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31.
Joji Ohshita 《Journal of organometallic chemistry》2006,691(9):1907-1911
Ring-opening halosilation of cyclic ethers with reagents of (Me2N)2SiMe2/4MeI (1a) and (Me2N)2SiMe2/4allylBr (1b) was studied. Tetrahydrofuran and cyclohexene oxide reacted with 1a and 1b to give ring-opened di(haloalkoxy)dimethylsilanes in good yield. With less strained tetrahydropyran, however, only reagent 1a gave the ring-opened product. Reactions of reagents 1a and 1b with propylene oxide also proceeded smoothly, although the regioselectivity was rather low. When similar reactions were carried out with (Me2N)2SiMe2/2MeI (2a) and (Me2N)2SiMe2/2allylBr (2b) in a ratio of cyclic ethers/2a or 2b = 1/1, the corresponding 1:1 adducts were obtained. 相似文献
32.
Development of fluorous Lewis acid-catalyzed reactions 总被引:1,自引:0,他引:1
Organic synthetic methodology in the 21st century aims to conform to the principles of green sustainable chemistry (GSC) and we may expect that in the future, the realization of GSC will be an important objective for chemical industries. An important aim of synthetic organic chemistry is to implement waste-free and environmentally-benign industrial processes using Lewis acids as versatile as aluminum chloride. A key technological objective of our work in this area has been to achieve a "catalyst recycling system that utilizes the high activity and structural features of fluorous Lewis acid catalysts". Thus, we have developed a series of novel fluorous Lewis acid catalysts, namely the ytterbium(III), scandium(III), tin(IV) or hafnium(IV) bis(perfluoroalkanesulfonyl)amides or tris(perfluoro- alkanesulfonyl)methides. Our catalysts are recyclable and effective for acylations of alcohols and aromatics, Baeyer-Villiger reactions, direct esterifications and transesterifications in a fluorous biphasic system (FBS), in supercritical carbon dioxide and on fluorous silica gel supports. 相似文献
33.
Yoshida H Fukushima H Ohshita J Kunai A 《Journal of the American Chemical Society》2006,128(34):11040-11041
A zwitterion, generated from an aryne and an imine, has been demonstrated to serve as an excellent molecular scaffold for capturing CO2, which results in the straightforward formation of diverse benzoxazinones. 相似文献
34.
Three sulfonated 1-(2-pyridylazo)-2-naphthols and six sulfonated 2-(2-pyridylazo)-1-naphthols were synthesized, and their application to the spectrophotometric determination of metals was studied. The acidity constants of the reagents and the stability constants of the nickel chelates are reported, and the relationship between their properties and the position of the sulfonic acid group is discussed. 1-(2-Pyridylazo)-2-naphthol-6-sulfonic acid (PAN-6S) and 1-(2-pyridylazo)-2-naphthol-7-sulfonic acid (PAN-7S) are sensitive and selective reagents for nickel. The determination of nickel in the presence of cobalt with PAN-6S is described. Extraction of the chelate as the ion-pair with tetraphenylarsonium ions into chloroform is suitable for the determination of 1–10 μg Ni at 570 nm; the molar absorptivity is 56 000 l mol-1 cm-1, and interferences are easily avoided. 相似文献
35.
Kazuyuki Nakai Joji Sonoda Masayuki Yoshida Masako Hakuman Hiromitsu Naono 《Adsorption》2007,13(3-4):351-356
The high resolution adsorption isotherms of N2 (77.4 K) and Ar (87.3 K) have been measured for two nonporous silicas with different silanol contents (3.3 and 0.35 OH/nm2) and for two MFI zeolite with different Al contents (Si/Al=12.5 and 500). Silanol groups and Al sites (acid sites) gives
the significant effect on the N2 isotherms at submonolayer, but the Ar isotherms are independent of silanols and Al sites. The Ar isotherms, therefore, are
preferable in calculation of microporosity of zeolites. The N2 and Ar isotherms for MFI zeolite (Si/Al=500) have been measured at temperatures of 77–94 K, from which the differential adsorption
energies of N2 and Ar are calculated. The interaction of N2 with channel surface of MFI zeolite is greater than that of Ar in the range of α
s
=0.1–0.7. The hystereses are detected for the N2 isotherm in p/p
o=0.1–0.3 at 77.4 K and for the Ar isotherm in p/p
o=3×10−4–2×10−3 at 87.3 K. However, it is difficult to explain the hysteresis phenomenon using differential adsorption energy. 相似文献
36.
Seven o,o′-dihydroxyazo dyes were synthesized and examined as spectrophotometric reagents for magnesium and calcium. These reagents are highly sensitive for magnesium (? = 47 000) and calcium (? = 39 000 l mol?1 cm?1). Of the reagents synthesized, 2-(2-hydroxy-3,6-disulfo-1-naphthylazo)-5-(N,N-diethylamino)phenol was the best because of its ease of preparation and purification, and its stability in alkaline solution. This dye was applied in the determination of magnesium and calcium by flow injection analysis. The total concentration of magnesium (0.1–1.2 mg 1?1) and calcium (0.4–4.0 mg 1?1) was determined by masking iron(III), aluminium(III), copper(II), zinc(II), manganese(II) and cadmium(II) with 2,3-dimercapto-1-propanol (DMP) and triethanolamine (TEA). Magnesium was determined by masking calcium and the other metal ions with a ligand buffer containing barium(II)—EGTA, DMP and TEA. The amount of calcium was obtained as the difference between the two peak heights. Results for the determination of magnesium and calcium in potable water and serum are presented. 相似文献
37.
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39.
Dr. Yohei Adachi Taishi Nabeya Keigo Kawakami Kosuke Yamaji Prof. Dr. Frieder Jäkle Prof. Dr. Joji Ohshita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(10):3306-3314
The introduction of unconventional elements into π-conjugated systems has been studied to manipulate the electronic states and properties of compounds. Herein, boron- and germanium-containing hybrid macrocycles, as a new class of element-hybrid conjugated systems, have been synthesized. The palladium-catalyzed Stille cross coupling of bis(bromothienyl)borane and bis(trimethylstannylthienyl)- or bis(trimethylstannylphenyl)-substituted dithienogermoles as the boron- and germanium-containing building blocks, respectively, produced a mixture of several macrocyclic compounds. Single-crystal X-ray analysis of the 2:2 coupling product revealed a planar structure with a cavity inside the macrocycle. The optical properties of the macrocyclic products indicated rather small electronic interactions between the building units. However, intramolecular photoenergy transfer from the dithienogermole unit to the boron unit was clearly observed with respect to the fluorescence spectra. 相似文献
40.