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[reaction: see text] It has been demonstrated for the first time that conjugated enynes can be employed as a facile substrate in olefin metathesis with the use of a bispyridine-substituted ruthenium benzylidene catalyst. Cross-metathesis of the enynes with alkenes turns out to proceed with preferential formation of (Z)-isomers over (E)-isomers up to >25:1 in moderate to good yields. The intramolecular version of conjugated enynes affords novel butadienyl cycloalkenes, which are a highly useful synthetic building blocks, in acceptable yields. 相似文献
117.
M. B. Gavini F. G. Rocco S. M. Kim 《Journal of Radioanalytical and Nuclear Chemistry》1981,67(2):437-444
A new and economical method for assay of environmental samples for uranium isotopes is proposed. Separation and radiochemical
purification of uranium isotopes (234U,235U and238U) from other elements is achieved on a single anion exchange column by washing with various concentrations of hydrochloric
acid. Iron, the principal interfering element is removed from the colum by washing with 4.5M hydrochloric acid with a combination
of reducing agents under the conditions described. Weightless samples of uranium are prepared by either evaporation in a polished
stainless steel dish or electroplated on a stainless steel planchet. This method is applicable for air particulates, soils,
sediments, coal, water, vegetation, and biologicals.
Text of the paper presented in the symposium on Practical Applications of Nuclear and Radiochemistry, at Las Vegas, Nevada,
August 25–29, 1980. Submitted for publication in Advances in Chemistry Series. 相似文献
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119.
The enolates produced from the conjugate addition reaction of lithium dialkylcuprates with α,β- unsaturated ketones react with aldehydes in the presence of zinc chloride to give overall β-alkyl α-hydroxyalkyl addition to the original alkene. Reaction of these enolates with carbon dioxide and ethyl formate is also reported. 相似文献
120.
Dong Han Kim Arthur A. Santilli Richard A. Fieber 《Journal of heterocyclic chemistry》1972,9(6):1347-1354
Syntheses of 11-acety1-2-phenylpyrimido[5,4-c][1,5]benzoxazepin-5(11H)one ( 16a ) and analogs ( 16b,c, 22 ) were described. The reaction of 4-chloro-2-phenyl-5-pyrimidinecarboxylic acid ethyl ester ( 7 ) with 2-aminophenol afforded 4-(2-hydroxyanilino)-2-phenyl-5-pyrimidine-carboxylic acid ethyl ester ( 8a ). The latter was also prepared by catalytic reduction of 4-(2-nitrophenoxy)-2-phenyl-5-pyrimidinecarboxylic acid ethyl ester ( 9 ), which was obtained from 7 and 2-nitrophenol. Involvement of 4-(2-aminophenoxy)-2-phenyl-5-pyrimidinecarboxylic acid ethyl ester ( 12a ) in this reduction as an intermediate was demonstrated by an independent synthesis of 12a and its subsequent rearrangement to 8a. Hydrolysis of 8a or 12a gave 4-(2-hydroxyanilino)-2-phenyl-5-pyrimidinecarboxylic acid ( 15a ). Reaction of 15a with acetic anhydride afforded 16a , the first member of a novel ring system, the pyrimido[5,4- c ][1,5]-benzoxazepin. Additional examples ( 16b,c ) were prepared similarly. The corresponding 11-ethyl derivative ( 22 ) was prepared in similar fashion, starting with 7 and 2-ethylaminophenol. A possible reaction mechanism for the formation of 16a-c from 15a-c and acetic anhydride was discussed. 相似文献