Retrospect and Prospect of the XAFS Spectroscopy

Ohta, Toshiaki

doi:10.3131/jvsj2.59.319

Cited by 2 publications

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References 43 publications

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“…[d] Yield of isolated product. [e] Absolute configuration was determined by comparison of the specific rotation of the literature known reduced alcohol 26…”

Section: Methodsmentioning

confidence: 99%

Z‐Selective Hydrothiolation of Racemic 1,3‐Disubstituted Allenes: An Atom‐Economic Rhodium‐Catalyzed Dynamic Kinetic Resolution

Pritzius

Breit

2015

Angewandte Chemie

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AZ-selective rhodium-catalyzed hydrothiolation of 1,3-disubstituted allenes and subsequent oxidation towards the corresponding allylic sulfones is described. Using the bidentate 1,4-bis(diphenylphosphino)butane (dppb) ligand, Z/E-selectivities up to > 99:1 were obtained. The highly atom-economic desymmetrization reaction tolerates functionalizeda romatic and aliphatic thiols.A dditionally,avariety of symmetric internal allenes,a sw ell as unsymmetrically disubstituted substrates were well tolerated, thus resulting in high regioselectivities.S tarting from chiral but racemic 1,3-disubstituted allenes adynamic kinetic resolution (DKR) could be achieved by applying (S,S)-Me-DuPhos as the chiral ligand. The desired Z-allylic sulfones were obtained in high yields and enantioselectivities up to 96 %ee.Recently we described several highly selective methods for the addition of pronucleophiles to terminal allenes [1,2] and alkynes, [3] which can be regarded as atom-economic [4] alternatives to known allylic substitutions [5] and allylic oxidations. [6] In this respect we developed the first asymmetric hydrothiolation [7] of free aromatic and aliphatic thiols to terminal allenes to obtain branched allylic thioethers,a nd after oxidation, the corresponding allylic sulfones with excellent regio-and enantioselectivities (Scheme 1). [8] Since many bioactive compounds such as Montelukast, [9a] Hepatitis Cvirus NS3/4A inhibitors, [9b] and others [9c-e] include a-stereogenic C À Sb onds,t he synthesis of higher-substituted allylic thioethers [10,11] and sulfones [12,13] could be seen as an important synthetic tool in organic chemistry [14,15] and drug synthesis.F urthermore, a-stereogenic allylic Z-configured thioethers showed activity against allergic asthma and other immediate hypersensitivity diseases.[16] Thus we were curious to see whether we could transfer our initial methodology to 1,3-disubstituted allenes.H erein we describe the first rhodium-catalyzed, highly Z-selective and, if desired, asymmetric, hydrothiolation of 1,3-disubstituted allenes.A fter optimization of the reaction conditions using naphthalene-2-thiol and nona-4,5-diene with addition of p-toluenesulfonic acid (PTSA), the sulfone 1 was obtained in 80 %y ield and 91:9 Z selectivity (Table 1). [17][18][19] Furthermore,weinvestigated the scope of different aromatic thiols for this hydrothiolation. Applying thiophenol as as uitable nucleophile the sulfone 2 was obtained in moderate Z/E selectivity of 78:22. Thelower selectivity compared with naphthalene-2-thiol (1)s uggested that steric reasons are important for ah igh Z selectivity. Accordingly, Z selectivities increased when going from p-methylthiophenol (3;7 4:26) to o-methylthiophenol (5; 91:9). When using the sterically demanding naphthalene-1-thiol, the allylic sulfone 6 was obtained in excellent Z/E selectivity of 93:7.An umber of functionalized thiophenol derivatives were tolerated (7-12;T able 1). Especially,s ulfones with electronwithdrawing substituents gave excellent Z selectivities w...

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“…[d] Yield of isolated product. [e] Absolute configuration was determined by comparison of the specific rotation of the literature known reduced alcohol 26…”

Section: Methodsmentioning

confidence: 99%

Z‐Selective Hydrothiolation of Racemic 1,3‐Disubstituted Allenes: An Atom‐Economic Rhodium‐Catalyzed Dynamic Kinetic Resolution

Pritzius

Breit

2015

Angewandte Chemie

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Investigation of Optimum Firing Degree of Calcined Dolomite Used for Insolubilization Treatment of Heavy Metals and Analysis on Crystal Structure Change of Dolomite by Firing

Itaya

Kuninishi

2019

J. Soc. Mat. Sci., Japan

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Calcined dolomite shows excellent adsorption ability for heavy metals, metalloids and halogens (hereafter collectively referred to as "heavy metals") in soil, compared with raw dolomite. It is well known that dolomite is thermally decomposed into MgO and CaO in two stages. To study the relation between the heavy metal adsorption ability and crystal structure of calcined dolomite, 1) adsorption test using a solution containing heavy metals 2) specific surface area measurement 3) quantitative determination of the crystal phase by Rietveld analysis, and 4) K-edge XANES (X-ray Absorption Near-Edge Structure) analysis of Mg and Ca, were performed. The results of measurement of specific surface area after calcination and Rietveld analysis showed that there is a relation between the dolomite phase reduced by thermal decomposition and the specific surface area value and adsorption ability for heavy metals. The measured XANES spectra revealed that the local structure around Ca atoms did not change during calcination but that the local structure of Mg atoms changed gradually during calcination. Furthermore, the Mg K-XANES spectra measured in Partial Fluorescence Yield (PFY) mode and in Total Electron Yield (TEY) mode showed different spectra variations. These results suggest that MgO derived from calcined dolomite has structural differences between the outermost layer and the inside.

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Retrospect and Prospect of the XAFS Spectroscopy

Cited by 2 publications

References 43 publications

Z‐Selective Hydrothiolation of Racemic 1,3‐Disubstituted Allenes: An Atom‐Economic Rhodium‐Catalyzed Dynamic Kinetic Resolution

Z‐Selective Hydrothiolation of Racemic 1,3‐Disubstituted Allenes: An Atom‐Economic Rhodium‐Catalyzed Dynamic Kinetic Resolution

Investigation of Optimum Firing Degree of Calcined Dolomite Used for Insolubilization Treatment of Heavy Metals and Analysis on Crystal Structure Change of Dolomite by Firing

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