TY - JOUR T1 - Enantioselective cascade Michael addition/cyclization reactions of 3-nitro-2H-chromenes with 3-isothiocyanato oxindoles: efficient synthesis of functionalized polycyclic spirooxindoles. AU - Tan,Fen, AU - Lu,Liang-Qiu, AU - Yang,Qing-Qing, AU - Guo,Wei, AU - Bian,Qiao, AU - Chen,Jia-Rong, AU - Xiao,Wen-Jing, PY - 2013/09/10/received PY - 2014/3/29/entrez PY - 2014/3/29/pubmed PY - 2014/12/15/medline SP - 3415 EP - 20 JF - Chemistry (Weinheim an der Bergstrasse, Germany) JO - Chemistry VL - 20 IS - 12 N2 - An unprecedented Zn(OTf)2-catalyzed asymmetric Michael addition/cyclization cascade of 3-nitro-2H-chromenes with 3-isothiocyanato oxindoles has been disclosed. This transformation provides an efficient access to various synthetically important polycyclic spirooxindoles in a highly stereoselective manner under mild conditions (72–99% yields, up to >95:5 d.r. and >99% ee). The reaction leads to the formation of three consecutive stereocenters, including 1,3-nonadjacent tetrasubstituted carbon stereocenters, in a single operation. A bifunctional activation model of the chiral Zn(OTf)2/bis(oxazoline) complex was proposed based on control experiments, wherein the ZnII moiety serves as a Lewis acid and the N atom of the free NH group acts as a Lewis base by a hydrogen-bonding interaction. SN - 1521-3765 UR - https://www.unboundmedicine.com/medline/citation/24677230/Enantioselective_cascade_Michael_addition/cyclization_reactions_of_3_nitro_2H_chromenes_with_3_isothiocyanato_oxindoles:_efficient_synthesis_of_functionalized_polycyclic_spirooxindoles_ DB - PRIME DP - Unbound Medicine ER -