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251.
252.
Kondo Y Morey JV Morgan JC Naka H Nobuto D Raithby PR Uchiyama M Wheatley AE 《Journal of the American Chemical Society》2007,129(42):12734-12738
Sequential reaction of HTMP (= 2,2,6,6-tetramethylpiperidine) with nBuLi and Et2Zn affords unsolvated polymer chains of EtZn(micro-Et)(micro-TMP)Li 6. The scope of this reagent in directed ortho metalation (DoM) chemistry has been tested by its reaction with N,N-diisopropylnaphthamide in THF to give EtZn(micro-C10H6C(O)NiPr2-2)2Li.2THF 7. Data reveal that 6 has undergone reaction with 2 equiv of aromatic tertiary amide and imply that it exhibits dual alkyl/amido basicity. DFT calculations reveal that direct alkyl basicity is kinetically disfavored and instead point to a stepwise mechanism whereby 6 acts as an amido base, liberating HTMP during the first DoM event. Re-coordination of the amine at lithium then incurs the elimination of EtH. Reaction of the resulting alkyl(amido)(arylamido)zincate with a second equivalent of N,N-diisopropylnaphthamide eliminates HTMP and affords 7. Both DoM steps involve the exhibition of amido basicity and each reveals a low kinetic barrier to reaction. Understanding of this reaction sequence is tested by treating 6 with N,N-diisopropylbenzamide in THF. On the basis of theory and experiment, the presence of THF solvent (in place of stronger Lewis bases) combined with the use of a sterically less congested aromatic amide is expected to encourage threefold, stepwise reaction. Isolation and characterization of the resulting tripodal zincate Zn(micro-C6H4C(O)NiPr2-2)3Li.THF 8 bears this out and suggests a significant new level of control in zincate-induced DoM chemistry through the combination of experiment and DFT studies. 相似文献
253.
Ueno M Yonemoto M Hashimoto M Wheatley AE Naka H Kondo Y 《Chemical communications (Cambridge, England)》2007,(22):2264-2266
A novel type of deprotonative arylation of nucleophiles was conducted using Et(3)SiH/cat. t-Bu-P4 and the powerful S(N)Ar reactions of aryl fluorides were accomplished using alcohols and malonates as nucleophiles. 相似文献
254.
Silicon substrate surface and silica particle surface were modified with five kinds of polymers, poly(2-methoxyethyl methacrylate) (pMEMA), poly(2-hydroxyethyl methacrylate) (pHEMA), poly(acrylamide) (pAAm), poly(methyl methacrylate) (pMMA), and poly(styrene) (pSt), using a combined polymerization of surface-initiated polymerization that gives dense polymer chain layers and atom transfer radical polymerization (ATRP) that yields polymers with a narrow molecular weight distribution. Measurements of water contact angle and polymer chain amount on the modified silicon substrate surface and adsorption amounts of proteins (albumin and fibrinogen) on the modified silica particle surface revealed that the amount of polymer on the modified surface greatly affects the suppression of protein adsorption on the surface. 相似文献
255.
Searching for the method for gene detection is vitally important with the development of genetic diagnosis. Generally gene detection is carried out by the judgment of existence of signal of DNA probe (labeled complementary sequence) bound to target DNA sequence. Since sample DNA is immobilized on the solid support, non-bound DNA probe is washed out from the support. 相似文献
256.
Yutaka Kuroiwa Naoki Sugimoto Yuki Kondo Tsuneo Manabe Setsuro Ito Arao Nakamura 《Optics Communications》1999,170(4-6):285-289
Quenching treatments were performed on CuCl microcrystallite-doped glasses prepared by a melting method. Radiative decay time measurement and χ(3) measurement for the quenched glasses were performed using ps and ns laser. The glasses showed that the radiative decay time were shortened by one order of magnitude without a decrease of third-order nonlinear susceptibility χ(3) after the quenching treatment from above 300°C. The distorted structure of CuCl microcrystallites quenched from high temperature was considered to be most effective for the shortening of the lifetime of Z3 exciton. 相似文献
257.
A schlieren method was used to generate time-resolved images of the tunneling ionization front produced when an ultrashort
high-power laser pulse irradiates He gas. By superimposing sequential schlieren images, we obtained information about the
laser propagation and found that the ionization front propagated farther with decreasing density of the target gas. Ray-tracing
suggested that this density dependence is a result of the spatial distribution of the laser intensity.
Received: 20 May 1999 / Revised version: 19 August 1999 / Published online: 27 January 2000 相似文献
258.
Masahiro Mitsuyama Koichi Kondo 《Journal of polymer science. Part A, Polymer chemistry》2001,39(6):913-917
11‐Dodecyn‐1‐ol as an achiral, aliphatic, monosubstituted acetylene was copolymerized with cholesteryl 3‐butynyl carbonate as a chiral, aliphatic, monosubstituted acetylene with Rh(nbd)[B(C6H5)4] (nbd = norbornadiene) in tetrahydrofuran. The main chain of the obtained copolymers seemed to be mainly composed of the cis‐type structure. The backbone π–π* transition of these copolymers showed significant circular dichroism (CD), indicating an excess of one‐handed helical conformation. These CD signals were varied with the contents of the cholesteryl units in the copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 913–917, 2001 相似文献
259.
260.