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
Synthesis of Monothiomalonates - Versatile Thioester Enolate Equivalents for C-C Bond Formations
作者:Oliver D. Engl、Jakub Saadi、Elena Cosimi、Helma Wennemers
DOI:10.1002/hlca.201700196
日期:2017.11
surrogates of thioester enolates that allow for stereoselective C–C bond formations under mild conditions and thereby afford access to synthetically versatile thioester derivatives. Here we present a straightforward synthetic route to MTMs that proceeds through nucleophilicring‐opening of Meldrum's acid derivatives followed by O‐alkylation of the resulting malonic acid half thioesters with alkyl triflates
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
A straightforward stereoselectivesynthesis route to indolin-3-yl acetates has been developed using organocatalytic addition reactions of monothiomalonates to ortho-bromo nitrostyrenes as the key step. The addition products of this highlystereoselectiveone-pot addition–deprotection–decarboxylation sequence were easily further converted to the target indolin-3-yl acetates, via an intramolecular Buchwald–Hartwig