Catalyst-Controlled Diastereoselectivity Switch in the Asymmetric [3 + 2] Annulation of Isatin-Derived MBH Carbonates and 5-Alkenylthiazol-4(5<i>H</i>)-ones
Ming‐Shun Mei, Yajie Wang, Yajie Wang, Gui-Shan Zhang, Jingyi Tang, Ping Tian, Yu‐Hui Wang, Yu‐Hui Wang
Abstract
Exploration of the diastereodivergent synthesis of spirocyclic oxindoles has been challenging. Herein we report asymmetric [3 + 2] annulations of isatin-derived Morita–Baylis–Hillman (MBH) carbonates and 5-alkenylthiazol-4(5H)-ones. Interestingly, two different chiral catalysts, amide-phosphine and 4-dimethylaminopyridine (DMAP)-thiourea, could lead to two kinds of diastereomeric dispiro oxindoles with three contiguous stereogenic centers. The hexafluoroisopropanol (HFIP) additive plays a vital role in accelerating the reaction and tuning the diastereoselectivity. Moreover, both annulation adducts could be further converted to structurally diverse spirooxindoles.