Isotope Effects and Mechanism of the Asymmetric BOROX Brønsted Acid Catalyzed Aziridination Reaction

The mechanism of the chiral VANOL-BOROX
Brønsted acid catalyzed
aziridination reaction of imines and ethyldiazoacetate has been studied
using a combination of experimental kinetic isotope effects and theoretical
calculations. A stepwise mechanism where reversible formation of a
diazonium ion intermediate precedes rate-limiting ring closure to
form the cis-aziridine is implicated. A revised model
for the origin of enantio- and diastereoselectivity
is proposed based on relative energies of the ring-closing transition
structures.

本研究结合实验动力学同位素效应与理论计算，对手性VANOL-BOROX布朗斯特酸（Brønsted acid）催化亚胺与重氮乙酸乙酯的氮丙啶化反应机制开展了探究。研究表明该反应遵循分步机制：重氮鎓离子中间体的可逆生成步骤先于限速环合过程，最终生成顺式氮丙啶产物。基于环合过渡态的相对能量，本研究提出了修正的对映选择性与非对映选择性起源模型。