C(sp2)−H Hydrogen‐Bond Donor Groups in Chiral Small‐Molecule Organocatalysts

Asymmetric catalysis of chemical transformations by chiral small organic molecules has become an important approach in organic synthesis. Attractive noncovalent interactions such as N(O)-H hydrogen-bonding, pi-stacking, and cation-pi interactions have been exploited as the primary and/or secondary function(s) of the catalysts, but C(sp(2))-H hydrogen-bonding interactions have been underutilized in this context. This Minireview showcases selected organocatalysts in which C(sp(2))-H hydrogen-bonding interactions are invoked in their mechanism of catalysis, examples of which can be inspirational for the development of new catalysts.