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31.
We demonstrate the efficiency of the optical poling process that depends on the CE phase-controlled quantum interference. For the experiment we employed our noncollinear optical parametric amplifier system for the self-stabilization of the CE phase, with the f-to-2f spectral interferometry system to control the CE phase. 相似文献
32.
A Reformatsky-type aldol reaction of alpha-chloroketones with aldehydes has been achieved using reactive barium as a low-valent metal in THF; this one-pot process is more effective for obtaining the desired beta-hydroxy ketones in high yields than the stepwise process in which barium enolates are prepared prior to the reaction with aldehydes. 相似文献
33.
Shibata T Fujimoto T Yokota K Takagi K 《Journal of the American Chemical Society》2004,126(27):8382-8383
An asymmetric [2+2+2] cycloaddition of an alpha,omega-diyne, possessing ortho-substituted aryl groups on its terminus, and a monoalkyne with oxygen functionalities gave various axially chiral teraryl compounds. The coupling proceeded with extremely high enantio- (>99.5% ee) and diastereoselectivities (dl/meso = >95/5) when catalyzed by an iridium-chiral phosphine complex. As the products were readily transformed into diol compounds by deprotection without racemization, the present procedure provides access to a new chiral pool of diol compounds with C2 symmetry. 相似文献
34.
We report here the low temperature emission spectra in the heterometal dinuclear 3d-4f assembled molecular system [(acac)2CrIII(μ-ox)LnIII(HBpz3)2] (Cr(ox)Ln:acac−=acetylacetonate, ox2−=oxalate, HBpz3−=hydrotris(pyrazol-1-yl)borate; Ln=La, Nd, Ho, Er , Tm and Yb) in comparison with those of Na[Cr(acac)2(ox)] and [(HBpz3)2Ln(μ-ox)Ln(HBpz3)2](Ln=Nd and Er). From 10 to 150 K the Cr(ox)Ln complexes show a broad emission band around 800 nm from the 2E state of Cr(III) moiety. At room temperature no 2E-4A2 emission was observed in the Cr(ox)Ln except for the La and Lu complexes. On warming from 10 to 300 K rapid quenching of the 2E-4A2 emission of Cr(III) is suggested to result from the energy transfer from Cr to Ln in the Cr(ox)Ln. The excitation spectra and the life-time were also measured with monitoring the 4f-4f emission peaks of the Cr(ox)Yb complex. 相似文献
35.
Kawai K Takada T Nagai T Cai X Sugimoto A Fujitsuka M Majima T 《Journal of the American Chemical Society》2003,125(52):16198-16199
The hole transfer causes the long-lived charge-separated state in DNA during the photosensitized one-electron oxidation of DNA. The combination of the transient absorption measurement and DNA damage quantification by HPLC clearly demonstrated that the yield of the DNA damage correlates well with the lifetime of the charge-separated state. 相似文献
36.
Kim H Ralph J Lu F Ralph SA Boudet AM MacKay JJ Sederoff RR Ito T Kawai S Ohashi H Higuchi T 《Organic & biomolecular chemistry》2003,1(2):268-281
Peroxidase/H2O2-mediated radical coupling of 4-hydroxycinnamaldehydes produces 8-O-4-, 8-5-, and 8-8-coupled dehydrodimers as has been documented earlier, as well as the 5-5-coupled dehydrodimer. The 8-5-dehydrodimer is however produced kinetically in its cyclic phenylcoumaran form at neutral pH. Synthetic polymers produced from mixtures of hydroxycinnamaldehydes and normal monolignols provide the next level of complexity. Spectral data from dimers, oligomers, and synthetic polymers have allowed a more substantive assignment of aldehyde components in lignins isolated from a CAD-deficient pine mutant and an antisense-CAD-downregulated transgenic tobacco. CAD-deficient pine lignin shows enhanced levels of the typical benzaldehyde and cinnamaldehyde end-groups, along with evidence for two types of 8-O-4-coupled coniferaldehyde units. The CAD-downregulated tobacco also has higher levels of hydroxycinnamaldehyde and hydroxybenzaldehyde (mainly syringaldehyde) incorporation, but the analogous two types of 8-O-4-coupled products are the dominant features. 8-8-Coupled units are also clearly evident. There is clear evidence for coupling of hydroxycinnamaldehydes to each other and then incorporation into the lignin, as well as for the incorporation of hydroxycinnamaldehyde monomers into the growing lignin polymer. Coniferaldehyde and sinapaldehyde (as well as vanillin and syringaldehyde) co-polymerize with the traditional monolignols into lignins and do so at enhanced levels when CAD-deficiency has an impact on the normal monolignol production. The implication is that, particularly in angiosperms, the aldehydes behave like the traditional monolignols and should probably be regarded as authentic lignin monomers in normal and CAD-deficient plants. 相似文献
37.
[reaction: see text] The Pt-catalyzed carboselenation of terminal alkynes with selenoesters provided vinylselenides regio- and stereoselectively in moderate yields. 相似文献
38.
[reaction: see text] Polymer-supported bisBINOL ligands were successfully utilized for the immobilization of multicomponent asymmetric catalysts. The polymer-supported Al-Li-bis(binaphthoxide) (ALB) catalyst was more effective than the dendrimer-supported ALB in the Michael reaction of 2-cyclohexen-1-one with dibenzyl malonate affording the adduct in 91% yield with 96% ee. The polymer was also effective for the immobilization of a mu-oxodititanium complex that promoted carbonyl-ene reaction of ethyl glyoxalate with alpha-methyl styrene to provide the adduct with up to 98% ee. 相似文献
39.
40.
Takahiro Gunji Takayoshi Tozune Hironori Kaburaki Kouji Arimitsu Yoshimoto Abe 《Journal of polymer science. Part A, Polymer chemistry》2013,51(22):4732-4741
Polymethyl(alkoxy)siloxane copolymers, poly(MTES‐co‐TEOS), and poly(MTMS‐co‐TMOS), are prepared by acid‐catalyzed controlled hydrolytic co‐polycondensation of methyl(trialkoxy)silane MeSi(OR)3 (R = Et (MTES) and Me (MTMS)) and tetra‐alkoxysilane Si(OR)4 (R = Et (TEOS) and Me (TMOS)), respectively. The products are purified by fractional precipitation to provide polymethyl(alkoxy)siloxane copolymers with molecular weight 1000–10,000 (poly(MTES‐co‐TEOS)) or 1700–100,000 (poly(MTMS‐co‐TMOS)) that are stable to self‐condensation. These polymers are soluble in common organic solvents except for hexane, and form flexible and transparent free‐standing films with a tensile strength of 4.0–10.0 MPa. The structure of the polymethyl(alkoxy)siloxane copolymers is thought to be a random or a block co‐polymer. They are found to provide coating films with an adhesive strength up to 10, a refractive index of 1.36–1.40, and a dielectric constant of 3.5–3.6. The products also show better weathering stability than polyethoxysiloxane due to the hydrolytic polycondensation of TEOS. Field emission‐scanning electron micrography analysis reveals that coating films are composed of a micro‐phase separated structure. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4732–4741 相似文献