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41.
2,5-Bis(4-aminophenyl)-3,4-diphenylthiophene, a polyimide-forming monomer, was prepared in three steps starting from benzyl chloride and sulfur. Novel polyimides were synthesized from the diamine and pyromellitic dianhydride or 3,3′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA). Polymerization was carried out either by the usual two-step procedure that included ring-opening polyaddition giving polyamic acids, followed by cyclodehydration to polyimides, or by the direct one-pot procedure involving cyclodehydration in situ. The polyimide derived from the diamine and BTDA, especially that prepared by the one-pot procedure in m-cresol containing isoquinoline, is soluble in various organic solvents and gave a yellow, transparent, tough, and flexible film. Solubility of this polyimide varied by the preparative method and by the copolymerization with bis(4-aminophenyl) ether. All the polyimides are highly thermally stable and exhibited no appreciable decomposition up to 450°C in air and nitrogen atmospheres.  相似文献   
42.
In order to develop analgesic compounds possessing a sulfur atom in the alicyclic ring, novel cis-fused heterocycles, [1]benzothiopyrano[3,4-b]pyrrole derivatives (II) were synthesized via a unique cyclization reaction starting from 4-(4-methoxyphenylthio)-2-butanone (1) or 6-methoxy-3,4-dihydro-2H-1-benzothiopyran-4-one (7). The analgesic effects of benzothiopyranopyrroles (16, 18) were measured by means of the writhing test. The phenolic derivative 18 completely inhibited the appearance of writhing at the dose of 50 mg/kg, but the methoxy derivative 16 had no analgesic effect.  相似文献   
43.
Copolymerization of NCA's was undertaken in a heterogeneous system in acetonitrile, which is not a solvent of the polypeptides. The reactivity ratio was calculated by using the Lewis-Mayo equation. Further, the conversion rate in the copolymerization and the configuration of the copolymer produced were compared with those of the copolymerization in the homogeneous system in nitrobenzene, in which the copolypeptides are swollen. The rate of copolymerization in acetonitrile was between the rates of polymerization of the individual monomers. It has been reported that the configuration of the copolymer obtained in dimethylformamide, in which the copolypeptides are swollen, is of the block type. On the other hand, many polypeptides obtained in acetonitrile, which is not a solvent of the copolypeptides, had a random configuration near to an alternating configuration.  相似文献   
44.
The determination of seven sulfonamides by means of HPLC with chemiluminescence detection is proposed for the first time. The analytes are derivatized with fluorescamine, separated and subsequently they participate in the post-column chemiluminescence (CL) peroxyoxalate system using imidazole as a catalyst. Among the different peroxyoxalates tested, bis[4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl] oxalate provides higher sensitivities and stabilities, avoiding precipitation problems. A rigorous optimization of the significant variables by means of experimental designs has been developed in order to reconcile the chromatographic conditions with the CL reaction. The method provides detection limits in the low microgl(-1) range and has been satisfactorily applied to the analysis of spiked raw milk samples.  相似文献   
45.
Catalytic actions of various additives were studied in the polycondensation of di(4-nitrophenyl) isophthalate with bis(4-aminophenyl) ether in N-methyl-2-pyrrolidone, and 1-hydroxybenzotriazole (HOBt) was found to be a highly effective catalyst that yielded high-molecular-weight polyamide. In addition to the polycondensation of the 4-nitrophenyl ester, the polymerization of negatively substituted phenyl esters like di(2,4,5-trichlorophenyl) isophthalate was also accelerated by HOBt. For the HOBt-catalyzed aminolysis of esters a bifunctional concerted mechanism that involves an eight-membered transition state was proposed.  相似文献   
46.
The relative stability of various organosulfur radicals is estimated by competitive elimination technique using tributyltin radical and acetophenone derivatives having two different sulfur substituents at α and α positions.  相似文献   
47.
Bile acids, such as cholic, chenodeoxycholic, deoxycholic, lithocholic and ursodeoxycholic acids, were allowed to react with hexafluoroisopropanol and tri-fluoracetic anhydride at 37 for 30 min. The resulting derivatives were gas chromatographed on QF-1, with flame ionization detection, and were identified by gas chromatography-mass spectrometry. Separation was good. By using this method, these acids were detected in samples of human duodenal fluid; the ratios of each were 24.4, 41.5, 24.9, 2.3 and 6.9%, respectively.  相似文献   
48.
Chemical investigation of leaves of Staphylea bumalda DC., collected in the suburbs of Hiroshima City, afforded 11 new megastigmane glucosides, named staphylionosides A-K (3-13), along with two known megastigmane glucosides (1, 2). The relative structures were elucidated from spectroscopic evidence, and the absolute structures of the aglycones were determined by means of the combination of beta-D-glucosylation-induced shift-trends and the modified Mosher's method.  相似文献   
49.
The reaction of the dianion of phenylsulfinylacetone with alkyl halides afforded beta-keto sulfoxides, which were first chlorinated with hexachloroethane and then treated successively with KH and t-BuLi to give carboxylic acids in three-steps in moderate overall yields from the alkyl halides. This procedure affords a good method for a synthesis of carboxylic acids from alkyl halides with three-carbon elongation.  相似文献   
50.
γ-Radiolysis reactions of eight 5-fluorouracil (5-FU) derivatives having sulfonyl group-containing substituents at the 1-position and five 5-fluorouridine (5-FUR) derivatives having thioureido group-containing substituents were studied under the conditions where hydrated electron (eaq?) and hydroxyl radical (HO·) become the principal reactive species. The 5-FU and 5-FUR derivatives were radiolyzed to give 5-FU and 5-FUR, respectively. The efficiency of the reactions depended upon the nature of reactive species and also upon the nature of substituents. The reactivity features of the γ-radiolysis reactions are discussed.  相似文献   
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