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Asymmetric Synthesis of α-Fluoro-β-Amino-oxindoles with Tetrasubstituted C–F Stereogenic Centers via Cooperative Cation-Binding Catalysis

Author:
Paladhi, Sushovan, Park, Sang Yeon, Yang, Jung Woon, Song, Choong Eui
Source:
Organic letters 2017 v.19 no.19 pp. 5336-5339
ISSN:
1523-7052
Subject:
catalysts, catalytic activity, chemical reactions, chemical structure, imines, stereoselectivity
Abstract:
Biologically relevant chiral 3,3-disubstituted oxindole products containing a β-fluoroamine unit are obtained in high yields and with excellent stereoselectivity (up to 99% ee, dr >20:1 for syn) through the organocatalytic direct Mannich reaction of 3-fluoro-oxindoles as fluoroenolate precursors and α-amidosulfones as the bench-stable precursors of sensitive imines by using a chiral oligoethylene glycol and KF as a cation-binding catalyst and base, respectively. This protocol can be easily scaled without compromising the asymmetric induction. Furthermore, this protocol was also successfully extended to generate tetrasubstituted C–Cl and C–Br stereogenic centers.
Agid:
5826997