分子内氮原子上亲核取代反应生成三元氮杂环的理论研究

采用密度泛函方法M062X在6-31+G**基组水平上以-CH(CHO)-CH₂-NFR(R=H, CH₃)为计算模型，考察分子内可能发生的2种竞争反应路径——氮原子上的亲核取代反应和消去反应。R=H的亲核取代反应能垒为49.7 kJ/mol，而R=CH₃亲核取代的反应能垒为68.6 kJ/mol，表明CH₃的空间位阻明显提高了反应能垒。R=CH₃的优势路径是亲核取代，产物为三元氮杂环，而消去历程的能垒为151.7 kJ/mol，得到的是开链副产物。计算结果表明，分子内氮原子上亲核取代反应生成三元氮杂环比较容易发生，且对其竞争路径消去反应有着明显的优势。  

Theoretical Study of Intramolecular Nucleophilic Substitution on Nitrogen to Three-Membered N-Heterocycle

Using- CH（CHO） -CH2-NFR（ R = H, CH3 ） as the computational model, two possible intramolecular reactions, nucleo- philic substitution on nitrogen and elimination reaction, were investigated by adopting a popular density functional theory-M062X with the 6-31 ＋ G＊ ＊ basis set. The energy barrier of nucleophilic substitution was predicted to be 49.7 kJ/mol for R = H, while it was 68.6 kJ/mol for R = CHz , showing the steric hindrance of CH3 significantly increases the energy barrier. For R = CH3 , the nucleophil- ic substitution with a three-membered N-heterocycle as product was the favorable pathway, while its elimination reaction has a higher energy barrier, 151.7 kJ/mol, with the chain compound as product. These theoretical prediction suggests the nucleophilic substitution on nitrogen for three-membered N-heterocycle can occur easily, and takes some advantage over the corresponding elimination reaction. Therefore, the nucleophilic substitution on nitrogen has certain potential for future experiment.