The Ion Tag Strategy as a Route to Highly Efficient Organocatalysts for the Direct Asymmetric Aldol Reaction

The installation of an imidazolium tag via acetate connection to the C-4 of cis-4-hydroxy-L-proline provides a highly efficient catalyst for the direct asymmetric aldol reaction, that works in a remarkably low catalyst loading (0.1 mol%) affording TONS up to 930 in the case of electron-poor aromatic aldehydes with ee up to > 99%.