Chiral ammonium betaine-catalyzed asymmetric Mannich-type reaction of oxindoles

• Masahiro Torii,
• Kohsuke Kato,
• Daisuke Uraguchi and
• Takashi Ooi

Beilstein J. Org. Chem. 2016, 12, 2099–2103, doi:10.3762/bjoc.12.199

• quaternary and tertiary stereogenic carbon centers on biologically intriguing molecular frameworks with high fidelity. Keywords: ammonium betaine; asymmetric catalysis; Mannich reaction; organocatalysis; oxindole; Introduction Chiral indole alkaloids possessing C-3 quaternary indoline frameworks are an

• the presence of a catalytic amount of chiral ammonium betaine 1a (5 mol %) in toluene with 4 Å molecular sieves (MS 4 Å) at −60 °C. Bond formation occurred smoothly and, after 24 h of stirring, the desired Mannich adduct 4aa was isolated as a mixture of diastereomers in 90% yield. Although the

• . Conclusion In summary, we have clearly demonstrated that chiral ammonium betaine 1c acts as a uniquely effective catalyst in promoting a Mannich-type reaction between 3-aryloxindoles and N-Boc aldimines with high levels of diastereo- and enantioselectivity under mild conditions. This study greatly expands