分子内氮原子上亲核取代反应的理论研究

在MP2(full)/631+G(d,p)理论水平上,以-CHR-(CH2)3-NFCH3(R=H,CH3,CH2CF3,CHO,COCH3)为计算模型,对分子内可能发生的两条反应路径—氮原子上的亲核取代反应及消去反应进行了理论研究.结果表明,当进攻基团-CHR为碱性较强的基团,即R=H、CH3、CH2CF3时,有利于发生消去反应而生成直链化合物R-CH2-(CH2)3N=CH2;而当R为吸电子基团-CHO、-COCH3时,主要发生分子内氮原子上的亲核取代反应,产物为含氮的五员杂环化合物.这些理论预测与已有的实验结果吻合.

Theoretical Study of Intramolecular Nucleophilic Substitution on Nitrogen

Using the -CHR-(CH_ 2)_ 3-NFCH_ 3(R=H, CH_ 3, CH_ 2CF_ 3, CHO, COCH_ 3) as the computational model, the two possible intramolecular reactions, nucleophilic substitution on nitrogen and elimination reaction, were studied at the theoretical level of MP2(full)/6-31+G(d,p). The results indicate that the elimination mechanism, when the -CHR radical is more basic (R=H, CH_ 3, CH_ 2CF_ 3) leading to linear products R-CH_ 2-(CH_ 2)_ 3N=CH_ 2 is preferred. In contrast, electro-withdrawing groups CHO and COCH_ 3 on the attacking site will favor the intramolecular nucleophilic substitution of nitrogen and form 5-membered heterocyclic compounds. These theoretical predictions agree with the available experiments.