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101.
We describe InBr3-catalyzed cyclization of 2-alkynylaniline derivatives having a variety of functional groups producing polysubstituted indoles. This methodology could be applied to the one-pot synthesis of an amino acid precursor by the addition of a catalytic amount of the indium salt, an imine, and TMSCl. 相似文献
102.
Norio Sakai 《Tetrahedron letters》2006,47(8):1261-1265
A catalytic amount of ytterbium triflate (Yb(OTf)3) promotes the cyclization of an N-silylenamine with in situ generated 2-methylene-1,3-cyclohexanedione and 2-methylenecyclohexanone to produce the corresponding 2,3-disubstituted 7,8-dihydroquinolin-5-one and 5,6,7,8-tetrahydroquinolin-5-one in moderate to good yields. A one-pot conversion of 7,8-dihydroquinolin-5-one to the quinoline derivative also proceeded in good yield. 相似文献
103.
Yamada H Kumauchi M Hamada N Zheng XG Park IH Masuda K Yoshihara K Tokunaga F 《Photochemistry and photobiology》2006,82(6):1422-1425
We report a unique lambdamax shift of the absorption maximum of a photoactive yellow protein (PYP) analogue reconstituted with a fluorinated chromophore (F-PYP). The difference in lambdamax between the free chromophore and the protein was significantly larger than that with the native chromophore. We concluded that the unusual lambdamax shift is caused by the electronegative character of the fluorine atom and not by steric hindrance. This result suggests that formation of a hydrogen bond between the fluorine atom and one or more amino acid residues could neutralize its electron-withdrawing character. The properties of analogues of PYP with brominated and methylated chromophore could be explained as an effect of steric hindrance. 相似文献
104.
105.
A practical synthesis of (R)-homopipecolinic acid methyl ester 1 and (R)-homoproline methyl ester 2 was performed utilizing (i) a direct intramolecular cyclization of ω-chloro-β-enamino esters 11 and 12, which were prepared from available (S)-1-phenylethylamine or (S)-1-(1-naphthyl)ethylamine and ω-chloro-β-keto esters 5 and 10, respectively and (ii) a highly diastereoselective NaBH4 reduction followed by hydrogenolysis. The present method is a short-step process using inexpensive and readily available substrates and reagents with fewer wasted materials. 相似文献
106.
Kohei Matsuzaki Kenta Okuyama Etsuko Tokunaga Motoo Shiro Norio Shibata 《ChemistryOpen》2014,3(6):233-237
A sterically demanding unsymmetrical pentafluorophenyl-triisopropylphenyl-λ3-iodane was developed as an effective reagent for the electrophilic pentafluorophenylation of various β-keto esters and a β-keto amide. 17 examples of α-pentafluorophenylated 1,3-dicarbonyl compounds 3 having a quaternary carbon center are provided. The resulting compounds were nicely transformed into chiral α-pentafluorophenyl ketones with an all-carbon stereogenic center in high yields and high enantioselectivities using asymmetric organocatalysis (up to 98 % ee) or asymmetric metal catalysis (up to 82 % ee). 相似文献
107.
108.
We measured FT-IR spectra of intact Acholeplasma laidlawii cells grown at 37 °C on palmitic acid (C16:0) or on binary palmitic acid-d31/oleic acid (C16:0-d31/C18:1(9)) at an initial mole ratio of 2:3, which have been previously reported to produce significant fluctuations in CH2 symmetric stretching (νsCH2) and CD2 asymmetric stretching (νaCD2) frequencies (Biochim. Biophys. Acta 1279 (1996) 49). Time courses for acyl chain νsCH2 and νaCD2 frequencies determined from fourth derivative spectra are presented. Fluctuations were detected with the C16:0 enriched cells at temperatures above 40 °C as well as with the cells enriched in 2:3 C16:0-d31/C18:1(9). These observations at temperatures above 40 °C for the C16:0 enriched cells were not in agreement with the conclusion in the previous work by Moore et al. Our results have suggested that the 2850 cm−1 νsCH2 band comprises two components arising from trans and gauche conformations, and that the fluctuations in νsCH2 frequency are caused by random temporal changes in the relative intensities of these two components. 相似文献
109.
Norio Tsubokawa Yukio Shirai Hideyo Tsuchida Satoshi Handa 《Journal of polymer science. Part A, Polymer chemistry》1994,32(12):2327-2332
The photografting of polymers onto ultrafine inorganic particles, such as silica and titanium oxide, initiated by azo groups introduced onto these surfaces was investigated. The introduction of azo groups onto the particles was achieved by the reaction of 4,4′-azobis(4-cyanopentanoic acid) with surface isocyanate groups, which were introduced by the treatment with tolylene 2,4-diisocyanate. It was found that the photopolymerization of vinyl monomers, such as methyl methacrylate (MMA), styrene, and N-vinylcarbazole, is initiated by ultrafine particles having azo groups. The corresponding polymers were effectively grafted onto these surfaces through the propagation of the polymer from the surface radicals formed by the photodecomposition of the azo groups: e.g., the percentage of grafting of PMMA and polystyrene onto silica was reached to 112 and 176%, respectively. The percentage of grafting onto silica in the graft polymerization initiated by photodecomposition of surface azo groups was much larger than that initiated by thermal decomposition. Polymer-grafted ultrafine particles thus obtained gave a stable colloidal dispersion in good solvents for the grafted chain. © 1994 John Wiley & Sons, Inc. 相似文献
110.