Using density functional theory (DFT), a systematic computation has been conducted on the reaction between an enal and an azadiene in the presence of N-heterocyclic carbene (NHC) to explore the catalytic mechanisms and origins of stereoselectivity. Several possible pathways leading to benzofuroazepinone have been investigated. We found that the preferred pathway proceeds via six steps, i.e. (1) the nucleohilic addition wherein the NHC adds to the enal, (2) 1,2- proton transfer allows to form the Breslow intermediate, (3) the carbon−carbon bond formation, (4) 1,3- proton transfer, (5) intramolecular cyclization and (6) catalyst regeneration that eventually leads to the RR-configurational cycloadduct benzofuroazepinone. The DFT results agree well with the experimentally observed stereoselectivity. We also found that HOAc plays a vital role as proton shuttle in proton transfer steps. The 1,3-proton transfer was the stereoselectivity-determining step. Furthermore, we conducted global reactivity index (GRI), distortion/interaction and noncovalent interaction (NCI) analyses to identify the role of the NHC in the reaction as well as the origin of the experimentally observed stereochemistry.

利用密度泛函理论（DFT），在存在N-杂环卡宾（NHC）的情况下，对烯醛与氮杂二烯之间的反应进行了系统的计算，以探索立体选择性的催化机理和起源。已经研究了导致苯并呋喃并pin庚酮的几种可能途径。我们发现，首选途径通过六个步骤进行，即（1）将NHC加入到烯醇中的核苷酸添加；（2）1,2-质子转移可形成Breslow中间体；（3）碳-碳键形成；（4）1,3-质子转移， （5）分子内环化和（6）催化剂再生，最终导致RR构型的环加合物苯并呋喃并pin庚酮。DFT结果与实验观察到的立体选择性非常吻合。我们还发现，HOAc在质子转移步骤中作为质子穿梭发挥着至关重要的作用。1,3-质子转移是确定立体选择性的步骤。此外，我们进行了全球反应活性指数（GRI），畸变/相互作用和非共价相互作用（NCI）分析，以确定NHC在反应中的作用以及实验观察到的立体化学的起源。