Predominant role of basicity of leaving group in α-effect for nucleophilic ester cleavage
作者:Yasuo Nomura、Takayasu Kubozono、Makoto Hidaka、Mineko Horibe、Naoki Mizushima、Nobuyuki Yamamoto、Toshio Takahashi、Makoto Komiyama
DOI:10.1016/j.bioorg.2003.09.003
日期:2004.2
esters and 4-methylbenzoate esters by HOO- have been systematically investigated in detail. When the leaving groups of substrates are sufficiently good (aryl, 2,2,2-trifluoroethyl, and 2,2-dichloroethyl esters), alpha-effect is evident. However, this effect drastically decreases as the leaving group gets poorer, and is only marginal for the cleavages of 2-fluoroethyl and methyl esters. In the nucleophilic
已经发现亲核反应中的α效应,由于相邻的未配对电子而出乎意料地大的亲核性,强烈依赖于底物的结构。已经系统地详细研究了HOO-对4-硝基苯甲酸酯和4-甲基苯甲酸酯的亲核裂解。当底物的离去基团足够好时(芳基酯,2,2,2-三氟乙基和2,2-二氯乙基酯),α效应是明显的。然而,当离去基团变得更差时,该作用急剧降低,并且对于2-氟乙基和甲基酯的裂解仅是微不足道的。在水杨醛肟和乙酰氧肟酸的亲核裂解中,α效应也仅对于具有良好离去基团的酯才显着。