Axially Chiral C2-Symmetric N-Heterocyclic Carbene (NHC) Palladium Complex-Catalyzed Asymmetric Fluorination and Amination of Oxindoles
作者:Rui Zhang、De Wang、Qin Xu、Jiajun Jiang、Min Shi
DOI:10.1002/cjoc.201200289
日期:2012.6
Chiral C2‐symmetric N‐heterocyclic carbene (NHC) palladium diaquo complex 5b prepared from (S)‐BINAM was found to be a fairly effective catalyst for the enantioselective asymmetric fluorination of oxindoles to give the corresponding products in moderate enantioselectivities along with good to excellent yields.
Structurally modified N-fluorobenzenesulfonimides (NFSIs) have been used to study the enantioselective fluorination of oxindoles in the presence of a bis-cinchona alkaloid, (DHQD)(2)PHAL, as the catalyst. We observe that the NFSI analogues bearing two tert-butyl groups at the para-position of the symmetric phenyl rings led to an enhanced enantioselectivity in most cases (up to 96% ee) compared with the unmodified NESIs (less than 69% ee). (C) 2013 Elsevier Ltd. All rights reserved.