Triethylamine Enables Catalytic Generation of Oxidopyrylium Ylides for [5+2] Cycloadditions with Alkenes: An Efficient Entry to 8-Oxabicyclo[3.2.1]octane Frameworks

An efficient method for the preparation of a range of 8-oxabicyclo[3.2.1]octane derivatives including synthetic intermediates of natural products is described, in which triethylamine effectively catalyzes [5+2] cycloaddition reactions between oxidopyrylium ylides and alkenes. This method can be applied not only to intermolecular cycloadditions with various alkenes but also to intramolecular cycloadditions. The key finding is that the combined use of organic bases having appropriate basicity and oxidopyrylium ylide precursors bearing a suitable leaving group facilitates the base-assisted generation of oxidopyrylium ylides in a catalytic manner.ArticleADVANCED SYNTHESIS & CATALYSIS.360(12):2377-2381(2018)journal articl

Development of hydrophobic platinum catalyst for oxidation of tritium in JAEA

AbstractTo design a recombiner packed with hydrophobic catalyst for passive tritium oxidation, the development of manufacturing technology for hydrophobic platinum catalyst and the following analysis on reaction rate are essential. This presentation deals with the reaction rate for tritium oxidation over a hydrophobic platinum catalyst at temperature between room temperature and 473K. Two kinds of hydrophobic platinum catalysts; supported with styrene-divinylbenzene and with silica were used for this test. The results indicate that 1) the particle size of platinum affects the reaction rate, 2) the order of reaction is 0.5 of hydrogen concentration at room temperature in case of a hydrogen content below 100ppm. The rate-determining step approximation method is applied for the discussion on the reaction mechanism of tritium oxidation over platinum catalyst

Efficient generation of an oxidopyrylium ylide using a Pd catalyst and its [5+2] cycloadditions with several dipolarophiles

An efficient method for the generation of an oxidopyrylium ylide from 6-acetoxy-6-acetoxymethyl-2H-pyran-3(6H)-one using a Pd catalyst and [5+2] cycloadditions of the resulting ylide are described. Among substituted styrene derivatives as dipolarophiles, electron-rich styrenes showed higher yield (up to 80%). The [5+2] cycloaddition reactions can also be applied to exo-methylene cyclic compounds, and an improved method for the synthesis of polygalolide intermediate has been demonstrated.ArticleCHEMICAL COMMUNICATIONS.54(9):1109-1112(2018)journal articl

Decomposition of methane with various precious metal catalysts for the tokamak exhaust processing

The Tokamak exhaust processing system (TEP) in the deuterium-tritium fuel cycle for DEMO is the key system where hydrogen isotopes and impurity gases are separated. Then the impurity gases are decomposed into hydrogen isotopes and other chemical species. The major impurity gas to be processed in TEP is tritiated hydrocarbons. Among tritiated hydrocarbons, tritiated methane is hard to be decomposed directly since the temperature of catalyst for thermal decomposition is 500oC or above with conventional precious metal supported catalysts such as Pt, Pd, and Rh. The effect of constitutive elements of catalysts on methane decomposition was investigated for a catalyst that could decompose methane efficiently at low temperatures. The investigation showed that the activity of the catalyst for methane decomposition depends on some constitutive elements such as precious metal species, particle sizes of metals, pore sizes of catalyst supports. The experimental results indicated that methane could be decomposed effectively by optimizing precious metal species and the particle sizes of precious metals. Especially the particle size of precious metals had a great influence on methane decomposition efficiency. It was notable that the decomposition efficiency rose 5 times by enlarging a particle size from 12nm to 23nm