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71.
72.
Yoshino Katsurayama Prof. Yasuhiro Ikabata Prof. Hajime Maeda Prof. Masahito Segi Prof. Hiromi Nakai Prof. Taniyuki Furuyama 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(2):e202103223
The high penetration of near-infrared (NIR) light makes it effective for use in selective reactions under light-shielded conditions, such as in sealed reactors and deep tissues. Herein, we report the development of phthalocyanine catalysts directly activated by NIR light to transform small organic molecules. The desired photocatalytic properties were achieved in the phthalocyanines by introducing the appropriate peripheral substituents and central metal. These phthalocyanine photocatalysts promote cross-dehydrogenative-coupling (CDC) under irradiation with 810 nm NIR light. The choice of solvent is important, and a mixture of a reaction-accelerating (pyridine) and -decelerating (methanol) solvents was particularly effective. Moreover, we demonstrate photoreactions under visible-light-shielded conditions through the transmission of NIR light. A combined experimental and computational mechanistic analysis revealed that this NIR reaction does not involve a photoredox-type mechanism with electron transfer, but instead a singlet-oxygen-mediated mechanism with energy transfer. 相似文献
73.
Deringoz Fatih Guliyev Vagif S. Nakai Eiichi Sawano Yoshihiro Shi Minglei 《Positivity》2019,23(3):727-757
Positivity - In the present paper, we will characterize the boundedness of the generalized fractional integral operators $$I_{\rho }$$ and the generalized fractional maximal operators $$M_{\rho }$$... 相似文献
74.
Abstract The first successful chemical synthesis of cellulose was achieved by a polycondensation of β-cellobiosyl fluoride monomer catalyzed with cellulase, an extracellular hydrolytic enzyme of cellulose, in a mixed solvent of acetonitrile and acetate buffer. The product, synthetic cellulose, was the crystalline allomorph cellulose II, a thermodynamically more stable form. More detailed examinations of the polymerization conditions led to the formation of the native cellulose I, a metastable allomorph, for the first time. The key to the success was to use partially purified cellulase and an appropriate mixed solvent of acetonitrile/buffer. The formation of the two allomorphs of cellulose implies that the polarity of the glucan chain ordering can be controlled in a test tube. Based on these findings, a new concept “choroselectivity,” meaning spacial control in ordering the macromolecular chain, has been proposed. Cellulose analogues, 6-O-methylated cellulose and xylan, have been synthesized regio- and stereoselectively by using the enzymatic polymerization technique. 相似文献
75.
Novel methods of synthesis of spiro acyloxyphosphoranes are described emphasizing the significance of the first isolated instance of these new species. Then, the no-catalyst alternating copolymerizations of the combinations of cyclic phosphorus(III) compounds (serving as nucleophilic monomer, MN) with acrylic acid derivatives and with α-keto acids (electrophilic monomer, ME) are mentioned. These copolymerizations proceed without added initiator. Spiro oxyphosphoranes play an important role in the copolymerization scheme in the equilibrium with the +MN - ME ? zwitterion, the key intermediate of the copolymerization. Finally, new reactions of spiro acyloxyphosphoranes with nucleophiles, alcoholysis and aminolysis polymerizations are presented. 相似文献
76.
Abstract Chiral crystals of tryptamine and achiral carboxylic acids such as p-chlorobenzoic acid, cinnamic acid, p-chlorocinnarnic acid and p-methylcinnamic acid were prepared by crystallization from the solutions of both components. All the crystals belonged to typical chiral space group P212121. The crystal chirality is generated through the formation of a unidirectional twofold helix between the two components through quaternary ammonium salt interaction and hydrogen bonding in the lattice. This kind of spontaneous crystallization necessarily gives crystals of both clockwise and counterclockwise helicites. Here, pseudo-seeding based on utilizing these crystals as seed crystals was examined, resulting in successful helicity control in crystallization from solutions of tryptamine and different carboxylic acids. 相似文献
77.
Eiichi Kimura Naomi Katsube Tohru Koike Motoo Shiro Shin Aoki 《Supramolecular chemistry》2013,25(2-3):95-102
We have previously shown that the nucleobase thymine binding to Zn2+ -cyclen (cyclen=1,4,7,10-tetraazacyclododecane) complex became stronger by appending acridine, naphthalene, or quinoline rings to the cyclen. Amongst these, the pendant bis((1-naphthyl)methyl) or bis((4-quinolyl)methyl) groups yielded the most effective thymine-recognizing Zn2+ -cyclen complexes [J. Am. Chem. Soc., 121 (1999) 5426]. The present study was undertaken to find causes of the bis(aromatic) ring effect by X-ray crystal structure analysis and NMR studies. The crystal structure of the Zn2+ -bis((1-naphthyl)methyl)-cyclen complex with a deprotonated 1-methylthymine (1-MeT) failed to show the anticipated evidence for the double ~ - ~ stacking interactions between the two naphthalenes and the Zn 2+ -bound 1-MeT m (1-MeT m =N(3')-deprotonated 1-MeT). Crystal data: formula C36 H47 N7 O7 Zn, M r =755.19, monoclinic, space group P21/ c (No. 14), a =15.438(2) Å, b =14.093(3) Å, c =16.726(2) Å, g =90.53(1) V =3638.7(8) Å 3 Z =4, R =0.035, R w =0.049. However, the 1H NMR studies of Zn2= -bis((4-quinolyl)methyl)-cyclen with 1-MeT in varying H2O/CH3 CN solution showed increasing upfield shifts of Me(5') and H(6') of the Zn2+ -bound 1-MeT in more aqueous media, indicating that the double intercalation with the two quinolines became more significant in more protic environments. We conclude that the double ~ - ~ stacking effect accounts for the enhanced recognition of thymine base by the appended bis((1-naphthyl)methyl) or bis((4-quinolinyl)methyl) groups. 相似文献
78.
Takayoshi Kimura Tasunori Suzuki Keisuke Takata Akina Soga Yutsa Nomoto Tadashi Kamiyama Yousuke Nakai Hideo Matsui Masao Fujisawa 《Journal of Thermal Analysis and Calorimetry》2013,113(3):1467-1474
The molar excess enthalpies of eight systems of butylamines + propanols were determined at 298.15 K using a twin-microcalorimeter. All excess enthalpies were exothermic and large. An equilibrium constant K 1 expressed in terms of mole fractions and standard thermodynamic properties of formation (Δf H, Δf G, Δf S) of 1:1 complex were evaluated by ideal mixtures of monomeric molecules and their associated complexes. Concentration dependence of the FT-Raman spectrum showed systematic changes of bands. Spectroscopic considerations based on this and ab initio calculations on molecules were performed at the Mp2/6-311G(d,p) level of theory. Interaction energies between butylamine and propanol were calculated by the supermolecular and NBO methods. The results were discussed with previous results to clarify the steric and positional effect of the amino and hydroxyl group. 相似文献
79.
We have recently found that the reaction of α-keto acids (1) with phosphorus (III) compounds (3) yielded cyclic acyloxyphosphoranes(C-AOPs, 4), a new class of pentacovalent phosphorus species having a P-OC(O) group.1, 2) The present paper deals with a new reaction of glyoxylic acid (2) with 3 to give C-AOPs (5) having no substituent at the C-3 position. 1 is an α-keto acid whereas 2 can be taken as an α-formyl acid. Although it is well known in the field of organic chemistry that the formyl group often behaves differently from a keto group, the reaction of 2 with 3 provides an example in which both groups behave in a similar manner. 相似文献
80.