- 作者: 許炎和; 郭禮青; 廖俊臣; 林和盛; 汪炳鈞
- 作者服務機構: Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 300
- 中文摘要:
The cycloadditions of the title compound, 1, a masked 3,6-dipropy1-o-benzo-quinone to various disubstituted (diethyl maleate, diethyl fumarate, trans- and cisstilbene, and cycloheptene) and monosubstituted alkenes (methyl acrylate, methyl vinyl ketone, styrene, ethyl vinyl ether, and l-hexene) have been studied; the yields of the Diels-Alder adducts, 2, are generally high (>75%) except for stilbenes.
These adducts are effectively transformed into the corresponding bicycle[2.2.2]oct-5-ene-2, 3-diones, 3, whose stereochemistries are determined from the ring current effect of the respective quinoxalines, 4, on the chemical shifts of the vinyl and the methane protons and/or the lanthanide (Eu(fod)3) induced shift on the pertinent protons of 3. It is interesting to note that the quinoxaline ring current makes the vinyl protons down-field shifted by 0.15-0.27 ppm whereas the methane protons (R3=H) syn to the quinoxaline moiety up=field shifted by 0.18-0.39 ppm as compares to the chemical shifts of the corresponding protons in 3. The transformations of a-diketones 3 into the corresponding I, 3-cyclohexadienes, 5, by irradiation with a Hanovia medium pressure lamp through a uranium glass filter are almost quantitative. The present study provides facile and effective methods for the preparation of bicycle[2.2.2]oct-5-ene-2, 3-diones and 1, 3-cyclohexadienes from catechols yia masked o-benzoquinones. - 英文摘要: --
- 中文關鍵字: Diels-Alder reactions; masked o-benzoquinone; alkenes; photolysis; bicyclo[2. 2. 2]oct-5-ene-2, 3-diones; 1, 3-cyclohexadienes.
- 英文關鍵字: Diels-Alder reactions; masked o-benzoquinone; alkenes; photolysis; bicyclo[2. 2. 2]oct-5-ene-2, 3-diones; 1, 3-cyclohexadienes.