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91.
92.
Treatment of sec-alkyl phenyl tellurides, except for the cyclohexyl system, with m-chloroperbenzoic acid(MCPBA) in diethyl ether readily afforded the corresponding olefins in good yields presumably via telluroxide elimination together with small amounts of alcohols and ketones. In the pri-alkyl and cyclohexyl cases the adducts between MCPBA and the tellurides were isolated as stable organotellurium(IV) compounds which gave similar elimination products by neat pyrolysis at 220–2500°C. 相似文献
93.
Three types of α-elimination (oxidative, photolytic, and thermal) of organotellurium(IV) halides to give organic halides have been disclosed. Treatment of organotellurium(IV) halides with some oxidants, preferably t-butyl hydroperoxide, in 1,4-dioxane, acetic acid, or acetonitrile affords the corresponding organic halides in good yields with retention of configuration and by ipso-replacement. The reactivity order of this α-elimination is roughly as follows: alkyl > aryl > alkenyl. The main reaction course seems to be a 1,2-tellurium halogen shift in unstable organotellurium(VI) compounds formed in situ by oxidation. Similar α-elimination also occurs by photolysis of these compounds with a high-pressure mercury lamp in benzene as the solvent. Here, a cross-coupling of the organic moiety with benzene scarcely occurs except for the cases of diaryltellurium(IV) dihalides. Neat pyrolysis of some alkyl(phenyl)tellurium(IV) dibromides at 200–250 °C (Kugelrohr distillation apparatus) again results in α-elimination to produce the corresponding alkyl bromides almost quantitatively. 相似文献
94.
Vanadium oxyacetylacetonate [VO(acac)(2)] works as a catalyst for the direct synthesis of 3-sulfanylindoles from indoles and thiols under an atmospheric pressure of molecular oxygen as a reoxidant. For example, the reaction of 2-phenylindole with benzenethiol in the presence of a catalytic amount of VO(acac)(2), potassium iodide, and 2,6-di-tert-butyl-p-cresol in chlorobenzene under molecular oxygen proceeds to afford 2-phenyl-3-(phenylsulfanyl)indole in 86% yield. This catalytic system can also be applied to 2-naphthols instead of indoles to give the corresponding 1-sulfanyl-2-naphthols in up to 57% yield. 相似文献
95.
Treatment of several cyclic olefins and allybenzene with a catalytic amount of [Rh3O(OAc)6(H2O)3]OAc in acetic acid in the presence of t-butyl hydroperoxide affords the corresponding α,β-unsaturated carbonyl compounds (enones) highly seletively via an ionic pathway. 相似文献
96.
The reaction of conjugated ene-yne-ketones 3 with a variety of alkenes in the presence of a catalytic amount of Cr(CO)(5)(THF) at room temperature gives (2-furyl)cyclopropanes in good yields. These cyclopropanation reactions proceed via (2-furyl)carbene-chromium intermediates 4 formed in situ from ene-yne-ketones 3. Late transition metals, such as [RuCl(2)(CO)(3)](2), [RhCl(cod)](2), PdCl(2), and PtCl(2), also catalyze effectively the cyclopropanation of styrene with 3. 相似文献
97.
Nishibayashi Y Inada Y Hidai M Uemura S 《Journal of the American Chemical Society》2002,124(27):7900-7901
Novel ruthenium-catalyzed cycloaddition of propargylic alcohols with 2-naphthols and phenols bearing electron-donating groups via allenylidene intermediates has been developed to give the corresponding 1H-naphtho[2,1-b]pyrans and 4H-1-benzopyrans, respectively, in moderate to excellent yields with complete regioselectivity. 相似文献
98.
Inagaki K Takatsu A Kuroiwa T Nakama A Eyama S Chiba K Okamoto K 《Analytical and bioanalytical chemistry》2004,378(5):1271-1276
Two types of sediment reference material (NMIJ 7302-a and 7303-a) for trace elements analysis have been prepared and certified by the National Metrology Institute of Japan in the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). The original materials were collected from a bay near industrial activity in Kyushu (NMIJ CRM 7302-a; marine sediment) and from Lake Biwa (NMIJ CRM 7303-a; lake sediment). The sediment materials were air-dried, sieved, homogenized, packaged in 1000 glass bottles (60 g each), and radiation sterilized. Certification of these CRM for trace elements was conducted by NMIJ, where each element was determined by at least two independent analytical techniques. Isotope-dilution inductively coupled plasma mass spectrometry (ICP–MS) was applied for certification of all the elements except mono-nuclide elements such as As and Co. Other techniques such as ICP–MS with quadrupole mass spectrometry and sector-field mass spectrometry, inductively coupled plasma atomic emission spectrometry (ICP–AES), and atomic absorption spectrometry (AAS), were also used. Certified values have been provided for 14 elements (Sb, As, Cd, Cr, Co, Cu, Pb, Hg, Mo, Ni, Se, Ag, Sn, and Zn) in both CRM. 相似文献
99.
Morita Y Kawai J Fukui K Nakazawa S Sato K Shiomi D Takui T Nakasuji K 《Organic letters》2003,5(18):3289-3291
[structure: see text] Topological symmetry-based extensions of a pi-conjugation network in an odd alternant phenalenyl radical have enabled us to control the spin density distribution systematically. ESR/ENDOR and NICS studies on the topological isomers of oxophenalenoxyl have revealed that the unpaired electron tends to localize in the antiaromatic ring systems. 相似文献
100.
Abstract— Difference spectrum for the reduction of A2 , a bound secondary electron acceptor of photo-system I, in the thylakoid membranes of a thermophilic blue-green alga, Synechococcus sp., was determined by subtracting the difference spectrum of P700 photooxidation from the difference spectrum for flash-induced absorption changes due to oxidation of P700 and reduction of A2 , or by measuring light-induced absorption changes under reducing conditions where reduced A2 accumulates. The spectrum showing a broad bleaching with two maxima at 420 and 440 nm indicates that A2 is an iron-sulfur center different from P430. 相似文献