3 research outputs found
Asymmetric Synthesis of α‑Fluoro-β-Amino-oxindoles with Tetrasubstituted C–F Stereogenic Centers via Cooperative Cation-Binding Catalysis
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 <i>syn</i>) 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
Asymmetric Synthesis of α‑Fluoro-β-Amino-oxindoles with Tetrasubstituted C–F Stereogenic Centers via Cooperative Cation-Binding Catalysis
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 <i>syn</i>) 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
Fluoride Anions in Self-Assembled Chiral Cage for the Enantioselective Protonation of Silyl Enol Ethers
The potential of Song’s
chiral oligoethylene glycols (oligoEGs) as catalysts was explored
in the enantioselective protonation of trimethylsilyl enol ethers
in combination with alkali metal fluoride (KF and CsF) and in the
presence of a proton source. Highly enantioselective protonations
of various silyl enol ethers of α-substituted tetralones were
achieved, producing chiral α-substituted tetralones in full
conversion and with up to 99% ee. The established protocol was successfully
extended to the synthesis of biologically relevant chiral α-substituted
chromanone and thiochromanone derivatives