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41.
Takushi Kurihara Mariko Sugiyama Hiroshi Hirano Ken-Ichi Tomita Masayoshi Sakaki 《Journal of heterocyclic chemistry》1975,12(3):541-545
Reaction of o-nitrobenzylideneacetylacetone ( 1a ) with hydrazine dihydrochloride in methanol gave 4-(α-methoxy-o-nitrobenzyl)-3,5-dimethylpyrazole hydrochloride ( 4a ), whose structure was unambigously confirmed by an X-ray crystallographic analysis, via 4-(o-nitrobenzylidene)-3,5-dimethylisopyrazole ( 2a ). Compound 2a was synthesized by condensation of 1a with hydrazine dihydrochloride in acetonitrile. Analogously the corresponding o-chloro derivatives ( 2b, 4b ) were obtained. These were converted to N-methyl ( 6b ) and N-acetyl ( 7a,b ) derivatives and the behaviors on bromination and pyrolysis were investigated. 相似文献
42.
Optically active polyisocyanides (poly(iminomethylenes)) have been prepared with much interest in developing new functional materials. Polyisocyanides have been considered to have a stable 4(1) helical conformation even in solution when they have a bulky side group. However, the conformational characteristics of poly(phenyl isocyanide) (PPI) derivatives are still under debate. We now report that an optically inactive PPI derivative, poly(4-carboxyphenyl isocyanide) (poly-1), shows optical activity in the polymer backbone induced by external, chiral stimuli through acid-base interactions under thermodynamic control and exhibits induced circular dichroism (ICD) in the UV-visible region in DMSO. The ICD intensities of the poly-1-chiral amine complexes in DMSO gradually increased with time, and, in one case, the value reached 3 times that of the original value after 2 months at 30 degrees C. The conformational changes also occurred very slowly for poly-1 alone and its ethyl ester with time on the basis of (1)H NMR spectroscopic analysis. These results indicate that PPIs bearing a less bulky substituent may not have a 4(1) helical conformation but have a different type of prochiral conformation, for instance, an s-trans (zigzag) structure which may transform to a dynamic, one-handed helical conformation when the PPIs have a functional group capable of interacting with chiral compounds. The mechanism of helicity induction on poly-1 through a dynamic conformational transition is discussed on the basis of the above results together with molecular dynamic simulation results for PPI. 相似文献
43.
Synthesis and binding affinity of rationally designed artificial ditopic nucleobase receptors are reported. The ditopic receptors were designed to recognize thymine-thymine dinucleotides by their two hydrogen-bonding moieties, which are connected to conformationally well-defined linkages such as ferrocene and biphenylene. The ditopic receptors exhibited a remarkably strong binding affinity for lipophilic TpT analogue in CDCl(3)/DMSO-d(6) (85:15, v/v). The binding affinity of the ditopic receptors for the dinucleotide was so high that even native TpT was extracted by them into CDCl(3). Detailed comparisons for the recognition abilities of the ditopic receptors were also conducted. 相似文献
44.
1H NMR chemical shifts of solutions of the following cationic surfactants in D2O were determined as a function of their concentrations: cetyltrimethylammonium chloride, CTACl, a 1 : 1 molar mixture of
CTACl and toluene, cetylpyridinium chloride, CPyCl, cetyldimethylphenylam-monium chloride, CDPhACl, cetyldimethylbenzylammonium
chloride, CDBzACl, cetyldimethyl-2-phenylethylammonium chloride, CDPhEtACl, and cetyldimethyl-3-phenylpropylammonium chloride,
CDPhPrACl. Plots of observed chemical shifts versus [surfactant] are sigmoidal, and were fitted to a model based on the mass-action
law. Satisfactory fitting was obtained for the discrete protons of all surfactants. From these fits, we calculated the equilibrium
constant for micelle formation, K, the critical micelle concentration, CMC and the chemical shifts of the monomer, δmon and the micelle δmic. 1H NMR-based CMC values are in excellent agreement with those which we determined by surface tension measurements of surfactant
solutions in H2O, allowing for the difference in structure between D2O and H2O. Values of K increase as a function of increasing the size of the hydrophilic group, but the free energy of transfer per CH2 group of the phenylalkyl moiety from bulk water to the micellar interface is approximately constant, 1.9±0.1 kJ mol-1. Values of (δmic–δmon) for the surfactant groups at the interface, e.g., CH3–(CH2)15–N+(CH3)2 and within the micellar core, e.g., CH3–(CH2)15–N+ were used to probe the (average) conformation of the phenyl group in the interfacial region. The picture that emerges is
that the aromatic ring is perpendicular to the interface in CDPhACl and is more or less parallel to it in CDBzACl, CDPhEtACl,
and CDPhPrACl.
Received: 23 February 1996 Accepted: 29 August 1996 相似文献
45.
