Carbonyl

“The in situ generation of an iminium ion from a carbonyl compound lowers the LUMO energy of the system. Iminium catalysis is comparable to Brønsted- or Lewis acid activation of carbonyl compounds. The LUMO energy is lowered, theα-CH acidity increases, and nucleophilic additions including conjugate additions as well as pericyclic reactions are facilitated.”

“β-Dicarbonyl compounds such as ethyl 3-oxobutanoate (acetoacetate) and diethyl propanedioate (malonate) are versatile synthetic building blocks for elaborating more complex molecules. Their unusual acidity makes it easy to form the corresponding anions, which can be used in nucleophilic displacement reactions with a wide variety of substrates. Their hydrolysis produces 3-ketoacids that are unstable and undergo decarboxylation on heating.”