exo-Addition of Diels-Alder Reactions

• Main Authors: Hus, Sheng-Kai, 徐聖凱
• Other Authors: Li, Yaw-Kuen
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/f2uh4z

碩士 === 國立交通大學 === 應用化學系碩博士班 === 102 === According to previous studies, Diels-Alder reactions prefer the formation of endo cycloadducts as an effect of secondary orbital interaction. In this study, the substrate controlled exo-selectivity of Diels-Alder reactions of 1,4-dimethyl- and 4-phenylsilyl enol ether as dienes with several ,-unsaturated esters and aldehydes as dienophiles under Lewis acid catalyzed and thermal conditions was investigated. Our results show that for the ester-substituted dienophiles, under the Lewis acid catalyzed condition, the -substituted compounds favor exo-selectivity; whereas under thermal condition, the ester-substituted dienophiles favor exo-selectivity no matter the ester dienophile is substituted or not. In contrast, under thermal condition, endo addition is favored for aldehyde dienophiles with -substituents or without -substituents. Finally, we will compare the stereoselectivity of Diels-Alder reaction using dienophiles with different electron withdrawing groups such as keto, cyano and nitro groups.