The scope of these small-molecule H-bond donors termed squaramide organocatalysis covers both non-stereoselective and stereoselective applications.
For enantioselective squaramide catalysis, chirality is induced via the tertiary amine group.
[1] H-bond accepting substrates include carbonyl compounds imines, Michael acceptors, and epoxides.
The nucleophile can be nitroalkanes, enolates, and even phenols (resulting in electrophilic aromatic substitution).
[1] Squaramide catalysts are developed in 2008 by Jeremiah P. Malerich, Koji Hagihara, and Viresh H.