monomeric Zr-hydroperoxo [W5O18Zr(?2-OOH)]3- and Zr-peroxo [HW5O18Zr(?2-O2)]3- species. Reactivity studies revealed that the dimeric peroxo is inert toward alkenes but is able to transfer oxygen atoms to thioethers, while the monomeric peroxo intermediate is capable of epoxidizing C?C bonds. DFT analysis of the reaction mechanism identifies the monomeric Zr-hydroperoxo intermediate as the real epoxidizing species and the corresponding α-oxygen transfer to the substrate as the rate-determining step. The calculations also showed that protonation of Zr-POM significantly reduces the free-energy barrier of the key oxygen-transfer step because of the greater electrophilicity of the catalyst and that dimeric species hampers the approach of alkene substrates due to steric repulsions reducing its reactivity. The improved performance of the Zr(IV) catalyst relative to Ti(IV) and Nb(V) catalysts is respectively due to a flexible coordination environment and a low tendency to form energy deep-well and low-reactive Zr-peroxo intermediates.
