New Developments of Chiral Palladium‐Aqua Complexes As Cooperative Brønsted Acid‐Base Catalysts in Organic Synthesis

Based upon their exceptional reactivity as cooperative Bronsted acid-base catalysts chiral diphosphane Pd-aqua complexes have successfully been utilized in a broad range of asymmetric transformations. Originally discovered by Sodeoka 25 years ago, they readily form reactive chiral Pd enolates upon deprotonation of beta-dicarbonyl compounds and simultaneously, a Bronsted acid liberated from the catalyst activates the electrophile. After the initial report and some ensuing papers had been published in the early 2000s, the field lay dormant for more than a decade. In recent years, however, new developments towards the enantioselective synthesis of various heterocycles and other useful compounds have evolved which take advantage of the unique properties of chiral Pd-aqua complexes.