Catalytic Asymmetric Construction of Vicinal Tetrasubstituted Stereocenters by the Mannich Reaction of Linear α-Substituted Monothiomalonates with Isatin <i>N</i>-Boc Ketimines
A highly diastereo- and enantioselective method for the construction of vicinaltetrasubstitutedstereocenters through the first catalytic asymmetric Mannich reaction of linear α-substituted MTMs with isatin N-Boc ketimines has been developed. This protocol provides atom-economic synthesis of less accessible 3-aminooxindoles bearing vicinaltetrasubstitutedstereocenters. Notably, it also constitutes
Organocatalytic Stereoselective Synthesis of Acyclic γ-Nitrothioesters with All-Carbon Quaternary Stereogenic Centers
作者:Yukihiro Arakawa、Sven P. Fritz、Helma Wennemers
DOI:10.1021/jo500403q
日期:2014.5.2
stereoselective synthesis of acyclic thioesters bearing adjacent quaternary and tertiary stereogeniccenters under mild organocatalytic conditions was developed. α-Substituted monothiomalonates (MTMs) were used as thioester enolate equivalents. They reacted cleanly with nitroolefins in the presence of 1–6 mol % of cinchona alkaloid urea derivatives, and provided access to γ-nitrothioesters with quaternary stereocenters
Stereoselective Organocatalytic Synthesis of Oxindoles with Adjacent Tetrasubstituted Stereocenters
作者:Oliver D. Engl、Sven P. Fritz、Helma Wennemers
DOI:10.1002/anie.201502976
日期:2015.7.6
Oxindoles with adjacenttetrasubstitutedstereocenters were obtained in high yields and stereoselectivities by organocatalyzed conjugate addition reactions of monothiomalonates (MTMs) to isatin‐derived N‐Cbz ketimines. The method requires only a low catalyst loading (2 mol %) and proceeds under mild reaction conditions. Both enantiomers are accessible in good yields and excellent stereoselectivities