DFT Insights into NHC-Catalyzed Switchable [3+4] and [3+2] Annulations of Isatin-Derived Enals and N-Sulfonyl Ketimines: Mechanism, Regio- and Stereoselectivity. - Yu, Saisai; Zhou, Wenxin; Jiang, Yueming; Wang, Hangyu; Zhou, Xiaoyu; Yang, Shengwen (Molecules, 2025)