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排序方式: 共有159条查询结果,搜索用时 0 毫秒
1.
A series of parallel reactions were carried out for the tandem Ugi/Diels-Alder reaction on our MPEG-O-CH2- platform. Ninety-six out of a 100 entries were successful to give complex heterotricycles. The stereoselectivity was found not to be influenced by the building blocks used for amine and carboxylic acid components. An unexpected side pathway was found but was suppressed by employing appropriate reaction conditions. The reaction was also performed on solid phase, by which a larger library is potentially realized by employing the split-pool method. 相似文献
2.
Ito F Ikoma T Akiyama K Watanabe A Tero-Kubota S 《The journal of physical chemistry. B》2005,109(18):8707-8717
We have studied the magnetic field effects (MFEs) on the charge-transfer fluorescence and transient photocurrent of a 1,2,4,5-tetracyanobenzene-doped poly(N-vinylcarbazole) film, which reflect the recombination and escape yields of the carriers, respectively. The recombination yield dependence of the external magnetic field (B) clearly shows two types of the MFEs, growth with increasing B due to the hyperfine mechanism (HFM) and a negative dip due to the level-crossing mechanism (LCM). On the other hand, the escape yield indicates complementary MFEs with a sharp decrease in yield with increasing B and then a positive dip. Simultaneous observation of the HFM- and LCM-MFEs proves the stepwise hole-hopping mechanism rather the long-range hole-jumping one. The quantitative analysis of the recombination and escape MFEs is performed using the stochastic Liouville equations (SLE) for a one-dimensional lattice model in which the stepwise hole hops take place between the nearest neighbor carbazole units with spin conservation. The SLE analysis provides the recombination and hole transfer rate constants of 7.0 x 10(7) and 4.5 x 10(8) s(-1), respectively. The boundary site number for the ion pairs in the one-dimensional model is estimated by the best fit to the experimental results. The interionic distance of the boundary ion pair in the one-dimensional model including eight sites agrees with the thermalization distance in the Onsager model. Hence, it is concluded that the elementary processes in the Onsager model applied to molecular amorphous solids are the stepwise hole hops rather than a long-range hole jump. 相似文献
3.
Diversity-oriented organic synthesis (DOS) is a key concept for construction of skeletally diverse small molecule libraries to discover drug-like small molecules. Here, we describe a DOS class to transform a complex 7-oxanorbornene skeleton, which is readily accessible by a tandem Ugi/Diels-Alder reaction, into two heterotricycle skeletons selectively by using tandem ROM/CM/RCM reaction. In the present study, the mode of cyclization is pre-encoded by building blocks used in the complexity-generating tandem Ugi/Diels-Alder reaction. Since variable alkenes can be used in the CM reaction, our approach can be extended to construct both skeleton- and appendage-diverse small molecule libraries. 相似文献
4.
To develop a sealed-type nickel-metal hydride battery for use in portable equipment or in electric vehicles, investigations
were conducted on negative electrodes using AB5-type hydrogen storage alloy and positive electrodes. For the cycle life performance of the battery, alkaline treatment of
the alloy and the substitution of more than 50% to the alloy with Co were effective. For the positive electrode, zinc as a
solid solution in the nickel positive electrode obviously prevented γ-NiOOH from being formed in the charging process of β-Ni(OH)2 and suppressed the migration of the electrolyte solution in the separator to the active material of the positive electrode.
Also, hydrophobic treatment of the surface of the alloy was effective to prevent the elevation of the battery internal pressure
of the battery in high rate charge. 相似文献
5.
Prof. Makoto Tadokoro Masaki Itoh Ryota Nishimura Kensuke Sekiguchi Dr. Norihisa Hoshino Dr. Hajime Kamebuchi Prof. Jun Miyazaki Dr. Fumiya Kobayashi Prof. Motohiro Mizuno Prof. Tomoyuki Akutagawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(47):e202201397
A new H-bonded crystal [RuIII(Him)3(Im)3] with three imidazole (Him) and three imidazolate (Im−) groups was prepared to obtain a higher-temperature proton conductor than a Nafion membrane with water driving. The crystal is constructed by complementary N−H⋅⋅⋅N H-bonds between the RuIII complexes and has a rare Icy-c* cubic network topology with a twofold interpenetration without crystal anisotropy. The crystals show a proton conductivity of 3.08×10−5 S cm−1 at 450 K and a faster conductivity than those formed by only HIms. The high proton conductivity is attributed to not only molecular rotations and hopping motions of HIm frameworks that are activated at ∼113 K, but also isotropic whole-molecule rotation of [RuIII(Him)3(Im)3] at temperatures greater than 420 K. The latter rotation was confirmed by solid-state 2H NMR spectroscopy; probable proton conduction routes were predicted and theoretically considered. 相似文献
6.
7.
Sekiguchi A Ishida Y Fukaya N Ichinohe M Takagi N Nagase S 《Journal of the American Chemical Society》2002,124(7):1158-1159
Dark red crystals of the halogen-substituted cyclotrigermenes [(tBu3Si)3Ge3X; X = Cl, Br, I] were obtained in good yields by the reaction of [(tBu3Si)3Ge3]+.TTFPB- (TTFPB- = tetrakis(2,3,5,6-tetrafluorophenyl)borate) with potassium halides (KCl, KBr, or KI) in diethyl ether. The crystal structures of the halogen-substituted cyclotrigermenes reveal a cis-bent Ge=Ge double bond, caused by the introduction of the electronegative halogen atom on the sp3 germanium atom of cyclotrigermene. In solution, an intramolecular halogen migration over the three-membered ring skeleton was observed. Facial stereoselectivity in the Diels-Alder reaction of new cyclotrigermenes with 2,3-dimethyl-1,3-butadiene is also reported. 相似文献
8.
9.
Ito F Ikoma T Akiyama K Kobori Y Tero-Kubota S 《Journal of the American Chemical Society》2003,125(16):4722-4723
Magnetic field effects on the charge-transfer (CT) fluorescence of a 1,2,4,5-tetracyanobenzene-doped poly(N-vinylcarbazole) thin film were investigated to clarify the primary process in photoconductive organic amorphous solid. The CT fluorescence increased with increasing magnetic field until 10 mT, and then it showed the dip around 40-50 mT. The hyperfine coupling mechanism observed in the low field and the level-crossing mechanism observed around 46 mT clearly indicate that the spin-conservative stepwise hole hops take place in the films. The boundary distance determined from the simulation based on the stepwise hopping model almost agreed with the interionic separation estimated within the Onsager analysis. 相似文献
10.
Norihisa Ikoma 《NoDEA : Nonlinear Differential Equations and Applications》2009,16(5):555-567
In this paper we study the uniqueness of nontrivial positive solutions for the following second order nonlinear elliptic system:
$\left\{\begin{aligned} -\Delta u_1+V_1(|x|) u_1 &= \mu_1 u_1^3+\beta u_1u_2^2 & &\quad{\rm in} \ {\mathbb R}^{N},\\ -\Delta u_2+V_2(|x|)u_2&=\beta u_1^2u_2+\mu_2 u_2^3&&\quad{\rm in} \ {\mathbb R}^{N}.\end{aligned}\right.$\left\{\begin{aligned} -\Delta u_1+V_1(|x|) u_1 &= \mu_1 u_1^3+\beta u_1u_2^2 & &\quad{\rm in} \ {\mathbb R}^{N},\\ -\Delta u_2+V_2(|x|)u_2&=\beta u_1^2u_2+\mu_2 u_2^3&&\quad{\rm in} \ {\mathbb R}^{N}.\end{aligned}\right. 相似文献 |