Asymmetric synthesis of ( R )-baclofen and (3 S ,4 S )-tetflupyrolimet via "on water" organocatalytic addition reactions: a tip on catalyst screening.

This work demonstrates asymmetric synthesis of the GABA derivative ( R )-baclofen and a new herbicidal mode-of-action inhibitor (3 S ,4 S )-tetflupyrolimet featuring low loading (0.5 mol%) organocatalytic addition reactions of dithiomalonates to nitrostyrenes under "on water" conditions. Importantly, we observed that increasing the hydrophobicity of the catalyst does not guarantee improved catalytic performance under "on water" conditions and the trends in the catalytic efficiency of different HBD catalysts under "on water" conditions (with hydrophobic additives) align more closely with those observed in pure hydrophobic organic solvents. These findings propose a valuable tip for screening organocatalysts in developing asymmetric hydrogen-bonding catalysis under "on water" conditions.