- 作者: 郭禮青; 廖俊臣
- 作者服務機構: Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 300
- 中文摘要: The cycloadditions of the titled two masked o-benzoquinones, 2 and 3, with monosubstituted ethylenes including ethyl acrylate, styrene, ethyl vinyl ether and 1-hexene were studied. The reactions proceeded with high stereoselectivity and regioselectivity to give endo head-to-head adducts when ethyl acrylate, styrene and ethyl vinyl ether were used as addenda. In the case of 1-hexene, the reaction with 2 took place with high regioselectivity but low stereoselectivity to afford endo as well as exo head-to-head adducts while the reaction with 3 occurred with less regioselectivity to produce presumably all the eight possible isomers. The regiochemistry of the adducts were determined by the /sup 1/H nmr analysis of their hydrolysis products, bicyclo[2.2.2]oct-5-en-2, 3-diones 6, and the subsequent photolysis products, 1,3-cyclohexadienes 7. The stereochemistry was established by the study of the lanthanide induced shifts of compounds 6a-6f with Eu(fod)/sub 3/. The regioselectivity and stereoselectivity of these cycloaddition reactions were explained in terms of frontier molecular orbital theory and steric effect. The present study provides also a facile method to prepare regioselectively bicyclo[2.2.2]oct-5-en-2, 3-diones (stereoselectively also) and 1, 3-cyclohexadienes from unsymmetric catechols via masked o-benzoquinones.
- 英文摘要: --
- 中文關鍵字: Regioselective and stereoselective cycloadditions; masked 3, 4-dipropyl-o-benzoquinones; monosubstituted ethylenes; photolysis; bicyclo[2.2.2]oct-5-en-2, 3-diones; 1, 3-cyclohexadienes.
- 英文關鍵字: Regioselective and stereoselective cycloadditions; masked 3, 4-dipropyl-o-benzoquinones; monosubstituted ethylenes; photolysis; bicyclo[2.2.2]oct-5-en-2, 3-diones; 1, 3-cyclohexadienes.