Y Naito T Goto F Akahoshi S Ono H Yoshitomi T Okano N Sugiyama S Abe S Hanada M Hirata 《Chemical & pharmaceutical bulletin》1991,39(9):2323-2332
A series of 2-[4-(thiazol-2-yl)phenyl]propionic acids substituted at various positions were prepared by the reaction of diethyl 2-methyl-2-(4-thiocarbamoylphenyl)malonates with alpha-bromoaldehyde diethyl acetals or alpha-haloketones followed by hydrolysis of esters. The inhibition of prostaglandin H synthetase (cyclooxygenase) was assayed by use of an enzyme preparation from guinea pig polymorphonuclear leukocytes. Examination of the structure-activity relationship of these compounds indicated that the substitution pattern with halogens at position 3 (R1) of the benzene ring and a methyl group in position 4 (R2) and/or 5 (R3) of the thiazole ring were favorable for inhibitory activity. The compounds bearing bulky alkyl or polar functional groups at the R2 position were weak inhibitors. The potent inhibitors of cyclooxygenase were tested for their ability to reduce carrageenin-induced inflammation of rat paws. These derivatives had strong anti-inflammatory activity based on their strong inhibition of cyclooxygenase, with some exceptions, including those with a thiomethyl group at R1. 相似文献
46.
The reaction of conjugated dienes such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2,5-dimethyl-2,4-hexadiene, 1,3-cyclopentadiene, and 1,3-cyclohexadiene, with thallium(III)acetate in acetic acid at 10–65° for 0.5–15 hr affords an isomeric mixture of the corresponding diacetoxyalkenes (1,2- and 1,4-addition products) in 10–92% yields. The 1,2-addition products are predominantly formed in all cases examined except the case of 1,3-cyclopentadiene. The reaction is assumed to proceed through acetoxythallation and dethallation steps, the latter step being accompanied and/or followed by an attack of acetoxyl group. An initial attack of thallium moiety is proposed to occur mainly at C-1 and C-2 carbons in the cases of linear terminal dienes and cyclic dienes, respectively. 相似文献
47.
Yamanaka N Kawano R Kubo W Kitamura T Wada Y Watanabe M Yanagida S 《Chemical communications (Cambridge, England)》2005,(6):740-742
Use of a new ionic liquid crystal, 1-dodecyl-3-methylimidazolium iodide, and iodine as an electrolyte of dye-sensitized solar cells leads to a high short circuit photocurrent density and a high light-to-electricity conversion efficiency, due to a self-assembled structure of the imidazolium cations, resulting in high conductivity of the electrolyte. 相似文献
48.
H. Mori H. Suzuki T. Okano H. MoriyamaY. Nishio K. KajitaM. Kodani K. TakimiyaT. Otsubo 《Journal of solid state chemistry》2002,168(2):626-631
The symmetric (s-) and unsymmetric (us-) BEDT-STF (=bis(ethylenedithio)diselenadithia-fulvalene) salts were prepared, and their crystal structures and electrical resistivities were investigated. Four us-BEDT-STF salts have the positional disorder of the Se atoms in the STF framework in crystals, whereas three s-BEDT-STF salts have no disorder. When κ-(us-BEDT-STF)2GaCl4 and κ-(cis-s-BEDT-STF)2GaCl4 are compared, the latter without the positional disorder of the Se atoms is more conductive than the former one with the disorder. 相似文献
49.
The Pictet-Spengler cyclization of the imines (3) prepared by the condensation of L-tryptophan methyl ester (1) and aryl methyl ketones (2), using titanium(IV) isopropoxide as an iminating reagent, quantitatively proceeded, when treated with trifluoroacetic acid (TFA) or formic acid, to provide two diastereomers, that is (1S,3S)-1-aryl-3-isopropoxycarbonyl-1-methyl-1,2,3,4-tetrahydro-beta-carbolines (4) and their (1R,3S)-diastereomers (5), of which the diastereomer ratios varied from 1 to 5 depending on the reaction conditions. The (1R,3S)-diastereomers (5) are thermodynamically more stable than their (1S,3S)-congeners (4), as shown by equilibration experiments in TFA. The conversion of 4 to 5 (also 5 to 4) should occur under acidic conditions by cleavage of the C(1)-N(2) bond with complete retention of configuration at the C-3 chiral center. The low diastereo-selectivity observed in the Pictet-Spengler reaction of 1 and 2 is concluded to be a stereochemical outcome under conditions of kinetic control (lower temperature, shorter reaction time), while the high diastereo selectivity with preferential formation of the more stable isomer (5) is the result of thermodynamically controlled experiments (higher temperature, longer reaction time). 相似文献
50.
Akira Matsumoto Yutaka Kukimoto Kazuhiro Aoki Masayoshi Oiwa 《Journal of polymer science. Part A, Polymer chemistry》1983,21(12):3493-3502
Seven glycol bis(allyl phthalate)s (GBAP) and four glycol bis(allyl succinate)s (GBASu) as reactive oligomers were prepared and their polymerization behaviors were investigated in detail in terms of cyclopolymerization and gelation as compared with diallyl dicarboxylates. Thus, the rates of polymerization of GBAPs were reduced compared to diallyl phthalate, being attributed to the steric effect on the intermolecular propagation of the uncyclized radical, whereas those of GBASus were enhanced as a consequence of intermolecular association by dipole–dipole interaction in polar GBASu monomers. Cyclization was enhanced in the following order: diallyl aliphatic dicarboxylates series < GBASu series < GBAP series. Gelation was discussed according to Gordon's theory; the actual gel-point conversions increased with an increase in the molecular weight of monomers, although the discrepancy between actual and theoretical gel-point conversion inversely tended to be decreased. The decreased delay in gelation with an increase of the molecular weight of monomers is ascribed to the reduction of excluded volume effects on crosslinking. 相似文献